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Re: [Electronics_101] Guitar Stack

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  • Robert Graf
    ... From: theshadow2754 To: Sent: Thursday, June 06, 2002 8:43 AM Subject: [Electronics_101]
    Message 1 of 5 , Jun 6, 2002
    • 0 Attachment
      ----- Original Message -----
      From: "theshadow2754" <theshadow2754@...>
      To: <Electronics_101@yahoogroups.com>
      Sent: Thursday, June 06, 2002 8:43 AM
      Subject: [Electronics_101] Guitar Stack


      > I tryed to post this message by email twice and it hasent gone
      > thrugh. Lets see if this works:
      >
      > I started a project a few days ago and now I need some help to finish
      > it. I am building a guitar amp "stack" (amplifier and
      > speakers build
      > separately, instead of together like most guitar amps) build to
      > output 300 Watts. There is no real time frame, because this is just a
      > project that I thought would be neat to build, and the monetary cap
      > sits around $1500, cause that's how much a real one costs. I have
      > been experimenting in electronics for a number of years, so I can
      > handle most anything that you throw at me (I did say most).
      >
      > Now for some background:
      >
      > In my stack, there are two speaker cabinets and an amplifier head.
      >
      > The speaker cabinets are 24" x 29" x 14", I have built
      > the first one
      > except for the front panel and the covering. Each has four identical
      > speakers; I have picked the ones that I would like to use but if
      > someone thinks that I should use other speakers, I'm all ears,
      > because I haven't ordered theses yet. The speakers are
      > "10" 110W
      > WOOFER, 8 OHM" All Electronics CAT# GW-2108. If you don't
      > have the
      > catalog, it has a 1.5" voice coil, and has a frequency range of
      > 40-
      > 5000 Hz. I think the speakers should be wired together in series-
      > parallel, because this allows for switching between two 4 ohm
      > channels and one 8 ohm channel. Any advice and/or comments on speaker
      > wiring, construction, or anything else is welcome.
      >
      > The head is going to be 12" x 24" x 10". Its output
      > should be between
      > 300 and 500 Watts. I haven't even begun construction on this yet,
      > and
      > any advice is welcome. I have a schematic of a 100-watt guitar
      > amplifier, but I need to know how to bump it up 200 watts. The URL is
      > http://sound.westhost.com/project27.htm. Any resources at all are
      > welcome. I think I am going to build the speakers before the head
      > though, so take your time answering this one.
      >
      > As I said before, any help at all would be greatly appreciated. I
      > hope you guys can help me,
      > Jacob D (KG4AUW)
      >
      >
      >

      I'll post couple of links for you later, but here's a quick response for
      starters:

      Have you heard the design you are planning on building? I took a look just
      to see what the basic design was, although reading your post gave me a
      pretty good idea of what I would find. My guess is that you would like the
      final product to resemble the venerable Marshall stack. Note that the
      typical Marshall stack is an EL-34 tube based amplifier that was basically
      copied from the Fender Bassman which in turn was based on Western Electric
      designs. Due to various circuit differences, the sound of tubes versus
      transistors can be quite different, especially when going from a clean sound
      to the famous cranked Marshall sound. Tube amps typically are one or 2 trick
      ponies: they may or may not sound good clean and they may or may not sound
      good turned up. Maybe both, maybe neither. However, there are plenty of good
      tube amps that will deliver a good clean tone as well as a good overdriven
      souind. I have an old BFSR with factory JBL 10 inch speakers that has a
      fantastic clean sound. This amp is considered by many to be the Holy Grail
      of tone. However, this amp will drill a hole in your head before it will
      break up. There's others of this make and model that distort nicely at much
      lower volumes. My Vibroverb RI is also a 40 watt amp like the Super, but
      turning it up past 4, it doesn't get much louder, it just starts breaking up
      nicely.

      There's many people that will tell you that solid state is complete junk for
      guitar amps. Many of the new solid state amps sound pretty good to me. I
      still prefer the tube stuff for some things, but solid state has it's uses
      as well. Tube amps are generally considered better at filling a room than
      solid state, try comparing a small amp like an old Fender Champ to a solid
      state amp of similar wattage. But I think for high powered rigs like you are
      planning on building, it is less of an issue. But I think 300 watts might be
      a bit of overkill. If you are looking for volume, a 3db increase in speaker
      efficiency will result in a greater sound pressure level increase than
      doubling electrical power. Acoustic watts are very much different from
      electrical watts.

