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Old 5th February 2013, 07:09 PM   #3901
shaan is offline shaan  India
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Quote:
Originally Posted by PauloPT View Post
I'm just asking because I see +-45V on the pcb. So +-35V would be OK?
Hi. Yes 35V should be okay.
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Old 6th February 2013, 09:09 AM   #3902
PauloPT is offline PauloPT  Portugal
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Hi shaan,

I need a favour from you. My laser printer doesn't print very dark so I have to print twice in the same sheet of paper. Your pcb layouts are at the middle of the pdf sheet and I can't get the two printouts aligned. Could you please send me a pdf with the layout on the top of the sheet so the disalignment is smaller?
Thank you.
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Old 6th February 2013, 12:37 PM   #3903
PauloPT is offline PauloPT  Portugal
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Quote:
Hi. Yes 35V should be okay.
But is 45V the prefered voltage? I'm not clear why the rails change from 28V to 45V... What is the optimum voltage?
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Old 6th February 2013, 12:52 PM   #3904
mikelm is offline mikelm  England
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what is optimum is not fixed, it depends upon several other factors.

How loud u want the music, how sensistive are you speakers, what the impedance of ur speakers is, how much you want to bias the amp towards class A, How big are your heatsinks ?

But to cut a long story short + / - 35V will be a pretty good starting place for an average kind of a set up.

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Old 6th February 2013, 02:18 PM   #3905
PauloPT is offline PauloPT  Portugal
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Hi mikelm,

How much rail voltage would be fine with just one pair of 2SJ162/SK1058 (this version of the SSA only has one pair) for 4 Ohms duty? Isn't 45V a bit too high?
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Old 6th February 2013, 02:50 PM   #3906
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You have your transformer ? Try-it. It is not loud enough ? Buy one to make 45v.
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Old 6th February 2013, 03:13 PM   #3907
PauloPT is offline PauloPT  Portugal
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The issue is not to be "loud enough" ist about safety. I don't want to blow up the output transistors. First I was thinking in using my 300VA 25-0-25V transfomer wich gives me +-35V dc and myabe regulate the voltage to +-30V so it would be close enough to the 28V of the schematics. Then I saw on the servo pcb +-45V and I tought - I have two 300VA 35-0-35V transformers, if I would use them and regulate the voltage to +-45V I could make a dual mono setup and have more sound quality. But isn't 45V too much specialy with 4Ohms speakers?
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Old 6th February 2013, 03:24 PM   #3908
mikelm is offline mikelm  England
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I think for 4 ohm speakers 35V sounds good - go for it
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Old 6th February 2013, 03:43 PM   #3909
PauloPT is offline PauloPT  Portugal
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Thanks mikelm, that's what I need to know!
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Old 6th February 2013, 04:12 PM   #3910
shaan is offline shaan  India
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Hi paulo.

I got your PM. But I'm sorry to say that right now I am typing from my cellphone and am far away from home, so can't help you with printing problems. Please don't mind.

Here are the answers to some of your previous questions.

I guess ESP P101 can deliver 150w because the FET's Safe Operating Area or SOA allows it at pulses shorter than 50mS or at 20Hz and above with 70v PS rails.

The 45V mod was the result of a fellow diy-er's request. You can safely run the amp from 35V rails into 4ohm with a single pair of FETs.

Happy listening.

shaan
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