Post pics of your builds....
Jan 6, 2011 at 12:15 AM Post #7,696 of 9,811

Minor problem... Pete Millett's last name should be spelled with two 't's.

That'd cost quite a bit to fix the spelling :p
Jan 6, 2011 at 6:14 AM Post #7,699 of 9,811

Love the stealthy look of this amp! Awesome!
Originally Posted by jlefley /img/forum/go_quote.gif
I finally got around to taking some pics of the β22/σ22 combo I finished up several months ago: (click for hi-res)

Some specs:
  1. β22 boards built with recommended parts, configured for gain of 5
  2. 4 channel, balanced configuration with selectable balanced/unbalanced input
  3. TPA Joshua Tree relay attenuator
  4. Dual XLR/TRS combo and 4-pin XLR output jacks
  5. Binding posts for speaker connections
  6. Dual σ22 boards built with recommended parts, configured for ±30V
  7. 80VA Avel-Lindberg main transformers
  8. 15VA Avel-Lindberg auxiliary transformer
  9. ε24 power switch driver circuit for power control
  10. σ25 power supply to provide DC to attenuation system
  11. DPDT relay switches power to both σ22 and σ25
  12. 16 contact umbilical cord provides power to β22 boards and attenuation system and also carries ground returns for unbalanced headphone connections, uses AMP CPC connectors
  13. Recessed LED on the power supply front panel provides power indication
  14. Par-Metal 20-12123B 12" x 12" x 3" enclosures ordered without panels and with 2 front frames per enclosure
  15. Custom 6mm panels machined from raw aluminum by Cam-Expert, black anodizing and white text fill completed after receiving panels
  16. Lian Li case feet
As for the performance, the amp sounds great. At this point I have been using it with a pair of Grado SR-60s and a Matrix Mini-i balanced DAC and the sound is phenomenal. Apart from this, I only have a Cmoy that I built ages ago so I don't have much to compare it to but the huge sound stage, clarity of individual instruments, and the speed this amp provides is nothing like I have heard before. The construction went fairly smoothly without any major problems. I was having some issues with noise and hum but ensuring that the case and panels were fully grounded eliminated nearly all the problems I was having. Even at full volume the amp is near silent with only a slight hiss which I assume is the noise floor of the DAC.

More pictures, including some taken during construction, can be found here:

Jan 6, 2011 at 6:17 AM Post #7,700 of 9,811
Wow, John you have been busy! These amps look sweet! Nice style you have going on there.

Top rig Beefy! Is your M3 still around? 
Here’s a shot of my set-up, the speakers are not DIY, these are Ed Schillings (Hornshoppe) Horns which use the Fostex 126e driver.
I’ve changed the front and back panels of my DAC and PSU, all done by Cam-Expert.

and... the mancave with my next beta22 in the works.


Jan 6, 2011 at 10:29 AM Post #7,701 of 9,811
Minor problem... Pete Millett's last name should be spelled with two 't's.

Yeah, it's such a drag. I bit the bullet and ordered another "t". It shouldn't be too much effort to fix.
Lil' Knight said:

That'd cost quite a bit to fix the spelling :p

Nah, it's not too much :wink:
Jan 6, 2011 at 7:32 PM Post #7,704 of 9,811
Thanks gents, I was definitely going for a vintage look on this one. The sound is very nice on my modest work room setup. The amp is crisp, clear and resolving without being clinical.

Holland, this is a photo I have from a few weeks ago of the inside before I finished the IEC wiring and added a little LED array board that I made. I used the last little bit of Oyaide I had for the input wiring, the couple of feet of output wire is Kimber. Resistors are nearly all carbon comp. Most parts are the ones specified in the BOM except for a few subs. Coupling Caps are Russian PIOs. This board is quite easy to populate aside from the MOSFETs which I had to add wire to in order to have enough room to reach the plate. No loop feedback.

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