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Re: [micbuilders] Re: hum&noise problems

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  • Bhakakhan
    ... Zapnsparks Generic int. ECM sounds even better than Sc.H. Circuit for int. FET ECMs.(to my taste) ... I wouldn t do that. Your capsules have a strong
    Message 1 of 12 , Jul 1, 2011
      On 01.07.2011 01:18, Janez Podolski wrote:
      >
      > hey again.
      > I've got some news.
      > I don't know if I mentioned before, but anyway. Yesterday I remembered
      > that before I get the "real" circuit board(today circuit board) I've
      > assembled two mic preamps, Behringer ECM8000 and this generic
      > preamp(in zapnspark's file) on vero board. I've tried them again.
      > Results are interesting and are connected with current design of my
      > preamp. The Behringer ECM8000 circuit doesn't have any hum. Almost
      > any, but nothing compared to scotthelmke design. Scotthelmke preamp
      > sounded better(i think), but there was hum.
      >
      Zapnsparks Generic int. ECM sounds even better than Sc.H. Circuit for
      int. FET ECMs.(to my taste)
      >
      > So, as you can see from my circuit, I added capacitors and resistors
      > to my preamp as on Behringer hoping there was the problem.(30 ohm,
      > 2n2, 1n5).
      >
      I wouldn't do that. Your capsules have a strong lo-end roll off anyway -
      no additional filters needed. Unless you want to design it exactly like
      this ( a thinny microphone with almost no bass).
      >
      > Scotthelmke circuit had hum without any added switches or capacitors.
      >
      > These days I tried these things.
      > -> I changed zener diode. I know that these things are preety noisy.
      > In my case, seems like zener is OK. I also tried to replace zener
      > diode with two 5V(5V6 actually) - I know that 5V zener diode has the
      > best characteristic. No change.
      >
      Zeners are usually not the cause for Hum - they are not the problem - i
      could have told you that before.
      >
      >
      > -> I tried to bridge(100k resistors). No change.
      >
      You live risky - i wouldn't do that. i meant, that the 10k and the
      following cap are interfering with your base resistors 100k, and so i
      would disconnect both. (the 10k and the following cap, NOT the 100k's) -
      both the 10k and the following cap don't belong there (according to the
      usual circuits, and according to my logic. They form a steady path
      between the two channels and this interferes with your Transistor Bases.
      Simply pull both components out.
      >
      > -> I tried to add 30k resistors from base to emmiter - similar to
      > behringer circuit.
      >
      Why? I see no sense in that. if you don't know, Why you are doing
      something, then better let it be....
      >
      > -> Remember the low cut switch I had added to original cirucit. It has
      > some effect. When low cut switch is in OFF position(no low frequency
      > cutting) the hum is enormous. When low cut switch is in ON position,
      > hum get's real quiet(if compared to other switch position, but still
      > too much present). So, if hum get's quiter when changing switch
      > position, it means hum si generated before switch - somewhere near
      > microphone.
      >
      That is logical, because hum is 50Hz noise - with a lo-cut, this becomes
      more quiet than before. But: Normally you don't need, nor want a low-cut
      with the capsules you are using - the capsule itself is less responsive
      in low end - and this is more of a problem than an advantage.
      >
      > Is it possible, that 5k6 resistors(source and drain resistors) are too
      > large - that microphone is generating some shit because it doesn't ave
      > enough current? Or something.
      >
      No - the Source Resistors of the FET can't generate hum, because Hum
      originates from the power net in your house, and is then injected via
      the cable and your board to your vulnerable components.
      >
      > Seems like my mixing console is OK, but I'll still try this microphone
      > on Monday with other mixing console and than report.
      >
      > If this is important: I bought 2n5087 transistors on ebay and used
      > them in both circuit, behringer and ScottH.
      >
      Bad Transistors cannot generate hum, but they can become noisy, if they
      are injured.
      >
      > Does anybody ever had any similar problems?
      >
      no - not myself. Except one single time: When i shield my capsules and
      its Fet not correctly.
      >
      > Thanks, d.
      >
      I've had a look on your board again. this is designed very risky, since
      the top layer consists of a lot of ground, with only small holes for the
      components. Maybe one component is licking ground via surface-conduction
      of some component housing. Inspect it all again...

      And Try this: DON'T connect the Capsule Housing (the big one you did
      DIY) directly to the capsule ground. Keep em seperated. Now, wire the
      Housing with a wire or a cable directly to the output ground of your
      circuit (Ground of Output-Connector). I mean in a way, that fault
      currents and noise "catched" by the body are not flowing through your
      circuit or your capsule, but directly to OV Output-Ground. You do a so
      called "separation of Chassis-ground and Audio-Ground" then. Wire the
      capsule to board as usual. After that, put your whole circuit board
      inside a Coffee-Box, or similar Metal Housing. You should have a very
      proper shielding, then. Maybe that helps, maybe not. I don't know. Look
      at the output connector: Is everything soldered okay? Or do you have
      made a mistake? Be very careful, when inspecting the whole board again -
      the Error HAS to lie somewhere there.

      But one thing: Whereever the fault lies, it is not a problem of the
      circuit(except those darn 10k+Capacitor i mentioned 10 times or so by
      now). It is also unlikely that components have malfunction. The Problem
      is your Board-Concept. So go through all again and search for mistakes
      you made. You MUST have made some, because on veroboard -as you say-
      everything is alright.

