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Plate voltage effect on an amp's tone

6/5/1999 8:00 PM
John S.
Plate voltage effect on an amp's tone
Ok amp gurus help me on this one.What effect does a higher or lower plate voltage have on an amp.This would be in regards to my Mesa/Tremoverb head.Does a lower plate voltage brown up the amp and give it more or less headroom as the voltages and the current to the output tubes goes lower,or is this all wrong....please enlighten me on this...Thanks in advance for the help...John S.
6/5/1999 10:00 PM

Read the thread just below titled "Voltage vs tone"
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6/5/1999 11:22 PM
Paul C

One thing about the dual rect series that I think Boogie could have done better is in the rect and bold/spongy switching. The bias voltage doesn't change with the different settings. Of all the ones I've worked the bias at the highest voltage setting ( SS rect/bold) is set a little low at around 28ma or so. When you go with a tube rect this goes down a bit more into the low 20ma range. The SS/spongy setting is lower, and the tube rect/ spongy setting has the tubes biased into the upper teens. At this setting with 6L6's you can actually run it in the EL34 bias setting. This will bias the tubes into the upper 30'sma. I've done several for guys where we pick a setting and stay with it - then bias the amp for that setting. When using the tube rects this really helps get a "better" tone to most people. What Boogie should've done IMO is to have made a switching matrix that whould have adjusted the bias along with the different bias settings - it would've made the amps sound much better - IMO.
6/6/1999 10:13 PM

In my experiences the high plate voltages usually cause an amp to produce more of the "harsh" highs and the amp also seems to feel a bit more "uptight."  
The lower voltages usually do tend to produce a "browner" sound as you were suggesting. The tone is usually warmer, creamier, and smoother.  
Some guys like the higher voltages. I favor the lower voltages for a warmer tone but that's just me.  
6/6/1999 11:18 PM
Paul C

Trace - I'm sorry man!!! I swear I'll get those schematics to you someday!!
6/7/1999 10:51 PM

You dog you!!! (ha, ha) Don't sweat it, it's only been 9 months or so.  
PS:I"m just teasing yah
6/7/1999 7:41 PM

I had the same problem with the DR amps.. why the lowest voltage setting is also the coldest is just silly... and a waste of the circuit IMHO. With all the other switches on the thing (and 8 million Vactrols) you'd think they would work in some kinda bias deal which worked along with your B+ and rectifier settings.. why go 9 yards and not score? I don't get it.
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