Tone Stack Question

[ampgeek]

I slapped the tone stack from the Clubman schematic below into an 18W mutation that I am throwing together and found only a very narrow useable band on the controls.

It then dawned on me that the output impedance of the preceeding gain stage in my plan (single triode) is ~3.2X that of the Clubman.

I suspect that I need to bring the tone stack input impedance up by ~3.2X to maintain the same I/O ratio as the Clubman plan.

Is that rationale correct? If so, would increasing the two 100K drain resistors to 330K get me close? Any other tweaks to the tone stack that I ought to consider while I am at it?

TIA
Dave O.

[roberto]

So you substitued a plate driven tonestack with a cathode driven one?

[Reeltarded]

What is the 18 watt mutation right before the tonestack?

[ampgeek]

No. I hung the Clubman tone stack below onto the plate of a single triode loaded with a 100K plate resistor. The Clubman hangs off of two parallel triodes loaded with a single 10K plate resistor.

If I "look" back at the gain stage of each, I calculate that the single triode condition output impedance is much higher.

Not sure how best to adjust the tone stack to maintain a similar impedance ratio/tonal performance.

I suspect that increasing the two 100Ks to ground by ~3X will get me headed in the right direction. Just need to complete the household chores before I can get to try it!!

Thanks for looking!!
Dave O.

[ampgeek]

It started as an Xits plan that morphed over to, primarily, Liverpool componant values.

Right now it is input-->gain stage--> volume--> gain stage--> T/B tone stack-->clipping stage-->pre PI master-->LTPI-->post PI master-->PA

Only the power tube plates and screens on a Hall VVR.

I am shooting for a ripping, one trick pony kick ass rock amp. It already sounds/behaves great...except....really difficult to dial in the tone. Both controls are just barely off of "0". Much beyond that on each is too much.

Lots of Sozo caps and PRP resistors about so I ran it for ~100Hrs with an iPod to get some break in on the caps.

Thanks guys,
Dave O.

[pdf64]

Sorry for the side track, but does the Clubman really run the EL34s that hot (>35 watts static plate+screen dissipation per tube)? If so, how long do they last?
Pete

[Reeltarded]

It seems they do it by using a very lossy tonestack!!!

lol

Feathered Hammer.. sounds like a military operation.

[dvnator]

I've messed around with those tone controls and I think the bass control works better, or has a greater effect, if it's directly after the first stage.

[ampgeek]

Thanks for the input DV!

Yes indeed. I contemplated that change and may end up doing just that before all is said and done. Fortunately, this is an amp for personal use so there is no time pressure to complete it.

I threw in some 330Ks for the 100Ks to ground around the bass pot
and obtained a marked improvement in the bass control. I will next try a higher value treble pot and/or tail resistor and see where I end up.

I also downloaded the Duncan tone stack simulator and played around with the "canned" stacks a bit. I haven't spent a lot of time with it....yet!

Hoping that it is fairly easy to start a stack from scratch using that program.

Anybody here use that simulation? Any high level words of wisdom to share before I sink a whole lot of time into it?

Of course, I could always just sit down and study/learn the technical details and math it all out like a good scientist/engineer should.

But...too many effects circuit boards to transfer/etch/play around with to do the "right" thing at the moment. A new DIY demon has just been unleashed in my workshop!!!

Thanks as always,
Dave O.

[dorrisant]

I am looking intently at this tone stack too. Using the paralleled 12AX7 thru the TS into an EF184 pentode and on to an SE EF84.
What pot taper are you using?
Treble seems fine, Bass is a bit lacking though. Any thought on how to bring it up?
I think I'll try tinkering with the ground resistor on the bass control first.

Tony

[TUBEDUDE]

Best tagline yet Reeltarded!

[ampgeek]

After dinking around with, literally, dozens of configurations, I ended up with Tubenits Bax stack plate coupled to the second stage after all was said and done.

I was using audio tapered pots when I had the Clubman approach back on the first stage. It didn't sound bad..but...had only a very narrow range of sounding good. Maybe I should have tried linear?

Good luck,

Dave O.