My sweet new 50watt

[thetasigma]

*Warning, long post ahead*
**Updated with new pictures**
***I apologize ahead for my gushing, but I'm extremely happy with this new amp!***

This was my third and favorite build so far (the first being a JTM45, the second a 12 series). The cool thing about this amp is it's been kind of piecemeal, but had turned out great. I had an extra Heyboer JTM45 PT and a smallbox head lying around doing nothing, so I thought "Hey, why don't I build a JTM-50, so in a way, I did. Luckily I all I really needed was an OT and a circuit board. I bought one Brian Wallace's 784-128, some more AB CC resistors, PEC Pots, and chassis hardware from George, and then for the coup de grace, some Premium Sozo caps from John.

Any way, before you get bored with this check out the pictures down below

So anyway here's the specs:
The power section is wired like a JTM45, but in George's steel chassis
Mains, Screens, Preamp, and PI filtering is 32uf
Split cathode on V1 (220uf/820 and .68uf/820)
.68uf boost cap on V2 A
.0022uf bypass cap
.022uf Phase inverter caps
100pf PI bypass cap
250pf bright cap
.1uf Presence cap
47k NFB resistor on the 8ohm tap
33k/500pf tone stack
470k mixers w/560pf
Split/Shared Cathode switch
Rockstah/Larry PPIMV
Homebuilt SS rectifier
Mullard ecc83 in v1 with JJ's in v2 and v3. JJ EL-34L, but once the amp has broken fully in I'm going to try out my Siemens RFTs in this bad boy.

So, it's an amalgam early and 1970 superlead circuit with a JTM power section and lower filtering. I was kind of worried that it would sound overly harsh, especially before the caps broke in, but this amp is not only my favorite build, but probably my favorite amp to play right now! I was going to just do a JTM50, but thought I'd try the lead circuit, and If I get tired of it, I'll swap some components, throw in a GZ34 and then have a truer JTM50. Also I can't say enough about the Premium Sozos...they're just f%$@ing great! I used sozos in my first two builds, but this is the first time I've used John's premium line. and...wow...is about all I can say! They're that good, so buy them! They may be more expensive, but they're worth it. The sound from this amp is almost tonal Nirvana for me!

So thanks again George for providing your time, your store, and this forum for all of us! And again, thanks John for your excellent caps!

[toner]

Nice job! My amp envy continues...

Is the 2w resistor by the bias caps burnt? The color looks weird.

[mwm523]

Nice job! My amp envy continues...

Is the 2w resistor by the bias caps burnt? The color looks weird.

Sure looks burnt... And where's your bias resistor?

[thetasigma]

Sure looks burnt... And where's your bias resistor?

Yep, it was. Accidentally posted the older pictures, I've updated them now. That'll be the last time I wire the buss wires under the board .
Turned that poor resistor into a light bulb. Wires are all fixed now, an 8.2k CC is in place now. Have to troubleshoot some squeal now, though it sounds damn good. Since the cab is shielded it's probably some lead dress or preamp tube issues.

I use a weber bias rite, so for the bias resistor I have a 100k linear pot with a 27k resistor to ground top mounted for doing bias adjustments. Makes it so I don't have to flip the amp over to do bias tweaks.

[thetasigma]

Fixed some lead dress, rerouted NFB/presence wire, and replaced a microphonic 12ax7 and that seemed to quiet the squeal nicely.

I installed my Siemens RFTs and holy sh%@ what a difference! I thought the NOS tube craze was mostly hype, but I guess I was wrong. The amp just seems to have more dynamics, hard to explain really, but it just plays better and just feels way more responsive. Of course that's what most people say about old tubes, but I can now agree!

[jerrydyer]

I dig anything different and that one is pretty cool. kinda like the offset panel ones material.