Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ambugaton on September 30, 2016, 02:47:54 pm
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Hi, I hope you read this tubenit, a while ago I was asking for advice for reducing the dry/harsh sound I was getting on a Stout TMB I put together. You offered the following advice:
"I'd start with the "enchance cap" 220p across the LTPI plate resistor & the smoothing cap on the 2nd gain stage that is 120p. Then I'd try lowering the V1b .022 coupling cap to .01 or .015. Then I'd try lowering the EL84's cathode cap from 47uf to 10uf. Then I'd try the PPIMV.
These may or may not be useful to you?"
I would love to make these modifications to the Deluxe Lite I have now. I am beginning to think I am more sensitive to higher frequencies and would like to smooth this amp over as well, while still maintaining that high end clarity that it has now. The amp sounds great, but I feel like it is still just a tad bit harsh/dry/brittle, i don't know how to explain it. I just want to verify how to apply these mods to this circuit?
Overall I am looking to make the amp a bit sweeter and more musical on the high end.
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Do it just like you did previously. Enhance Cap goes across the LTPI entrance plate resistor.
Provide a schematic showing what you have and I'll try to help with the rest of the questions.
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Not sure if this is your schematic? This is what I personally would do. I am NOT saying this would sound better than Sluckey's design.
Just stating this would be closer to my preference based on my experience with Fender amps.
I would use Orange Drop PS series caps or Doug's Jupiter caps where I've indicated changes to .02 or .047 values.
with respect, Tubenit
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...the Deluxe Lite I have now... The amp sounds great, but I feel like it is still just a tad bit harsh/dry/brittle...
Overall I am looking to make the amp a bit sweeter and more musical on the high end.
I've never thought of a 6V6 AB763 as sounding harsh/dry/brittle. Maybe you still have a gremlin in the amp. Did you ever prove that the NFB is the correct phase? Sometimes having it wrong will make an amp sound harsh rather than outright squealing. Swap the OT plate leads. If it gets better, leave them swapped. If it starts squealing, howling, or just sounds worse, swap them back.
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Thanks for the reply tubenit. I figured it would be the same application just wanted to double check.
Sluckey, I'm sure about the ot leads. Was squealing originally and web away when I removed nfb so I swapped them. This weekend I will try to get some quality recordings. Maybe I'm just crazy. Maybe I should use a listening amp? I just a lot of reading to do on that process.
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I solved my problem... I put a 5751 in the PI and it sounds sooo much better to my ears.
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I solved my problem... I put a 5751 in the PI and it sounds sooo much better to my ears.
What tube was in the PI hole?
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I was swapping between a couple of 12ax7's. EH, JJ, Sovtek, and Tung-Sol. I was thinking that with such high plate voltage I would need a higher gain tube to get any overdrive out of it. But I am liking the 5157 and using my OCD/Soul Food for that.
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I was swapping between a couple of 12ax7's. EH, JJ, Sovtek, and Tung-Sol. I was thinking that with such high plate voltage I would need a higher gain tube to get any overdrive out of it. But I am liking the 5157 and using my OCD/Soul Food for that.
BF Fenders use a 12AT7 for PI, try 1 out. It has a little less gain than a 5751.
Don't worry about the gain with the plate dcv.
Just try it. :icon_biggrin:
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I think I have a mullard 12AT7 laying around. I'll give it a try!