      I only just glanced at the amp plans, but here's my thoughts on building:

      I would build the preamp first. The preamp will contribute the most to the
      sound of the 3 parts. I take it you already have an amp that works, so you
      can try the preamp through that amp first. Build the preamp in a rack mount
      single space enclosure, preferably gold anodized to get the Marshall look.
      I'll look up a source for the Marshall knobs if you'd like. I've seen them
      somewhere. If you front mount the preamp and rear mount the power amp(s),
      you can obtain a close look to the real thing from the front anyway. as for
      the power amp, modding the design to increase the power output is not a
      trivial task. I would suggest instead that you build the design as is and
      build a second one for another 100 watts. There's pleny of other options as
      well. Realize, however, that output power is directly proportional to
      transformer iron, so the more watts, the more iron. You should be able to
      build the power amps in dual height rack boxes and still fit your desired
      cabinet dimensions.

      As for speakers, generally mi (musical instrument) speakers make poor hi fi
      speakers and hi fi speakers work poorly in mi applications. Speakers also
      have a big effect on sound as well, so I'd inquire about this on
      alt.guitar.amp.

      If you would consider modding an amp, Duncan Convertible 100 watt heads can
      be had pretty cheap and they have modules that are replaceable to alter the
      sound.
    • J. Dilles
      Thank you for all advice... I think that it is a good idea to build the pre amp first. I think what I am going to do is build a 3 slot rack, with the top one
      Message 2 of 5 , Jun 7, 2002
      • 0 Attachment
        Thank you for all advice...

        I think that it is a good idea to build the pre amp first. I think what
        I am going to do is build a 3 slot rack, with the top one exposed and
        the bottom two covered by a removable grill, so that it looks like a
        real Marshall head. Umm that would make it about 19" across and 10"
        high, but how deep is standard rack mount? The cabinet is 14" deep so it
        would have to be no more then a foot. Ouch, would that work? I will stop
        by radio shack and see what they have, but I'm problem going to have to
        order the enclosures from radio shack.

        I was looking around for a different schematic and I found this:
        http://www.mif.pg.gda.pl/homepages/tom/schematics.htm. It has a LOT of
        schematics. I found 2 solid state circuits that I like; they are
        http://www.mif.pg.gda.pl/homepages/tom/files/150W.gif%c2%a0%c2%a0%c2%a0and
        http://www.mif.pg.gda.pl/homepages/tom/files/350W.gif, being 150 and 350
        watts respectively.

        You said that I could not wire the speakers in parallel if I built the
        amp from the old schematic; Why not? How about these two?

        I have another question about the speakers... if the head has 2 output
        jacks (for two cabinets) and I normally ran it with just one, would I
        have to do anything special when I plugged the other one in? I am asking
        this because I realized that if the jacks are in parallel the impedance
        of the load would drop in half (if they were the same) and would double
        if the switches were in series (using the "not plugged in" contact on
        the jack). After reading around the web and a fender catalog, I became
        rather confused because some amps can output, for example, 100 watts
        into 8 ohms and 200 watts into 4 ohms. Others, however, can output 100
        watts into 16, 8, and 4 ohms. I understand how a speaker array (with all
        speakers rated at, say 100 watts at 8 ohms) can take 200 at 4 ohms or
        400 watts at 2 ohms, but I do not understand the amp output. (I hope you
        got all of that)

        Much thanks for time and effort,
        Jacob D (KG4AUW)

        ------------------------------------------------------------------------
        --
        ORIGINAL MESSAGE:
        ------------------------------------------------------------------------
        --

        I'll post couple of links for you later, but here's a quick response for
        starters:

        Have you heard the design you are planning on building? I took a look
        just
        to see what the basic design was, although reading your post gave me a
        pretty good idea of what I would find. My guess is that you would like
        the
        final product to resemble the venerable Marshall stack. Note that the
        typical Marshall stack is an EL-34 tube based amplifier that was
        basically
        copied from the Fender Bassman which in turn was based on Western
        Electric
        designs. Due to various circuit differences, the sound of tubes versus
        transistors can be quite different, especially when going from a clean
        sound
        to the famous cranked Marshall sound. Tube amps typically are one or 2
        trick
        ponies: they may or may not sound good clean and they may or may not
        sound
        good turned up. Maybe both, maybe neither. However, there are plenty of
        good
        tube amps that will deliver a good clean tone as well as a good
        overdriven
        souind. I have an old BFSR with factory JBL 10 inch speakers that has a
        fantastic clean sound. This amp is considered by many to be the Holy
        Grail
        of tone. However, this amp will drill a hole in your head before it will
        break up. There's others of this make and model that distort nicely at
        much
        lower volumes. My Vibroverb RI is also a 40 watt amp like the Super, but
        turning it up past 4, it doesn't get much louder, it just starts
        breaking up
        nicely.

