2nd gen entrance question

[Luthierwnc]

Hi all,

I'm fiddling with a #40 variant and would like to hit the first half of the OD tube a little harder. It has the 1m2/33k voltage divider. At noon on both OD controls I'm at slightly less than parity with the clean on PAB.

Is there a quick and easy way to dial that in a little more? thanks, sh

[talbany]

Yeah..Lower the 1.2m resistor

Tony

[ToneMerc]

I'm curious as to what value of resistor that you have after V2b?

TM

[ElectronAvalanche]

Since I recently completed my 2nd generation hybrid:

I really think that the 1.2M is a good choice. You have three modes of OD if you make your FET switchable:

OD: crunchy with SC, mild OD with HBs
OD+PAB: Lead sound
OD+PAB+FET: über-Lead-Sound
OD+FET: nice as well

With the Drive at noon I have more gain than Clean+PAB.

IMHO the 2nd gen do really shine with the FET.

Cheers,

Electron

[Luthierwnc]

The FET is switchable. I like it. I had to try a couple different resistor values to get around 11v.

My first inclination is to drop in a 1m in place of the 1m2 and leave the 33k alone. It only needs just a little bit more. I'm in the very fine-tuning stage now.

This amp has dual masters so there is a 1m resistor after the cap going into a 1ma pot with a 180k resistor across it. There is a 2nd gen layout diagram on the forum and I think Gary posted one just like it about the same time.

Thanks, sh

[ToneMerc]

SH, I dropped that 1M to 560K and still kept the 180K to ground. I think it balances nicely. I orginally had it wired with the dual masters, but rewired it.

[talbany]

You might not notice that much difference volume in 1m2 to 1m in OD entrance..Lowering that resistor will increase gain so it will also change the tone of the OD (similar to increasing the OD trigger in later gen) so if you like the tone and breakup character of the 1m2 leave it..Not sure I understand?..So the OD controls don't balance out at noon, wont't they go higher..

Tony

[Luthierwnc]

Tony, it is more that I am used to using more modern builds with 12 o'clock on both the OD controls being about as loud as where I usually leave the clean master.

ToneMerc, I'll probably leave it as is until I tame the PAB a little. Those long, 1m 10-turn pots would fit nicely where the 1m2 resistor is so I might just season to taste later.

Thanks to both of you and good luck with your next builds, Skip

[talbany]

Tony, it is more that I am used to using more modern builds with 12 o'clock on both the OD controls being about as loud as where I usually leave the clean master.

That's because the OD entrance in the 2nd gen is a much lower gain network than the later 220k 100k trigger, but still a big part of the tone of the OD in the 2nd generation, so you have to make up for it on the other end..Sort of speak.. Probably why Dumble didn't see the need for an OD Master..

Tony

[ToneMerc]

Tony, it is more that I am used to using more modern builds with 12 o'clock on both the OD controls being about as loud as where I usually leave the clean master.

That's because the OD entrance in the 2nd gen is a much lower gain network than the later 220k 100k trigger, but still a big part of the tone of the OD in that generation..so you have to make up for it on the other end..Sort of speak..

Tony

Skip, Tony is dead on about the lower gain and what I did was try several high gain NOS RFT's and a Frenchie Mazda ECC83 in V1 just so I could hit V2 a bit hotter.

TM

[Luthierwnc]

It will just take some getting used to -- but the mojo is certainly there.

I'm looking forward to airing this out. The speaker on its way back from Orange County is an EV SRO-12. It needed a new cone and regaussing. Something tells me this is a marriage made in heaven.

Cheers, sh

[sonicmojo]

SH, I dropped that 1M to 560K and still kept the 180K to ground. I think it balances nicely. I orginally had it wired with the dual masters, but rewired it.

So along these lines, after some experimentation in my new 3G build with OD master additional, I tried a few options and I decided on a 180K instead of the 1M that TM mentions and left the 180K to ground also. I'm using standard JJ 12AX7s in V1 and V2. Now for me, noon to 2:00 works pretty well balancing with the clean channel, of course this depends a little on how everything is cranked up. Once things burn in a bit and I get it in a live situation, I may reassess, but it's good for now.

For my 50W without an OD master, I left as is. I feel it is nicely balanced already.

[markusw]

The FET is switchable. I like it. I had to try a couple different resistor values to get around 11v.

My first inclination is to drop in a 1m in place of the 1m2 and leave the 33k alone. It only needs just a little bit more. I'm in the very fine-tuning stage now.

This amp has dual masters so there is a 1m resistor after the cap going into a 1ma pot with a 180k resistor across it. There is a 2nd gen layout diagram on the forum and I think Gary posted one just like it about the same time.

Thanks, sh

Sorry, if this has been discussed before. Isn't the 180k wired from V2b plate cap to ground? Or did you add another 180k across the 1M pot?

Peace,

Markus

[Luthierwnc]

There is a 1m resistor after the last coupler. That goes to a 1 meg MV with a 180K in parallel. I've never seen a taper chart of a pot (linear or audio) with a resistor across it but parallel resistance to ground at 10 on the pot is about 150k. Half way up at a 30% taper is 117k or 22% so the combination seems to increase the taper. Course, that varies with the pot.

Here's the original schemo, sh

[markusw]

There is a 1m resistor after the last coupler. That goes to a 1 meg MV with a 180K in parallel. I've never seen a taper chart of a pot (linear or audio) with a resistor across it but parallel resistance to ground at 10 on the pot is about 150k. Half way up at a 30% taper is 117k or 22% so the combination seems to increase the taper. Course, that varies with the pot.

Here's the original schemo, sh

Thanks a lot!
Interesting, moving the 180k after the 1M will also shift the high-pass knee of the 10n V2b cap to lower frequencies (compared to the single master variant).

Peace,

Markus