pictures of my new amp build

[yunger]

fyi, i found some old tubes at a shop down the street and plugged in a 12au7 as the power tube. WOW!
the 12at7 sounded ok but compared to the 12au7, it sounded like an angry teenager armed with a bunch of distortion pedals.
12au7 wins.
in the preamp i tried a telefunken and a sylvania 12ax7 in place of the current production tung-sol. i didn't hear much difference. if it's there, it's subtle.

[Chuck H]

it sounded like an angry teenager armed with a bunch of distortion pedals.

LOL

I did some math and found that your 12at7 was biased at 3.75 watts. So that would be a lot. And might be why the amp broke up so much. Could you take new voltage readings with the 12au7? I'd be interested.

[yunger]

I did some math and found that your 12at7 was biased at 3.75 watts. So that would be a lot. And might be why the amp broke up so much. Could you take new voltage readings with the 12au7? I'd be interested.

so: Plate Dissipation in Watts = (Plate Voltage - Cathode Voltage) x Plate Current.
is plate current the same as cathode current? and cathode current is cathode volts/rk?

btw, the 12at7 is rated for 2.5w per triode so in parallel 5w right?

anyway here's the new voltages

[ATTACH]16993[/ATTACH]

[Chuck H]

btw, the 12at7 is rated for 2.5w per triode so in parallel 5w right?

Oh, right. I was figuring for the single triode dissapation.

So you did change the cathode resistor? It looks to be 8.8 watts idle dissapation with the 12au7?!?

[yunger]

So you did change the cathode resistor? It looks to be 8.8 watts idle dissapation with the 12au7?!?

youre right. i went back to 470 rk and calculated 6.5w. maybe the tube can handle that until i can order some 510-620 resistors

[Jack Sparrow]

I had to join just to say that that's one nice amp (both of them, actually). I've been thinking about something similar for awhile now but I've got a few concerns that have kept me from doing anything yet. I want to use stainable wood and a front plate like yours but with a wooden grill design. How did you attach the front to the sides? Dowels? Biscuits? Is the front 3/4" thick? What are the dimensions of the cabinet, if you don't mind sharing?

Thanks.

[yunger]

I had to join just to say that that's one nice amp (both of them, actually). I've been thinking about something similar for awhile now but I've got a few concerns that have kept me from doing anything yet. I want to use stainable wood and a front plate like yours but with a wooden grill design. How did you attach the front to the sides? Dowels? Biscuits? Is the front 3/4" thick? What are the dimensions of the cabinet, if you don't mind sharing?

Thanks.

thanks!
-big amp is 20x18x11 3/4" pine, 1/2" ply baffle
-little amp is 11x10x7 1/2" pine, 3/8" ply baffle
if by plate you mean fascia, it's just 4 pieces cut at 45 degrees on end and glued inside the box in the final step of assembly. no need for dowels or biscuits...lateral loads are not a problem here.
hope that helps.

[Jack Sparrow]

That makes sense. For some reason I assumed it was a frame of four pieces preassembled and attached to the front edges of the sides, top and bottom like a face frame on a kitchen cabinet.