bottlehead crack with channel oddity [resolved]

[mastershake]

so first ill start by saying i have now built over a dozen crack's for family and friends and i build / repair guitar amps on the side. not new to tubes. so this newest crack w/ speedball is odd. one channel is thinner and has less low end and maybe a tadddddd less overall volume but its slight. its more the difference is the overall sound sig. swapped cables changed channels with said cables, many different headphones, a number of sources etc. i have literally tore it down fully to nothing and got new cables and rewired it. also pulled all components off including speedball boards and tested / resoldered each one part at a time. the only thing left is the tubes (at the moment i dont have anything i can swap to that would work well at the moment)

checked ALL joints tested voltage there is a SLIGHT difference in the 2 channels but i mean its not usually enough to change the sound like that. the only thing i didnt swap besides the normal parts i.e. switch, plug receptacle, trans, are the caps because they test fine out of the build. but i may do that next to be sure. any thoughts? could it be the pot causing it? this is the one that comes in the build for now ill upgrade it later for my friend when he is ready. i know these can have an imbalance sometimes with the stock one. never have had a single issue building these for people and never came across this issue. its simply like one side sounds like it just has less overall low end and is a bit thinner and harsher at the same volume levels as the other side??

thoughts? also triple checked for any cold solder joints, none i can find.

[Doc B.]

Try different tubes. Look for voltage differences between channels.

[mastershake]

yeah thats my next step. i ordered a few to test out. im used to guitar tube amps so i know tubes but we are trying to create gain and distortion where this is a bit different lol the channels are not like night and day from each other but i can def pick up some differences (i have a LOT of headphones and amps) i even grabbed my personal crack / speedball and tested the same headphones / source and i dont hear this. the channels as i said are super close volume wise just a bit off which does not change with volume that difference is pretty steady all the way up. just they overall have different tone to them. its odd for sure. i had hoped maybe someone else exp this before so i thought id ask. i might swap the caps out also since i have some nice audio ones sitting here i use in amps. ill reassemble it again with the new caps (just because) and test it later today voltage wise, again.

[Paul Birkeland]

When I have heard that, I have generally found a ground connection that wasn't well soldered on the channel that didn't sound right.  Still, trying a different set of tubes isn't a bad idea.  Otherwise, I would be taking needlenose pliers and tugging gently on every black wire in the amp to see if any are loose in their joints.

[mastershake]

every connection is super tight, i have 25+ years soldering exp. i really dont think i have any bad joints. i used to work at ibm basically soldering all day long. i also do smd stuff here and have microscopes to look at the joints, hot air, etc etc. i even went through and FULLY stripped it down to nothing and resoldered everything using new diodes and resistors on the speedball boards just in case even though the stock ones tested fine. i had them here so why not. im VERY ocd and meticulous when soldering making sure everything is as perfect as i can make it even things like the spacing of the diodes, wire length, the way they cross etc. this is why i was a bit stumped i just dont have any compatible 12au7 tubes here. i even make a small pcb to hold the led's for the tube socket to be sure they dont break in the future with my crack builds. this is prob my 15th (ballpark) crack ive built.

[mastershake]

okay once again put it back together

test voltages small speedball board:

OA- 74.8 (75.1 when first fired up it seems to drop a bit after a few minutes)
IA- 177.0V
B-A/B- 0V
IB- 177.0V
OB- 75.4 (this side does not change after it heats up at all)

RESISTORS TEST:
147.4
151.0

large board:
OA- 102.4V
OB- 101.1V
G- 0V
B+- 174

RESISTORS TEST:
46.58
46.59

checked EVERY ground, checked every pin on the tube sockets to follow voltage and grounds, tested diodes, checked transistors for shorts, checked tip-50's,

question which voltage is the trans wired for in the "completed picture of speedball upgrade" in the instructions?

i did now notice a SLIGHT bleed over to louder channel when using the quieter channel hmmmm if i swap the rca to the other input there is not bleed to the other channel.

[borism]

MS - if you have your 'personal crack' at hand have you tried swapping your tubes into the new build just to see if it makes a difference?

[mastershake]

these are my tubes. he didnt give me his tubes with the kit

[Paul Birkeland]

i did now notice a SLIGHT bleed over to louder channel when using the quieter channel hmmmm if i swap the rca to the other input there is not bleed to the other channel.

Can you post some photos of your RCA jacks and pot wiring?

[mastershake]

it was a bad pot. i pulled one out of another project i was working on it was basically the same stock one it comes with. and all is fine now. it was like i had to VERY slowly turn it JUST right to get both sides equal. it would hit these random spots where it would kick the one side lower and i have to turn back and forth to get it to go away. so even though it "tested" okay it had some weird issue. this was the original one that came with the kit he bought. he ordered a new one i had him get the Valab 23 Step one which should work really well. and we will put some better caps in when i do that just because of the issue i put it all back to stock for now so he can use it in the meantime. not a great pic but for the time being this is how it looks. we will rebuild it when the new parts get here. ill post some pics after that