Tone controls don't do enough

[Guitarist]

I just recapped my Peavey VTM 60 and it sounds really amazing. I really beefed up the power supply too. I've leaned the cap on the first two stages and I still get loads of low end. Any more and they'd have to be .0022 & .0047. The bass has to go down to 3 and any more is WOOLY. At one point all the tone controls were nearly off. So go from 47K to 33K or upwards to 100K? Can the tone cap go .01 for bass and .0067 for mids or is this silly? I'm on a mac so no Duncan Calc.

Effect Loop in is nice and round, rather full frequency's. Presence works well.
Pair of KT66 in.
Sure is quiet noise and hum wise.
Went with 12AT7 PI values: 33k plate resistors & 120 ohm cathode resistor. This sounds awesome.
Lar-Mar PPinvMV - highly recommended.

Should I increase the feedback a tad?

One strange thing: the OT never gets even mildly warm - even when wailing at max for an hour. The PT sure does though. Any ideas?
I was hoping for some sweet mids with this OT but may have to replace it.

[Chuck H]

Can the tone cap go .01 for bass and .0067 for mids or is this silly?

Not silly. But you do still have generous low mids going through that stage. And subsequently the next depending on the coupling cap. Try a ,01 for bass and a .01 for mids. That will cut a little bit more low mids. The more typical values of .022 bass and .022 mid will cut MORE low mids than the smaller caps you're using. This is significant because a lot of that "wooly" sound is in the low mids. You may also like an increase in the treble cap size. If you haven't already tried it, increase the treble cap (from what, 250p?) to 390p or 470p. The added low treb and upper mids improve the OD and help define the botom end.

Lar-Mar PPinvMV - highly recommended.

AAhhhh... Here's where the tone controls lose it. You're clipping the PI and that means any EQ effect prior to the PI gets lost. The tone controls become more like "distortion character" controls. Unless you move your stack AHEAD of the clipping they will only be effective for clean tones. For overdrive they will work more like Bass=flub, mid=smooth, treble=bite.

Should I increase the feedback a tad?

I wouldn't. Since you're clipping the PI and NOT the power tubes with the PPMV you do have a lower ratio of NFB using the master volume though. But increasing the FB will change the clean tones and OD when the master is up high. For the worse IMHE.

One strange thing: the OT never gets even mildly warm - even when wailing at max for an hour. The PT sure does though. Any ideas?

Well, the OT not getting too hot doesn't surprise me. You're using a master volume. The amp isn't putting out the OT's rated wattage. The PT getting hot may be due to the filament winding having to supply over an amp of extra current for the KT66's. Check the filament voltage. If it's not low, and the PT isn't too hot to hold your finger on, I'd just play it and hope it doesn't blow up.

I was hoping for some sweet mids with this OT but may have to replace it.

Using the PPMV you're not really hearing the OT much. At least not how it would sound if pushed. IMHE a saturating OT is only a good tone for a few vintage models anyway (but that's MHO). If you're after a more saturated sound you would need a smaller OT. Then you couldn't turn the amp up without blowing the OT?!?

For sweeter mids, try this: Go back to .022 bass and .022 mid caps in the tone stack. Make the slope resistor 100k or even 150k. If you can get it, change the bass pot to a 250k (10% or 15% taper if possible). Then increase the treble cap. If it's 250p go up to 390p. If it's 330p go up to 470p. If it's 470p go up to 680p. You get the idea.

Remember, you're voicing the distortion, not the EQ now. EQ has been left to the OT and speakers. Even an EQ in the effects loop won't be very effective when the amp is clipping.

JM2C

[Guitarist]

Hey, really appreciate the insights Chuck, thank you. It's all getting clearer.
I like low mids but not 40Hz et al. When I use a graphic EQ in my amp rack rig, I actually boost 100 to 400 Hz. I haven't patched it into the VTM yet though.
Treble cap is only 220 pF ceramic (not a fan of silver mica here).

I shall put a trimpot into the slope resistor position. Then try those bigger pF treble caps say .001 or .0022. This nets another idea — if I were to add a 680+pf and a pot to ground later, then this adds a band of eq tone shaping. With that tone stack cap helping the upper mids sail though, which is another boost preference on my rack eq.

I was using the amp cranked and still the OT was still cool as a cucumber. I didn't know Peavey had internal liquid cooling.

I 've also got one CF bootstrapped ala Valve Wizard, which kicks aßß. (bottom:The Valve Wizard) I'd love to get a reverse 12dw7 (ECC823) in this amp. Lately I'm into optimizing/biasing a circuit for the right tube and am moving towards 12at7 and 12ay7 tone in certain stages—such a thick-silvery tone. But don't get me wrong I love huge distortion and crunch. Still love the full spectrum from Ampeg clean to VHT lava.

[Chuck H]

I like low mids but not 40Hz et al. When I use a graphic EQ in my amp rack rig, I actually boost 100 to 400 Hz. I haven't patched it into the VTM yet though.

This is still boosting low mids POST clipping. Too much low mid getting clipped can become muddy and undefined.

My MO for EQing pre distortion is actually to cut low mids somewhat. The amp doesn't really have a tone stack anymore once it's overdriven. And if you think about it, any amp with the tone stack omitted has plenty of low mid in the final tone. I try to get the lows up just enough to NOT get mushy, then trim the low mids to about the same level and then boost treble frequencies. With the treble cap sized to get into the upper mids a little. This has worked for me. Once you allow as much lows through the circuit as possible without getting mushy, that's all the lows the amp will make anyway. Remember that there is virtually no EQ now. If the PI and power tubes are clipping the lows then thats all there is. No point in trying to make more, you won't get it. You'll just get more mush.

Treble cap is only 220 pF ceramic (not a fan of silver mica here).

Then try those bigger pF treble caps say .001 or .0022. This nets another idea — if I were to add a 680+pf and a pot to ground later, then this adds a band of eq tone shaping.

That's sort of like the mid boost switch in the SF Fender amps. It's a good circuit IMHO. It's a good idea. Maybe a 250k pot with an "infinity" scrape in the track.

If you're using a 220pf treble cap now, increasing to 1000pf will be a VERY dramatic increase. Changing the entire character of the amp. I would start with 390pf and not go over 680pf. In "my" personal amp (that is overdrivenpost EQ) I have a 390pf. Smaller was too thin and over 680pf made the treble control too much of a mid control.

[Guitarist]

Just hit this amp again. The trick of adding a trimpot for the slope resistor worked great. A 470K worked well and is set around 250K. Added a 470k resistor in // to the bass pot too= smoother sweep. The 470pF treble cap is a bit weird now, ok with low settings working but not anything higher. This then goes through a 470kΩ R towards the effects loop.

The über power supply caps are be making things incredibly bassy, and I even had to wean the first stage overdrive output cap to a meagre 820pF. OT is still cool as a cucumber but the PT is sure warm.