knob adjustment

[Tdale]

I can finally start playing my hybrid-a, and wondered where you guys usually put the drive/level knobs? I tried different settings, and they give different sounds in different positions, but if I turn them up too much, the sounds gets real distorted, in a bad way. In other positions they are ok, but it would be nice to hear what your favorite adjustements are, for that slightly overdirven tone..?

Tommy

[Bob-I]

I like the clean gain at about 12:00 on an audio taper pot, the OD trim at about 2:00 on a linear pot and the OD gain at about 10:30-11:00 on an audio pot. More than that gives that gritty distortion that's not so pleasant.

As for the tones, with my humbucker guitars I like the tones all on 12:00, maybe a tad more treble and presence at about 9:00-10:00.

[Icetech]

preamp 7, od level 10, od volume 10, master 7... if i want less gain i dial the guitar back to bout 1-2...

I am actually finding the od level control fairly useless and next amp i will hardwire it and delete that pot... oh and i keep presence around 7... higher and i get some hiss:(

[Darkbluemurder]

Preamp 5-7, OD input 5-6 (in most amps I fixed this control with a voltage divider), OD gain 9, OD level 3-4, master 3-4. This is quite a lot of gain. Tone controls treble 8-10, mid 3-8 (depending on the guitar), bass 0-2 (more with less gain), midboost on or off depending on the guitar. This is for solo tones only.

My experience is that the D-style circuit is the most sensitive to different guitars and playing styles. I must say I haven't played a TW-style amp yet for the simple fear that they may be too loud for any of my applications.

[Tdale]

OD trim/input... are we talking about the trim pot at the od entrance?

also...level, volume, gain... I named mine Drive and Level... I'm getting confused here

Tommy

[Bob-I]

OD trim/input... are we talking about the trim pot at the od entrance?

also...level, volume, gain... I named mine Drive and Level... I'm getting confused here

Tommy

Yes it's confusing. Here's the names I use.

Gain = the first volume control, between CL1 and CL2
OD Entrance / Trim = the trim pot just before OD1
Drive / OD gain = the pot between OD1 and OD2
Level / Ratio = the OD output's pot.
Master = the final volume control.

CL1 = V1a
CL2 = V1b
OD1 = V2a
OD2 = V2b

I hope that helps.

[Tdale]

Od endtance pot at 2:00 that means that the wiper is closer to the grounded side of the pot than of the input side?

Have you ever measured the resistance between ground and the wiper of the OD entrance pot?

I have a 10-turn pot in that position, and right now I think it's adjusted to about mid position....

Tommy

[Bob-I]

I am actually finding the od level control fairly useless and next amp i will hardwire it and delete that pot...

I'm confused by this. OD level I think of as the final volume control after OD2. I use it to balance the volume between OD and CL.

If you're talking about the drive, I find that this control running too high really makes the amp get nasty. It's best to try to drive both OD stages at about the same distortion level. If you look on a scope you'll see that OD1 distorts only the top half of the sine wave, then inverts the signal, OD2 then distorts the top half of the sine again. Since the signal is inverted you now have both sides overdriven.

The way you're setting this control you'll have one half of the sine wave overdriven and the other almost clean. If you like the tone that's ok, but the goal of these amps is smooth almost clean overdrive. I don't get that unless both sides are slightly overdriven.

JMO

[Tdale]

That's what happened when I tried to get max overdrive.

I put the master pretty low, and the clean volume all the way up. I then put the drive pot all the way up, and the level pretty low, and the overdrive sound was not nice at all!

I looked at the picture Gil posted of RF's Dumble at a show, and that has the drive right below 4(10:45) and the level at about 5(12:00)

I'm looking forward to tweak and test.

By the way! I looked over my 5V rectifier, and discovered that I soldered wrong! I was supposed to solder the - side of the bridge to ground, but I soldered one of the 5V inputs to ground in stead... Got it fixed now.

Tommy

[dogears]

Here are my settings. Take 'em for what they are worth but I find these get me closest to the tones most talk about.

