Tubelab SE build

[bberkom]

I just wrapped up my first DIY amplifier build, and I chose a Tubelab SE using 2A3 output tubes. I bought a piece of 1/8" aluminum for the top and bottom of the case and used a nice piece of air-dried Tennessee black walnut for the case wrap. I plan to add a perforated metal screen over the opening in the amp with cutouts for the tubes. I do a lot of woodworking and have some fabrication experience, but this was still a really challenging project getting everything laid out and put together.


I used some 10 watt 3k output transformers from Transcendar. I hooked up the 8ohm and 16ohm taps. I am glad I went with these over some cheaper options, as they are really heavy with nice wiring and quick turnaround. I'd highly recommend them, and they're made to order and can be customized. The 2A3's are new EH's, but I also have some older Shuguang's I'll try out this weekend.

Initially, I had some hum due to some ripple in the 2.5v regulated supply, which is common when using 2A3's. The regulator drops out of regulation if it doesn't have a high enough supply voltage, but adding some capacitance to the input cap of the regulator eliminated the hum completely. Took me a while to sort out, but I found some old threads where George had some issues with certain newer 2A3 tubes. It's dead quiet now. I actually thought I had screwed something up and that it wasn't working when I fired it up last night because there is absolutely zero idle noise through my 98db speakers. You can see the top half of the ripple being sawed off by the regulator before I added a bigger cap, even if my scope is kinda crappy.


It sounds great with my Sony SS-3300 speakers, and I'm just using a Schiit Sys passive preamp. I'll switch to a pre with a little gain eventually, but I still have plenty of drive for my speakers. I've always wanted to try a SET amp with them, and I've always wanted to build an amp. I am really happy with how it turned out.

 

[Squidward]

Neat build, thanks for sharing!

 

[mkane]

2 piece top plate. Excellent

 

[invaderzim]

... I do a lot of woodworking and have some fabrication experience...

It shows, that is gorgeous

 

[Lavane]

Very nice! I like the two part top plate. I built the 300B version. The one in my Avatar. I used 15 watt Transcendar outputs and a Transcendar choke. I was suprised as well how quiet it was. Even with everything jumpered spread out all over my bench it was dead quiet. I used a 12"×12" aluminum plate. Then used the bare pcb as a template to punch and drill holes. Then mounted all the parts except for the resistors on the bottom of the board. With the 5v regulator for the 300B's I had to use a big heatsink. Mounting it off board.

 

[bberkom]

Very nice! I like the two part top plate. I built the 300B version. The one in my Avatar. I used 15 watt Transcendar outputs and a Transcendar choke. I was suprised as well how quiet it was. Even with everything jumpered spread out all over my bench it was dead quiet. I used a 12"×12" aluminum plate. Then used the bare pcb as a template to punch and drill holes. Then mounted all the parts except for the resistors on the bottom of the board. With the 5v regulator for the 300B's I had to use a big heatsink. Mounting it off board.

I thought about mounting the components under the board as well, but since this was my first amp build, I tried to keep it simple. I have a big secondary heatsink on my regulator as well. It still runs hot, but no problems with it shutting down or anything (yet). The Transcendar trannies are really solid, and I like the color scheme on your end bells.

Did you add a supplemental capacitor to C5 in your amp, as is suggested on the Tubelab site as an upgrade? I have a big 100uf motor run capacitor that you can see hanging out under the output transformers in my photos. I haven't wired up yet, but I wanted to make sure the amp was stable first.

 

[Lavane]

I thought about mounting the components under the board as well, but since this was my first amp build, I tried to keep it simple. I have a big secondary heatsink on my regulator as well. It still runs hot, but no problems with it shutting down or anything (yet). The Transcendar trannies are really solid, and I like the color scheme on your end bells.

Did you add a supplemental capacitor to C5 in your amp, as is suggested on the Tubelab site as an upgrade? I have a big 100uf motor run capacitor that you can see hanging out under the output transformers in my photos. I haven't wired up yet, but I wanted to make sure the amp was stable first.

Yes I added the cap. I also tried the resistor instead of the choke before putting the board on the chassis. It sounded fine that way, but I used the choke in the end. I used socket savers on the 9 pin drivers to raise them up a little since they are so short. It makes it easier to pull those stubby little things. Plus it helps getting some of the heat away from the board.

 

[Lavane]

Using socket savers gets the tubes up away from the board. I mounted most of the parts on the underside, but I still didn't want the tubes below the top plate. With those short drivers, half the tube was below the plate. The socket savers also made it much easier to grip and remove them. While I was at it I made 4 pin socket savers for the 300B's. I couldn't find any for 4 pin tubes. I used ceramic sockets with pins on the bottom instead of eyed solder lugs. Then bought some small diameter brass tubing from a hobby store and soldered the tubing on to the pins. It fit the socket on the board perfectly.

 

[Yukon888]

Nice build!

 

[Lavane]

The perforated top will look good. We used to have a steel supply here and it was handy for stuff like this. They would sheer, bend and punch for a reasonable price.

 

[Ezd]

Very nice build...