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previous: Joseph Futral This is my first foray into an amp ... -- 10/10/2000 6:59 PM View Thread

Re: Looking for feedback

10/10/2000 9:52 PM
Scott Swartz
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Re: Looking for feedback
quote:
"1. The plate voltage at the PI tube seem kind of high. Since I am looking for more overdrive sound, should I try to lower these? How?"
 
 
 
 
The split load phase inverter you are using should drop 25-30% of B+ across each resistor (47K on your schem). Try increasing them to maybe 68K for a higher drive voltage.  
 
 
 
 
 
 
 
quote:
"2. I've never tried to work out a fixed bias amp, everything else I have built have been cathode bias. This amps bias circuit seems just a tad different from what I have sen on other schematics. Any thoughts?"
 
 
 
 
Looks pretty standard to me, but the cap should be rated 100VDC.  
 
 
 
 
 
quote:
"3.The power filter caps' values seem small when compared to some Fender or Marshall amps. What difference does this make?"
 
 
 
 
More capacitance gives a little tigher bass, I prefer about the range shown on your schem  
 
 
 
 
 
quote:
"4. The power tubes are Svetlana 6L6GC so they can handle the voltages, but do I really want them this high with what I am looking for out of this amp? Is the only way to affect this significantly to change the power tranformer?"
 
 
 
 
Lower B+ will distort easier if thats what you are looking for.  
 
 
 
For a Full wave rectifier you can put a 50W zener in the CT lead and drop some voltage, not sure if you can do this with a bridge, I'd have to think about it, or maybe someone else knows how.  
 
 
 
You are running the SV6L6GCs at 23 watts dissipation, which may be a little hot.  
 
 
 
 
 
[QUOTE]5.Any other thoughts? Feel free to email me  
 
directly if you prefer[/QUOTE]  
 
 
 
If you want more distortion, you could cascade the preamp stages, use master volume, switch stages in and out, and use a DPDT to switch between the two tone stacks for the Fender/Marshall EQ changes, etc.  
 
 
 
Or maybe this  
 
 
 
 
 
Fender  
 
 
 
Gain  
 
Tone  
 
Gain  
 
Master  
 
 
 
 
 
Marshall  
 
 
 
Gain(first stage from Fender preamp)  
 
Gain  
 
Cathode follower+Tone Stack  
 
Master  
 
 
 
A switch or relay would select the Fener or Marshall path  
 
 
 
Check out Boogie or late Marshall schems, you'll see similar approaches