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previous: Steve Slick Re: Anyone with a real understanding of power tube distortion? -- 7/16/2000 9:45 PM

Signal grid resitors values & output tube distortion???

7/16/2000 11:30 PM
T.B.	Signal grid resitors values & output tube distortion??? Well, I'll try this one more time. AOL has been a real pisser tonight. I wrote a nice long post asking about the values of signal grid resistors and effects on output tube distortion and tube life. Just as I was reviewing my post, I got knocked off. About ready to go to cable or another server real soon! Anyway, if I can remember and clear my now clouded brain, ha, ha. What I've read in recent months is to lower the "typical" 220K resistor to a 100K or even lower to 68K and I've even seen them as low as 48K (silverface twin?) Anyway, that's like installing a "set" master volume as I see it. So the idea with this lower resistor is that we'll be kinder to the output tubes and we will also have more preamp and PI distortion. Is any of this correct? My understanding is that it is. Question now is wouldn't it be easier to drive the output tube and consequently the output transformer by allowing more signal to hit the grids? If that is the goal, then why lower the resistors in the first place? I personally do not crank my amps to the max but on a rarest of occasions so can't see that I'd be burning up tubes any too fast. Also, does not the bias setting control the current and what about the screen grid voltage in relation to the plate, etc.? Bottom line is if a person desires to get more ass from their output tubes wouldn't it make sense to hit them with more juice up front by keeping the grid resistor up to the max? How does this affect P-P and single ended? I'd love to hear from some real pros on this subject, also anyone else who has opinions, ideas, etc.

7/16/2000 11:30 PM

T.B.

Signal grid resitors values & output tube distortion???

Well, I'll try this one more time. AOL has been a real pisser tonight. I wrote a nice long post asking about the values of signal grid resistors and effects on output tube distortion and tube life. Just as I was reviewing my post, I got knocked off. About ready to go to cable or another server real soon!

Anyway, if I can remember and clear my now clouded brain, ha, ha. What I've read in recent months is to lower the "typical" 220K resistor to a 100K or even lower to 68K and I've even seen them as low as 48K (silverface twin?) Anyway, that's like installing a "set" master volume as I see it.

So the idea with this lower resistor is that we'll be kinder to the output tubes and we will also have more preamp and PI distortion. Is any of this correct? My understanding is that it is. Question now is wouldn't it be easier to drive the output tube and consequently the output transformer by allowing more signal to hit the grids? If that is the goal, then why lower the resistors in the first place? I personally do not crank my amps to the max but on a rarest of occasions so can't see that I'd be burning up tubes any too fast.

Also, does not the bias setting control the current and what about the screen grid voltage in relation to the plate, etc.?

Bottom line is if a person desires to get more ass from their output tubes wouldn't it make sense to hit them with more juice up front by keeping the grid resistor up to the max? How does this affect P-P and single ended?

I'd love to hear from some real pros on this subject, also anyone else who has opinions, ideas, etc.

Replies:

JohnC If the previous stage supplied the ... -- 7/17/2000 5:49 AM
Stephen Conner Actually the value of that grid res... -- 7/17/2000 11:03 PM