After reviewing some schematics of Friedman amps, I keep finding this off of V1a tube plate resistor, rather the just a 330k plate, he uses a 220k and 100k in series with a partial 500p bypass capacitor over the 100k. Why not just use one resistor and cap instead of 2 resistors? I've never tried this arrangement before and has be interested to try it on an amp to see the results, I am guessing there is a tone difference between the 2 and that is why it's done. Have any of you guys tried this before?
V1a, 220k - 100k plate resistor Friedman values sound difference?
- Thread starter jasonP
- Start date
I am going to try it and put it on a switch to see if I can hear a difference! I see it being used in a lot of places now.That arrangement softens the influence of anode resistor bypass cap. But 220K in series with shunted 100k I believe has almost no effect in comparison with simple 330k. Maybe he would just like to know, who copied his amp
So green and red line is 220k and 100k resistor in series, with and without the 500p bypass cap on v1a?
Then the purple line is one 330k resistor and a 500p bypass cap on v1a?
FourT6and2
Well-known member
I've tried it each way. 330K, 100K/220K with cap bypassing 100k, bypassing 220K and in each order 100K first then 220K and 220K first then 100K. Differences are subtle, but there. You'll just have to try it to see. Fortin does the same thing.
mcstinger
Well-known member
psychodave
Well-known member
I seem to like 220k with a 47pf snubber. To me that 500fp that Friedman uses makes the high end really weird sounding.
glpg80
Well-known member
I really don’t like snubbers at all. Shifts the whole response of the phase of the gain stage to the bass side to my ears and I just don’t like what they do throwing away top end tone. I did use 47pF for a year or so but much preferred the majority of them out of circuit. I’ve found that if 47pF seems like too much on a stage I just leave it out all together - no use in going smaller. Could also be my hearing is fucking shit anymore so who knows
Last edited:
psychodave
Well-known member
I agree. I just seem to like the 47pf.... although I have no issue using nothing. The 47pf is almost more like a "feel" thing. I'm not sure how much is audible using something so small with human hearing. Honestly, it was something Cameron told me to try. Not just use it and forget it, but to listen and play with and without it.
glpg80
Well-known member
Yeah that’s a cookbook recipe trick - hell you and I know some amps are just bright and anemic and could use the help on the top end. Other amps do better without. I’ve found I can use more of the tonestack from 0-10 with them in circuit but I seem to gravitate to one or two settings on the tonestack without them. So from a user/amp builder perspective I can see a more universal approval with them in circuit than out strictly from a business perspective and nothing else. For my own use though they toss out a lot of the harmonic content on solos - you know the stuff under the notes when you bend up a whole step. Seems more character of the amp comes through without them at those points versus with them in.
Another perspective- If I’m burning unobtainium preamp tube glass I want to squeak all of the tone they’ve got out of them. Im paying for all of it I’m using all of it god damnit
psychodave
Well-known member
Slightly off topic, but still relevant, I like tinkering with snubbers with the NFB resistor as well. A 100-250pf cap across the NFB resistor on a stock JMP/JCM 800 can do wonders for it. Of course different types of caps have audible differences as well. I made a video doing it years ago. Let me find it and post it.Yeah that’s a cookbook recipe trick - hell you and I know some amps are just bright and anemic and could use the help on the top end. Other amps do better without. I’ve found I can use more of the tonestack from 0-10 with them in circuit but I seem to gravitate to one or two settings on the tonestack without them. So from a user/amp builder perspective I can see a more universal approval with them in circuit than out strictly from a business perspective and nothing else. For my own use though they toss out a lot of the harmonic content on solos - you know the stuff under the notes when you bend up a whole step. Seems more character of the amp comes through without them at those points versus with them in.
Another perspective- If I’m burning unobtainium preamp tube glass I want to squeak all of the tone they’ve got out of them. Im paying for all of it I’m using all of it god damnit
glpg80
Well-known member
Yeah it’s a great way to take out some top end. I personally don’t like them there for a different reason - the changes are very very drastic and noticeable - it’s a huge difference and not only does value matter there but also composition as well.
Thank you for the clarification! Could you plot this for me? It would be fun to compare.
