Tone shaping the Overdrive section in a non-HRM

[heisthl]

In the OD section (V2) fiddling with snubber cap values, plate values, bypass cap values, seriesed entrance caps and bleeder caps at the exit are all great ways to adjust tone in a non-HRM overdrive section. Lets start a discussion on tweaking this part of the amplifier - failures and sucess stories.
I've developed a few good non-technical rules of thumb.
For the purpose of this post assume preamp Baseline is 220k/150k plates w/ 5uF bypass on V1 using a .05 uF coupler to the OD section (standard non-HRM values).
R.O.T. 1. If you use larger bypass caps or lower plates on V1 (or both) series in another .05 cap after the relay so the OD gets less bass. Adjust cap value to taste.
R.O.T. 2. If the overdrive sounds great but the overall tonality does not match the preamp i.e. noticeably less bass in OD mode or noticably more bass. Adjust the value of V2a coupling cap I've had good sucess witrh values all the way from .05 (makes OD bassier) to .002 (removes bass from OD tone).
R.O.T. 3. OD has top end fizz - use a circuit like Gil's at the level pot - I like .001 feeding 150k to ground.

Looking for more of these - anyone?

[ic-racer]

Increasing series resistance seems to tame high end buzz.
The 100k, 150k and the two grid stoppers 67k and 180k seemed to behave this way for me when values were increased. Got more buzzy with decreased values.

[massygt6]

thanks for the inputs!
What you suggest to slightly scoop the overall mid freqs of the amp?
I like my amp now, but I really want to scoop some mids and let some "air" in into the sound, clean and OD without loosing smoothness, any suggestion?
thanks!

[butwhatif]

Like many, I've experimented all of these non hrm values. What is the consensus if there is one on the input resistance feeding OD1 -from relay to trimmer, for a fat tone into an EVM12L ? And, are there any actual verified HAD examples of series caps for hi pass here ? I also like a .01 coming out of OD2 instead of a .005, better bottom to go with all the mid. -but it takes an input cap to keep it from getting muddy.

[heisthl]

thanks for the inputs!
What you suggest to slightly scoop the overall mid freqs of the amp?
I like my amp now, but I really want to scoop some mids and let some "air" in into the sound, clean and OD without loosing smoothness, any suggestion?
thanks!

If you have a standard values skyliner just change the 390pf to 330pf (which is no change at all when using mid boost). You may also have to put the mid cap at .02 or .047(strat) depending on guitar choice. If still not enough change the 500pf at v1b grid to 330pf. I would not recommend the last one because it hurts the OD tone.

[heisthl]

Like many, I've experimented all of these non hrm values. What is the consensus if there is one on the input resistance feeding OD1 -from relay to trimmer, for a fat tone into an EVM12L ? And, are there any actual verified HAD examples of series caps for hi pass here ? I also like a .01 coming out of OD2 instead of a .005, better bottom to go with all the mid. -but it takes an input cap to keep it from getting muddy.

The only reason to do this is if you've changed the preamp for a fatter clean tone (no longer "stock") but want to feed the OD section like it was still stock.

[massygt6]

thanks for the inputs!
What you suggest to slightly scoop the overall mid freqs of the amp?
I like my amp now, but I really want to scoop some mids and let some "air" in into the sound, clean and OD without loosing smoothness, any suggestion?
thanks!

If you have a standard values skyliner just change the 390pf to 330pf (which is no change at all when using mid boost). You may also have to put the mid cap at .02 or .047(strat) depending on guitar choice. If still not enough change the 500pf at v1b grid to 330pf. I would not recommend the last one because it hurts the OD tone.

thanks man, really precious

[ayan]

thanks for the inputs!
What you suggest to slightly scoop the overall mid freqs of the amp?
I like my amp now, but I really want to scoop some mids and let some "air" in into the sound, clean and OD without loosing smoothness, any suggestion?
thanks!

Give Henry's suggestions a try, they're all steps in the right direction. But the answer to your questions may be that the easiest way to do what you want would be to HRM the amp. With the PAB on, you will always get a very honky sound out of the non HRM configuration, especially in overrdrive mode. If you make chenges to the circuit such that you successfully scoop some of the mids without the PAB on, then when you turn the PAB on it would be like playing another amp. If that's something you would like, then it would be something to try. In my case, if I have an amp dialed in, I would like for the PAB to give me a little more of the same... so having a scooped voicing would not work for me.

Now, I don't know what kind of Middle pot you use in your amp. If you use a 100KL, change it to a 250KA and that will give you more of a scooped sound until the pot hits the 2 o'clock position or so. That and lowering the treble cap (stock is 390pF, in series with .0022uF for normal mode) is the way to go to scoop the tone.

Gil

[heisthl]

With the PAB on, you will always get a very honky sound out of the non HRM configuration, especially in overrdrive mode. If you make chenges to the circuit such that you successfully scoop some of the mids without the PAB on, then when you turn the PAB on it would be like playing another amp. If that's something you would like, then it would be something to try. In my case, if I have an amp dialed in, I would like for the PAB to give me a little more of the same... so having a scooped voicing would not work for me.

