Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bieworm on January 13, 2021, 11:05:56 am
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Hey guys.
As some of you know I built an imperial clone a while ago..
But time playing it has told me that the OD channel is not what I expected. You can dial in a nice tweedy tone but when the midbite knob is dialed that nice tone changes into a raspiness that's out of control. I ended up changing the paraphase PI into a LPT PI which I find much better. But I still don't like the midbite overriding the tone knob settings. I have drawn a schematic to turn that channel into something more 'marshallesque'. Could some of you wizards check out if it's a go or no-go? And what changes do I need to perform?
Thanks mucho 😉
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Nobody?
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Sometimes people just don't have any comments. Doesn't mean we don't still love you. :icon_biggrin:
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I had the chance to perform the changes yesterday evening. It works actually, but there are some (un)expected side effects . I haven't had the chance to fully test it.. but first findings here:
- I have the impression the overall volume is less than before
- still fizz I think, but clearly less.. like I said, I have to test it somewhat better
- looking at the voltages I noticed that V2B (2nd stage clean channel) have gone up. I will leave that for now and try to tweak the voltages of the OD channel
- V1B and V2A: raise the plate resistor from 100k to 120k and see where that puts them? Should I simultaneously lower the cathode resistors or do that as step 2?
- OR... should I Raise the plate resistor of V1B to start off with higher voltages and see where that puts the rest?