      The Error is NOT external, but lies in YOUR concept. So better revise
      the Concept again.
      >
      > --- In micbuilders@yahoogroups.com
      > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan <bhakakhan@...> wrote:
      > >
      > > On 27.06.2011 18:01, Janez Podolski wrote:
      > > >
      > > > here are results. Half of them a've already done before, but i'd
      > tested
      > > > them again.
      > > > -> Disconecting the switch didn't change anything. Hum still
      > exsist.btw,
      > > > any other suggestions for mute switch without BANG while switching?
      > > >
      > > not the switch, but the 10k and the cap also....they form a path
      > between
      > > the two channels...and bridge your 2 100k resistors...
      > > >
      > > > -> Testing only with mixer is what I'm doing all the time. So, no
      > > > changes.
      > > > ->I'll take microphone to friend's mixing console in a short time and
      > > > than we'll see.
      > > >
      > > i'll wait...before "oracling" again..
      > > >
      > > > -> Than I connect modified microphone directly (as you described,
      > but I
      > > > aded resistor from source to ground).
      > > >
      > > sorry - i was in a hurry and forgot the source resi to mention...
      > > >
      > > > Yep, hum disapeared. So, I assume
      > > > my problem is bad phantom power supply or what?
      > > >
      > > possible...but unlikely - more likely, your board is the problem
      > > >
      > > > I've got some exams right now, so microphones will have to wait. But
      > > > I'll dolater some more tests and then post results here!thanks for
      > > > quick reply.
      > > > --- In micbuilders@yahoogroups.com
      > <mailto:micbuilders%40yahoogroups.com>
      > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan <bhakakhan@> wrote:
      > > > >
      > > > > Something is indeed wrong with your setup - not only with the
      > > > microphone.
      > > > >
      > > > > Try this:
      > > > > Cut Off the 10k and the following capacitor including the
      > mute-switch.
      > > > > Just cut it away - DISCONNECT it, throw it to the side - don't
      > bother
      > > > > about it - don't even THINK about it. It looks like this is the
      > wrong
      > > > > place for the switch. if that fails:
      > > > >
      > > > > Unconnect your whole computer/usb things. You have only your mixing
      > > > > console and your mic, then. Connect a headphone to your mixing desk.
      > > > Is
      > > > > the Hum Still there?
      > > > >
      > > > > Take your setup to another power plug - maybe in the kitchen or at
      > > > some
      > > > > friend's house or something. Hum still there?
      > > > >
      > > > > Take your microphone to some friend's mixing console/phantom supply
      > > > and
      > > > > re-try. Hum Still there? If yes, then its your preamplifier.
      > > > >
      > > > > Another thing to try: Take a 9V Battery and connect + to Capsule
      > > > Drain.
      > > > > Connect - to ground. Put a cap at the source connection (10µF
      > > > > electrolytic will do...). and connect the other end of the capacitor
      > > > to
      > > > > a mono-jack. Ground of course to jack's ground. Connect this to your
      > > > > mixing desk WITHOUT Phantom power. Hum still there? Connect it
      > > > directly
      > > > > to your soundcard's mic-in. Hum still there?
      > > > >
      > > > > If everything fails, then i recommend, to quickly build up the
      > > > original
      > > > > schematic (look in files section/zapnspark/DIYgenericIntFET.pdf)
      > > > without
      > > > > any extra dingledongle (especially the 10k resistor and the
      > following
      > > > > capacitor looks very very suspicious to me) - only the circuit and
      > > > > wires. Connect this again to you mixing desk. If it fails, then you
      > > > have
      > > > > a problem in your house/mixing desk/computer whatsoever.
      > > > >
      > > > > Cheers, Johannes.
      > > > >
      > > > > On 27.06.2011 10:24, Janez Podolski wrote:
      > > > > >
      > > > > > Hey!
      > > > > > I've just upload 2 more pictures of microphone and preamplifier
      > > > case.
      > > > > > I'll try to make some shield around the preamplifier. The wierd
      > > > thing
      > > > > > is, that when I get closer to the circuit with my hand or some
      > metal
      > > > > > stuff, nothing happens. Usually some noise or whatewer is
      > generated,
      > > > > > but not here.
      > > > > > I've also try to switch diferent cables, one of them was good
      > > > shielded
      > > > > > cable small length. Nothing changed.
      > > > > > Thanks for your reply. Hope we can manage this thing.
      > > > > >
      > > > > > --- In micbuilders@yahoogroups.com
      > <mailto:micbuilders%40yahoogroups.com>
      > > > <mailto:micbuilders%40yahoogroups.com>
      > > > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan bhakakhan@
      > wrote:
      > > > > > >
      > > > > > > You wrote in your info, that the case is plastic, without any
      > > > shield.
      > > > > > >
      > > > > > > May i suggest, that you try some coffe-box or similar METAL case
      > > > for
      > > > > > > test purposes? Especially the capsule should be properly
      > shielded.
      > > > > > >
      > > > > > > But i don't know if that is the ultimate solution. Can you
      > provide
      > > > more
      > > > > > > photos of the mike WITH capsule and Case?
      > > > > > >
      > > > > > > THX,
      > > > > > >
      > > > > > > Johannes
      > > > > > > On 27.06.2011 00:11, Janez Podolski wrote:
      > > > > > > >
      > > > > > > > Hey! I've just made new file NOISE PROBLEM. There is a
      > note with
      > > > > > > > accurate descritpion of my problem, so please check it out. In
      > > > few
      > > > > > > > words: my diy microphone has extra hum! I've made some hum
      > > > recording
      > > > > > > > and upload everything to make solving as easy as possible.You
      > > > can
      > > > > > leave
      > > > > > > > your suggestions here, or email me. But I think here is
      > the best
      > > > > > place,
      > > > > > > > maybe someone has the same problems.
      > > > > > > > Best regards, d.
      > > > > > > >
      > > > > > > > [Non-text portions of this message have been removed]
      > > > > > > >
      > > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > > [Non-text portions of this message have been removed]
      > > > > > >
      > > > > >
      > > > > >
      > > > >
      > > > >
      > > > >
      > > > > [Non-text portions of this message have been removed]
      > > > >
      > > >
      > > > [Non-text portions of this message have been removed]
      > > >
      > > >
      > >
      > >
      > >
      > > [Non-text portions of this message have been removed]
      > >
      >
      >



      [Non-text portions of this message have been removed]
    • Janez Podolski
      hmm. Maybe the important part of my post was the following sentence. - Scotthelmke circuit had hum without any added switches or capacitors. Compared to
      Message 2 of 12 , Jul 1, 2011
        hmm.
        Maybe the important part of my post was the following sentence.
        -> Scotthelmke circuit had hum without any added switches or capacitors.
        Compared to Behringer ECM8000 which didn't have any hum. That's strange. I assembled both of them on vero board and than record them.

