So I was tapping and poking around with a pencil and I've found some microphonic issues after the clean tonestack.
The wire that goes from the treble wiper to the preamp volume pot is very noisy when I tap on it. The coax cable that runs from the volume output to the grid resistor of CL2 also is noisy but not as much as the other one.
I tapped on all of the caps around it and the .002 midboost cap makes noise when tapped, but not the 390p on the switch. But pots aren't scratchy sounding at all. Also, the .002 only makes noise when in PAB mode.
I think, that your "2-nd floor" is on the wrong place and interacts via crosstalk with the clean area on the 1-st floor. Might it be, that you forgot a cable, which insures, that the OD input is set to ground in Clean mode
Lift up the 2-nd floor and push a grounded, but w/ foil insulated metal plane between both floors - and I bet your amp is sweet after it!
Watching the 3-th photo again I assume, that rather the OD's input is via crosstalk coupled w/ the OD's output - the 2-nd tone stack directly above the input trimmer. Input and output of the OD area are 360° out of phase, means 'in phase again', but w/ one cycle difference.
That's what's necessary, to build an oscillator
Push a metal plane in between, as I've mentioned above!
Question: When an amp sounds that good do you call it finished never to be tweaked again? Or are you going to put the BM PI in there? Switch to EL-34s? etc etc
Question: When an amp sounds that good do you call it finished never to be tweaked again? Or are you going to put the BM PI in there? Switch to EL-34s? etc etc
Cool clip Scott! I love it when these amps have that almost "do do" vowel sound in the low mids when played with light pick attack. Gives an almost living human quality to their "voice". Kind of a "chesty" tone. Like that clip a bunch.
stelligan wrote:I love it when these amps have that almost "do do" vowel sound in the low mids when played with light pick attack.
Mine sounds like the other kind of "doo doo"
I think I've found THE problem in the second clean stage. Everything that is connected to the CL2 grid makes noise when I tap it. I've replaced all the caps connected before it and still no luck. swapped tubes with the same result.
when I tap on the tube socket itself (especialy the problematic pin) I get a loud low frequency rumble.
can tube sockets be bad like this? Would this also be the cause of the harsh ice-pick highs I'm hearing with the OD engaged?
SED winged C 6L6. 2 of them. The tranny is a Marshall 50 watter though. 3.4K primary with M27 iron and Drake winding. I did replace the 1K screen resistors with 470 ohm for the 6L6 tubes. I am getting an M6 Heyboer Fender 50 watt tranny tomorrow. 4K primary and Fender style interleaves. I bet it is much better still.......
That was a Celestion G1265 and SM57 mic.....
Thanks!
novosibir wrote:Awesome playing and sound, Scott! My congrats!
yeahyeah wrote:Mine sounds like the other kind of "doo doo"
Sorry to lose site of the topic. And I am laughing at your comment, not your plight. I only wish I could be of some help. I just suffered through a chop sticking, board pulling nightmare that I had to give up on and send to a fellow forumite. I am a total noob. Here's hoping the thread gets on track and you get your amp do do-ing instead of doo doo-ing!
Yeah - this may sound silly, but I have found some wires much more microphonic than others. Is the socket microphonic, or the wire connected to it the problem? Do you have the local FB loop in the CL2 stage? I didn't look at the photo before I started typing.....
Just trying to help......
D
Remove the tubes, pack it in a box and send it to me. I'm doing a couple of builds for an upcoming Blues Cruise Ocober 13th so Worse case you won't get it back until end of October. More likely I'll return it the same week I get it.
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