Let's talk tone stacks

[Bob-I]

I wired up the tone stack on my build using the Hybrid_A schem, excluding the deep control and mid boost which I may add later. I'm less than thrilled, in fact dissapointed. The issues are...

1) The bass control is ineffective. Plenty of bottom end but the control does nothing.
2) The jazz/rock switch is not responding as I expected. When it's in rock mode the tone stack loses effectiveness.

positives are

1) Excellent mid control, extremly effective range
2) The boost control's sound is good, telling me the amp's voicing is not at all bad since this bypasses the tone stack

Neutrals

1) Treble control is ok. Scott suggested a 315pF treble cap by looking for a 330 that reads low. I'll try that.
2) tone at "flat" setting is ok.

I'll experiment with this tone stack using various schematics but let's discuss what's worked not.

[dobbhill]

I'm making the assumption that we are talking about clean sounds only.
Also, I have never used the Jazz setting.
The bass control has everything to do with the bass response capability of the speaker/cabinet you are using: try a speaker with extended low frequency response to experiment.
I like the .01 midrange cap vs the .047, but I also use a 250K audio taper pot with it.
Do you have the .001 cap across the bass control? I don't know what changes it does for the tone/control, but I have one on mine.
My experience is that the bass control is not as dramatic a control as the Marshall or Fender stacks, but I like the system as a whole.
My $0.02
D

[Bob-I]

I'm making the assumption that we are talking about clean sounds only.

Not really, but yes clean settings mostly.

Also, I have never used the Jazz setting.

I'm thinking of using that switch for the mid boost instead.

The bass control has everything to do with the bass response capability of the speaker/cabinet you are using: try a speaker with extended low frequency response to experiment.

No, the Fender channel has plenty of range of bass control. Again, it's not lacking on the bottom end, just in the control of the bottom.

I like the .01 midrange cap vs the .047, but I also use a 250K audio taper pot with it.

I got plenty of pot and plenty of cap.... I'll give that a shot.

Do you have the .001 cap across the bass control? I don't know what changes it does for the tone/control, but I have one on mine.

I've tried it both ways and I'm not sure I can hear the difference.

My experience is that the bass control is not as dramatic a control as the Marshall or Fender stacks, but I like the system as a whole.

That's been my experience too, but this one is almost completley ineffective. I'd bet the mid cap will change that too.

My $0.02
D

Thx. Let's keep this discussion more open too, not just about my amp.

[Normster]

To add some science to it, you can record a clip and EQ to taste. Once you know what frequencies are lacking, you can use Duncan's TSC to calculate the values that work best. Don't tell Dogears I gave away his secret.

FWIW, I like a 270pF treble, .047uF mid, .1uF bass. I also think the Ck values effect the bass quite a bit. I'm using 25uF on V1 and 5uF on V2. I don't like the 1uF at all. To my ears, it thins out the tone.

BTW, after building a few of these with the same circuit, I'm convinced that every amp needs to be tuned to the iron.

[Bob-I]

To add some science to it, you can record a clip and EQ to taste. Once you know what frequencies are lacking, you can use Duncan's TSC to calculate the values that work best. Don't tell Dogears I gave away his secret.

I won't tell if you won't tell.

FWIW, I like a 270pF treble, .047uF mid, .1uF bass. I also think the Ck values effect the bass quite a bit. I'm using 25uF on V1 and 5uF on V2. I don't like the 1uF at all. To my ears, it thins out the tone.

Right now I have 330pF on treble, .047uF on mid and .1uF on bass with the .001uF across the bass. Starting to shape up, the bass for some reason is effective now but I don't know why because I made so many changes.

BTW, after building a few of these with the same circuit, I'm convinced that every amp needs to be tuned to the iron.

I agree.

[Icetech]

well figure it out.. as my bass pot seems to do nothing and my mid seems to do mid/bass:) i hate tone stacks:( i have used 3 different ones now and cant find a happy place...

[Normster]

I think the most effective tone stack layout I've tried was oldmacman's:
http://maximoaudio.com/forum/files/dubblelay_278.png

Might be interesting to compare your layout to his and look for differences.

[oldmacman]

That layout is pretty much straight '70s values.

I really do need to redraw it to reflect all the changes I've made, and some of the lead dress is awful. Take a look at the photos of #0040.

Right now, I have a half-Skyliner stack in there, and it sounds great:

.02 midcap, 270pF treble cap, 25uF Ck's in the clean pre, a .047uF cap from V1B, the rest of the tonestack values as in the Skyliner stack, 44M/.047uF feedback loop on V1B.

[dogears]

Yep.... Dats a good one Ben.

Fwiw, I think Norm was referring to the layout. Not sure he meant the 70s values.

[oldmacman]

The couple of things I would change about the tonestack in my original layout are:

1) The switches are upside down when you use mini-toggles like you can get from WeberVST, but they're right if you use slide switches like the bright switch on a Fender.

2) If you look at Dumble's original layout, the three wires coming from the treble, middle, and bass caps and going to to the pots on the front panel are twisted together. Not sure what effect (if any) this would have on tone, but it makes the wiring neater.

3) The midcap and bass cap are switched. The .047 uF cap should be in the rightmost position.

4) Don't use the 250pF cap there. It gets too thin. Sounds much better with 300-330 pF if you're going with the '70s values. I ended up putting another 250pF cap in series with a 1M pot in parallel with the treble cap - I didn't think the mid switch gave me enough control.

Other minor things that Dumble does differently:

- The wiring of the output tubes. I have it set up like on the layout on Blue Guitar. Dumble did it more like a BF Fender. If you do it like I did, make sure to anchor the grid resistors to a terminal strip of some sort.

- The wiring of the PI - you can put the cap for the presence control on the eyelet board. See the photos of gooped '80s Dumbles here.

[Normster]

As Dogears guessed, I was referring to the basic tonestack configuration. I've changed many of the values as well. I also followed #40 closely and tried to copy lead dress and component layout as closely as possible (including swapping mid/bass cap positions).

One thing I've noticed about Dumble's tone stack is that it's very subtle and tends to emphasize frequencies rather than merely increase or decrease them. For example, it won't do the Fender mid scoop thing very well, but it will add richness to the mids. The bass control will allow you to cut bass, but it doesn't have the range to get soft and woofy like a Fender. Treble, on the other hand, seems to have a very broad range, from rolled off jazzy tone to Tele sparkle.

While the amp does reasonably well at bedroom levels, my guess is that it was designed primarily to cut through a live mix without excessive volume. (But it DOES get loud if you crank it up, )

[BobW]

Bob, I shared your exact likes and dislikes, too much bass, etc. My layout hardwired the midboost switch(S1), and just recently discovered a missing 4M7 at the Mid Boost. Adding this resistor brought the tone controls into an acceptable range. However, the .001 across the Bass pot still seems to have no effect, but haven't tried a 100% A/B comparison on both channels and all tone combinations. btw, I'm using single coils not humbuckers. hth

[BobW]

Bob, I shared your exact likes and dislikes, too much bass, etc. My layout hardwired the midboost switch(S1), and just recently discovered a missing 4M7 at the Mid Boost. Adding this resistor brought the tone controls into an acceptable range. However, the .001 across the Bass pot still seems to have no effect, but haven't tried a 100% A/B comparison on both channels and all tone combinations. btw, I'm using single coils not humbuckers. hth

[oldmacman]

Are those 4M7 resistors supposed to change the tone? I thought they were just there to stop it from popping when you switch the mid boost.

[Bob-I]

Are those 4M7 resistors supposed to change the tone? I thought they were just there to stop it from popping when you switch the mid boost.

That's what I thought too.