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Re: MAX410 amplifier question

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  • userno232000
    ... pots ... component ... The goal was to not have the pot in the signal path, YMMV.
    Message 1 of 18 , Jan 8, 2009
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      ---
      >
      > When I was seriously doing stuff more than a decade ago, high value
      pots
      > were MUCH more unreliable than lower value ones. For Guru Latchaw's
      > circuit, I might use a 5k pot as the source resistor, save one
      component
      > and increase reliability.
      >

      The goal was to not have the pot in the signal path, YMMV.
    • dayVel
      ... bias is ... mics first ... resistor ... are ... one so ... lines ... any FET. ... pots ... component ... half the ... next ... I am not a guru; I am a
      Message 2 of 18 , Jan 8, 2009
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        --- In micbuilders@yahoogroups.com, Richard Lee <ricardo@...> wrote:
        >
        > > http://mp3forkidz.com/mic/tsb-165a.html
        > >
        > > Of the circuits there, the third one with 2n4416A and 150k/270k
        bias is
        > probably best. AKGtypBatt.jpg in my directory may have slightly better
        > distortion. I'll let the other gurus recommend their favourites.
        >
        > > I just wanted to point out that that page is from when the TSB
        mics first
        > came out and we were still spit-balling stuff. The chances of that
        resistor
        > ratio in the biasing scheme being correct for any particular 2N4416A
        are
        > pretty remote
        >
        > About as remote as a 2k or 2k2 source resistor optimally biasing any
        > particular FET as all the circuits on the net seem to imply.
        >
        > But that third circuit will always have more swing than the second
        one so
        > worth the small extra complexity even if not exactly right.
        >
        > Could some guru show how to select source resistors by drawing load
        lines
        > on Id vs Vgs curves?
        >
        > > I put a 500k SMT pot in my circuit, PITA to solder but it biases
        any FET.
        >
        > When I was seriously doing stuff more than a decade ago, high value
        pots
        > were MUCH more unreliable than lower value ones. For Guru Latchaw's
        > circuit, I might use a 5k pot as the source resistor, save one
        component
        > and increase reliability.
        >
        > For yus non gurus, the adjustment is to get the source at 4V, ie
        half the
        > supply rail of 8V. This gives maximum output before clipping if the
        next
        > stage is relatively high Z.
        >

        I am not a guru; I am a drummer. Which is probably why I can't hear
        the difference between different types of capacitors. Anyhow, in the
        mics I built for actual use I used split source resistors. With 1%
        resistors, there are lots of combos within spitting distance of the
        magic 2.2k (a value I accepted on faith because everything on the
        internet is true.)

        But at one point I did all that hard math with the mic sensitivities
        and the pascals and dBs and the logs and whatnot and found out we were
        way too worried about optimizing the voltage swing with respect to
        clipping. With a 9 volt supply, the diaphragm would be stuck to the
        backplate long before you came anywhere near to clipping these circuits.

        It's my philosophy not to overthink this stuff. Not that I could anyway.

        Dave Latchaw
      • Richard Lee
        ... probably best. AKGtypBatt.jpg in my directory may have slightly better distortion. I ll let the other gurus recommend their favourites. ... came out and
        Message 3 of 18 , Jan 9, 2009
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          > http://mp3forkidz.com/mic/tsb-165a.html
          >
          > Of the circuits there, the third one with 2n4416A and 150k/270k bias is
          probably best. AKGtypBatt.jpg in my directory may have slightly better
          distortion. I'll let the other gurus recommend their favourites.

          > I just wanted to point out that that page is from when the TSB mics first
          came out and we were still spit-balling stuff. The chances of that resistor
          ratio in the biasing scheme being correct for any particular 2N4416A are
          pretty remote

          About as remote as a 2k or 2k2 source resistor optimally biasing any
          particular FET as all the circuits on the net seem to imply.

          But that third circuit will always have more swing than the second one so
          worth the small extra complexity even if not exactly right.

          Could some guru show how to select source resistors by drawing load lines
          on Id vs Vgs curves?

          > I put a 500k SMT pot in my circuit, PITA to solder but it biases any FET.

          When I was seriously doing stuff more than a decade ago, high value pots
          were MUCH more unreliable than lower value ones. For Guru Latchaw's
          circuit, I might use a 5k pot as the source resistor, save one component
          and increase reliability.

