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!

Waiting

I have most of the amp put together, at least roughly. At this point I'm just waiting on my output transformers to arrive. I bought them from Edcor, a company in New Mexico that makes them to order so it can take 5-6 weeks.

 

Here's a picture with the tubes in place temporarily. I bought all JJ Electronics tubes because they were relatively inexpensive. For tube-people who want to know, the amp uses:  GZ34S rectifier, ECC81 preamp, and EL34 output tubes (matched pair). JJ was a subsidiary of TESLA, a company with a long history in former Czechoslovakia, named after the famous engineer and physicist Nikola Tesla. When I started this project I thought it might be neat to get all parts made in the USA or something like that, but it seemed hard to find tubes made in USA now unless they are vintage. So I have an Allied (Hammond) power transformer made in Canada, Edcor output transformers from New Mexico, tubes from Slovak Republic, PCB from an engineer in Florida, miscellaneous passive components from who-knows-where, and the run capacitor I think was assembled in Mexico.

 

I got only a medium sized run capacitor--apparently this is an inexpensive way to get a film capacitor which works well on an amplifier. It's oil-filled I guess for cooling. These are normally found in automotive or HVAC applications, so they are easy to find. I could have bought a 100uF capacitor but it would be bigger and in my opinion, ugly sticking up so high, so I got one that is 45uF. I'm not trying to build an ultimate stereophile amplifier, just one that sounds pretty good. I also didn't like the look of a run capacitor mounting bracket so I superglued it to the top panel. Wouldn't survive a big bump or hit, but neither would the tubes, right?

 

At this point, I'm still thinking the design of the amplifier is a bit plain--it's a wood box with aluminum panels, a switch and a knob. It needs some sort of character or artwork. Part of me wants to make up a logo to put on it--is that a function of my expectations that all good products are branded with a commercial name? I'll keep thinking on this and maybe come up with something to add a unique element. The output transformers will be painted blue (Edcor design) which I'm wondering if it will look either good or strange. We'll see...

Assembly

Ok, things are coming along just grand. Lots more work to finish up the chassis so I could actually start getting this thing put together. I finished the wood with stain and two coats of semigloss polyeurethane. I finished drilling all of the holes and sanding the aluminum, and have mounted the power supply, PCB board, and done quite a bit of wiring inside.

I bought a power choke and supplemental capacitor (motor run) not shown here. These are optional, but I've put so much into this thing that another $8-10 for each of those was worth it, assuming they do the stuff they are purported to do. Once again, I'm not much of an electrical engineer so I don't really understand it. I think the choke filters the AC power to take the alternating pattern out of the signal somehow and leave only the DC signal. I don't know, something like that. And the capacitor just adds extra ability to provide power needed for peak demands of amplification.

You'll notice a blue knob in the picture above that I thought was a bit too heathkitish, and later I bought a different black knob. I still don't like that one either, it's so boring. I can't seem to find a knob that looks right.

The power choke

back panel with connectors mounted

My soldering skills faltered a bit on the potentiometer (volume control) when I first wired it backward and didn't have enough length of my wires to make it work. So I have some giant globs of solder holding it together. I used some old RCA cables for my audio signal wiring, and sliced open an old PC power cable to reuse the wire from it for the power switch and ground wiring.

You will also see my blog skills are weak as I can't seem to get these pictures to flow right on the page. Whatever, right? You want to see what I'm working on, deal with it.

Coming together inside

More Chassis Work

The chassis is turning out to be a lot of work. I haven't blogged after a week or two, so I've made a lot of progress. I'll split this into two posts.

I finished all my wood cuts and most drill holes. So I was ready to assemble the box. I glued and screwed it together, let it dry, and sanded/finished it. I'll show more pictures later of the finished wood. It came out quite nice, despite my less than perfect corner cuts. A little wood putty in the cracks helped smooth things over. It's not perfectly square in all dimensions, but close enough.

The aluminum is a bit of a hassle. Lots of holes to drill, needing to be perfectly aligned, and if my drill bit wasn't exactly the right size, I often had to widen things out with a file. Cutting out the hole for the power connector was pretty unpleasant--drilled holes, then inserted a hacksaw to cut out the shape, then filed. As with many of the steps on this project, I did some things once, then realized a mistake and did it again. For example, I drilled holes exactly the diameter of the speaker connectors, then realized they should be bigger for the plastic mounts so the shaft doesn't actually touch the metal and short circuit.

A flush mount screw hole

I wanted the screws that held the top aluminum panel to the wood frame to be flush with the top--nice and clean. I didn't have a countersink bit, so I just used a larger drill bit and carefully drilled part way down. It's not perfect, but not bad. The other screws for the transformers, etc. will still be rounded top screws mounted on top. Who do you think I am? Some sort of metal working master?


The hole for the power connector

At first, I thought I would sand and polish the metal to a mirror finish, but I don't have the sandpaper and buffing tools for this, plus I ran out of patience. So I thought a scratched aluminum texture could still look good. Sanded with 220 and then 400 all moving in the same direction. The aluminum is so soft that it scratches easily. Maybe there's a protective coating I could put on, but I'm not going to be a perfectionist on getting it to be flawless.

The back panel with holes (that I later had to drill bigger)

For the bottom, I used the back of an old picture frame--you know, that sort of thick cardboard woodish sort of material. I won't really finish this until the very last step, and will probably drill more holes for air flow.

Bottom panel.

My workbench has become a mess. I cleaned it up after this.

Chassis

Developing the top layout.

I was able to work on the chassis this weekend, thanks to my good friend Matt, who has a garage full of tools. I probably finished about 2/3 of the work, with a few more cuts needed on the back panel, lots of drilling on the top, then assembly, sanding and finishing.

There were no real shortfalls on the part of the tools. The designer and craftsman, however, left a bit to be desired. I did ok on the table saw, cutting the sides at 45 degree angles and a shallow slot on the top to hold the aluminum. On the back side, I used a bandsaw to cut out what should have been a pretty easy shape to allow an aluminum plate for the backside components. But I wasn't really precise with my cut and it was sort of B+ work there (to use a tube amp voltage joke).



Pretty good cuts on the table saw.

On the front, I changed my mind mid-stream and altered the size of the panel that will hold the power switch and volume control. I thought that my original design didn't leave enough wood for good support, though as I thought about it later, it would have been fine. I had some complicated plans to use a router, and instead just drilled it out and used a hand jigsaw to cut out the rectangle, and then used knife and chisel to get the edges and corner pretty close to accurate (again B+ work).



Chisel work. Ugh.

On the top, I used a hole saw to cut out the openings for the larger output and rectifier tubes. I didn't have the right size for the smaller driver tube, so I drilled this out with the biggest drill bit I had, then used a round file to widen the opening slightly.

Overall I only somewhat enjoyed this part of the project. It helps to have the right tools, but for my next amp (oh, yes, there will be more), I will spend way more time on the design phase to make sure I have a really solid plan and the best visual appearance.




Couldn't resist a bit of wiring.

Large holes done.