[thoppa]

Excellent - thanks !

So I think I'll keep the TPS79333 reg and use a 5.1V zener in the σ11 and not use a 4.75V reg - this will be fine right ?

I also plan to use a double-bobbin 0-9V trans and an iso trans too (if I can find a suitable one), so hopefully it will be super-clean power to the y1/y2.

I found some ultra-fast recovery diodes - just 25nS - so they seem slightly better than the legendary MUR820 at 35nS.

Thanks for your help.

 

[amb]

Quote:

Originally Posted by thoppa /img/forum/go_quote.gif So I think I'll keep the TPS79333 reg and use a 5.1V zener in the σ11 and not use a 4.75V reg - this will be fine right ?

Even better would be to use a 5V voltage reference (i.e., LM336BZ-5.0 as described on the σ11 website).

 

[linuxworks]

Quote:

Originally Posted by amb /img/forum/go_quote.gif My own testing of USB-power vs. σ25 external PSU on both γ1 and γ2 showed a measurable reduction in noise floor "hash". My computer's USB power is relatively clean, and I can't hear any of the noise even though I see it in the spectrum analyzer. FWIW, a few people have reported hearing noise with certain computers, and cured it by changing to either σ25 or σ11 external power.

have you seen any diff on the rmaa run between the s11 and s25? and a 317 based reg?

 

[rille2]

My gamma2 makes problems. It outputs music but it is distorted. Where should I start to look at? Voltages are ok. No shorts between the pins of the WM8741 or SRC4192. A sinus looks a bit like a square wave at the oscilloscope. It's likely not the opamp beause the signal looks the same before it.

I made a screenshot:



This should be a 1kHz sinus.

Edit: I should also say that the gamma1 is ok. At his output there's no distortion.

 

[amb]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif have you seen any diff on the rmaa run between the s11 and s25? and a 317 based reg?

No, I don't have an available 5V σ11 to test with currently, or for that matter, a LM317-based one.

 

[amb]

Quote:

Originally Posted by rille2 /img/forum/go_quote.gif My gamma2 makes problems. It outputs music but it is distorted. Where should I start to look at? Voltages are ok. No shorts between the pins of the WM8741 or SRC4192. A sinus looks a bit like a square wave at the oscilloscope. It's likely not the opamp beause the signal looks the same before it.

That's a strange one. I'd start by checking all the solder joints for good connectivity. As I said in the past, 90% of γ1/γ2 problems are solder-joint related.

 

[ujamerstand]

rille2, at least your gamma2 has sound! Mine doesn't even sing at this point.

The voltage readings looks fine, no visible solder joints anywhere; I'm quite puzzled by this...
Gamma1 sections are working, so the problem must be on gamma2 section. But where should I start troubleshooting?

 

[amb]

ujamerstand, have you read through this thread to get ideas first?

 

[linuxworks]

one thing that sometimes happens to my y2 is that the bridge between the lower and upper boards can get loose. I get a whine and burst of static on mine. then I 'slap' the box and it works again. I must have not had the pins aligned well enough when I 'married' the 2 boards together.

I am going to re-align both boards and resolder at least one of the rows of pins. I think others may also have to re-check their pin alignment. its really easy to get those off center just a wee bit.

check that. especially if you had the 'worked once but not now' syndrome.

 

[ujamerstand]

Quote:

Originally Posted by amb /img/forum/go_quote.gif ujamerstand, have you read through this thread to get ideas first?

I have, but that was quite a while ago... I'm just depressed that it didn't work for the first time, that's all. I'll report back when I'm really stuck.

 

[pixeljedi]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif one thing that sometimes happens to my y2 is that the bridge between the lower and upper boards can get loose. I get a whine and burst of static on mine. then I 'slap' the box and it works again.

Like this?

 

[linuxworks]

Quote:

Originally Posted by pixeljedi /img/forum/go_quote.gif Like this?

man oh man, what a blast from the past

 

[thoppa]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Even better would be to use a 5V voltage reference (i.e., LM336BZ-5.0 as described on the σ11 website).

Excellent - much lower noise and accurate enough - thanks again !

BTW the rectifier diodes I chose are Fairchild FFPF10H60STU

FAIRCHILD SEMICONDUCTOR|FFPF10H60STU|DIODE, FAST, 10A, 600V, TO-220F | Farnell Hong Kong

 

[rille2]

Quote:

Originally Posted by amb /img/forum/go_quote.gif That's a strange one. I'd start by checking all the solder joints for good connectivity. As I said in the past, 90% of γ1/γ2 problems are solder-joint related.

They look ok. I will order connectors to make cables for the connection between the boards so I could test them better.

I also had a bad 3,5mm jack in one gamma1 so one output was shorted.

P.S. I built 3 gamma2, the other 2 are working.

 

[linuxworks]

I just fixed 2 y2 baseboards (the y2 board part). both mine and another one (friend's) had misaligned pins (like I was referring to). I did not have to unsolder them, they are not hard to bend and straighten by hand. so folks, do check that: solder the pins to the board, bend them so they're perfect, then use THAT as a guide to place and solder the mating female socket on the y1 board part. that will ensure they both mate and align well.

just regular finger pressure bends them back into alignment.