          For yus non gurus, the adjustment is to get the source at 4V, ie half the
          supply rail of 8V. This gives maximum output before clipping if the next
          stage is relatively high Z.
        • Nick Zuccaro
          SSIA, where can i get primo capsules in the US? i think i want to put together a set of these mics before i do what i really want to do, get a set of neumann
          Message 4 of 18 , Jan 9, 2009
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            SSIA, where can i get primo capsules in the US? i think i want to put together a set of these mics before i do what i really want to do, get a set of neumann AK40, shoeps MK4 or MBHO KA200 capsules and build a single ended, line level output mic body for these... :)

            Nick
          • userno232000
            ... put together a set of these mics before i do what i really want to do, get a set of neumann AK40, shoeps MK4 or MBHO KA200 capsules and build a single
            Message 5 of 18 , Jan 9, 2009
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              --- In micbuilders@yahoogroups.com, Nick Zuccaro <nmz77@...> wrote:
              >
              > SSIA, where can i get primo capsules in the US? i think i want to
              put together a set of these mics before i do what i really want to do,
              get a set of neumann AK40, shoeps MK4 or MBHO KA200 capsules and build
              a single ended, line level output mic body for these... :)
              >
              > Nick
              >
              Hi Nick

              I just finished a second set Saturday based on these (the omni ones).
              I was hoping to post a little write up since this time I used almost
              nothing but things from the Lowes small parts and plumbing bins. All
              my capsules came from used Nakamichi mics off of ebay. They vary a lot
              but I got some whole mics with two capsules for as little as $15.
            • dayVel
              ... With the latest iteration of Altoid boxes, they ve started embossing the lids which actually makes them less suitable if you want to mount something right
              Message 6 of 18 , Jan 9, 2009
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                --- In micbuilders@yahoogroups.com, Richard Lee <ricardo@...> wrote:
                > your supa dupa
                > Altoid EMI proof enclosures seem to be only from the Unobtainium Box Co.
                >
                > Are lesser brands acceptable?
                >
                With the latest iteration of Altoid boxes, they've started embossing
                the lids which actually makes them less suitable if you want to mount
                something right where they've crunched it. Fotunately, my sainted
                mother is addicted to Altoids and has saved me a large supply of the
                old ones.

                Scott Helmke built one of his projects in another brand of mint box,
                so I know they're out there.
              • Richard Lee
                ... were MUCH more unreliable than lower value ones. For Guru Latchaw s circuit, I might use a 5k pot as the source resistor, save one component and increase
                Message 7 of 18 , Jan 10, 2009
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                  > I put a 500k SMT pot in my circuit, PITA to solder but it biases any FET.

                  >> When I was seriously doing stuff more than a decade ago, high value pots
                  were MUCH more unreliable than lower value ones. For Guru Latchaw's
                  circuit, I might use a 5k pot as the source resistor, save one component
                  and increase reliability.

                  >The goal was to not have the pot in the signal path.

                  In the original Schoeps CMC circuit, I meant removing R3 (2k) and making P1
                  2k instead. As the output of that stage is the source, the pot doesn't
                  appear in the signal path except dimly via R1, the 1G. For that, a 2k pot
                  is MUCH better than 1M.

                  Like Guru Latchaw, I don't think adjustment is necessary but if you must
                  have a twiddle, a 2k pot is more reliable than 500k.

                  > But at one point I did all that hard math with the mic sensitivities and
                  the pascals and dBs and the logs and whatnot and found out we were way too
                  worried about optimizing the voltage swing with respect to clipping.

                  Which is why I'm quite happy with your third 2n4416 circuit. The second
                  one mi....iight clip with ve..ery loud sounds according to Eric's
                  measurements of TSB165 mikes.

                  > I am not a guru; I am a drummer.

                  You do yourself a dis-service, Guru Latchaw. I'm mightily impressed by the
                  simplicity, elegance and effectiveness of your stuff. But your supa dupa
                  Altoid EMI proof enclosures seem to be only from the Unobtainium Box Co.

                  Are lesser brands acceptable?
                • Scott Helmke
                  ... Did I? I think I tried once or twice but the dimensions weren t quite right. I m only using Altoids boxes for a little guitar piezo pickup buffer these
                  Message 8 of 18 , Jan 10, 2009
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                    dayVel wrote:
                    > Scott Helmke built one of his projects in another brand of mint box,
                    > so I know they're out there.

                    Did I? I think I tried once or twice but the dimensions weren't quite
                    right. I'm only using Altoids boxes for a little guitar piezo pickup
                    buffer these days and the embossing doesn't cause any problems for that.

                    -Scott

                    --
                    ---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
                    And you'll visualize not taking any chances
                    But meet them halfway with love, peace, and persuasion
                    And expect them to rise to the occasion
                    (from "Glad Tidings", by Van Morrison)
                  • userno232000
                    ... making P1 ... doesn t ... 2k pot ... Sorry, I was talking about a totally different circuit anyway. But a few 100k Baxandall tone stack users might
                    Message 9 of 18 , Jan 10, 2009
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                      > In the original Schoeps CMC circuit, I meant removing R3 (2k) and
                      making P1
                      > 2k instead. As the output of that stage is the source, the pot
                      doesn't
                      > appear in the signal path except dimly via R1, the 1G. For that, a
                      2k pot
                      > is MUCH better than 1M.

