Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: embotone on December 05, 2011, 03:41:04 pm
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I am still pondering an interesting circuit for an acoustic guitar amp. Would there be any issues combining the preamp form RicharD's Janitor amp http://www.el34world.com/Forum/index.php?action=dlattach;topic=11329.0;attach=22892;image (http://www.el34world.com/Forum/index.php?action=dlattach;topic=11329.0;attach=22892;image) with a power amp like this http://www.r-type.org/static/5-20b.jpg. (http://www.r-type.org/static/5-20b.jpg.) How could I incorporate reverb into this amp?
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why not build the whole ckt?
--DL
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don't really need that kind of power and would prefer to keep the amp lighter than what I think that one would end up weighing
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don't know if i would build an acoustic amp with cathode bias EL34 - IMO, not enough headroom, yes, you could join the two - tweak the PI to drive the EL34s or leave it alone, or just steal AB763 LTPI or something similar.
--DL
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> RicharD's Janitor amp
Power stage has gain near 9.
> a power amp like this
Power stage has gain of 57.
Big difference.
> don't really need that kind of power
Probably not a huge difference. 35W vs 50W?
Change Richard's plan to 6K OT, convert bias to the 470 ohm cathode resistors; power will come down the few watts. Vacuum rectifier will drop a bit more. For "Clean", I'd change his PI tube to 6SL7 so the NFB is more solid.
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The Janitor never made it off the protoboard. Honestly it wasn't all that loud, but it was 100% clean sound. A little deceptive to the ears. Heavy? Uh yeah! The choke alone is massive. I like PRR suggestion about the PI given my recent NFB experiments. I think I'd keep it fixed bias which is not the norm for me (I like cathode bias). I am flattered people are still looking at this circuit. It was a very cool experiment which I may revisit some day.
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Well, I would like to incorporate the ideas in this amp, but I am really trying to avoid building a heavy beast(by request of friend who asked me to build him something). If I could reduce this down to 35- 40 watts or so, I could use lighter transformers and choke. My buddy doesn't really need anything too loud, he probably will be using it in his living room 99% of the time. Heck, he could probably just use a Mr Microphone, that's about how discriminating his ear for tone is. I just wanted to build something that I found interesting. By the way, what specifically is a Zilla supply. I realize it is a regulated power supply for the heaters.
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>what specifically is a Zilla supply
Me being too lazy to redraw the 12VDC regulated supply that lives on my protoboard, named Zilla. Here's a picture of the protoboard and a schematic that has the 12VDC supply shown.