Skyliner Mid Control Turnover Frequency?

[exocet]

What are the turnover frequencies (-3dB points) of the mid range control in the standard Skyliner config (0.01) and what does this shift to when changed to a 0.047?

I know how to calculate for a standard TMB stack but having the mid pot in parallel with the bass and treble throws me a bit so I'm not sure how this changes the calculation (if indeed it does).

[Tonegeek]

What are the turnover frequencies (-3dB points) of the mid range control in the standard Skyliner config (0.01) and what does this shift to when changed to a 0.047?

I know how to calculate for a standard TMB stack but having the mid pot in parallel with the bass and treble throws me a bit so I'm not sure how this changes the calculation (if indeed it does).

Using a different cap does change the turnover point although it is less obvious with the mid pot cranked.

I seem to remember trying to figure out this same issue using the Duncan Tone Stack calculator. There is no exact circuit matching the Dumble one but maybe the Vox or Fender one is close enough.

[llemtt]

attached you find the skyliner mid pot response both with 10n and 47n mid cap (47n lowers turnover freq)

basically mid control is a first-order low pass filter with r=150k and c=mid cap, you can easily calculate -3dB points by 1/(2pi*R*C)

cheers
teo

[exocet]

Thanks Teo, that's just what I was looking for.

The .047 gives greater mid range scoop - like a standard
BF Fender tonestack.

What I'm trying to workout is why this variation of the tonestack should make a Skyliner (high plate), more strat friendly. I can understand the changes to the clean sound being more typically 'fender' but I can't see how this improves the OD tone where I find myself having to usethe 'mid boost' function with my strat to give a more typical Dumble singing sustain. I don't have to do this with my Telecaster. Guess I'll just have to break out the soldering iron to try it for real.

Thanks once again, Marc

[Tonegeek]

attached you find the skyliner mid pot response both with 10n and 47n mid cap (47n lowers turnover freq)

basically mid control is a first-order low pass filter with r=150k and c=mid cap, you can easily calculate -3dB points by 1/(2pi*R*C)

cheers
teo

I memorized that formula years ago. The hard part is figuring out where to apply it Looks easy when someone else points it out...
I just use my ears mostly to tweak but its good to back it up with numbers at times.
thanks

[Tonegeek]

Thanks Teo, that's just what I was looking for.

The .047 gives greater mid range scoop - like a standard
BF Fender tonestack.

What I'm trying to workout is why this variation of the tonestack should make a Skyliner (high plate), more strat friendly. I can understand the changes to the clean sound being more typically 'fender' but I can't see how this improves the OD tone where I find myself having to usethe 'mid boost' function with my strat to give a more typical Dumble singing sustain. I don't have to do this with my Telecaster. Guess I'll just have to break out the soldering iron to try it for real.
Thanks once again, Marc

Its not etched in stone about the .047 being more Strat friendly across the Dumble variants w/Skyline. For Strats, I like the .01 better on a HRM amp and the .047 on a low plate, non HRM. R U using a HRM or NON-HRM amp? The HRM seems to need PAB or mid boost in OD but the NON HRM OD tone should sound pretty good without those extra functions but you may have to adjust the Mid control in OD to get the fatness (well, then it will be too fat in clean right?) Its a real trick to get the clean tone and the OD tone to be what you want without adjusting the contols. I have been tempted to use a relay with more poles or 2 relays chained together to make other adjustments when going from clean to OD - especially to adjust the mid content between clean/OD

[exocet]

Thanks Teo, that's just what I was looking for.

The .047 gives greater mid range scoop - like a standard
BF Fender tonestack.

What I'm trying to workout is why this variation of the tonestack should make a Skyliner (high plate), more strat friendly. I can understand the changes to the clean sound being more typically 'fender' but I can't see how this improves the OD tone where I find myself having to usethe 'mid boost' function with my strat to give a more typical Dumble singing sustain. I don't have to do this with my Telecaster. Guess I'll just have to break out the soldering iron to try it for real.
Thanks once again, Marc

Its not etched in stone about the .047 being more Strat friendly across the Dumble variants w/Skyline. For Strats, I like the .01 better on a HRM amp and the .047 on a low plate, non HRM. R U using a HRM or NON-HRM amp? The HRM seems to need PAB or mid boost in OD but the NON HRM OD tone should sound pretty good without those extra functions but you may have to adjust the Mid control in OD to get the fatness (well, then it will be too fat in clean right?) Its a real trick to get the clean tone and the OD tone to be what you want without adjusting the contols. I have been tempted to use a relay with more poles or 2 relays chained together to make other adjustments when going from clean to OD - especially to adjust the mid content between clean/OD

I'm using non HRM.
Agreed that shared tonestack is a compromise, I guess I was lucky that the only guitar that I had when I first got the amp was my Telecaster - with that guitar I'm very happy with clean and OD without having to change EQ. The strat is very different, I have to increase input volume and crank up bass / mid to get anywhere close with OD sound. Ironically the clean sound is quite usable with same EQ as Telecaster.

