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

[luvdunhill]

Quote:

Originally Posted by boinger /img/forum/go_quote.gif the sigma wont power up now... so just wondering if any have had this happen before so i dont have to start testing each thing any help would be appreciated....

I've had this exact same symptom before. I had my power supply plugged into a power strip, but the power strip itself wasn't turned on. Perhaps I correctly guessed what your problem is?

 

[Fitz]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif I've had this exact same symptom before. I had my power supply plugged into a power strip, but the power strip itself wasn't turned on. Perhaps I correctly guessed what your problem is?

But what did you have to do to fix it??

 

[luvdunhill]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif But what did you have to do to fix it??

I replaced the MOSFETs. Then it worked fine.

 

[boinger]

Quote:

Originally Posted by amb /img/forum/go_quote.gif boinger, "won't power up" isn't very much info...

well i heard a loud pop when the v+ line from my sigma power supply shorted to the signal ground (input) on one of the beta boards

so im sure something blew out in the sigma cause it will no longer give me any voltage readings... you think it could be the mosfets ?

 

[johnwmclean]

Fuse?

 

[oneplustwo]

in my experience, it's either the mosfets or one or more of the transistors. might want to check the 0.47Ohm resistors as well.

 

[boinger]

ok thanks will do


Edit:

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif Fuse?

no its not the fuse cause my other sigma (from the same mains) is working fine

 

[pistolsnipe]

just starting in on a beta 22 build, so im sure you guys will hear more from me haha

i want to build a balanced b22, with each board having a gain of 8.

ive looked around on the amb site and searched a bit here, but couldn't find the answer to this question.

what are the trade-offs in choosing the output voltage of the sigma 22? i would rather have stable than performance, so is 24 volts a better choice than 30?

 

[amb]

+/-30V rails will give you more output voltage swing capability before clipping than +/-24V, and will cause the MOSFETs to run a bit hotter given the same quiescent current settings. There is no difference in "stability", at least not in the established definition of the term with respect to amplifiers.

 

[luvdunhill]

Quote:

Originally Posted by amb /img/forum/go_quote.gif +/-30V rails will give you more output voltage swing capability before clipping than +/-24V, and will cause the MOSFETs to run a bit hotter given the same quiescent current settings. There is no difference in "stability", at least not in the established definition of the term with respect to amplifiers.

Ti:

what's your opinion on how much current and voltage swing is really necessary to drive the more mainstream headphones (i.e. leave out the various outliers with special needs) to reasonable levels?

 

[amb]

Depending on the headphone, of course, since there is a 10+:1 impedance range and varying sensitivities, it's hard to pin down what "mainstream headphones" are. Anyway, a couple hundred mAs and 20Vp-p should be enough for most. But, "enough" is a qualitative description. Just like 100 hp/100 lb.ft of torque is "enough" for a car to get the job done...

 

[fault151]

Hi guys, I finally got round to taking some pics of my B22 amp. It has taken me over a year to get to this point and I thought i'd share my hard work with you all. First of all, a [size=x-large]MASSIVE[/size] thank you to everyone who has helped me with this project especially, Ti (AMB LAbs), MR Majestic, and johnwmclean. I would not have been able to do it without your help and patience!

The amp sounds bloody amazing, really happy with it. Its safe to say its not the easiest amp I have ever built, there is a lot that can go wrong (and did go wrong!) but got there in the end. I will be adding some more pics for those interested on the post pics thread (I didn't want to clutter this thread too much).

 

[digger945]

That is indeed Refined. Great pics of a very nice looking amp.

 

[nattonrice]

Very sexy!
I love the layout =)

 

[fault151]

Cheers guys, i tried to go balanced/symmetrical all the way even in the layout.