Great Sound

I needed a really nice photo to show this off, so here's a better look with decent lighting and plain background. I'm not the most patient photographer so I might do more with this later. I've now been listening for about 5-6 hours over the course of the weekend. It sounds really awesome and I'm very pleased with it.

As a side note, I've been trying out Beats Music (formerly MOG) and am liking it so far. I'm still in the 7 day trial and might upgrade to the paid service. It has just about anything I might want and streams in high quality on the computer or mobile. The PC interface seems clunky, but I haven't spent much time on it. Two recommended tunes for testing a new amp:  first..."S'Wonderful" by Diana Krall. Yes, it really is wonderful. Thank you, Diana. Second, the power-song I still remember auditioning in a stereo store when I was about 16 years old buying my first amp and speakers (an Onkyo receiver and big Marantz speakers)... "Owner of a Lonely Heart" by Yes. Awesome.

I have a few things left to do. First, I haven't thought of a nifty way to ground the run capacitor casing. If you recall, I used the professional mounting technique of superglue which apparently isn't a conductor between the top plate and capacitor casing. I can test a small amount of voltage present between the casing and ground and am not comfortable ignoring the need to ground this for safety. For now, I wrapped some loose copper wire a few times and connected it to a transformer bolt. It sort of looks cool, like "Oh yeah, and a dab of copper wire just so..." Maybe I'll leave it or think of something else.

I also still need to solder my output wires to the speaker terminals; they are currently bolted on but not the best connection. And I'll finish the bottom panel by drilling a few more holes for air flow and then can cover the bottom for safety. Feels like the whole thing weighs about 20 pounds. Not sure, but it's heavy.

This might be my last post unless something else is relevant. Overall, was an awesome project. Kudos to George Anderson who designed the Tubelab SSE and provided such great instructions. I think next I might build a DIY DAC to improve my input signal instead of using my laptop headphone output. We'll see! Thanks for reading.

First tests

With all the parts finally in place, I could wire things up. My chassis is snug, but not unworkable in terms of space. It's tricky to get the input audio connected right next to the chassis wall. The picture at right is still with most of the wires loose. I twisted them where possible and wired it up first for basic triode mode without cathode feedback or supplemental capacitor.

Grounding is still a bit mysterious to me, but after reading some online posts, I think I get the concept... I have only one place on the PCB that goes to ground (through one of the input connectors) and then all the metal things around the chasssis (top, back and front panels, transformer bolts, choke frame) get grounded to a star ground point that goes to the earth ground on the power plug. I didn't quite grasp a few things but think I finally understand that the speaker terminals without cathode feedback need to ground not direct to the star ground (chassis) but back to the PCB to avoid ground loops that may create hum.

I first set things up with my old Infinity speakers that I refurbished (see a few posts back). I connected it all up with a cheap CD player with a simple headphone plug, plugged in a fuse, and turned it on from a power strip across the room... a few moments later the tubes warmed up, a nice little glow, and... music! It worked and sounded pretty good!




Glowing nicely with the lights out!

Once again, I don't know much about electronics, but I read a few things about measuring voltage so I tested the B+ and saw it rising 100, 200, 450, 700, 1000+ uh oh! That sounds way too high! Then I realized I had my multimeter set to AC and once I finally got things sorted out I see it hovering in the 469-479 range, sounds better. I also tested the cathode voltage on one of the output tubes and with a few calculations I estimate about 55 mA per tube and roughly 24 watts, seeming to match what might be expected. If I was smarter about this stuff, I'd do more measuring, and some of my next steps are to understand the circuit better to really grasp what's going on.

 

The CD player was not very good, so I switched over to use my iPhone (I know, probably still not the best quality) and that bumped up the quality a bit. I also tested wiring the amp using cathode feedback, which didn't sound dramatically different to me. I haven't tried ultralinear mode, but may test that later. I then moved the amp to my living room and connected my bigger and better quality Klipsch speakers (F1s, not great, but pretty efficient and better bass) and my laptop with MOG (now Beats) for pretty good quality digital streaming. So far so good!



Output Transformers Arrived!

Finally, the output transformers arrived. Edcor makes them to order and says it takes five to six weeks; it took seven. But that's ok. I've been busy with a lot of other things lately.

I had already taken a risk and drilled my holes based on the dimensions listed, and fortunately it all lined up ok. The wire gauge was a bit thicker than I expected but I was still able to squeeze the three primary wires and two secondaries through my rubber grommets and mount them fairly easily.

I bought relatively small transformers, to save money. They were $27 each, plus $17 shipping. For anyone who wants model info, they are Edcor GXSE10-8-5K. They are 10 watts each, and rated for a frequency range of 40Hz - 18kHz. I'm not expecting to get thundering bass out of them or very loud power overall, but still should be decent.

I'll share my test info on my next post, so this is slighly out of order, but I wanted to try the amp without the power choke first, which meant I first used a resister soldered onto the board. I did this and all was ok, so I had to remove the board, clip off the resister, and re-mount it with the choke wired in. While I had it off, I took the opportunity to drill a few extra holes on the top panel for a heat vent. I don't know if this makes much difference or not, but I really had no place for heat to go--all my other holes, including the tube socket holes, were pretty tight, so I was concerned things might get overheated inside. I drilled nine holes relatively close to the edge of the PCB near a few capacitors (if you read my previous post, you'll know that I accidently bought two caps rated for a lower temperature than I should have).

 

Next...the maiden voyage!