Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on November 11, 2021, 03:14:02 pm
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I was thinking of building a 2204 style 6v6 Marshall head, the schematic l’d use is the same one for a 50 watt Marshall J800 series 2204 (early eighties) with changes necessary for 6v6s, would be diode rectified. My question is l never played one but read some great reviews, Robinette’s site has some praising info on the build along with schematic.
I know input 2 skips input 1’s gain stage for a cleaner tone and more pedal friendly, using input 2 would that be close in tone to what a 1987 6v6 Plexi sounds like? Any info on input 1’s tone would appreciated. I’d use an AO43 chassis and PT, opt for a 30 watt OT with, 8 and 16 taps. I know it’s a tight fit in the narrow chassis but l got the 6v6 Plexi to fit nicely, might use a cap can for build.
Thanks in advance.
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The Low input gain stage uses a 10K kathode resistor (cold clipper). That's not the case in a plexi, where you have 2K7 + 0.68 uF for the bright channel, and 820 + 330 uF for the normal channel. I've build a 2204 where I used only 1 input. The first gain stage with 2K7 + 0.68 uF and made the cold clipper stage switchable.
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Auke, that's a good idea as the faceplates I have on hand are one input for the 6V6, 1987 Plexi. I could add a switch in one of the volumes, under the switch would be "bright vol" I could live with that rather than make new faceplates.
I would assume the "cold clipper" channel would be a little cleaner than a 6V6 plexi as it by passes the 2K7, .68 and 820, 330.., this is the question I don't know..?
Trying to use this faceplate, guess I could use two inputs, second input in the normal vol, and the preamp in the bright volume..? Hope I have the editing software saved so I don't have to start over, then I could change wording...?
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Nice AO43 to Silver Jubilee conversion thread here:
https://ampgarage.com/forum/viewtopic.php?f=9&t=32020 (https://ampgarage.com/forum/viewtopic.php?f=9&t=32020)
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If you switch in the cold clipper stage, you have the gainstructure of a 2204. I saw that Rob Robinette's site is backup. He has a nice explanation there how the 2204 works.
If you have enough room in the fronpanel, I would suggest having 2 MV's. One for the bright channel and one for the 2204. There's quit some difference in volume between the two).
Without an extra tube or some elaborate switching scheme, you do not have the combination normal and bright channel on one side and the 2204 channel on the other side. Tubenit has some very nice examples where he replaces the cathode folower with a solid state device. That gives you an extra triode to work with.