Another PV C30 mod

[tubeswell]

Well after months of saying I'll get around to it, yesterday I pulled it apart for the zillionth time (bored inside with the rain outside) and re-did the pre-amp with Soldano SLO values for the first three stages. I also took all the presence and resonace and MV mods out of it. (Makes it easier to maintain). I don't really care about getting a 'fender' sound out of it anymore (since I've built several fender clones and have that sound elsewhere) - so I thought I'd rip the guts out of it and start afresh.

I prefer the OD channel sound this way. The clean isn't to bad either.

So now it has SLO100ish preamp, Blue Guitar tone stack, and a couplof ot minor tweeks elsewhere

If anyone wants the details, I'll post a schematic and a sound clip (when I get around to it).

[Steve A.]

Well after months of saying I'll get around to it, yesterday I pulled it apart for the zillionth time (bored inside with the rain outside) and re-did the pre-amp with Soldano SLO values for the first three stages. I also took all the presence and resonace and MV mods out of it. (Makes it easier to maintain). I don't really care about getting a 'fender' sound out of it anymore (since I've built several fender clones and have that sound elsewhere) - so I thought I'd rip the guts out of it and start afresh.

I prefer the OD channel sound this way. The clean isn't to bad either.

So now it has SLO100ish preamp, Blue Guitar tone stack, and a couple of minor tweeks elsewhere

If anyone wants the details, I'll post a schematic and a sound clip (when I get around to it).

Post away! I ended up removing a lot of the extra controls (like resonance and presence) on my Classic 30 since all of those flying leads made it such a hassle to pull the circuit boards out... I always found the pre-MV to be very useful to set the room volume so I did leave that one in.

And I finally did come to terms with the Classic 30 Clean Channel, which has its own charm even though it is quite unlike a Fender Blackface amp.

And heaven help me- I just bought a brand new Peavey Delta Blues 115 because I thought it was the best sounding amp in the store...

Steve Ahola

P.S. The half dozen or so brave souls who have tried the "Tweed Bassman" mod have generally been very impressed with the results. I don't think that any other amp has quite the same architecture as the OD channel. Gain stage => DC coupled pair/cathode follower => gain stage => Marshall style tone stack fed from anode... and then on to the predriver and cathodyne PI. Having that extra gain stage between the DC coupled pair and the tone stack gives it a really nice crunchiness! (I always wanted to recreate that circuitry in a handwired chassis, with perhaps a LTP PI instead of the predriver and cathodyne PI. Or maybe with the predriver feeding the LTP... and with 6L6 or 6V6 output tubes.)

[tubeswell]

Yep I finally got fed up with the extra leads and cables too

A new PV DB aye? - A nice fresh clean set of boards to mod with - Hmmm :-)

I liked something about the 'tweed bassman' CF mod when I got the cathode resistor on the driver to 820R (I think I had the plate resistor at 150k as well) and the cathode resistor on the follower to (was it?) 56k (- can't remember). It seemed to have a 60's primitive grunge on the power chords, but I couldn't get the level (VR3) pot right to my liking after several attempts at messing around with it. It either would jump up way too fast, or it wouldn't cut the vol completely (or both?). Ah well, it was a valuable and productive lesson in custom pot tapering.

The SLO100 values are much simpler to adapt to the C30 and the result is quite okay. There's only three things you have to solder on the back of the lower board besides changing a heap of other caps and resistors around (I must get to drawing up that schematic)

[tubeswell]

Heres that schem and my notes

The values through the OD channel (except for the 22pF across the input to ground, and the 1M grid load resistor at R9, both of which I forgot to take out after my last lot of modding, and which I might yet dump since these aren't in the SLO preamp, but it sounds okay with them in, so I might just leave it for now - jeez wayne) are the SLO preamp values up to VR3.

Basically I:

Dumped R6, C8 (was already gone from previous modding)
Upped R4 to 220k
Put 1uF/1k8 at cathode of V1A
New C3 (.02uF - orange drop)
New C4 (.002uF - orange drop, bypassed with 470k)
Bypassed VR2 input to wiper with .001uF (mallory 150)
Dumped C7 (was already gone from previous mod) but left 1M from previous mod at R9 (which as I said, still might go)
Inserted 470k stopper at grid pin of V2A
Dropped R2 to 100k
Put 1uF/1k8 at cathode of V2A
Changed C2 to .02uF - orange drop
Dumped C1
Put R5 back to 470k (was changed in previous mod)
Upped R11 to 1M
Bypassed R3 with .001uF (mallory 150)
put 39k at cathode of V2B (unbypassed i.e. no C15)
Swapped C5 and R7 around and put a .02uF orange drop where R5 used to be and a 220k where C5 used to be (but I might dump this resistor, cos I'm not sure whether its necessary anymore)
Dumped R13 and C16 (already dumped in previous mod)

I put supply resistors R59 and R60 back to stock 10k

As I mentioned previously, I took out previous MV in front of V3A, and the presence and resonance controls, at the cathode of V3A, and put back the stock configuration, but left R56 changed at 330k

I still have the Ahola tone stack in there, (that is a keeper)

I REALLY like the sound of the OD channel now, good sustain and it doesn't sound like a buzzing insect anymore - its a bit hissy, but I'll leave that for now (I've given up on trying to make it into a blues amp), and I don't really care that it hasn't got that full round fendery sound in the clean channel anymore. (Who needs all these Bl**dy channels anyhow?) Anyway I took it to a jam last nite and really enjoyed playing it again after 10 months of hiatus, but its probably going to sit in the cupboard for another year while I enjoy my tweedy-build thangs.

[Steve A.]

A new PV DB aye? - A nice fresh clean set of boards to mod with - Hmmm :-)

It must be that old timer's disease I keep hearing about because I think that the DB 115 sounds great right out of the box! That 15 inch speaker gives it a really full sound from the clean channel. I thought that the OD channel worked better than the stock OD channel on my Classic 30: I could turn the Pre control down to 3 or 4 without having the sound turn into mud with no definition.

I was *sure* that they had revised the circuit but Enzo says it has been the same circuit since Day One back in 1995... So if it isn't the circuit that has changed I think that it must be the JJ tubes that they are using these days (instead of the Sovteks that were in my circa 1995 Classic 30).

The new Delta Blues and Classic 30 amps come with a tube shield which on one hand is great in protecting the tubes, but on the other hand it prevents you from adding extra switches and pots on the bottom of the chassis. So I might just keep things simple and redo the tone stack and boost circuit, and tone down the OD channel a little bit. And probably add a bias adjustment pot...

It seemed to have a 60's primitive grunge on the power chords, but I couldn't get the level (VR3) pot right to my liking after several attempts at messing around with it. It either would jump up way too fast, or it wouldn't cut the vol completely (or both?). Ah well, it was a valuable and productive lesson in custom pot tapering.

Well, I did the Tweed Bassman mod on my Classic 50 amp, which has a master volume control so I didn't have to keep fiddling with the Post gain control (as you would in a Classic 30 that does not have a master volume).

[Steve A.]

Hey, thanks!

Your report of rewiring the preamp to SLO values inspired me to do the same to my #3 now-discontinued Crate V18-112, and the results are pretty amazing. Plenty of distortion- as smooth as you like it- and it cleans up very nicely by turning down the controls on your guitar. I also did the same to my Crate V-33H head, with similar results- only that one has channel switching and a few other switches- plus a SLO-inspired Clean/Crunch switch for the Clean channel.

So thanks a million!

Steve Ahola

[tubeswell]

You're welcome Steve.