        Also, the idea to bridge 2 100k resistors was yours. Maybe you replied in hurry, but, as you can see, my knowledge about electronic isn't on souch high level than yours. I just did that you have said(although it seemed to me a little strange).
        > > > not the switch, but the 10k and the cap also....they form a path
        > > between
        > > > the two channels...and bridge your 2 100k resistors...


        Anyway. I'll try what you have suggested and than we'll see. The results on veroboard really confusing me all the time. About mute switch and all related parts-> I've removed all of them. Hum didn't get any quieter so there is no problem.
        I must try this with ground, I've been thinking about that a lot, but, I do have some test capsules on good shielded cable without aluminium case. I did wrap them with some metal foil once, but there was no change.
        well, thanks for help. Maybe I shouldn't be doing microphones, since I've got only problems with them. :|




        > On 01.07.2011 01:18, Janez Podolski wrote:
        > >
        > > hey again.
        > > I've got some news.
        > > I don't know if I mentioned before, but anyway. Yesterday I remembered
        > > that before I get the "real" circuit board(today circuit board) I've
        > > assembled two mic preamps, Behringer ECM8000 and this generic
        > > preamp(in zapnspark's file) on vero board. I've tried them again.
        > > Results are interesting and are connected with current design of my
        > > preamp. The Behringer ECM8000 circuit doesn't have any hum. Almost
        > > any, but nothing compared to scotthelmke design. Scotthelmke preamp
        > > sounded better(i think), but there was hum.
        > >
        > Zapnsparks Generic int. ECM sounds even better than Sc.H. Circuit for
        > int. FET ECMs.(to my taste)
        > >
        > > So, as you can see from my circuit, I added capacitors and resistors
        > > to my preamp as on Behringer hoping there was the problem.(30 ohm,
        > > 2n2, 1n5).
        > >
        > I wouldn't do that. Your capsules have a strong lo-end roll off anyway -
        > no additional filters needed. Unless you want to design it exactly like
        > this ( a thinny microphone with almost no bass).
        > >
        > > Scotthelmke circuit had hum without any added switches or capacitors.
        > >
        > > These days I tried these things.
        > > -> I changed zener diode. I know that these things are preety noisy.
        > > In my case, seems like zener is OK. I also tried to replace zener
        > > diode with two 5V(5V6 actually) - I know that 5V zener diode has the
        > > best characteristic. No change.
        > >
        > Zeners are usually not the cause for Hum - they are not the problem - i
        > could have told you that before.
        > >
        > >
        > > -> I tried to bridge(100k resistors). No change.
        > >
        > You live risky - i wouldn't do that. i meant, that the 10k and the
        > following cap are interfering with your base resistors 100k, and so i
        > would disconnect both. (the 10k and the following cap, NOT the 100k's) -
        > both the 10k and the following cap don't belong there (according to the
        > usual circuits, and according to my logic. They form a steady path
        > between the two channels and this interferes with your Transistor Bases.
        > Simply pull both components out.
        > >
        > > -> I tried to add 30k resistors from base to emmiter - similar to
        > > behringer circuit.
        > >
        > Why? I see no sense in that. if you don't know, Why you are doing
        > something, then better let it be....
        > >
        > > -> Remember the low cut switch I had added to original cirucit. It has
        > > some effect. When low cut switch is in OFF position(no low frequency
        > > cutting) the hum is enormous. When low cut switch is in ON position,
        > > hum get's real quiet(if compared to other switch position, but still
        > > too much present). So, if hum get's quiter when changing switch
        > > position, it means hum si generated before switch - somewhere near
        > > microphone.
        > >
        > That is logical, because hum is 50Hz noise - with a lo-cut, this becomes
        > more quiet than before. But: Normally you don't need, nor want a low-cut
        > with the capsules you are using - the capsule itself is less responsive
        > in low end - and this is more of a problem than an advantage.
        > >
        > > Is it possible, that 5k6 resistors(source and drain resistors) are too
        > > large - that microphone is generating some shit because it doesn't ave
        > > enough current? Or something.
        > >
        > No - the Source Resistors of the FET can't generate hum, because Hum
        > originates from the power net in your house, and is then injected via
        > the cable and your board to your vulnerable components.
        > >
        > > Seems like my mixing console is OK, but I'll still try this microphone
        > > on Monday with other mixing console and than report.
        > >
        > > If this is important: I bought 2n5087 transistors on ebay and used
        > > them in both circuit, behringer and ScottH.
        > >
        > Bad Transistors cannot generate hum, but they can become noisy, if they
        > are injured.
        > >
        > > Does anybody ever had any similar problems?
        > >
        > no - not myself. Except one single time: When i shield my capsules and
        > its Fet not correctly.
        > >
        > > Thanks, d.
        > >
        > I've had a look on your board again. this is designed very risky, since
        > the top layer consists of a lot of ground, with only small holes for the
        > components. Maybe one component is licking ground via surface-conduction
        > of some component housing. Inspect it all again...
        >
        > And Try this: DON'T connect the Capsule Housing (the big one you did
        > DIY) directly to the capsule ground. Keep em seperated. Now, wire the
        > Housing with a wire or a cable directly to the output ground of your
        > circuit (Ground of Output-Connector). I mean in a way, that fault
        > currents and noise "catched" by the body are not flowing through your
        > circuit or your capsule, but directly to OV Output-Ground. You do a so
        > called "separation of Chassis-ground and Audio-Ground" then. Wire the
        > capsule to board as usual. After that, put your whole circuit board
        > inside a Coffee-Box, or similar Metal Housing. You should have a very
        > proper shielding, then. Maybe that helps, maybe not. I don't know. Look
        > at the output connector: Is everything soldered okay? Or do you have
        > made a mistake? Be very careful, when inspecting the whole board again -
        > the Error HAS to lie somewhere there.
        >
        > But one thing: Whereever the fault lies, it is not a problem of the
        > circuit(except those darn 10k+Capacitor i mentioned 10 times or so by
        > now). It is also unlikely that components have malfunction. The Problem
        > is your Board-Concept. So go through all again and search for mistakes
        > you made. You MUST have made some, because on veroboard -as you say-
        > everything is alright.
        >
        > The Error is NOT external, but lies in YOUR concept. So better revise
        > the Concept again.
        > >
        > > --- In micbuilders@yahoogroups.com
        > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan <bhakakhan@> wrote:
        > > >
        > > > On 27.06.2011 18:01, Janez Podolski wrote:
        > > > >
        > > > > here are results. Half of them a've already done before, but i'd
        > > tested
        > > > > them again.
        > > > > -> Disconecting the switch didn't change anything. Hum still
        > > exsist.btw,
        > > > > any other suggestions for mute switch without BANG while switching?
        > > > >
        > > > not the switch, but the 10k and the cap also....they form a path
        > > between
        > > > the two channels...and bridge your 2 100k resistors...
        > > > >
        > > > > -> Testing only with mixer is what I'm doing all the time. So, no
        > > > > changes.
        > > > > ->I'll take microphone to friend's mixing console in a short time and
        > > > > than we'll see.
        > > > >
        > > > i'll wait...before "oracling" again..
