Trying to understand the tonestack

[Bob-I]

Bob, if you want to increase the range on the Skyliner stack, decrease the tail resistor on the bass pot to 3k9 (more attenuation of bass and mid), and increase the 10n feeding the mid pot to 22n (more mid scoop). That will give you something closer to Fender BF range. Don't worry a bit about the resistor types ;^)

I like it, and I will try this once I rule out or fix PO.

Yes, I not too concerned about resistor and cap types, those are subtle but sometimes significant differences.

[Bob-I]

I pulled out the scope, I can't see any PO. Every stage looks correct to me. I captured the speaker out with a sine wave on both clean and OD. Looked at the scope with signal and no signal, ran it up to max gain and frequency and looked for any anomalies, nuffin wrong.

Here are the captures, it looks like what I'd expect.

[talbany]

Yeah those look OK Great.

Try this real quick. Try putting a 100 Pf cap across the PI plates (ala Marshall/Blues master)
If it's still there then try the 6L's and see what you get then

Curious to see what this does

Tony

[Bob-I]

Yeah those look OK Great.

Try this real quick. Try putting a 100 Pf cap across the PI plates (ala Marshall/Blues master)
If it's still there then try the 6L's and see what you get then

Curious to see what this does

Tony

The 100pF did nothing, which tells me everything's fine.

[Bob-I]

Bob, if you want to increase the range on the Skyliner stack, decrease the tail resistor on the bass pot to 3k9 (more attenuation of bass and mid), and increase the 10n feeding the mid pot to 22n (more mid scoop). That will give you something closer to Fender BF range. Don't worry a bit about the resistor types ;^)

I didn't have a 3k9 but I have a 3k3. I did what you suggested, big difference and I like it. That's the TS I wanted, very effective and voiced where my ears like it. But now the OD section is lacking bottom end, remember I swapped the 10uF bypasses for 1uF, seems too drastic a change.

Thx folks, I forgot how much fun piddling with amps is. These Dumble style amp just seem to cut through the mix and I got lethargic. I can make this better

[martin manning]

Bob, if you want to increase the range on the Skyliner stack, decrease the tail resistor on the bass pot to 3k9 (more attenuation of bass and mid), and increase the 10n feeding the mid pot to 22n (more mid scoop). That will give you something closer to Fender BF range. Don't worry a bit about the resistor types ;^)

I didn't have a 3k9 but I have a 3k3. I did what you suggested, big difference and I like it. That's the TS I wanted, very effective and voiced where my ears like it. But now the OD section is lacking bottom end, remember I swapped the 10uF bypasses for 1uF, seems too drastic a change.

Cool, glad it worked out! Should be easy enough to get the low end back with larger cathode bypass caps.

[talbany]

What do you recommend

Bob
If you are interested in experimenting in different resistors to use Here is what I've found sound great in these amps and have the most impact are obviously the plates. Here are the ones I tried and are transparent and smooth.NTE's HW-415's and Roederstien MK'3's (Dumble used these)You can sometimes find these on the Bay. There is a Dealer in Taiwan that (sometimes)sells the MK'3's shipping is quick and they sell singles. A newer resistor are the KOA Speer's are also a good sounding one. These obviously have no impact on bass just helps smooth out the top end.If thats where you want to go.

Martin wrote
Don't worry a bit about the resistor types ;^)

BTW< Hey Martin
Plate resistors have nothing to do with a tone stack. I was telling Bob that the resistors he had did not sound anything like the ones in the originals and there were IMO better alternatives out there. This was obviously unrelated to the low-end content of the amp you addressed. Thats A different issue altogether. Don't worry a bit about it.
Tony

[Bob-I]

Ok folks, tell me my ears are playing tricks on me. I took the amp out into the family room, connected to a 1x12 ET-65 and recorded some.

One clip is clean and OD, the other is showing the range of the TS with the 22nF and 3k3 tail.

[martin manning]

Tony, that was me winking at the notion that there is any mojo in resistors :^,

[martin manning]

Ok folks, tell me my ears are playing tricks on me. I took the amp out into the family room, connected to a 1x12 ET-65 and recorded some.
One clip is clean and OD, the other is showing the range of the TS with the 22nF and 3k3 tail.

Sounds pretty good to me. Nice range of clean and distorted sounds, and I can definitely hear the tone controls working. Are you thinking there is still something amiss?

[Bob-I]

Ok folks, tell me my ears are playing tricks on me. I took the amp out into the family room, connected to a 1x12 ET-65 and recorded some.
One clip is clean and OD, the other is showing the range of the TS with the 22nF and 3k3 tail.

Sounds pretty good to me. Nice range of clean and distorted sounds, and I can definitely hear the tone controls working. Are you thinking there is still something amiss?

Not anymore. The changes I made were, the TS 10nF to 22nF mid cap and 10K to 3.3K tail, 180-220k OD entrance resistor, 10uF to 5uF bypass on V2a/b, and I swapped the 100K OD drive pot for a 250K, 6Vs to 6Ls and rebias. My ears were telling me something else was wrong, but the recording is telling me my ears are messed up.

Each change is subtle, so I kept thinking there was something more.

FYI, the clean/OD clip was everything at nickels...EVERYTHING.

[talbany]

Ok folks, tell me my ears are playing tricks on me. I took the amp out into the family room, connected to a 1x12 ET-65 and recorded some.
One clip is clean and OD, the other is showing the range of the TS with the 22nF and 3k3 tail.

Sounds pretty good to me. Nice range of clean and distorted sounds, and I can definitely hear the tone controls working. Are you thinking there is still something amiss?

Not anymore. The changes I made were, the TS 10nF to 22nF mid cap and 10K to 3.3K tail, 180-220k OD entrance resistor, 10uF to 5uF bypass on V2a/b, and I swapped the 100K OD drive pot for a 250K, 6Vs to 6Ls and rebias. My ears were telling me something else was wrong, but the recording is telling me my ears are messed up.

Each change is subtle, so I kept thinking there was something more.

FYI, the clean/OD clip was everything at nickels...EVERYTHING.

Bob
Sounds OK to me I don't know what it is your hearing that sounds off?.

BTW. Moving up from a 100k to 250k "drive pot" will also add more low mids.(similar to adding a larger coupling cap in the OD).
Tony,

that was me winking at the notion that there is any mojo in resistors :^,

[Bob-I]

Agreed Tony. I noticed that another amp I built has that punchy low mid drive where this amp didn’t. I compared the schems and saw the difference in the gain pot.

It all comes down to these amps being a complete system, no one thing makes it great.

[talbany]

Agreed Tony. I noticed that another amp I built has that punchy low mid drive where this amp didn’t. I compared the schems and saw the difference in the gain pot.

It all comes down to these amps being a complete system, no one thing makes it great.

Bob
Right on!. I generally start lifting things after all the gain stages (OD Level) first this seems to help keep the low end on the OD side a bit tighter and a bit smoother.. On the other side if you like loose aggressive low mid snarl on the low notes and double stops then I would lift the drive pot before the last gain stage(ala 183)..IMO/Just what I think/My .02cents

Tony