Complete - DIY35 in SCA-35 chassis

[wicked1]

So, I finished my DIY 35, built into the SCA-35 chassis.

I completely disassembled the sca-35, and cleaned all of the chassis components. I took out the middle section which everything mounted to, and held the unit together. I replaced it w/ aluminum angle bars to hold the chassis together. I took two aluminum flat bars and put them going across the amp, left to right, as support braces.
Then I mounted all of the components to a 10x12 aluminum sheet, which fits perfectly into the SCA case, on top of the aluminum bars.
Unfortunately I didn't get the idea to start snapping photos until it was finished. If anyone wants to see how it is held together, let me know and I'll get a photo of the under side. From there you can see all the screw heads, and aluminum frame I built, etc.

Here is the top of the amp



There was barely enough clearance. It's pretty much like the original SCA35, in that the tubes are about 1mm below the mesh top when it's assembled.
I don't have it installed right now, but there is room for the original selector switch, so I could add another input, and wire up the selector.
I am going to put all the pots and knobs back on the amp, but none other than the volume (and maybe input selector) will do anything.

The metal work was actually pretty easy, and took about the same amount of time as stuffing/soldering the PCB. Doing the wiring took far longer.

[mesherm]

Congrats on shoe-horning that PCB in. Its amazing what a guy will go through to get the all important WAF (Wife Acceptance Factor) Yellow_Light_Colorz_PDT_08

[wicked1]

As for the sound... It sounds great! My original SCA had quite a bit of hum, and was a bit muffled. This one is quiet and clear.
When I use my volume pot, I get a buzzing sound. If I turn the pot all the way up, the buzz goes away. I need to figure that out. For now I am just using the volume control of my pre amp (mp3 player).

In comparison to other amps, it falls right where I thought it would. Better than my collection of random old solid state amps, but it doesn't have the magic of my single ended vt-225 triode amp.
My single ended amp is in another league, tho. Every component, each cap and resistor was carefully chosen. The DIY35 is mostly the mouser parts list, w/ some upgraded coupling caps.

I tried several combos of input/phase splitter tubes, and ended w/ the combo of 5751 and 12av7. To my ears, that combo stood out way above the rest. (also, out of my collection of tubes, those were the only new(old stock) I purchased. The 12ax7 and au7 and others I tried were just old random used tubes I had laying around.)

So, overall, I think it's a great amp! Missing something the set has, but on the other hand, it gets a LOT LOUDER than the set, and sounds great at those high levels.

Here's a pic of my vt-225 amp.. It's still a work in progress, so you don't see the chassis. Actually, i got a drill press a couple of days ago, so I can finally finish it.. The strange sockets on the output tubes are adapters I made so I can run the vt-225 tubes in 300b sockets.

[wicked1]

Congrats on shoe-horning that PCB in. Its amazing what a guy will go through to get the all important WAF (Wife Acceptance Factor) Yellow_Light_Colorz_PDT_08

Thanks!
and yeah.. it is amazing what a guy will go through.

I still need to sort out the heat issue, but Im thinking I'll mount a small fan on the inside of the SCA cover, bolted to the cover, blowing air out the top. There should be enough room off to one of the sides for it.

[wicked1]

I worked w/ the amp a little more last night.

I didn't have the PCB grounded to the chassis. Once I did, the buzzing problem w/ the volume pot went away.

It was a little high heavy/bass light, so I adjusted the negative feedback, allowing more to pass through. It has really helped a lot! I just adjusted it by ear, but I'll check it out today to see what I ended up setting the resistance to.

I also learned that it likes to be loud!! I hooked it up to some lower efficiency speakers and cranked up the volume, and it sounds VERY good!