        > > > >
        > > > > -> Than I connect modified microphone directly (as you described,
        > > but I
        > > > > aded resistor from source to ground).
        > > > >
        > > > sorry - i was in a hurry and forgot the source resi to mention...
        > > > >
        > > > > Yep, hum disapeared. So, I assume
        > > > > my problem is bad phantom power supply or what?
        > > > >
        > > > possible...but unlikely - more likely, your board is the problem
        > > > >
        > > > > I've got some exams right now, so microphones will have to wait. But
        > > > > I'll dolater some more tests and then post results here!thanks for
        > > > > quick reply.
        > > > > --- In micbuilders@yahoogroups.com
        > > <mailto:micbuilders%40yahoogroups.com>
        > > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan <bhakakhan@> wrote:
        > > > > >
        > > > > > Something is indeed wrong with your setup - not only with the
        > > > > microphone.
        > > > > >
        > > > > > Try this:
        > > > > > Cut Off the 10k and the following capacitor including the
        > > mute-switch.
        > > > > > Just cut it away - DISCONNECT it, throw it to the side - don't
        > > bother
        > > > > > about it - don't even THINK about it. It looks like this is the
        > > wrong
        > > > > > place for the switch. if that fails:
        > > > > >
        > > > > > Unconnect your whole computer/usb things. You have only your mixing
        > > > > > console and your mic, then. Connect a headphone to your mixing desk.
        > > > > Is
        > > > > > the Hum Still there?
        > > > > >
        > > > > > Take your setup to another power plug - maybe in the kitchen or at
        > > > > some
        > > > > > friend's house or something. Hum still there?
        > > > > >
        > > > > > Take your microphone to some friend's mixing console/phantom supply
        > > > > and
        > > > > > re-try. Hum Still there? If yes, then its your preamplifier.
        > > > > >
        > > > > > Another thing to try: Take a 9V Battery and connect + to Capsule
        > > > > Drain.
        > > > > > Connect - to ground. Put a cap at the source connection (10µF
        > > > > > electrolytic will do...). and connect the other end of the capacitor
        > > > > to
        > > > > > a mono-jack. Ground of course to jack's ground. Connect this to your
        > > > > > mixing desk WITHOUT Phantom power. Hum still there? Connect it
        > > > > directly
        > > > > > to your soundcard's mic-in. Hum still there?
        > > > > >
        > > > > > If everything fails, then i recommend, to quickly build up the
        > > > > original
        > > > > > schematic (look in files section/zapnspark/DIYgenericIntFET.pdf)
        > > > > without
        > > > > > any extra dingledongle (especially the 10k resistor and the
        > > following
        > > > > > capacitor looks very very suspicious to me) - only the circuit and
        > > > > > wires. Connect this again to you mixing desk. If it fails, then you
        > > > > have
        > > > > > a problem in your house/mixing desk/computer whatsoever.
        > > > > >
        > > > > > Cheers, Johannes.
        > > > > >
        > > > > > On 27.06.2011 10:24, Janez Podolski wrote:
        > > > > > >
        > > > > > > Hey!
        > > > > > > I've just upload 2 more pictures of microphone and preamplifier
        > > > > case.
        > > > > > > I'll try to make some shield around the preamplifier. The wierd
        > > > > thing
        > > > > > > is, that when I get closer to the circuit with my hand or some
        > > metal
        > > > > > > stuff, nothing happens. Usually some noise or whatewer is
        > > generated,
        > > > > > > but not here.
        > > > > > > I've also try to switch diferent cables, one of them was good
        > > > > shielded
        > > > > > > cable small length. Nothing changed.
        > > > > > > Thanks for your reply. Hope we can manage this thing.
        > > > > > >
        > > > > > > --- In micbuilders@yahoogroups.com
        > > <mailto:micbuilders%40yahoogroups.com>
        > > > > <mailto:micbuilders%40yahoogroups.com>
        > > > > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan bhakakhan@
        > > wrote:
        > > > > > > >
        > > > > > > > You wrote in your info, that the case is plastic, without any
        > > > > shield.
        > > > > > > >
        > > > > > > > May i suggest, that you try some coffe-box or similar METAL case
        > > > > for
        > > > > > > > test purposes? Especially the capsule should be properly
        > > shielded.
        > > > > > > >
        > > > > > > > But i don't know if that is the ultimate solution. Can you
        > > provide
        > > > > more
        > > > > > > > photos of the mike WITH capsule and Case?
        > > > > > > >
        > > > > > > > THX,
        > > > > > > >
        > > > > > > > Johannes
        > > > > > > > On 27.06.2011 00:11, Janez Podolski wrote:
        > > > > > > > >
        > > > > > > > > Hey! I've just made new file NOISE PROBLEM. There is a
        > > note with
        > > > > > > > > accurate descritpion of my problem, so please check it out. In
        > > > > few
        > > > > > > > > words: my diy microphone has extra hum! I've made some hum
        > > > > recording
        > > > > > > > > and upload everything to make solving as easy as possible.You
        > > > > can
        > > > > > > leave
        > > > > > > > > your suggestions here, or email me. But I think here is
        > > the best
        > > > > > > place,
        > > > > > > > > maybe someone has the same problems.
        > > > > > > > > Best regards, d.
        > > > > > > > >
        > > > > > > > > [Non-text portions of this message have been removed]
        > > > > > > > >
        > > > > > > > >
        > > > > > > >
        > > > > > > >
        > > > > > > >
        > > > > > > > [Non-text portions of this message have been removed]
        > > > > > > >
        > > > > > >
        > > > > > >
        > > > > >
        > > > > >
        > > > > >
        > > > > > [Non-text portions of this message have been removed]
        > > > > >
        > > > >
        > > > > [Non-text portions of this message have been removed]
        > > > >
        > > > >
        > > >
        > > >
        > > >
        > > > [Non-text portions of this message have been removed]
        > > >
        > >
        > >
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
      • Bhakakhan
        ... In my original answer i meant, that the 10 k and the cap are bridging you base resistors(or at least influencing them ), i have not meant, that you should
        Message 3 of 12 , Jul 1, 2011
          On 01.07.2011 10:47, Janez Podolski wrote:
          >
          > hmm.
          > Maybe the important part of my post was the following sentence.
          > -> Scotthelmke circuit had hum without any added switches or capacitors.
          > Compared to Behringer ECM8000 which didn't have any hum. That's
          > strange. I assembled both of them on vero board and than record them.
          >
          > Also, the idea to bridge 2 100k resistors was yours. Maybe you replied
          > in hurry, but, as you can see, my knowledge about electronic isn't on
          > souch high level than yours. I just did that you have said(although it
          > seemed to me a little strange).
          > > > > not the switch, but the 10k and the cap also....they form a path
          > > > between
          > > > > the two channels...and bridge your 2 100k resistors...
          >
          In my original answer i meant, that the 10 k and the cap are bridging
          you base resistors(or at least "influencing them"), i have not meant,
          that you should do it....;)...
          >
          >
          > Anyway. I'll try what you have suggested and than we'll see. The
          > results on veroboard really confusing me all the time. About mute
          > switch and all related parts-> I've removed all of them. Hum didn't
          > get any quieter so there is no problem.
          > I must try this with ground, I've been thinking about that a lot, but,
          > I do have some test capsules on good shielded cable without aluminium
          > case. I did wrap them with some metal foil once, but there was no change.
          > well, thanks for help. Maybe I shouldn't be doing microphones, since
          > I've got only problems with them. :|
          >

