Tone stack

[Lynxtrap]

Call me lazy, but searching through the files feels a bit overwhelming.
I'm building a bass preamp where one channel is basically a typical Fender/Alembic with TMB tone stack.
Testing it and also experimenting with the Tone Stack Calculator mademe a bit frustrated with the tone stack, so I'm looking for options.

I started thinking about Dumbles, and got curious about this one that I stumbled on over at schematicheaven: http://www.schematicheaven.net/dumbleam ... lschem.pdf
What is the first tone stack right after the first gain stage? From what D-amp is that? What is the thought behind it? And would it be worth trying?

[10thTx]

Many amps including Fender amps have the tone stack after the first gain stage.

In the Dumble files, look up 102,124,183 & any one of the 50 watt Dumble amps ............. and see which one of those has a tone stack after the first gain stage.

With respect, 10thtx

[erwin_ve]

It's called a skyliner tonestack, usually in 4th gen and newer amps. Some well documented amps in the files section: #124, #102 and #183 all have this tonestack. Combined with the jazz/rock switch there are a lot of flavours to choose from.
Edit: crosspost with 10th

[Lynxtrap]

Thanks! Ok, so that's the skyliner! I'll read up on it.
Do you know if there exists a file for the TSC to download somewhere?

It wasn't that it comes after the first gain stage that seemed odd, (besides the stack in itself). It seemed strange in the schematic that there's another, more standard looking stack further down the line in the OD channel. I thought all ODS amps had one shared EQ. And also that there were no switches. Made me wonder if this was some odd D-stack or just made up by someone else.

I have an ODS clone myself, so I'm no stranger to these amps, but mine does not have the skyliner.

[erwin_ve]

Im not aware of any tsc files for the skyliner.
However in this topic: https://ampgarage.com/forum/viewtopic.p ... 9#p390395 can give some clues.
The schematic you posted is what they call a HRM model. The tonestack in the last gain stage is specific for the overdrive. Usually with the preamp boost on.
Also this schematic is from the era when there was not much info on Dumble amps.
When you look in the Dumble files section of the forum you can have very good and detailed schematics and lay-out.

[Lynxtrap]

I got a bit confused with the PAB wired together with the J/R switch...
I don't need the PAB in this build, but the J/R switch could be nice.

So, would this work?

Sorry for the messy sketch... I'm guessing some of you guys could draw this in your sleep
Output from Vol wiper to next stage not drawn.
The funny jumper from the 100K plate resistor to the 150K slope resistor is due to the existing circuit board already being laid out for a different circuit.

[Lynxtrap]

...also, I started wondering about the cap to the treble pot.
Looking at the #183 schematic, the capacitance is actually .002 + 390pF without the mid boost engaged, or am I missing something?

[Reeltarded]

The 390p is the mid-boost.

The Dumble stack is a Fender with different values, decoupled mids (as you have) and I can't tell about your switching because I can't concentrate in this room full of freaking noise. lol

Seems like a crazy treble cap, huh? It really is.

I used 330p in a skyliner. I like it as much.

[Charlie Wilson]

Caps in series. 1/390+1/2000=1/x. Which comes out to...well ask Reeltarted.
CW

[Lynxtrap]

Thanks! That's right, I forgot how to calculate capacitors in series.
.002 and 390pF should give a total of 326pF, so 330 is the closest you can get.

But the way I understand it, the mid boost shorts the signal around the 390pF, thus resulting in .002 to the treble pot with mid boost engaged?
So 330-390 should do it as I don't need the mid boost.

I'd still be grateful if someone wanted to take the time and check the R/J circuit in my drawing

[Reeltarded]

Yeah, it looks like that works. I would not be able to keep myself from making the slope variable from around 82k-150k. That is an exciting change.

That .002 is not so useful to your application. With the 390 bypassed the controls don't do much but the boost is so big and wide it would be like putting Groucho Marks glasses on your bass.. huge nose! Honka.. Honka..

You will really like this tone stack.

[Lynxtrap]

Thanks, Reeltarded!
I'll be happy if it works for bass, and works better than the standard Fender stack - I've got high hopes for that mid control.
I've got the chassis drilled, wired and armed, but maybe I can squeeze in a trim pot for the slope.

[Reeltarded]

Thanks, Reeltarded!
I'll be happy if it works for bass, and works better than the standard Fender stack - I've got high hopes for that mid control.
I've got the chassis drilled, wired and armed, but maybe I can squeeze in a trim pot for the slope.

Even a switch with 150k and hold on let me arithmetic without coffee.. uhh 180k for 80 ish and 300k for 100. Continuously variable really is the ticket though. Dial in pretty much any instrument to fit any situation.

[Max]

It's called a skyliner tonestack, usually in 4th gen ... .

Just to avoid misunderstandings:
Most 4th generation ODS amps without a later "Skyline" modification: "classic" tone stack.

Additional info: https://ampgarage.com/forum/viewtopic.p ... 16#p237429

Cheers,

Max

[erwin_ve]

It's called a skyliner tonestack, usually in 4th gen ... .

Just to avoid misunderstandings:
Most 4th generation ODS amps without a later "Skyline" modification: "classic" tone stack.

Additional info: https://ampgarage.com/forum/viewtopic.p ... 16#p237429

Cheers,

Max

Yes correct, my bad!