        There's many people that will tell you that solid state is complete junk
        for
        guitar amps. Many of the new solid state amps sound pretty good to me. I
        still prefer the tube stuff for some things, but solid state has it's
        uses
        as well. Tube amps are generally considered better at filling a room
        than
        solid state, try comparing a small amp like an old Fender Champ to a
        solid
        state amp of similar wattage. But I think for high powered rigs like you
        are
        planning on building, it is less of an issue. But I think 300 watts
        might be
        a bit of overkill. If you are looking for volume, a 3db increase in
        speaker
        efficiency will result in a greater sound pressure level increase than
        doubling electrical power. Acoustic watts are very much different from
        electrical watts.

        I only just glanced at the amp plans, but here's my thoughts on
        building:

        I would build the preamp first. The preamp will contribute the most to
        the
        sound of the 3 parts. I take it you already have an amp that works, so
        you
        can try the preamp through that amp first. Build the preamp in a rack
        mount
        single space enclosure, preferably gold anodized to get the Marshall
        look.
        I'll look up a source for the Marshall knobs if you'd like. I've seen
        them
        somewhere. If you front mount the preamp and rear mount the power
        amp(s),
        you can obtain a close look to the real thing from the front anyway. as
        for
        the power amp, modding the design to increase the power output is not a
        trivial task. I would suggest instead that you build the design as is
        and
        build a second one for another 100 watts. There's pleny of other options
        as
        well. Realize, however, that output power is directly proportional to
        transformer iron, so the more watts, the more iron. You should be able
        to
        build the power amps in dual height rack boxes and still fit your
        desired
        cabinet dimensions.

        As for speakers, generally mi (musical instrument) speakers make poor hi
        fi
        speakers and hi fi speakers work poorly in mi applications. Speakers
        also
        have a big effect on sound as well, so I'd inquire about this on
        alt.guitar.amp.

        If you would consider modding an amp, Duncan Convertible 100 watt heads
        can
        be had pretty cheap and they have modules that are replaceable to alter
        the
        sound.
      • Robert Graf
        ... From: J. Dilles To: [Electronics 101] Sent: Friday, June 07, 2002 4:09 PM Subject: Re:
        Message 3 of 5 , Jun 7, 2002
        • 0 Attachment
          ----- Original Message -----
          From: "J. Dilles" <theshadow2754@...>
          To: "[Electronics 101]" <Electronics_101@yahoogroups.com>
          Sent: Friday, June 07, 2002 4:09 PM
          Subject: Re: [Electronics_101] Guitar Stack


          Thank you for all advice...

          I think that it is a good idea to build the pre amp first. I think what
          I am going to do is build a 3 slot rack, with the top one exposed and
          the bottom two covered by a removable grill, so that it looks like a
          real Marshall head. Umm that would make it about 19" across and 10"
          high, but how deep is standard rack mount? The cabinet is 14" deep so it
          would have to be no more then a foot. Ouch, would that work? I will stop
          by radio shack and see what they have, but I'm problem going to have to
          order the enclosures from radio shack.

          I was looking around for a different schematic and I found this:
          http://www.mif.pg.gda.pl/homepages/tom/schematics.htm. It has a LOT of
          schematics. I found 2 solid state circuits that I like; they are
          http://www.mif.pg.gda.pl/homepages/tom/files/150W.gif and
          http://www.mif.pg.gda.pl/homepages/tom/files/350W.gif, being 150 and 350
          watts respectively.

          You said that I could not wire the speakers in parallel if I built the
          amp from the old schematic; Why not? How about these two?

          I have another question about the speakers... if the head has 2 output
          jacks (for two cabinets) and I normally ran it with just one, would I
          have to do anything special when I plugged the other one in? I am asking
          this because I realized that if the jacks are in parallel the impedance
          of the load would drop in half (if they were the same) and would double
          if the switches were in series (using the "not plugged in" contact on
          the jack). After reading around the web and a fender catalog, I became
          rather confused because some amps can output, for example, 100 watts
          into 8 ohms and 200 watts into 4 ohms. Others, however, can output 100
          watts into 16, 8, and 4 ohms. I understand how a speaker array (with all
          speakers rated at, say 100 watts at 8 ohms) can take 200 at 4 ohms or
          400 watts at 2 ohms, but I do not understand the amp output. (I hope you
          got all of that)

          Much thanks for time and effort,
          Jacob D (KG4AUW)

          If you mount the preamp from the front, on the bottom and mount the power
          amp(s) from the rear, you should be able to make it look pretty close to a
          Marshall. You can buy rack mount cases in just about whatever depth you
          need. Probably only 6 inches or maybe less for the preamp, 8 inches deep or
          so for the power amp. I think the 19" measurement does not include the
          mounting ears. There's no standards for dept, just height and width. Height
          is 1-3/4", I think for 1 unit. I don't think Radio Shack has this type of
          enclosure. See if you have any electronics dealers locally, they can order
          them.

