New 12000 build making weird noise on bottom end

mightymike · Post by **mightymike** » Tue Nov 21, 2006 11:58 am

It has an original Dagnal 67 Self Lead 1.5 OT, and LAydown 69 PT

43v on pin 5s

3v on all my heaters
PT is at frigin 499 plates

biased to about 33mA
I'd have to change the bias range resistor to go lower.

I initially thought I blew a speaker, because the bottom end falls apart unless you have the amp heavily atenuated at bedroom level. The sound is like like motor boating through a speaker with a hole in it. Right now it sounds like ass compared to my aluminum 12000.

going over my work.
and wondering if higher rated CC 100ks on v1 and v2 are causing this.
They're all in the 114 to 117 range.

5150LoveEddie was saying something about not going overboard on the off values with 100ks, so that's where I'll start I guess. Is this what you experienced?

45auto · Post by **45auto** » Tue Nov 21, 2006 3:53 pm

surely not the tolerances causing it to get that bad? do you have a sample yet?

mightymike · Post by **mightymike** » Wed Nov 22, 2006 3:28 am

No sample yet. I'm noit set to record yet

Chop sticks are telling me the noise is somewhere on ch1. Farting after the note sound too.
and now it's lost most of it volume, so somehting probaby fried.
Then if I lift the amp up something moved and the soubnd came back.
Like a loose connection.

So I'm gonna take off the tone controls, filp over the board, and compare it to my working 12000.

If it wasn't for this noise, it's not a bad sounding amp, but that presense ciurcuit and V3 cap has got to go, and that plate voltage has to come way down. Even if it means changing PTs.

robert · Post by **robert** » Wed Nov 22, 2006 6:37 am

Hi Mike,

maybe it's only a bad/flubby contact in the V1 valve socket or a cold soldering point?

Regards

Robert

45auto · Post by **45auto** » Mon Nov 27, 2006 1:42 pm

MM were you ever able to isolate the prob? I'd love to compare my 12k to some others. It sounds decent, but I still wonder if the tone isn't kind of colored in some odd respects? I mean we're not talking hi-fi here, but you know what I mean.