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Diy stripped down ac30

Discussion in 'Amp Tech Center' started by Newbcaster, Mar 4, 2021.

  1. Newbcaster

    Newbcaster Tele-Holic

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    Hey guys I just want to build a normal channel only ac30. No extraneous bs.

    Where would I find a p a rts list?
     
  2. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    Do you mean Top Boost only? Doug Hoffman has a somewhat minimal AC30 layout (no tremolo) with a BOM. The Trainwreck Rocket is basically a Top Boost only AC30 with some power rail tweaks.
     
  3. Newbcaster

    Newbcaster Tele-Holic

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    Not the top boost but the Normal channel
     
  4. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    To clear things up... you want a *Normal Channel* only, one *Volume Control*, one *Top Cut*, and 4 x EL84 AC30. You do not want reverb. You do not want Vibrato/Tremolo. You do not want tone controls other than the *Top Cut*, Correct?
     
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  5. gusfinley

    gusfinley Tele-Afflicted

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    If you run the Top Boost at '10' and the Top Cut at '10' do you get "Normal"? :p

    Asking for a friend....
     
  6. Dacious

    Dacious Poster Extraordinaire

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    No, there's still difference.

    So what you're going to end up with is a low gain 30w Bassman with four EL84s.

    It won't sound particularly Voxy. It will still chew expensive tubes at a great rate, but that's as far as it's Voxiness will extend.

    You've plugged into and prefer the Normal channel of an AC30?
     
  7. LightningPhil

    LightningPhil Tele-Meister

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    The normal channel is great with a “cough” Les Paul and fat sounding humbuckers, played into a well damped sealed cabinet with something like the G12H55 or 2 in it. All the windows shake! And hurrah for very old, very nice and quit deaf neighbours! Unfortunately it’s emigrated with the wife and daughter and it’s a month or so before I follow them. Travel restrictions are not just breaking up the family, they’re preventing noise too!

    There’s a non top boost circuit diagram here:
    https://www.korguk.com/voxcircuits/

    However, on models with top boost (at least the C2 I have) the first gain stage for the normal and top boost channels share a cathode resistor/cap. In essence, this allows a little control of the lows when playing the normal channel. So to get the True Tone, the whole circuit is required. However it’s probably simple enough to dump all the top boost bits and simply fatten up an early coupling cap to taste.

    If basing the amp on a modded top boost version, there’s a good chance half the first tube will become redundant. Suggest wiring as per the parallel Chanel of the marshal 18w. It’ll probably fatten up the sound and should lower the noise floor a bit too. Circuits here:
    https://mhuss.com/18watt/schematics/

    Are you going for tube rectifier with choke or solid state?
     
  8. Oldsmobum

    Oldsmobum Tele-Holic

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    Brian May does well with this setup. Normal channel only, no reverb/vibrato, and bypassed tone stack for maximum gain. He runs through a treble booster however...
     
  9. Newbcaster

    Newbcaster Tele-Holic

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    Yeah. Same as Brian May.
     
  10. JamesAM

    JamesAM Tele-Meister

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    Might be cool to build this with a germanium rangemaster on a tagboard in the chassis- there should definitely be room in there with no trem or reverb. You could even bypass it with a footswitch. I’m a vox guy and I can dig that.

    of course, this is almost exactly the original vox top boost mod but with a transistor instead of a tube, so it might run counter to what the OP is after.
     
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  11. cnlbb

    cnlbb Tele-Afflicted

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    But how will you channel jump?
     
  12. Oldsmobum

    Oldsmobum Tele-Holic

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    If your favorite show is on do you look for the remote?
     
  13. Oldsmobum

    Oldsmobum Tele-Holic

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    Now I want to try an AC30 because I have always wondered how a tube based range master type setup would affect the gain characteristics.

    I run a home brew silicon into my boogie mark 1 clone and it really tightens things up. It’s kind of a POS build quality wise so at some point I’ll be building a lower watt version, and I’ve thought about the concept of wiring the treble booster directly to the board like you said.
     
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  14. JamesAM

    JamesAM Tele-Meister

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    Nice! I run a naga viper into the normal channel on my ac15hw and it’s a monster. The original vox top boost was actually a bolt-on upgrade to the 60s vox amps- the normal channel is actually pretty dark, and the addition of an extra gain stage and Eq brightened it up a lot. http://www.voxshowroom.com/uk/amp/ac30_tb_hood.html

    I actually like the normal + naga sound better than just the top boost channel, but it also sounds amazing to me with both channels jumpered and no boost.
     
  15. Dacious

    Dacious Poster Extraordinaire

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    That's not the same as a Bryan May AC30.- which Vox used to sell.

    His amps are like a power slave unit. They have no topboost or normal channel. Only a volume control.

    Bryan uses a whole rack of effects including a comprehensive preamp array that shapes tone. Basically it plugs into the amp where the effects loop 'in' would be, right in front of the phase inverter tube. There's no preamp at all in his amp.
     
  16. Newbcaster

    Newbcaster Tele-Holic

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    Here's a quote from a friend who knows alot about these amps.

    As for the rest of your message, I have all of the necessary tone shaping pedals and such.

    The Brian May special AC30 (originally designed and made by David Petersen) are a single channel amplifier. Basically David took out all of the vib/trem and top boost circuitry and valves related to those two channels and retained the normal channel. He then custom voiced the single channel. The result of removing the extra circuitry is that the amplifiers run cooler, the PCB’s are removed and the circuitry is done on good old fashioned tag boards - so the risk of PCB failure is gone. This makes them much more roadworthy. The BM amps were made in response to the failure rate of the 1993-2004 AC30/6 reissues.
     
  17. Newbcaster

    Newbcaster Tele-Holic

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    Tube. Always. Tube.
     
  18. Oldsmobum

    Oldsmobum Tele-Holic

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    To be fair, none of this is applicable to the mid 70’s when he developed his “tone”.
     
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  19. Mexitele Blues

    Mexitele Blues Tele-Afflicted

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    It's not the same as his current setup, but Rangemaster into AC30 Normal channel is the main sound on the early Queen records.

    @Newbcaster if you find a schematic, please share. I liked the normal channel on my AC15 far better than the top boost, and don't think that it is any less Voxy.
     
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  20. Newbcaster

    Newbcaster Tele-Holic

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    Brian may never used any of the other features of the amp.

    So if I wanted a parts list of things to buy for the normal channel. Where would I look to ensure I end up building what I want. To me the normal channel with a treble booster is the sound of vox
     
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