          The original schematic specs said the amp had a rated load impedance of 4
          ohms, which is why I said you couldn't use parallel wiring of the speakers
          you mentioned. With a 16 ohm driver you could, but only 1 cabinet. The amps
          that put out the same power regardless of load are most likely tube amps and
          you must switch the tap of the output transformer that feeds the speakers. I
          haven't looked at any shorting jack arrangements, but most tube amps are
          extremely sensitive to load mismatches because the output transformers. I
          looked at the schematics of the amps you posted, but I can't tell the load
          they are meant for. If you want 200 watts, just build two of the power amps,
          in separate cases. You'll need a separate power supply for each amp.

          If you are building this to play outside, how large is the space? My little
          Princeton easily fills a normal backyard. The Super could probably be heard
          a couple of blocks away.
        • J. Dilles
          Ok thank you for your advice. I will post again when I get done with the preamp. ... From: Robert Graf [mailto:rgraf@myyellowstone.net] Sent: Friday, June 07,
          Message 4 of 5 , Jun 7, 2002
          • 0 Attachment

            Ok thank you for your advice… I will post again when I get done with the preamp. 

             

            -----Original Message-----
            From: Robert Graf [mailto:rgraf@...]
            Sent: Friday, June 07, 2002 4:44 PM
            To: Electronics_101@yahoogroups.com
            Subject: Re: [Electronics_101] Guitar Stack

             


            ----- Original Message -----
            From: "J. Dilles" <theshadow2754@...>
            To: "[Electronics 101]" <Electronics_101@yahoogroups.com>
            Sent: Friday, June 07, 2002 4:09 PM
            Subject: Re: [Electronics_101] Guitar Stack


            Thank you for all advice...

            I think that it is a good idea to build the pre amp first. I think what
            I am going to do is build a 3 slot rack, with the top one exposed and
            the bottom two covered by a removable grill, so that it looks like a
            real Marshall head. Umm that would make it about 19" across and 10"
            high, but how deep is standard rack mount? The cabinet is 14" deep so it
            would have to be no more then a foot. Ouch, would that work? I will stop
            by radio shack and see what they have, but I'm problem going to have to
            order the enclosures from radio shack.

            I was looking around for a different schematic and I found this:
            http://www.mif.pg.gda.pl/homepages/tom/schematics.htm. It has a LOT of
            schematics. I found 2 solid state circuits that I like; they are
            http://www.mif.pg.gda.pl/homepages/tom/files/150W.gif and
            http://www.mif.pg.gda.pl/homepages/tom/files/350W.gif, being 150 and 350
            watts respectively.

            You said that I could not wire the speakers in parallel if I built the
            amp from the old schematic; Why not? How about these two?

            I have another question about the speakers... if the head has 2 output
            jacks (for two cabinets) and I normally ran it with just one, would I
            have to do anything special when I plugged the other one in? I am asking
            this because I realized that if the jacks are in parallel the impedance
            of the load would drop in half (if they were the same) and would double
            if the switches were in series (using the "not plugged in" contact on
            the jack). After reading around the web and a fender catalog, I became
            rather confused because some amps can output, for example, 100 watts
            into 8 ohms and 200 watts into 4 ohms. Others, however, can output 100
            watts into 16, 8, and 4 ohms. I understand how a speaker array (with all
            speakers rated at, say 100 watts at 8 ohms) can take 200 at 4 ohms or
            400 watts at 2 ohms, but I do not understand the amp output. (I hope you
            got all of that)

            Much thanks for time and effort,
            Jacob D (KG4AUW)

            If you mount the preamp from the front, on the bottom and mount the power
            amp(s) from the rear, you should be able to make it look pretty close to a
            Marshall. You can buy rack mount cases in just about whatever depth you
            need. Probably only 6 inches or maybe less for the preamp, 8 inches deep or
            so for the power amp. I think the 19" measurement does not include the
            mounting ears. There's no standards for dept, just height and width. Height
            is 1-3/4", I think for 1 unit. I don't think Radio Shack has this type of
            enclosure. See if you have any electronics dealers locally, they can order
            them.

            The original schematic specs said the amp had a rated load impedance of 4
            ohms, which is why I said you couldn't use parallel wiring of the speakers
            you mentioned. With a 16 ohm driver you could, but only 1 cabinet. The amps
            that put out the same power regardless of load are most likely tube amps and
            you must switch the tap of the output transformer that feeds the speakers. I
            haven't looked at any shorting jack arrangements, but most tube amps are
            extremely sensitive to load mismatches because the output transformers. I
            looked at the schematics of the amps you posted, but I can't tell the load
            they are meant for. If you want 200 watts, just build two of the power amps,
            in separate cases. You'll need a separate power supply for each amp.

            If you are building this to play outside, how large is the space? My little
            Princeton easily fills a normal backyard. The Super could probably be heard
            a couple of blocks away.


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