Here's the schematic for the iteration presented in reply #24. I plugged the output straight into the high-impedance input of a tube amp. The cable's capacitance is 530 pF according to my DMM.

Quote from: RookieRecurve on June 25, 2024, 12:54:31 AMHopefully this isn't a zombie post.  You said you burnt up components using a laptop charger.  Was it too much voltage, or was it an issue with current?

Regarding the excess gain from the 1-8 jumper, what cap did you use?  I might dabble with this option once I get my kit, and put it together.

Most laptop chargers are 19v or 20v, either is way too much for this kit.  Max voltage is 16v.  Recommended voltages depend on what the speaker load is.

4 ohm : 6-9v DC
8 ohm : 6-12v DC
16 ohm : 6-16v DC


This yields this power output:

4 ohms = Max 0.35w (clean 0.25w) @ 6v supply, Min 0.35w @ 6v
8 ohms = Max 0.85w (clean 0.5w) @ 12v supply, Min 0.3w @ 6v
16 ohms = Max 1.6w (clean 1.2w) @ 16v supply, Min 0.2w @ 6v

Last month Boss released the new Gen 3 version of the ever-popular Katana amp series.  Consisting of general model updates, this seems like a decent amp still but nothing to toss your old Gen 2 model out for.

https://www.gearnews.com/boss-katana-gen-3-amp-series-enhanced-tube-logic-tone/

Hopefully this isn't a zombie post.  You said you burnt up components using a laptop charger.  Was it too much voltage, or was it an issue with current?

Regarding the excess gain from the 1-8 jumper, what cap did you use?  I might dabble with this option once I get my kit, and put it together.

Great to hear you fixed it. Good work G1 
Phil.

I ended up running to my electronics store (yay big city living), picking up a pack of 2.7k 1/2 watt resistors, and getting them into the amp.  It works like a champ now!  Thank you so much for the help and direction.

No problem. I breadboarded it to see how it sounds and shared my findings for others to have a point of reference because I had trouble finding any. Maybe my recordings will not get lost over time.
NB: I plugged the output of the preamp directly into the effects loop return of my DIY tube amp for this recording. Later I ran it through a buffer (a bypassed Boss DS-1) and it sounds different than in the sound sample.
EDIT: Of course, I can post the schematic if anyone's interested.

I was on the road for a while, so today was my first opportunity to open up the amp and take a peak. What a mess. Some of the soldering looks like it's been done by a 5yr old. The tube sockets are mounted on stilts.
Anyway, visual inspection didn't really bring any results. I took a few measurements and these put the biasing VR on the suspect list. I can't get a steady reading from it. There's also a crack in the PCB near the VR, although I don't see an immediate correlation there.
All 9-pin sockets feel a bit loose, but I suppose that's just wiggle room.
Respect for those in this thread who opened this soab and lived to tell the tale.

Quote from: Miyagi_83 on June 12, 2024, 04:57:39 AMI added another gain stage and tweaked it again. Here's how it sounds now

https://m.soundcloud.com/user-996907905/joe_davisson_preamp_modded_bc3

EDIT: Again, I'd like to apologize for the sloppy playing.

Sounds great!  Thanks for sharing!

Yes, they would likely be 1/2 watt resistors.
It's a bit odd they are using 5 band color code (usually precision) resistors.  With a green band in there it would be 2570 ohms.  I would have expected regular 4 band color code with red-violet-red and gold for tolerance.