          Stay cool, don't throw it all away. There is a mistake and you're gonna
          find it, for sure. And after that, everything will work out and will
          make sense to you. Just stay cool and do not give up finding a solution.
          Building a mic is difficult, as we all know, and the first mic has done
          problems to every micbuilder there ever was. So you are not exceptional
          untalented or so...we all drive into strange problems from time to
          time.just follow the way, and you'll get to the finish. It is only a few
          steps away. If all fails, then build a second exactly identical circuit
          on veroboard - and do it the good old way - without any extra
          dinglegongle: Spread your components like in school days on a big-board
          and solder every component pin-to-pin, so that you have a concept board.
          With this you test it all again. IN A METAL BOX.

          BTW: Scott Helmkes Circuit is built a thousand times - certified hum
          free - you can count on that. If it Hums, then you made a mistake or you
          are working with faulty equipment (test this with a 100% functional
          48V-phantom-powered mic - industrial built, NOT DIY - VERIFY THAT YOU
          ARE WORKING WITH PROPER EQUIPMENT BEFORE DIY'ing).

          The mistake has likely to do with grounding/earthing/shielding.
          >
          >
          > > On 01.07.2011 01:18, Janez Podolski wrote:
          > > >
          > > > hey again.
          > > > I've got some news.
          > > > I don't know if I mentioned before, but anyway. Yesterday I
          > remembered
          > > > that before I get the "real" circuit board(today circuit board) I've
          > > > assembled two mic preamps, Behringer ECM8000 and this generic
          > > > preamp(in zapnspark's file) on vero board. I've tried them again.
          > > > Results are interesting and are connected with current design of my
          > > > preamp. The Behringer ECM8000 circuit doesn't have any hum. Almost
          > > > any, but nothing compared to scotthelmke design. Scotthelmke preamp
          > > > sounded better(i think), but there was hum.
          > > >
          > > Zapnsparks Generic int. ECM sounds even better than Sc.H. Circuit for
          > > int. FET ECMs.(to my taste)
          > > >
          > > > So, as you can see from my circuit, I added capacitors and resistors
          > > > to my preamp as on Behringer hoping there was the problem.(30 ohm,
          > > > 2n2, 1n5).
          > > >
          > > I wouldn't do that. Your capsules have a strong lo-end roll off
          > anyway -
          > > no additional filters needed. Unless you want to design it exactly like
          > > this ( a thinny microphone with almost no bass).
          > > >
          > > > Scotthelmke circuit had hum without any added switches or capacitors.
          > > >
          > > > These days I tried these things.
          > > > -> I changed zener diode. I know that these things are preety noisy.
          > > > In my case, seems like zener is OK. I also tried to replace zener
          > > > diode with two 5V(5V6 actually) - I know that 5V zener diode has the
          > > > best characteristic. No change.
          > > >
          > > Zeners are usually not the cause for Hum - they are not the problem - i
          > > could have told you that before.
          > > >
          > > >
          > > > -> I tried to bridge(100k resistors). No change.
          > > >
          > > You live risky - i wouldn't do that. i meant, that the 10k and the
          > > following cap are interfering with your base resistors 100k, and so i
          > > would disconnect both. (the 10k and the following cap, NOT the
          > 100k's) -
          > > both the 10k and the following cap don't belong there (according to the
          > > usual circuits, and according to my logic. They form a steady path
          > > between the two channels and this interferes with your Transistor
          > Bases.
          > > Simply pull both components out.
          > > >
          > > > -> I tried to add 30k resistors from base to emmiter - similar to
          > > > behringer circuit.
          > > >
          > > Why? I see no sense in that. if you don't know, Why you are doing
          > > something, then better let it be....
          > > >
          > > > -> Remember the low cut switch I had added to original cirucit. It
          > has
          > > > some effect. When low cut switch is in OFF position(no low frequency
          > > > cutting) the hum is enormous. When low cut switch is in ON position,
          > > > hum get's real quiet(if compared to other switch position, but still
          > > > too much present). So, if hum get's quiter when changing switch
          > > > position, it means hum si generated before switch - somewhere near
          > > > microphone.
          > > >
          > > That is logical, because hum is 50Hz noise - with a lo-cut, this
          > becomes
          > > more quiet than before. But: Normally you don't need, nor want a
          > low-cut
          > > with the capsules you are using - the capsule itself is less responsive
          > > in low end - and this is more of a problem than an advantage.
          > > >
          > > > Is it possible, that 5k6 resistors(source and drain resistors) are
          > too
          > > > large - that microphone is generating some shit because it doesn't
          > ave
          > > > enough current? Or something.
          > > >
          > > No - the Source Resistors of the FET can't generate hum, because Hum
          > > originates from the power net in your house, and is then injected via
