Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: firemedic on January 28, 2011, 05:46:30 pm
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I'm amazed it took so little tweaking. Mine is kind of a hybrid of Tubenit's & Dageezer's versions; the VVR instead of PPIMV, a couple of component values like tubenit's, "F" node, higher voltages & fatness pot, etc. like dageezer's. This is my first high-gain amp but the hum is minimal w/ no oscillations so far, thanks to the best practices I found in this forum.
Plus I put in a Pentode/Triode switch, and switchable 6V6/6L6 cathode bias. Also a F/S relay which is finally working (thanks guys).
I use a 12AY7 V1, V2 is a 5751, V4 12AT7. With 6V6s the clean channel is pretty crunchy. The fatness pot & VVR are crucial.
Will post a schem as soon as I'm done with it. Thanks for the inspiration guys!
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That is wonderful! Congrats on getting the build up and running.
With respect, Tubenit
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Cool I think you will really enjoy it.
Bill
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Just finished some more "tweaks" i.e., returning some caps & resistors to the values on the schematic (I originally put "kind of close" values in that I had on hand.
So far the 6V6s are blowing the 6L6s away, to my ears....
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The TOS that I sold had JJ 6V6's in it and the buyer preferred those over the 5881's. However, I prefer the Tung-Sol 5881's myself in my TOS. Both sound good though.
Are you getting pretty smooth sustain? Can you get some of that blooming feature where the notes swell and have kind of a vowel tone?
Definitely would like to see the schematic.
With respect, Tubenit
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Tentatively this will be my version. It's missing the Pentode/Triode switch, line out & other peripherals but you get the idea. Tubenit is helping walk me through the final stages. She sounds awesome with 5881s or 6V6GTs, at any VVR level. I'm crazy about the 5879/parallel triode combination. You can't buy that sound, at least around here.
I always loved the "jangly" sound of tubes, even before I knew anything about them. This amp has it in spades.
This is my 2nd amp that features the HoSo56-style 5879 stage and it's been a whole new world since I first tried it.
Very nice sustain, & I do get some "blooming" but I suspect it will need just a tiny change or 2 to get all the way there, tubenit. I know I must be close because I lost track of time playing and messing with the controls, trying to find any possible weak link.
It's a tossup, jacking up the OD with high-gain PA tubes gives more OD but it limits my clean channel voicings somewhat, if that makes any sense.
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It's a tossup, jacking up the OD with high-gain PA tubes gives more OD but it limits my clean channel voicings somewhat, if that makes any sense.
Yeah it makes total sense IMHO, hotter OP tubes take less on the control grid (g1) to goose them over the top. If you want a wider range between clean and distortion, maybe use a little cooler OP stage with a little wider/hotter preamp to be able to adjust? Are you looking to be able to control the clean/distortion ratio from your guitar's volume pot?
Brad :smiley:
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I figured since the OD is supposed to be all in the preamp then a little cooler bias would be fine. Plus I won't have to replace power tubes as often. I needed to make a couple of changes since I prefer 12AY7s to 12AX7s and I do like a more scooped midrange.
So it's really really done now, I borrowed Tubenit's preamp mods and kept Geezer's power section mostly intact, except the bias resistors. It performed extremely well at all its settings today, It's labeled and in its cabinet which is a kind of final step.
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Glad to hear those tweaks worked out reasonably well for you!
With respect, Tubenit