102 as Lowplate Classic

[ToneMerc]

The input stage grid resistor won't affect pickup loading; that will be dominated by the 1M to ground at the input. The grid stopper's effect is more about the high-end roll-off and RF noise rejection.

Exactly Martin

Also folks need to entertain the fact that sometimes the only mystery is that he used whatever value or type he had on hand.

TM

[Charlie Wilson]

Mike, I REALLY have a hard time with the Dumble used whatever he had laying around concept and maybe it is that I choose not to believe that. It just doesn't make sense to me that he would work on an amp for that long and be so deliberate about some aspects, measured values and all, and then just throw in a resistor that may affect the sound because he didn't have a certain value. I choose to believe that he put metal films on some grids and carbon films on others because of what they sounded like. I even think that he used the formica boards because he liked the sound of them and was well aware of the electronic limitations of the stuff, well and because of the hippy look. I may be wrong(and usually am) but if I can hear the difference between a Piher resistor and Xicon on a grid and choose the Xicon or hear that a 1 meg volume pot that measures over 1meg adds more bass and mids than a 940k certainly Dumble did and does. I think the problem is looking for formulas with these amps when each one was probably treated on an individual basis. Just my .02 cents. Oh yeah, I tried the .02 coupler on V1b and love it. It really helped clear up some muddiness in my OD and balance out the clean channel.
CW

[ToneMerc]

Mike, I REALLY have a hard time with the Dumble used whatever he had laying around concept and maybe it is that I choose not to believe that. It just doesn't make sense to me that he would work on an amp for that long and be so deliberate about some aspects, measured values and all, and then just throw in a resistor that may affect the sound because he didn't have a certain value. I choose to believe that he put metal films on some grids and carbon films on others because of what they sounded like. I even think that he used the formica boards because he liked the sound of them and was well aware of the electronic limitations of the stuff, well and because of the hippy look. I may be wrong(and usually am) but if I can hear the difference between a Piher resistor and Xicon on a grid and choose the Xicon or hear that a 1 meg volume pot that measures over 1meg adds more bass and mids than a 940k certainly Dumble did and does. I think the problem is looking for formulas with these amps when each one was probably treated on an individual basis. Just my .02 cents. Oh yeah, I tried the .02 coupler on V1b and love it. It really helped clear up some muddiness in my OD and balance out the clean channel.
CW

CW; I have said before when concerning these amps, looks for the pattern because there are definite patterns. However, there are locations in these amps where he most certainly used whatever he had on hand, even the chassis construction.

Yes, there was a reason he used metal films on the plates of let's say #183

Honestly, do you really know why it took so long to deliver some of these amps? It only adds to the lore that it took 4 years to deliver and the perception that whole year of that was spent tweaking it.

It's been over two decades since I last had my last conversation with him, but hidden in his genius is also the ability to be his own biggest hype man as well.

TM

[Charlie Wilson]

Mike, fair enough. Being pretty new to amp building(have repaired for a long time), I guess I wanted to create a discipline based on an ideal that may never actually have existed or maybe partially existed. That is why I used "choose to believe" in my statements. Oh well, at least if you see a 33k grid resistor or 120k drive pot in one of my amps, it is on purpose.
CW

[lovetone]

It might be that 33k is a near value to the standard, Fender as example has input resistance when using input one (high level) of 34K which is the two 68K resistors in parallel?

[aflynt]

33k grid stopper would just roll off a bit more high end and maybe be less susceptible to RF than 22k, right? I just left the 33k in mine since that was in the official #102 layout and the early '80s amps seemed to have either or. Maybe I'll try 22k at some point to get back some sparkle if other tweaks don't pan out.

-Aaron

[ToneMerc]

It might be that 33k is a near value to the standard, Fender as example has input resistance when using input one (high level) of 34K which is the two 68K resistors in parallel?

I have wondered the same thing.

TM

[ToneMerc]

33k grid stopper would just roll off a bit more high end and maybe be less susceptible to RF than 22k, right? I just left the 33k in mine since that was in the official #102 layout and the early '80s amps seemed to have either or. Maybe I'll try 22k at some point to get back some sparkle if other tweaks don't pan out.

-Aaron

http://www.ampbooks.com/home/amplifier- ... d-stopper/


TM

[aflynt]

33k grid stopper would just roll off a bit more high end and maybe be less susceptible to RF than 22k, right? I just left the 33k in mine since that was in the official #102 layout and the early '80s amps seemed to have either or. Maybe I'll try 22k at some point to get back some sparkle if other tweaks don't pan out.

