wlowes

The amps continued to run in and proved to be keepers. Well worth doing some final spit and polish. There was a little hum on one amp and some noise / hash on the tweeters of both channels. Nothing major, but certainly audible at 1 foot.
Using AC filament supply for all but the input tube, I figured I should re read the best practices on wire dressing, hum pots, virtual center tap etc.
Looking back there were some spots to improve.
1. tight wire twist on path from bridge rectifier to first caps. Done, no real change.
2. tight twist on b+ supply to input tube plus added BG 3uF 250v cap right at the tube. No change to noise but love the improvement in sound
3. tight wire twist from psu to b+ on all power tubes plus BG 10uF 250v on each power tube. Like the input tube the BG brought an immediate lowering of noise floor that really brought a finishing to the SQ. Quiet background, micro details and just a smooth rich sound. Not colored, just the way it...

Done! The second went much faster and was playing music in 2 weeks.

Now that they are running I will borrow from the circuit designer's own description of the sound as it really does sum it up..

"There is no substitute for power and that is what this amp has. Complex musical passages are effortlessly reproduced with a natural depth and breadth unmatched by any other amp. Subtle nuances are clearly revealed underneath pounding crescendos.

Striking imaging causes instruments to be layered in a three dimensional sound stage that recreates the experience of a live performance. The music "opens up" and leaps out of the loudspeaker eliminating any box like sound. The most minute and subtle sounds are revealed producing uncanny realism. Musical voices are warm and lifelike yet completely neutral with a razor sharp focus."

In my own words.. incredibly natural. 3D and layered sound. Deep bass with weight creates...

This is the continuation of my personal journey to build my first tube amp.
It was a very happy day yesterday when the first mono bloc powered up and produced music. I was pretty comfortable that I had not made mistakes that would result in smoke, but really did expect some issues with hum, grounding or tube substitution. But nothing! Hum was barely audible with my ear on the speaker or from the chassis. And music played! My first test flight was one channel only driven by a Sony Walkman on a small Totem speaker. Even under these conditions the sound was pretty good, and really started to open up after the first 60 minutes. I was like a proud father
The first picture shows the pair with a Rotel CDP in the middle for scale.
I will not be able to fully know the sound until both are wired, broken in and hooked to the good speakers and source. I think they will be amazing. Already better than the very respectable chip amp they replace. There is a switch...

I am keeping this journal for my own record. There is no new engineering in this project. This is just my own journey while building my first tube amp.

Major milestone achieved today. I finally took the plunge and cut the aluminum. I am very happy with the results. Each and every part fits perfectly.

I planned this project around Front Panel Express. I used their tool designing and redesigning the lay out until I was confident in my layout and fit. Problem is FPE is expensive. Then I saw some comments from other builders that the edge FPE leaves is not really finished. I went searching for a more cost effective solution. I landed on cutting using WaterJet while searching for local CNC shops. There is a company in Toronto close to where I work www.pva-enterprises.com that has an advanced waterjet cutting machine. I exported my FPE file and sent it in for a quote. Given I need a left and a right panel for the 2 mono's I got them to cut both panels...

Over the past few weeks I continued to build out and test the power supplies. I really am pleased with the decision to make each supply as a module that can be fully developed and tested outside the box.

After the success with the first supply for small tubes, I moved on to the power tubes. After abandoning the large Sangamo can caps, I ordered in 8 2200uf snap in caps.. 2 per rail, 4 per monoblock. After they arrived I realized that these things are pretty big. The question was how to securely mount them. I settled on another wood block so they can be mounted securely under the chokes. As before, I mounted them through the wood using some silicon cement. There are some nice mills wire wound bleeder resistors. The B+ power supply design calls for a single center tapped 230v transformer. I had scored 2 pairs of 120v 500va Toroidal transformers. I must admit it took a lot of research and a couple of helpful posts before I was sure that I really had this figured...