Roll Call: Who's building, built, or thinking of building a beta22?

[ting.mike]

Well it gives me the bragging rights that I have the same set up that johnwmclean has.

 

[jezz]

"Overkill" is a relative term I think. I define it as the amount of time or money one is willing to spend to ensure performance. My opinion comes from the semiconductor market, these days at AMD/ATI. The discrete graphics market is dominated by mainstream cards basically, and the ultra-high-end cards are used by a select few, which I liken a bit to the high-end amp market. You can get whatever you want .

Original intent of posting: I'm gonna build me a 3ch β22. Eventually. Still trying to pick out a chassis or figure out what I'm going to do to a NABU. I don't have access to a shop these days; does anyone have any tips regarding either ventilating a NABU or a chassis of similar milling ease? Frankly, I don't care much how it looks as I don't tend to stare intently at my amp while listening to music, and I'm capable enough with a circular saw to make a fair looking wooden front panel.

 

[keyid]

Can a single e22 w/ 100va power four b22 boards to drive Senn 600/650?

 

[oneplustwo]

keyid - this was covered just a few posts ago. short answer, yes. but you need to be careful of heat management.

 

[amb]

If by "e22" you mean σ22, the answer is yes. The σ22 PSU was designed to power up to four β22 boards serving only headphone duty. That said, the σ22 MOSFETs will run quite hot in this configuration so be sure to ventilate the case well, and use larger heatsinks if possible.

EDIT: oneplustwo beat me to it. I love it... now that there is enough β22/σ22 expertise in the community I could rely on more of you to support each other!

 

[oneplustwo]

HAHAHA! I have a long way to go before I am able to balance out the "takes" with any "gives" I may be able to contribute. And of course, I still have a lot to learn. But that's why I'm in this... to learn!

 

[UKToecutter]

I wish my boards would get here.

I'm aching to make a start

 

[deerinheadlights]

I am having difficulties getting my b22 into a case. It has been two months of listening enjoyment.

I was unable to zero the DC offset on the right and left channel boards so I swapped either Q1 and Q2 or Q3 and Q4. Afterward the the DC offset zeroed out.
A few days after completing the boards I may have shorted the output jack to the volume pot. This resulted in a blown fuse. Replaced a bad Q23 on the ground channel board. Ran initial setup again. Amp sounds great.

But I started worrying after reading about about what happens when R9 sparks during the initial setup. The same thing happened with my ground board. A diode check revealed... Q25 on the ground board was bad. Q2 on the s22 was bad.
For all other BJTs the diode check with a fluke 12b showed .56-.65 on the BJTs. When reversing the polarity the diode check showed 0L on one leg and 1.2-2.0 on the other leg. So I compared each measurement of each component to the same component of the other boards and they were all in the same 1.0-2.0 range for one leg and 0L on the other leg. A diode check of the newly installed components before power up yielded... Q25 measures .59 one way and 1.06 and 1.27 with polarity reversed. Q2 measures .65 and .65 one way and 1.995 and 0L (started at 2.33 and after a few seconds read 0L) the other way.
Measured resistance of R32, R28, R34, R35, R33, R29, Q23, Q21, Q22, Q24, Q17, and Q18. The MOSFETs and the JFETs are not shorted. The resistors are measuring correct. The .47 ohm resistors show .5 ohms.

There are some voltages that are look very wrong for all 3 of the b22 boards.
Voltages around VR1 area, R13, R20, R21, R22, VR2 area seem to be the most off.
Sigma22 Voltages
Beta 22 Ground channel voltages
Beta 22 Left Channel voltages
Beta 22 Right Channel voltages

There is a hum at approximately 1-3 o'clock on the alps 50K volume pot. The hum is present when connected to an ipod, d10 or gamma1/2++ powered by s11. Plugging in the USB or touching the USB cable to the gamma1/2++ case will kill the hum.

Also the right channel board heatsinks feel quite a bit hotter than the ground and left channel.

 

[amb]

dearinheadlights, all your voltages look reasonable. If your amp is uncased then there is no "chassis ground" and I am not surprised that there is hum. I wouldn't worry about it until you get it all cased up and wired according to the β22 website "Wiring & ground" section.

 

[ShinyFalcon]

I don't think I seen this mentioned, but is the σ11 capable of outputting inverted voltage (-24V) after replacing the N-channel MOSFETs with P-channels?

 

[amb]

Quote:

Originally Posted by ShinyFalcon /img/forum/go_quote.gif I don't think I seen this mentioned, but is the σ11 capable of outputting inverted voltage (-24V) after replacing the N-channel MOSFETs with P-channels?

No, that won't work, but you could simply call the V+ output "ground" and then V- would be "negative"...

 

[UKToecutter]

Quote:

Originally Posted by amb /img/forum/go_quote.gif No, that won't work, but you could simply call the V+ output "ground" and then V- would be "negative"...

Making sure that your PS Ground and signal ground are isolated (of course)

 

[LeMat]

2 quick questions for helping me moving forward on this project :

1. Casing : I see the vast majority of people having built a b22 encased it into a square edged enclosure. Assuming I'd like something with curved edge, like these exemples :
RE77
W-8
326S

Where could I get such case ? I'm aware that high-end audio companies have the ressources to machine their own fancy faceplate but audio-gd seem to use a quarter cylinder to round-up the corner.

2. Toroid : I received a 120VA 30+30 toroid transfo. After a test, unloaded, its output is 35,6 VAC. Shouldn't it be more closer to 30 ? or do I received a 36+36 ??

tx

 

[jezz]

Quote:

Originally Posted by LeMat /img/forum/go_quote.gif 2. Toroid : I received a 120VA 30+30 toroid transfo. After a test, unloaded, its output is 35,6 VAC. Shouldn't it be more closer to 30 ? or do I received a 36+36 ??

No, your transformer is fine. The ratings of a transformer refer to their loaded voltage. The unloaded voltage of transformers is often designed to be higher than their quoted voltages because the windings in the transformer have resistance and thus the currents through the primaries and secondaries will drop a little voltage.

 

[LeMat]

Quote:

Originally Posted by jezz /img/forum/go_quote.gif No, your transformer is fine. The ratings of a transformer refer to their loaded voltage. The unloaded voltage of transformers is often designed to be higher than their quoted voltages because the windings in the transformer have resistance and thus the currents through the primaries and secondaries will drop a little voltage.

Glad to hear that ! I know it's usually higher than specified but I wasn't expecting it to be that much.
So I'll be able to connect it to my s22 tonight and see how it goes.
Thanks

Any suggestion regarding the enclosure ?