Gil

Ooops I forgot that part, if you want the scooped Blackface tone and still want a decent PAB connect the bass pot to the treble pot eliminating the PAB switch for that purpose but reuse the switch to lift the mid and bass pots 470k off ground (just tie their ground points together and ground them through the switch). Very nice way to get a fat boosted raw tone and works in both clean and OD modes. I've done a lot of these and it works great. It does make it sound like a different amp though, but in a solo voice type of way.

[massygt6]

thanks for the inputs!
What you suggest to slightly scoop the overall mid freqs of the amp?
I like my amp now, but I really want to scoop some mids and let some "air" in into the sound, clean and OD without loosing smoothness, any suggestion?
thanks!

Give Henry's suggestions a try, they're all steps in the right direction. But the answer to your questions may be that the easiest way to do what you want would be to HRM the amp. With the PAB on, you will always get a very honky sound out of the non HRM configuration, especially in overrdrive mode. If you make chenges to the circuit such that you successfully scoop some of the mids without the PAB on, then when you turn the PAB on it would be like playing another amp. If that's something you would like, then it would be something to try. In my case, if I have an amp dialed in, I would like for the PAB to give me a little more of the same... so having a scooped voicing would not work for me.

Now, I don't know what kind of Middle pot you use in your amp. If you use a 100KL, change it to a 250KA and that will give you more of a scooped sound until the pot hits the 2 o'clock position or so. That and lowering the treble cap (stock is 390pF, in series with .0022uF for normal mode) is the way to go to scoop the tone.

Gil

thanks Gil, I say that most of the time I use the OTS with the PAB OFF, I really like it this way, the pot is already a 250kA so a cap substitution is the next step to take.

[Fischerman]

Regarding ROT1...do you usually add a 4M7 in parallel with the added cap? I thought that was a mod that Gil always did to his non-HRMs...but I thought it was a .0047uF cap and a 4M7 resistor. IIRC I asked him and he said the resistor was just to prevent pops.

Regarding ROTs 1 and 2...IMLE the mods to the OD entrance tend to affect the OD tonality a bit more than the actual frequency response (eg - you can really clean up/dirty up the low end OD here while the actual frequency response doesn't change as much) where as mods to the V2b entrance tend to affect the frequency response more than the tonality of the OD. Mods in both areas affect both...but one tends to favor the OD tonality and the other tends to favor the frequency response. Hope that made sense.

Which goes back to Gil's OD entrance mod...there is a balancing act between 'smooth' and honky/nasally mids...try to get too smooth and it will get nasally/honky...go the other way too far and it might get too ratty/fuzzy. And IMLE; you might adjust the OD to what seems to sound good on it's own but then it isn't very 'compatible' with the clean (i.e. the two tones are just too different to smoothly transition between the two).

Just my limited experience.

[heisthl]

Regarding ROT1...do you usually add a 4M7 in parallel with the added cap? I thought that was a mod that Gil always did to his non-HRMs...but I thought it was a .0047uF cap and a 4M7 resistor. IIRC I asked him and he said the resistor was just to prevent pops.

I'm not talking about the "BluesMaster" r/c entrance style here This ROT is strictly to counter too much bass so the resistor would go to ground (10M works good) at the junction between the new cap and the relay.

Regarding ROTs 1 and 2...IMLE the mods to the OD entrance tend to affect the OD tonality a bit more than the actual frequency response (eg - you can really clean up/dirty up the low end OD here while the actual frequency response doesn't change as much) where as mods to the V2b entrance tend to affect the frequency response more than the tonality of the OD. Mods in both areas affect both...but one tends to favor the OD tonality and the other tends to favor the frequency response. Hope that made sense.

My thinking here is to correct what you can at the entrance to compensate for what changes you might have done in the preamp and then if the overall tonality does not match the clean tone in a way that suits you, move on to the other side of V2A, but try not to upset the "distortion" balance between the halves of V2 which does change the response.

Which goes back to Gil's OD entrance mod...there is a balancing act between 'smooth' and honky/nasally mids...try to get too smooth and it will get nasally/honky...go the other way too far and it might get too ratty/fuzzy. And IMLE; you might adjust the OD to what seems to sound good on it's own but then it isn't very 'compatible' with the clean (i.e. the two tones are just too different to smoothly transition between the two).

Just my limited experience.

Yeah, there is a reason we love this OD tone and we don't want to get so far off the reservation with tweakings that the magic is lost.

[danotron]

R.O.T. 3. OD has top end fizz - use a circuit like Gil's at the level pot - I like .001 feeding 150k to ground.

Going into the pot or out of the pot?

[danotron]

R.O.T. 3. OD has top end fizz - use a circuit like Gil's at the level pot - I like .001 feeding 150k to ground.

Going into the pot or out of the pot?

[heisthl]

into the pot