          > > the cable and your board to your vulnerable components.
          > > >
          > > > Seems like my mixing console is OK, but I'll still try this
          > microphone
          > > > on Monday with other mixing console and than report.
          > > >
          > > > If this is important: I bought 2n5087 transistors on ebay and used
          > > > them in both circuit, behringer and ScottH.
          > > >
          > > Bad Transistors cannot generate hum, but they can become noisy, if they
          > > are injured.
          > > >
          > > > Does anybody ever had any similar problems?
          > > >
          > > no - not myself. Except one single time: When i shield my capsules and
          > > its Fet not correctly.
          > > >
          > > > Thanks, d.
          > > >
          > > I've had a look on your board again. this is designed very risky, since
          > > the top layer consists of a lot of ground, with only small holes for
          > the
          > > components. Maybe one component is licking ground via
          > surface-conduction
          > > of some component housing. Inspect it all again...
          > >
          > > And Try this: DON'T connect the Capsule Housing (the big one you did
          > > DIY) directly to the capsule ground. Keep em seperated. Now, wire the
          > > Housing with a wire or a cable directly to the output ground of your
          > > circuit (Ground of Output-Connector). I mean in a way, that fault
          > > currents and noise "catched" by the body are not flowing through your
          > > circuit or your capsule, but directly to OV Output-Ground. You do a so
          > > called "separation of Chassis-ground and Audio-Ground" then. Wire the
          > > capsule to board as usual. After that, put your whole circuit board
          > > inside a Coffee-Box, or similar Metal Housing. You should have a very
          > > proper shielding, then. Maybe that helps, maybe not. I don't know. Look
          > > at the output connector: Is everything soldered okay? Or do you have
          > > made a mistake? Be very careful, when inspecting the whole board
          > again -
          > > the Error HAS to lie somewhere there.
          > >
          > > But one thing: Whereever the fault lies, it is not a problem of the
          > > circuit(except those darn 10k+Capacitor i mentioned 10 times or so by
          > > now). It is also unlikely that components have malfunction. The Problem
          > > is your Board-Concept. So go through all again and search for mistakes
          > > you made. You MUST have made some, because on veroboard -as you say-
          > > everything is alright.
          > >
          > > The Error is NOT external, but lies in YOUR concept. So better revise
          > > the Concept again.
          > > >
          > > > --- In micbuilders@yahoogroups.com
          > <mailto:micbuilders%40yahoogroups.com>
          > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan <bhakakhan@> wrote:
          > > > >
          > > > > On 27.06.2011 18:01, Janez Podolski wrote:
          > > > > >
          > > > > > here are results. Half of them a've already done before, but i'd
          > > > tested
          > > > > > them again.
          > > > > > -> Disconecting the switch didn't change anything. Hum still
          > > > exsist.btw,
          > > > > > any other suggestions for mute switch without BANG while
          > switching?
          > > > > >
          > > > > not the switch, but the 10k and the cap also....they form a path
          > > > between
          > > > > the two channels...and bridge your 2 100k resistors...
          > > > > >
          > > > > > -> Testing only with mixer is what I'm doing all the time. So, no
          > > > > > changes.
          > > > > > ->I'll take microphone to friend's mixing console in a short
          > time and
          > > > > > than we'll see.
          > > > > >
          > > > > i'll wait...before "oracling" again..
          > > > > >
          > > > > > -> Than I connect modified microphone directly (as you described,
          > > > but I
          > > > > > aded resistor from source to ground).
          > > > > >
          > > > > sorry - i was in a hurry and forgot the source resi to mention...
          > > > > >
          > > > > > Yep, hum disapeared. So, I assume
          > > > > > my problem is bad phantom power supply or what?
          > > > > >
          > > > > possible...but unlikely - more likely, your board is the problem
          > > > > >
          > > > > > I've got some exams right now, so microphones will have to
          > wait. But
          > > > > > I'll dolater some more tests and then post results here!thanks for
          > > > > > quick reply.
          > > > > > --- In micbuilders@yahoogroups.com
          > <mailto:micbuilders%40yahoogroups.com>
          > > > <mailto:micbuilders%40yahoogroups.com>
          > > > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan <bhakakhan@>
          > wrote:
          > > > > > >
          > > > > > > Something is indeed wrong with your setup - not only with the
          > > > > > microphone.
          > > > > > >
          > > > > > > Try this:
          > > > > > > Cut Off the 10k and the following capacitor including the
          > > > mute-switch.
          > > > > > > Just cut it away - DISCONNECT it, throw it to the side - don't
          > > > bother
          > > > > > > about it - don't even THINK about it. It looks like this is the
          > > > wrong
          > > > > > > place for the switch. if that fails:
          > > > > > >
          > > > > > > Unconnect your whole computer/usb things. You have only your
          > mixing
          > > > > > > console and your mic, then. Connect a headphone to your
