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Old 29th June 2009, 01:01 PM   #771
McGyver is offline McGyver  Poland
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The voltage should be at safe level. If the tube stage is powered from 200V, then safe voltage of the capacitors is 250VDC.
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Old 30th June 2009, 12:16 AM   #772
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Quote:
Originally posted by McGyver
The voltage should be at safe level. If the tube stage is powered from 200V, then safe voltage of the capacitors is 250VDC.

Ahh got it, so I need to build or buy the power-board first to get an idea what power I'll need for the caps.
I'm still trying to find a suitable board with no luck, did you get a chance to draw a schematic of your power board to give me a rough idea.

Thanks
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Old 30th June 2009, 12:28 AM   #773
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Well, I got this DAC working with these custom transformers, very transparent if a little bit shy down low.

Maybe I just need to adjust some R&C values. hmm...
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Old 30th June 2009, 10:14 AM   #774
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Quote:
Originally posted by shuggi67



Ahh got it, so I need to build or buy the power-board first to get an idea what power I'll need for the caps.

No. You need to know first what voltage needs the tube you're going to use. And then you get an idea what voltage must give your power supply. For example ECC88 needs about 90V, and 6N6P needs about 120V.

Quote:

I'm still trying to find a suitable board with no luck, did you get a chance to draw a schematic of your power board to give me a rough idea.

Thanks
My power supply is something like that:
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Old 30th June 2009, 11:26 AM   #775
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Quote:
Originally posted by data
Well, I got this DAC working with these custom transformers, very transparent if a little bit shy down low.

Maybe I just need to adjust some R&C values. hmm...
Well Done. You'll have to fill us in on the trafos you used, ratio and DCR and such.
I found a small increase in bass when I went from 250R to 500R on the primaries, but the change to 1K didn't seem to make any difference.
I have my NOS A-22s in there now so I can A-B them against the Sescoms. The Sescoms still win but the margin is smaller than the Jensen JT123 comparison. Still, any of them beat my old setup (PCM63-discrete I/V) in resolution and organic texture.

Bill
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Old 30th June 2009, 12:40 PM   #776
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I don't have any info on these tranfos, I just tried different loads on the primaries and secondaries.
They seem to need at least 50k on the secondaries that carry the signal.

Am I supposed to load the negatives on the secondaries too?


This is very difficult when not knowing the specs of the tranfos
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Old 30th June 2009, 02:24 PM   #777
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If you want to do a little detective work you can measure the DCR with a 1K resistor in series with the meter to protect the trafo from possible saturation, then just subtract the 1K from your reading. The nominal impedence is generally 10 to 20 times the DCR so that will give you a ballpark impedence number. If the DCR comes out at 50 ohms or lower then they are probably 600 ohm, if it comes out to 100s or 1000s DCR then you have a high impedance trafo which does need a load resistor. Your secondary wiring should be completely isolated from everything and go directly to your RCA jacks, and your load or filter should go right across the output, pos to neg. There is no difference between them except phase, and either can be used as ground on the RCAs so long as you hook up both channels the same.

Best, Bill
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Old 30th June 2009, 10:03 PM   #778
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Hello folks:

Apologies in advance for not reading all 32 pages of this thread. I will, though. I promise.

I bought a Gigalab dac to turn my Mac Mini into a music server. (This is all a bit new for me.) I have it connected via USB, BTW.

I've burned a few CDs and one SACD to the drive in Apple Lossless format and took the DAC for a test drive. Everything sounds very nice, but I noticed a posting that said single speed sampling it optimal for playback.

If I set the DAC for single speed (00 or 01), there's no sound. It plays fine on double speed (10) and quad speed (11).

Any advice or suggestions on my configuration.

Steve

PS. I was immensely relieved to find a thread on this device.
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Old 30th June 2009, 11:14 PM   #779
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Default Small Polypropylene Caps

Hi guys


Can anyone suggest a manufacturer (or web shop) for 1nF polypropylene caps?

Earlier in this thread I read that polypropylene caps are best for the primary & secondary tran filters, but I can only find them in big values.


Thanks!
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Old 30th June 2009, 11:39 PM   #780
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Wima makes them, I have a bunch of them. Farnell should have them over there. Also Sprague Orange drop 715 or 716, many others.

Steve, I think you'll have to tell us which one you have, there's at least three different versions. How about a pic.

Best, Bill
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