[Structo]

If you look at Duncan's Tone Stack Calculator it can give you a good idea how the different caps affect the plot.

What I see when I change the middle cap from 10n (.01) to 47n is more low mids.
Mainly around 100Hz.

The 10n cap shifts the mids higher in the spectrum.

I know it's not the same as the Dumble stack but you can still see the effects of the cap changes.

What I noticed going larger with the mid cap is a bit more harshness in the upper mids as they are turned up, which I didn't like.

On my D'lite (50w) I have a switch to choose between .01 and .06 (.01 and .05 in parallel).
It mainly stays in .01.

If you want to reduce the suddenness of the bass coming on, play with the 10K tail value on the bass pot.
I ended up with a 1K for now.
Now the bass doesn't become real noticeable until around 11:00.

[butwhatif]

.047 gives a better throughput sound, esp for the od sound, more like the classic sound many of us are after, but it also cuts a lot of the bass in doing so.
.01 cuts a lot of higher mid and allows much more bass to come thru, but does have a thinner top end sound -it doesn't have the nice low mid throughput component in the od, but this can be modified by the use of alternate component values.

[David Root]

Someone who knows how to do it should sticky this thread in the Dumble files, this is all good stuff!

Thank you all.

[glasman]

Here is what I remember off the top of my head.

Bass control shelf ~ 80 hz
Middle cotnrol (control centered 30% taper pot) ~ 400hz
Treble - dont remember off the top of my head, But around 2.5K

FWIW..

Bluemaster

Bass control shelf ~ 120 hz
Middle cotnrol (control centered 30% taper pot) ~ 800hz

Gary

Middle freqs are the minimum point. THese are based on measured results.

[Structo]

Fender centers their middle frequency at 400Hz as well.
But the treble can shift that either way.

The Dumble as most of you know is pretty interactive, it takes a while to dial in your tones.

For me though, it was too bass heavy and of course the louder you turn it up the heavier it gets.

I'll have to try it with out the .001uf cap across the bass pot.
What is that suppose to do anyway?

[talbany]

From my notes

Skyliner Amps - Skyliner amps can either be with or without the post overdrive stack. The word skyliner refers to the clean tone stack. This stack has a bass knee of around 80 hertz and give a hard attack on the bass notes. The middle control is centered approximatelty at 400 hertz and this give the more pronounced upper mids that many folks talk about.

The skyliner amps also used more negative feedback in the power amp stage which gave better control of the bass response (flattens over PA response).

The skyliner also had a unique boost circuit that breaks the connections between the treble and the bass controls as well as the top of the bass control to the wiper of the bass. This gives about 10+dB of boost on the top end with a gradual rolloff in response starting at around 600 to 800 hertz. This helps the bottom end from getting "wolfy".

Later amps used the Bluesmaster setup. Once again Bluesmaster refers to the clean stack and changes in the power amp. The Bluesmaster stack as a little more gain due to its circuit layout. The Bass control is centered around 130 hZ. This gives the bass a softer / spongier feel/attack (to my ears, your ears my be diferent). The middle control centers at around 800 hertz and give a more scooped mid range sound.

The power amp section is roughly the same as a Marshall Plexi (a few component changes). This has reduced negative feedback and gives more PA gain and a large bass response.

The Bluemaster also used a completed different boost arrangement that simply lifts the entire tone stack off of ground. This give a HUGE amount of boost, especially in the lower registers. This boost system also tends to roll the high end off just a little bit (6 to 8 dB) as compared to the bottom end.

In general it is accepted that the Tone stack boost must be used when running a post overdrive tone stack amp in Overdrive mode. This reason is that most of these amps (not all) had a large amount of padding on the input of the overdrive stage that makes it necessary to have a large signal on the input of the OD section to get any reasonable amount of gain. You can decrease the input padding, but it does not sound as good.

The early Dumbles used a tone stack that was similar to the Skyliner with different values and different plate loads. These amps were generally a little brighter and for some are the holy grail of Dumbles. They also have a little less bass response due to the 100k plates

Tony

[bluesfendermanblues]

@Gary and Tone

Thanks for sharing overview over these designs.

Wasn't aware of the fact that the pre-skylinger amps used less global feedback and therefore had more bass in the pa.

Gonna build a #13/#40 someday to complement #102, BM, #183 and HRM, already have under my belt.

[Tonegeek]

Fender centers their middle frequency at 400Hz as well.
But the treble can shift that either way.

The Dumble as most of you know is pretty interactive, it takes a while to dial in your tones.

For me though, it was too bass heavy and of course the louder you turn it up the heavier it gets.

I'll have to try it with out the .001uf cap across the bass pot.
What is that suppose to do anyway?

I have listened with and without the 1n cap on the bass pot and the cap makes the bass more defined as you turn the bass control up. It appears to be dumping some low mid content, but it is pretty subtle.