          > mixing desk.
          > > > > > Is
          > > > > > > the Hum Still there?
          > > > > > >
          > > > > > > Take your setup to another power plug - maybe in the kitchen
          > or at
          > > > > > some
          > > > > > > friend's house or something. Hum still there?
          > > > > > >
          > > > > > > Take your microphone to some friend's mixing console/phantom
          > supply
          > > > > > and
          > > > > > > re-try. Hum Still there? If yes, then its your preamplifier.
          > > > > > >
          > > > > > > Another thing to try: Take a 9V Battery and connect + to Capsule
          > > > > > Drain.
          > > > > > > Connect - to ground. Put a cap at the source connection (10µF
          > > > > > > electrolytic will do...). and connect the other end of the
          > capacitor
          > > > > > to
          > > > > > > a mono-jack. Ground of course to jack's ground. Connect this
          > to your
          > > > > > > mixing desk WITHOUT Phantom power. Hum still there? Connect it
          > > > > > directly
          > > > > > > to your soundcard's mic-in. Hum still there?
          > > > > > >
          > > > > > > If everything fails, then i recommend, to quickly build up the
          > > > > > original
          > > > > > > schematic (look in files section/zapnspark/DIYgenericIntFET.pdf)
          > > > > > without
          > > > > > > any extra dingledongle (especially the 10k resistor and the
          > > > following
          > > > > > > capacitor looks very very suspicious to me) - only the
          > circuit and
          > > > > > > wires. Connect this again to you mixing desk. If it fails,
          > then you
          > > > > > have
          > > > > > > a problem in your house/mixing desk/computer whatsoever.
          > > > > > >
          > > > > > > Cheers, Johannes.
          > > > > > >
          > > > > > > On 27.06.2011 10:24, Janez Podolski wrote:
          > > > > > > >
          > > > > > > > Hey!
          > > > > > > > I've just upload 2 more pictures of microphone and
          > preamplifier
          > > > > > case.
          > > > > > > > I'll try to make some shield around the preamplifier. The
          > wierd
          > > > > > thing
          > > > > > > > is, that when I get closer to the circuit with my hand or
          > some
          > > > metal
          > > > > > > > stuff, nothing happens. Usually some noise or whatewer is
          > > > generated,
          > > > > > > > but not here.
          > > > > > > > I've also try to switch diferent cables, one of them was good
          > > > > > shielded
          > > > > > > > cable small length. Nothing changed.
          > > > > > > > Thanks for your reply. Hope we can manage this thing.
          > > > > > > >
          > > > > > > > --- In micbuilders@yahoogroups.com
          > <mailto:micbuilders%40yahoogroups.com>
          > > > <mailto:micbuilders%40yahoogroups.com>
          > > > > > <mailto:micbuilders%40yahoogroups.com>
          > > > > > > > <mailto:micbuilders%40yahoogroups.com>, Bhakakhan bhakakhan@
          > > > wrote:
          > > > > > > > >
          > > > > > > > > You wrote in your info, that the case is plastic,
          > without any
          > > > > > shield.
          > > > > > > > >
          > > > > > > > > May i suggest, that you try some coffe-box or similar
          > METAL case
          > > > > > for
          > > > > > > > > test purposes? Especially the capsule should be properly
          > > > shielded.
          > > > > > > > >
          > > > > > > > > But i don't know if that is the ultimate solution. Can you
          > > > provide
          > > > > > more
          > > > > > > > > photos of the mike WITH capsule and Case?
          > > > > > > > >
          > > > > > > > > THX,
          > > > > > > > >
          > > > > > > > > Johannes
          > > > > > > > > On 27.06.2011 00:11, Janez Podolski wrote:
          > > > > > > > > >
          > > > > > > > > > Hey! I've just made new file NOISE PROBLEM. There is a
          > > > note with
          > > > > > > > > > accurate descritpion of my problem, so please check it
          > out. In
          > > > > > few
          > > > > > > > > > words: my diy microphone has extra hum! I've made some hum
          > > > > > recording
          > > > > > > > > > and upload everything to make solving as easy as
          > possible.You
          > > > > > can
          > > > > > > > leave
          > > > > > > > > > your suggestions here, or email me. But I think here is
          > > > the best
          > > > > > > > place,
          > > > > > > > > > maybe someone has the same problems.
          > > > > > > > > > Best regards, d.
          > > > > > > > > >
          > > > > > > > > > [Non-text portions of this message have been removed]
          > > > > > > > > >
          > > > > > > > > >
          > > > > > > > >
          > > > > > > > >
          > > > > > > > >
          > > > > > > > > [Non-text portions of this message have been removed]
          > > > > > > > >
          > > > > > > >
          > > > > > > >
          > > > > > >
          > > > > > >
          > > > > > >
          > > > > > > [Non-text portions of this message have been removed]
          > > > > > >
          > > > > >
          > > > > > [Non-text portions of this message have been removed]
          > > > > >
          > > > > >
          > > > >
          > > > >
          > > > >
          > > > > [Non-text portions of this message have been removed]
          > > > >
          > > >
          > > >
          > >
          > >
          > >
          > > [Non-text portions of this message have been removed]
          > >
          >
          >



