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Old 24th August 2010, 06:10 PM   #3011
McGyver is offline McGyver  Poland
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Quote:
Originally Posted by RichLund View Post
Mcgyver, would you need separate power supplies for filament and heaters etc?
What do you mean? Filament=heaters.
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Old 24th August 2010, 06:18 PM   #3012
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Sorry, I'm quite inexperienced with tube designs.

For instance with the Aikido and Andrea Ciufolli's DAC-end designs, there is two supply rails: one 12V for the tube heaters and one larger one (200V) for, i think, the filament. I could be wrong. I'm just wondering if your tube stage needs any form of additional power supply. I'm guessing at least 12V for ECC88 (6922) type tubes.
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Old 24th August 2010, 06:21 PM   #3013
Ryssen is offline Ryssen  Sweden
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Quote:
Originally Posted by RichLund View Post
Ryssen I had 47R on each primary!

Was this wrong?
Yes,from each primary winding to ground?I havent tried my PCM1798 yet but I was advised to try with 120 ohms resistors,I think (if Im not wrong) that will give a larger signal than with 47 ohm.
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Old 24th August 2010, 06:30 PM   #3014
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Ok Ryssen, just to clarify -

When you say "from each primary winding to ground" do you mean that the primary leads are attached to the output pins on the DAC adapter and the resistors go from the pins to signal ground.

Not, like previously, the resistors are in series with the leads to the transformers, like here:

Click the image to open in full size.


And you are using no resistors across secondaries?
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Old 24th August 2010, 06:44 PM   #3015
Ryssen is offline Ryssen  Sweden
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Those resistors seems to be in series,they should be to ground,as the PCM1798 is a current output DAC it needs the resistors to ground to generate a outputsignal across them from the current.So remove the resistors,connect the wires directly to the trafo and from each wire a resistor to ground.The resistor and cap at seconary is a filter and should have nothing to do with this so leave them there.
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Old 24th August 2010, 07:02 PM   #3016
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Thanks Ryssen. Yes the pic above is of my old setup and used as an example of what not to do!

Thanks for the advice.

Two more questions:

I suppose it matters little if the resistors are connected at the DAC end or transformer end - to ground.

Would a suitable ground be to return to the power supply 0V or find a nearer one to the DAC?
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Old 24th August 2010, 07:41 PM   #3017
Ryssen is offline Ryssen  Sweden
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You could connect them on the DAC board with the ground where the 2 caps meet (104) like on this photo.

Click the image to open in full size.
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Old 24th August 2010, 10:39 PM   #3018
danrap is offline danrap  Belgium
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Hi Ryssen,
where do you bought that dac board?
thank you so much
dan
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Old 25th August 2010, 12:54 AM   #3019
Ryssen is offline Ryssen  Sweden
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See this post:Experience with this DIY DAC ?
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Old 25th August 2010, 01:08 AM   #3020
danrap is offline danrap  Belgium
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Thank you!!
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