                      Sorry, I was talking about a totally different circuit anyway. But a
                      few 100k Baxandall tone stack users might disagree about the 500k
                      pots. :) keep smiling DIY is fun.
                    • Richard Lee
                      ... were MUCH more unreliable than lower value ones. ... pots. :) Sorry. I should have been more specific. I was talking about trim pots. You can get big
                      Message 10 of 18 , Jan 12, 2009
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                        >> When I was seriously doing stuff more than a decade ago, high value pots
                        were MUCH more unreliable than lower value ones.

                        > But a few 100k Baxandall tone stack users might disagree about the 500k
                        pots. :)

                        Sorry. I should have been more specific. I was talking about trim pots.
                        You can get big beautiful pots to stick knobs on and eg the more expensive
                        Alps are very reliable.

                        However, I used to have access to long term service records for several
                        famous brand HiFi and guitar electronic makers from before the war to
                        present day and ....

                        High value eg 500k/100k pots (mainly in Baxandall tone controls) are much
                        more likely to become noisy than 20k volume and balance pots.

                        Components have become MUCH (OK mostly) better in the intervening years but
                        if I have to have a trim pot. eg in a power amp bias circuit, I'd always
                        design for a fairly low value and arrange for failsafe if it goes wonky.
                      • mstrong56
                        We have most of the interesting Primo capsules in stock
                        Message 11 of 18 , Jan 12, 2009
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                          We have most of the interesting Primo capsules in stock
                        • Nick Zuccaro
                          Can you send me a link? I can t seem to find them on your site...I think I am looking for a cardioid capsule, do you carry more than one type?? ... From:
                          Message 12 of 18 , Jan 12, 2009
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                            Can you send me a link? I can't seem to find them on your site...I think I am looking for a cardioid capsule, do you carry more than one type??

                            --- On Mon, 1/12/09, mstrong56 <mstrong@...> wrote:

                            From: mstrong56 <mstrong@...>
                            Subject: [micbuilders] Re: US distributor for primo capsules??
                            To: micbuilders@yahoogroups.com
                            Date: Monday, January 12, 2009, 9:01 AM






                            We have most of the interesting Primo capsules in stock















                            [Non-text portions of this message have been removed]
                          • umashankar mantravadi
                            dear mark why didnt you say so before? i was building ten tetrahedral microphones for angelo farina, and ended up using tsb 140s. i would have loved to have to
                            Message 13 of 18 , Jan 12, 2009
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                              dear mark

                              why didnt you say so before? i was building ten tetrahedral microphones for angelo farina, and ended up using tsb 140s. i would have loved to have to used the primo small cardioid capsules (i forget the number just now).

                              umashankari have published my poems. read (or buy) at http://stores.lulu.com/umashankar



                              To: micbuilders@yahoogroups.comFrom: mstrong@...: Mon, 12 Jan 2009 14:01:47 +0000Subject: [micbuilders] Re: US distributor for primo capsules??



                              We have most of the interesting Primo capsules in stock





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                            • mstrong56
                              They are not on the web site. We keep 2 in stock an omni and a card I will put info up tommorow
                              Message 14 of 18 , Jan 13, 2009
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                                They are not on the web site.

                                We keep 2 in stock an omni and a card

                                I will put info up tommorow
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                              • Richard Lee
                                ... value? Short Circuit Noise is the relevant spec for this application. ie Short the input. ... Doesn t matter. Use the input Z of your recorder if you re
                                Message 15 of 18 , Jan 14, 2009
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                                  > 1. What do I put across the input (cap) (resistor) or (short) and what
                                  value?

                                  Short Circuit Noise is the relevant spec for this application. ie Short
                                  the input.

                                  > 2. Do I use a load resistor (what ohms)?

                                  Doesn't matter. Use the input Z of your recorder if you're fussy.

                                  > 3. On the 42 db setting (82 ohms) that is a low uv reading and a normal
                                  reading I should expect using the Richard Lee circuit.

                                  > MAX410 339nv of noise is this in the real world?

                                  If you build it to Guru standards you should get within 1.5dB of this on
                                  the 42dB gain setting.

                                  339nV (-127dBu) is the Equivalent Input Noise ein which is referred to the
                                  input. This is output noise divided by the gain.

                                  Here, the output noise should be -127dBu + 42dB = -85dBu ie 43.6uV

                                  The 339nV is over 20kHz bandwidth. If you are measuring at the output of
                                  the amp, you need a very sharp 20kHz filter.

                                  Or use A weighting which will gain you another 5dB or so.

                                  If you feed this amp into a (decent) A/D sampling at 44.1kHz, the
                                  anti-aliasing filters will do the sharp filter and you can analyse the
                                  recorded noise.

                                  However, (good) A/D dither introduces noise; which on 16b Digigram VX440 or
                                  Maya 44, is -83dBu which is more noise than the amp.
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