          [Non-text portions of this message have been removed]
        • zephyrmic
          Just an encouragement to keep on going. Don t give up! In sorting out the problems, you will have the joy of overcoming, and have something functional that you
          Message 4 of 12 , Jul 1, 2011
            Just an encouragement to keep on going. Don't give up! In sorting out the problems, you will have the joy of overcoming, and have something functional that you have made yourself.

            There have been times when I have been tempted to throw a project on the floor and jump on it, but I am glad I resisted the temptation. In solving the problems, I have learned more that I ever would if I had not persisted. Someone wisely said, " Problem SOLVING is the key to character building."

            Stick with it! You will win in due time.

            Kindest regards,

            zephyrmic


            --- In micbuilders@yahoogroups.com, "Janez Podolski" <janez.podolski@...> wrote:
            >
            > hmm.
            > Maybe the important part of my post was the following sentence.
            > -> Scotthelmke circuit had hum without any added switches or capacitors.
            > Compared to Behringer ECM8000 which didn't have any hum. That's strange. I assembled both of them on vero board and than record them.
            >
            > Also, the idea to bridge 2 100k resistors was yours. Maybe you replied in hurry, but, as you can see, my knowledge about electronic isn't on souch high level than yours. I just did that you have said(although it seemed to me a little strange).
            > > > > not the switch, but the 10k and the cap also....they form a path
            > > > between
            > > > > the two channels...and bridge your 2 100k resistors...
            >
            >
            > Anyway. I'll try what you have suggested and than we'll see. The results on veroboard really confusing me all the time. About mute switch and all related parts-> I've removed all of them. Hum didn't get any quieter so there is no problem.
            > I must try this with ground, I've been thinking about that a lot, but, I do have some test capsules on good shielded cable without aluminium case. I did wrap them with some metal foil once, but there was no change.
            > well, thanks for help. Maybe I shouldn't be doing microphones, since I've got only problems with them. :|
          • Janez Podolski
            Hey! thanks, I appriciate that. I actually didn t mean to give up, but I was angry because I ve only had worries. So! Today I went to the bands mixing console,
            Message 5 of 12 , Jul 4, 2011
              Hey! thanks, I appriciate that.
              I actually didn't mean to give up, but I was angry because I've only had worries.
              So!

              Today I went to the bands mixing console, pluged the microphone in and enjoj the sound of silence.:) Microphone sound was great, no hum or anything that would bother me. So, the problem is with my Tapco MIX100 mixing console. Preamp is working great and I'm happy now:) Well not so happy because of mixing console, but glad to know what is the problem.
              Thanks everyone for help, I really appriciate it and I know that someday I'll help someone as you did to me. Thanks!
              domen.


              --- In micbuilders@yahoogroups.com, "zephyrmic" <wusiwus@...> wrote:
              >
              > Just an encouragement to keep on going. Don't give up! In sorting out the problems, you will have the joy of overcoming, and have something functional that you have made yourself.
              >
              > There have been times when I have been tempted to throw a project on the floor and jump on it, but I am glad I resisted the temptation. In solving the problems, I have learned more that I ever would if I had not persisted. Someone wisely said, " Problem SOLVING is the key to character building."
              >
              > Stick with it! You will win in due time.
              >
              > Kindest regards,
              >
              > zephyrmic
              >
              >
              > --- In micbuilders@yahoogroups.com, "Janez Podolski" <janez.podolski@> wrote:
              > >
              > > hmm.
              > > Maybe the important part of my post was the following sentence.
              > > -> Scotthelmke circuit had hum without any added switches or capacitors.
              > > Compared to Behringer ECM8000 which didn't have any hum. That's strange. I assembled both of them on vero board and than record them.
              > >
              > > Also, the idea to bridge 2 100k resistors was yours. Maybe you replied in hurry, but, as you can see, my knowledge about electronic isn't on souch high level than yours. I just did that you have said(although it seemed to me a little strange).
              > > > > > not the switch, but the 10k and the cap also....they form a path
              > > > > between
              > > > > > the two channels...and bridge your 2 100k resistors...
              > >
              > >
              > > Anyway. I'll try what you have suggested and than we'll see. The results on veroboard really confusing me all the time. About mute switch and all related parts-> I've removed all of them. Hum didn't get any quieter so there is no problem.
              > > I must try this with ground, I've been thinking about that a lot, but, I do have some test capsules on good shielded cable without aluminium case. I did wrap them with some metal foil once, but there was no change.
              > > well, thanks for help. Maybe I shouldn't be doing microphones, since I've got only problems with them. :|
              >
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