Just finished my Stereomour

[crooner12]

After a few days, I finally finished the amp. Everything seems to work fine. Incredibly, all of my measurements were well within the 10-15% tolerance.

The only interesting measurements were terminals 4 and 12, where the voltages were 11.7 and 13.4, respectively. Any thoughts on why these might be off when everything else was within spec?

Listening test is next...

[Paul Joppa]

T4 and T12 are conected to the 2A3 grid through the small 200 ohm resistors. A small leakage current will flow through those resistors. 12 volts is too much, but 12mV is not.  :^)  If it's really 12 volts, let it burn in for a few hours and check again.

[crooner12]

@Paul Thanks for the info! I'll try to let it burn in later tonight. Just need to get speaker wire. Does the amp need to be connected to speakers or a source when powered on? I've read instructions on other tube amps that advised against running a tube amp without being connected to speakers.

Also, A3 and C3 seem a little higher than normal (0). Perhaps this also needs some time to burn in?

Just for fun, here are the rest of my voltage measurements at each terminal:

1: 368
2: 232
3: 0
4: 11.7
5: 59.3
6 - 10: 0
11: 61.3
12: 13.4
13: 0
14: 226
15: 366
16: 59.4
17: 397
18: 0
19: 396
20: 61.3

Four pin socket


A1: 60
A2: 368
A3: 14.2
A4: 59.8
C1: 61.8
C2: 366
C3: 14.6
C4: 61.9

Active load PC board
IA: 396
IB: 396
OA: 233
OB: 226
kreg (both): 2.49
-reg (both): 0

[crooner12]

In addition, I want to echo what others have said in that this kit is a lot of fun to build and the instructions are excellent and easy to follow for a novice amp builder like myself.

I only had a few issues, but they were easily resolved:

1. Two pairs of resistors were missing so Eileen promptly sent them to me via priority mail
2. There wasn't enough red wire in the kit, so I had to use some leftover black wire instead...no biggie
3. I didn't realize that the ceramic tube sockets for the 2A3's had different size holes, so when I initially installed them, I put the C socket 180 degrees backwards. After spending 10 minutes wondering why the tube wouldn't fit, I realized my mistake and, to my embarrassment, had to undo, rotate, and re-solder that tube socket. I'd suggest mentioning this difference in the next iteration of the manual.
4. I felt the wire lengths were a bit too generous, so oftentimes I had to re-cut them so the installation would be tight and not sloppy with too much slack in the wires. Although, I can see how this might be a good thing for those who plan on modding the kit after it's built.

I'll also post a link to my blog where I've uploaded some pics and perhaps upload a video to YouTube when everything is hooked up and running!

[Paul Joppa]

A3 and C3 are the grids mentioned in my earlier post. I expect you are measuring 0.014 volts, not 14 volts - if it's an auto-ranging meter, the m for millivolts is often not obvious on the display. I have this suspicion because the other A and C socket voltages are extremely close to what they should be.

It does not matter whether a speaker or other load is connected. Pentode amps are sensitive to there being load, and high-feedback amps are also, but triodes without feedback such as the Stereomour are not.

[crooner12]

Finally got to updating my tumblr blog, so here's a link for more Stereomour build pics, an unedited first-listening test video, and a quick (and totally not apples-to-apples) comparison to my B&W MM-1 speakers.

http://krakleandpop.tumblr.com/

My next project will be experimenting with different tube circuits to see what the sonic differences are. I want to understand the theory behind the tubes and design and acquired a dozen or so 50's and 60's textbooks on the subject.

I'm so glad I decided to build the Stereomour. This has been a very fun learning experience, but I'm ready to take it to the next level!