Dumble stack vs. Fender stack - wiring difference

[TimS]

I've got a pretty good idea what the changes in slope resistor, treble/mid caps, and pot values do, but what difference does the wiring change make between the Fender and Dumble tone stacks?

In other words, if you were to wire up two tone stacks with identical values, the only difference being that one is wired in the Fender configuration and the other in the Dumble configuration, what difference would you see on a scope, and how does that translate into the effectiveness and/or overall sound of the stack?

[glasman]

I've got a pretty good idea what the changes in slope resistor, treble/mid caps, and pot values do, but what difference does the wiring change make between the Fender and Dumble tone stacks?

In other words, if you were to wire up two tone stacks with identical values, the only difference being that one is wired in the Fender configuration and the other in the Dumble configuration, what difference would you see on a scope, and how does that translate into the effectiveness and/or overall sound of the stack?

The Bluesmaster (Fender style) stack offers less insertion loss and smoother comparing the two stacks. THis are with stock values for the respective designs.

Gary


Here are the graphs..

[glasman]

Also notice that the Mid Frequency is shifted between the two. The will give a more scooped mid range texture.

Gary

[Fischerman]

There are 2 curves on each plot...what is what? Is this with all controls at '5'? Cool plots...I think I understand the solid line but the dashed line...I dunno.

[TimS]

Thanks for the graphs, Glasman.

By "Skyliner" and "Bluesmaster", are you referring to the actual tone stacks themselves or just the way they are wired? In other words, do those graphs reflect the standard cap/pot/resistor values associated with Skyliner and Bluesmaster tone stacks (in which case a lot of the difference between them could be attributed to the differences in component values), or did you keep those values constant between the two graphs and just change the wiring?

[glasman]

There are 2 curves on each plot...what is what? Is this with all controls at '5'? Cool plots...I think I understand the solid line but the dashed line...I dunno.

Each graph has two plots, One is amplitude response and the other is phase response.

Gary

[glasman]

Thanks for the graphs, Glasman.

By "Skyliner" and "Bluesmaster", are you referring to the actual tone stacks themselves or just the way they are wired? In other words, do those graphs reflect the standard cap/pot/resistor values associated with Skyliner and Bluesmaster tone stacks (in which case a lot of the difference between them could be attributed to the differences in component values), or did you keep those values constant between the two graphs and just change the wiring?

The Bluesmaster is a Fender style stack with .02uf/.02uf mid and bass caps with 47K slope. It can have one of two different boost wiring schemes.

The Skylilner is HADs own stack with a .01 mid cap and .1 bass cap and 150K slope resistor.

Both graphs were set to the "physical" center of their ranges. Assuming

Bluesmaster

Treble - Linear (some Bluesmasters used Audio)
Mid - Linear
Bass - Audio

Skyliner

Treble - Linear
Middle - Audio
Bass Audio (w/.001uf)

Gary

Gary

[TimS]

The Bluesmaster is a Fender style stack with .02uf/.02uf mid and bass caps with 47K slope. It can have one of two different boost wiring schemes.

The Skylilner is HADs own stack with a .01 mid cap and .1 bass cap and 150K slope resistor.

Both graphs were set to the "physical" center of their ranges. Assuming

Bluesmaster

Treble - Linear (some Bluesmasters used Audio)
Mid - Linear
Bass - Audio

Skyliner

Treble - Linear
Middle - Audio
Bass Audio (w/.001uf)

Thanks for the info, but I guess I need to clarify what I'm asking about here. What I'm wondering is: keeping all caps, pots, and resistors the same, what difference does the change in wiring configuration between the Fender (which has the mid pot connected to the bottom of the bass pot) and Dumble (which has the mid pot disconnected from the bass pot) tone stacks make?

Sorry for the confusion.

[tele_player]

There are 2 curves on each plot...what is what? Is this with all controls at '5'? Cool plots...I think I understand the solid line but the dashed line...I dunno.

Each graph has two plots, One is amplitude response and the other is phase response.

Gary

Are those measured response curves, or SPICE simulations?

[DanteCarrer]

The answer is simple.

The "Fender" style stack has it's mid and bass controls essentially wired in series. The "Dumble" style stack has it's mid and bass controls essentially wired in parallel. This parallel wiring allows more mid frequencies to pass through the stack.

As far as effectiveness is concerned... this has more to do with the values of caps and pot and the frequencies they are associated with. It is also a subjective thing - some people will find that having more mids all the time makes it more difficult to shape their tone while others will prefer more mids. The loading on the first gain stage will be slightly different but this difference is negligible and probably not perceivable.

If you look at the big picture, Dumble's gain stages and interstage attenuators are setup without much/any frequency/gain shaping/emphasis which is perceived as a more mid-range-y tone. In clean mode the EQ will work fairly well but since the EQ is so early in the chain (in single EQ models) when in OD mode the EQ will be much less effective than if the EQ were placed later in the gain chain. This is a compromise... yes... Dumble made compromises. He chose to have more control over the clean tone than the distorted tone.

[TimS]

Thanks. So does the parallel wiring have any effect on the range of frequencies affected by the mid knob, the location/width of the mid scoop, etc. or is it pretty much just a matter of passing more of the same frequency range?

[Darkbluemurder]

I replaced the Fender tone stack in two amps with a Dumble tone stack. The Dumble stack has a lot more mids to my ears, and to get a Fender like scooped tone you have to set the midrange control below 3 (or 9 o'clock).

[TimS]

I replaced the Fender tone stack in two amps with a Dumble tone stack. The Dumble stack has a lot more mids to my ears, and to get a Fender like scooped tone you have to set the midrange control below 3 (or 9 o'clock).

Did you just disconnect the mid pot, or did you also change the pots/caps/etc.?

[Darkbluemurder]

I used the same cap values - 330pf treble, 0.1uf bass, 0.047uf mid. I replaced the existing 10k midpot with a fixed 10k resistor to ground and added a 250kA mid pot for the mid cap. I tried to use as many of the Fender stack parts to see what the difference in wiring would be.

[glasman]

There are 2 curves on each plot...what is what? Is this with all controls at '5'? Cool plots...I think I understand the solid line but the dashed line...I dunno.

Each graph has two plots, One is amplitude response and the other is phase response.

Gary

Are those measured response curves, or SPICE simulations?

Those are spice simulations which explain the extended high end response.

I will have live measurements, maybe this weekend. I have an Ono Sokki CF5220 that is perfect for these kinds of measurements.

I will be swapping my D-clone combo from Skyliner to Bluesmaster this weekend and I will take before and after spectrum measurements.

Gary