-Aaron

http://www.ampbooks.com/home/amplifier- ... d-stopper/


TM

That's pretty awesome, thanks! Looks like it would make some kind of difference: -0.68 dB @10k for 22k grid vs -0.92 dB @10k for 33k grid. Maybe perceptible as less sparkle? Seems to have a much bigger rolloff in general with high plates: -1.35 dB @10k for 22k grid vs -1.72 dB @10k for 33k grid.

So you'd have to go up to like 68k / 270k , 100k / 220k to get the same rolloff with lowplates as you do with highplates, on v1a/v1b, v2a/v2b then as you get with the usual 33k/220k, 68k/180k grid stoppers?

-Aaron

[jam-mill]

Seems like a 33K grid stopper might help tame some of the inherent brightness of a single-coil pick-up.


Martin,

Thank-You for responding to the PM and posting that info here. Hopefully, others will benefit from your response.

-jack

[ToneMerc]

33k grid stopper would just roll off a bit more high end and maybe be less susceptible to RF than 22k, right? I just left the 33k in mine since that was in the official #102 layout and the early '80s amps seemed to have either or. Maybe I'll try 22k at some point to get back some sparkle if other tweaks don't pan out.

-Aaron

http://www.ampbooks.com/home/amplifier- ... d-stopper/


TM

That's pretty awesome, thanks! Looks like it would make some kind of difference: -0.68 dB @10k for 22k grid vs -0.92 dB @10k for 33k grid. Maybe perceptible as less sparkle? Seems to have a much bigger rolloff in general with high plates: -1.35 dB @10k for 22k grid vs -1.72 dB @10k for 33k grid.

So you'd have to go up to like 68k / 270k , 100k / 220k to get the same rolloff with lowplates as you do with highplates, on v1a/v1b, v2a/v2b then as you get with the usual 33k/220k, 68k/180k grid stoppers?

-Aaron

Yes in the context of 10Khz, but what about(1.32Khz)1320Hz, highest fundamental freq of a 24 fret guitar?

TM

[aflynt]

Yes in the context of 10Khz, but what about(1.32Khz)1320Hz, highest fundamental freq of a 24 fret guitar?

TM

I was thinking upper harmonics and overtones, but you've got a point.

-Aaron

[martin manning]

Also consider your (or anyone else's) ability to perceive a difference of a fraction of a dB.

[Charlie Wilson]

Well now that I figured out my master volume issue I have a very bright Low Plate Classic with a 22k grid resistor. I am going to try the 33k(and a 3K3/270 ohm NFB) grid resistor. I will do the grid resistor first and report back.
CW

[groovtubin]

Mike, I REALLY have a hard time with the Dumble used whatever he had laying around concept and maybe it is that I choose not to believe that. It just doesn't make sense to me that he would work on an amp for that long and be so deliberate about some aspects, measured values and all, and then just throw in a resistor that may affect the sound because he didn't have a certain value. I choose to believe that he put metal films on some grids and carbon films on others because of what they sounded like. I even think that he used the formica boards because he liked the sound of them and was well aware of the electronic limitations of the stuff, well and because of the hippy look. I may be wrong(and usually am) but if I can hear the difference between a Piher resistor and Xicon on a grid and choose the Xicon or hear that a 1 meg volume pot that measures over 1meg adds more bass and mids than a 940k certainly Dumble did and does. I think the problem is looking for formulas with these amps when each one was probably treated on an individual basis. Just my .02 cents. Oh yeah, I tried the .02 coupler on V1b and love it. It really helped clear up some muddiness in my OD and balance out the clean channel.
CW

CW; I have said before when concerning these amps, looks for the pattern because there are definite patterns. However, there are locations in these amps where he most certainly used whatever he had on hand, even the chassis construction.

Yes, there was a reason he used metal films on the plates of let's say #183

Honestly, do you really know why it took so long to deliver some of these amps? It only adds to the lore that it took 4 years to deliver and the perception that whole year of that was spent tweaking it.

It's been over two decades since I last had my last conversation with him, but hidden in his genius is also the ability to be his own biggest hype man as well.

TM

Face it, w/all the diff topologies, n weird tweaks, and ALL of these in his head, don`t you think it mighta drove him MAD wondering what to do w/all those new toys n how to implement into the correct amp?? Sometimes i think no matter WHATS in your hand, how you use it, n what mood you might be in really does matter building these things! Like today, i was determined to fig out a diff X factor, and of course, right B4 the ""revelation"" comes..., all hell breaks loose, i can`t hold my pick, it actually jumps outa my hand! the dator tube starts freakin out, just sayin......