Hi guys,
I have a harvard build (built by the late David Root) using 7 pin tubes (6At6 front end 6AV6 driver and phase inverter and 6AQ5 output tubes). He wanted to attempt a build with all 7 pin tubes. I added a small .0056 cap piggybacked onto the input coupling stage to add a little warmth and bass, however I've noticed the amp has a very weird overdrive with humbuckers. It's fine sounding with a strat but the humbuckers sound overdriven and the bass sounds spacey. Any ideas where in the circuit I begin to look to resolve?
Harvard Question
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Re: Harvard Question
The Fender model 5f10 that uses a 6at6 as a first gain stage does not have a input coupling cap from the input jack to the first gain stage, so what is the value of the as built cap that you jumped with that small .00056 cap?
Does the humbucker sound crappy at any volume output level set from the guitar?
Does the humbucker sound crappy at any volume output level set from the guitar?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Harvard Question
Maybe the cap is just parallel to one of the 68Ks. Sunn did that with the Bright inputs on their amps.
Re: Harvard Question
Hi correct. It has a .022 for tone stack and I strapped a .0056 across to raise the value. Input is a 1.5k resistor and 25uf filter cap. Guitar is ok sounding with volume lowered to 7ish. Changed the Mallory 150s to Sprague brown drops that improved the tone a lot but still has a weird space like bass full volume.Stevem wrote: ↑Sat May 29, 2021 4:15 pm The Fender model 5f10 that uses a 6at6 as a first gain stage does not have a input coupling cap from the input jack to the first gain stage, so what is the value of the as built cap that you jumped with that small .00056 cap?
Does the humbucker sound crappy at any volume output level set from the guitar?
Re: Harvard Question
Replace that 25µF cathode bypass cap with a 5µF or even .68µF. Maybe use a SPDT switch to change cap values.
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Re: Harvard Question
What is the plate voltage on that first gain stage?
I bet it’s pretty low which is why you loose so much gain without that cap there, and thats likely also why the sound browns out so much with the added mid’s of a humbucker!
I bet it’s pretty low which is why you loose so much gain without that cap there, and thats likely also why the sound browns out so much with the added mid’s of a humbucker!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!