Input Gain at 1-2 oclock
Rock on
Treble (250k lin) at 10 oclock
Mid (250k aud) at 2 oclock
Bass (500k aud) at 2 oclock

Keep in mind that Dumbel used 30% taper and mine are no more than 20%

The internal gain trimmer is set about 1/2

The OD drive is at 10 oclock to noon
The OD level is at 10 oclock to noon depending on balance to cleans

Presence on 10-11oclock

My stack is Skyline with .01midcap The mids need to be up at least to 1-2oclock when using the .01 cap. Unless you have a 30% taper 250k and then 11-12 oclock is OK.

[jaysg]

Scott, that's a lot of bass from my limited experience. Are those tone settings an average between your Fuchs and Glaswerks HRM? Is the Fuchs HRM?

[dogears]

Not really. With the .01 midcap and the .001 on the audio taper bass pot, my ears say the tone is best up past noon..... The .001 cap has an effect on the highs and running the bass up at 1 to 2 oclock seems to yield the best results. Remember, the audio taper pots of today can be as low as 15% or so. Dumble used 30%. Big difference.

Scott, that's a lot of bass from my limited experience. Are those tone settings an average between your Fuchs and Glaswerks HRM? Is the Fuchs HRM?

[ayan]

If you're talking about the drive, I find that this control running too high really makes the amp get nasty. It's best to try to drive both OD stages at about the same distortion level. If you look on a scope you'll see that OD1 distorts only the top half of the sine wave, then inverts the signal, OD2 then distorts the top half of the sine again. Since the signal is inverted you now have both sides overdriven.


JMO

Justa note: what you see on a scope is the way in which tube amps can achieve preamp overdrive musically. At some point, usually on the order of a volt or so, the input signal at the grid becomes too large and the grid voltage exceeds that of the cathode. At that point the tube loses its bias and ceases to conduct, and you see the clipping at the top of the input. For the bottom half of the input signal to be clipped as well, you'd have to hit the power supply rails and it wouldn't be a very musical overdrive IMHO.

Cheers,

Gil

[ayan]

Not really. With the .01 midcap and the .001 on the audio taper bass pot, my ears say the tone is best up past noon..... The .001 cap has an effect on the highs and running the bass up at 1 to 2 oclock seems to yield the best results. Remember, the audio taper pots of today can be as low as 15% or so. Dumble used 30%. Big difference.

Some observations on the Dumble: the older amps that were later Skylined had a combination of pots... The old pots were CTS and probably had the larger taper. I personally never measured those pots myself, but it would make sense that they be 30% since it's what was available at the time the amps were built in the 70s and early 80s. Also, note that HAD only used the pot values that Fender used in their amps during those times... the 100KB pots were used for the reverb by Fender and HAD put them to work in the middle, level and ratio controls. When moddying these amps HAD removed the old 250KA bass pot and put it in the middle position, and installed a brand new 500KA ALPHA pot w/.001uF cap on the bass position, with its 15% or so taper.

In the 90s amps, HAD used ALPHA pots for the bass (500KA), treble (250KB) and presence (2KB) controls, but used NOS CTS 1 MA and 250KA for the volume, middle, OD in and masters. The 250KA NOS pots he used were definitely NOT 30% taper; they were a batch of CTSs that tended to measure on the shy side (as low as 230K, and pretty consistently at that) and had strictly a 10% taper (lower than ALPHA's). These facts could be easily measured on the Middle control of the new amps, which have one unused lug; the codes on the middle and OD in were identical. The volume and masters were also CTS and did NOT behave like they were 30% taper as per my experience, but it would be impossible to measure those pots in circuit inayway, since they are wired as voltage dividers. Just by chance I believe I bought the remaining stock of those 250KA CTS pots, as well as the Amphenol AC receptacles, in 1999 at Apex Electronics when my partners in crime and I built our first clones.

Gil

[dogears]

90's amps use PAB in OD mode so the pot taper on the stack is moot. The older 80s amps with the Skyline stack had 30% taper. I had one measured.