Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on April 14, 2017, 01:17:29 pm
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I recently just finished a 50 watt version of toni iommis la100bl. When i play through my rangemaster treble booster, it sounds amazing. On its own the amp is very muddy and its hard to get clean sounds. with the gain on 10 theres just not enough overdrive for me. Coming right off the rectifier there is 503v, when i add in a drop resistor (i have tried many values here) i have gotten the voltage down to 430v at the beginning of the chain and 304v at the end (so 304v on the pate resistor of the first gain stage) the amp starts cutting out and just general nastiness. I have replaced all B+ resistors (the 22k and 2.7k) with 10k's and that did seem to help alot. I also have a variable bias supply i keep between -54v and -56v. There is a 12ax7 triode thats unused (i only built one channel unlike the original laney) and im thinking of adding another gain stage at the beginning. I added a 100k feedback resistor that helps with the noise a bit and a .68uf bypass on the 820 ohm cathode resistor that adds a bit of crunch but not enough. So heres the main questions:
For the issue on plate voltage, could i add a tube rectifier (there is a ground return for b+) instead of a SS recto? I have a 5y3 lying around would that work?
How can i get rid of the muddy tone (or could this just be my crappy BC rich?)
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How can i get rid of the muddy tone
The tone stack values are very non standard...and I assume it's a mistake, even though the controls aren't marked
They'd be 'more correct' if you swapped C7 and C8
As is, you have no mid scoop and it will sound bass heavy due to all of the low mids that are present
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That did the trick! Thanks
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How can i get rid of the muddy tone (or could this just be my crappy BC rich?)
Pahaha!! :icon_biggrin:
I think BC rich's are pretty cool man, I don't really dig pointy guitars, but some of their stuff is pretty great!
Glad you got it figured out!
-Brett
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that is a very ineffective tone stack. mostly it's near like 3 volume controls. with the treble full CW and the bass and mid controls at full CCW, the LF is 100Hz. and has virtually no loss.
put the 270pF at the top of the treble the 22nF at the bottom of the treble.
use bassman/marshall tone stack values as shown in many online reference.
there's probably nothing wrong with your guitar.
--pete