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At it again - updated

fdesalvo

fdesalvo

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While I wait for my guitar to be finished, I let my impatience get the better of me.  I finished protoyping a single channel amp back in 2009 and liked it so much I didn't rework it.  Now I have a lil' free time, I decided to rework things into a smaller package - 12" chassis ~ overhead compartment/carry on friendly.

Anyhoo - 35w-45w, push-pull 2x6l6GC (or 5881) @ 460vP via 5u4 recto (or 498vP with SS diodes- El34 tasty zone :icon_scratch:??), single channel a'la AB763 with chassis mounted bias points, selectable output impedance, and a possible buffered fx loop. 

1:1 layout~ managed to get filters on the board this time around.  Board is only about 10.5" - could've shaved another 2" off of the board, but I wanted to give the power rail dropping resistors some room to breathe without cooking my caps. 
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Turrets mounted.  Today's goals: Lace up busses on board during lunch break and mount componets tonight after work.  I was orignially going to use this board to test layouts, but I love the breadboard look and the FR4 is so damn stiff.  Love it.
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Waiting on a few filter caps and 1 resistor, then the board is finished.  On to the chassis (when it arrives...)!
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Thanks, Cagey - the solder blobs should appear nice and shiny indicating a cood connection, but you may notice mine are dull.  Normally this would indicate a cold joint, but I am retentive and use a wire brush to flake off the dried rosin  :laughing7:.  This is my first time mixing in some Sozos with the Mallory 150s.  Not sure if the effect will be dramatic, but should be interesting.

Crash - once I have the amp up and running, I will share a schematic that I drew up.  I want to verify that it will work before someone invests time/money haha.  The layout diagram is actually in the first post, though :P.

It's basically a Blackface Fender (AB763) minus vibrato/reverb.  When comparing the schematics, you'll notice that I removed the voltage divider before the phase inverter to allow it to see the votages it would with the rest of the circuitry still in place..
 
SOZOs are Mallorys, so don't worry about it. They just put a different wrap on them and bump the price hard enough to make you think you're getting something special. There are a surprising number of people out there who believe capacitors have a "sound", and SOZO has capitalized on that the same way Monster has with cables. Barnum was right - there's a sucker born every minute.

You can clean rosin splashes and blobs off with denatured alcohol and a little utility brush, if you don't want to eat up a lotta time scrubbing on the joints with a wire brush.
 
I believe you re: the SOZOs.  Same exact construction it would seem.  I can hear the difference between a ceramic and silver mica in a tone stack, but honestly, that's even subtle.

Yah, I just use a lil utility brush to knock the crud off and move on.  If I was a retired man, I'd probably buff em out  :laughing7:.

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Took the boys out of hibernation.  The chassis can't get here fast enough.
 
Still waiting on chassis and power tranny.  I thought I could salvage some tube sockets from my stash, but they are too far gone.  The rest of my filter caps came in today and I finished up the board.


V1a's first stage cathode resistor/bypass cap and plate resistor along with the tone stack...
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V1 and phase inverter's filter caps..
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Business end..
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Bias supply nestled between first two stages of power supply filtering..
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Tone stack surrounded by V1a/b's cathode resistors and bypass caps
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Can't wait to start punching the chassis  :guitarplayer2:
 
Not really an update but....the chassis is finally in...just waiting on combo pwr/stdby switch, pilot lamp assembley, fuse holder assembley, and power tranny.  With those dimensions on hand, I can layout a 1:4 scale mockup and drill accordingly.

Rotary impedance selector
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Mock 1:4 layout of rear panel
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Score!  Got a pair of NOS JAN/Philips 6l6WGB's from the 1960s, a NOS GE 5U4GB from the 50's (IIRC), a NOS JAN Philips 12AX7, and NOS GE 12AT7 to play with!  These 6L6WGBs are rugged military tubes and are perfect for lowering the headroom of a 6L6GC amp with 470 or lower plate volts.  Brian Setzer uses these in his Blonde Bassman along as it turns out.  I think they deliver the goods by producing sweet, fat midrange with tons of sparkle and harmonics when overdriven.  These will bias up to 23w/each, givin me a theoretical 46W of raunchy blues tone with some signtature Blackface sparkle and twang.
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WWII vintage
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12AT7 and 6L6's from 1967
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Power tranny and bias pot
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Bias test points
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Rear deck.  impedance selector..
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Final update until cabitet and faceplate arrive.

http://s443.photobucket.com/albums/qq151/frank_desalvo/Scratch%20built%20amp/?albumview=slideshow
 
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