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Roll Call: Who's building, built, or thinking of building a beta22? - Page 162

post #2416 of 2875
2/18/10 at 11:38pm
Quote:
Originally Posted by boinger View Post
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?
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post #2417 of 2875
2/18/10 at 11:44pm
Quote:
Originally Posted by luvdunhill View Post
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??
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post #2418 of 2875
2/18/10 at 11:50pm
Quote:
Originally Posted by Fitz View Post
But what did you have to do to fix it??
I replaced the MOSFETs. Then it worked fine.
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post #2419 of 2875
2/19/10 at 3:33am
Quote:
Originally Posted by amb View Post
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 ?
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post #2420 of 2875
2/19/10 at 4:39am
Fuse?
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post #2421 of 2875
2/19/10 at 4:40am
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.
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post #2422 of 2875
2/19/10 at 8:25am
ok thanks will do


Edit:

Quote:
Originally Posted by johnwmclean View Post
Fuse?

no its not the fuse cause my other sigma (from the same mains) is working fine
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post #2423 of 2875
2/20/10 at 6:35pm
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?
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post #2424 of 2875
2/20/10 at 9:04pm
+/-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.
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post #2425 of 2875
2/20/10 at 11:07pm
Quote:
Originally Posted by amb View Post
+/-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?
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post #2426 of 2875
2/21/10 at 2:12am
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...
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post #2427 of 2875
2/21/10 at 9:14am

B22 Headphone Amplifier finished pictures - Refined Audio

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 MASSIVE 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).











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post #2428 of 2875
2/21/10 at 9:40am
That is indeed Refined. Great pics of a very nice looking amp.
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post #2429 of 2875
2/21/10 at 9:42am
Very sexy!
I love the layout =)
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post #2430 of 2875
2/21/10 at 9:56am
Cheers guys, i tried to go balanced/symmetrical all the way even in the layout.
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