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Old 20th September 2013, 03:07 AM   #1
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Default Transformer selection for DAC

Hi Everyone,

I am looking at out transformers for a DAC. Basically I am planning to modify a AKM 4396 voltage out DAC. I intend to feed the output voltage of the DAC chip into a buffer (direct without any capacitors) probably based on a Nelson Pass B1 design. There would be two output stage per DAC chip with regards to the differential output. The output will be fed a line output transformer.

I am looking out for a suitable transformer. Looked at a few websites, can't figure out which one to choose.

I am looking at a budget of about $100 for one pair. I could see Jensen being a good candidate but which model? I would like to have an amorphous core if possible, supposedly better, but I don't think it is really in the budget.

Any suggestions?

Oon
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Old 20th September 2013, 04:01 AM   #2
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I use Jensen JT-11-DMCF transformers on a CS4398 DAC. The Experience with this DIY DAC thread has a lot of discussion of various transformers from cheap to expensive.
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Old 20th September 2013, 07:39 AM   #3
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Thanks,

That thread is too long to go through.. at over 400 pages... But found some nice references...

SOWTER DAC I/V TRANSFORMERS

Thanks.

Oon
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Old 20th September 2013, 10:11 AM   #4
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I use Jensen JT-11-EMCF on a AKM-4393 with very good results.
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Old 20th September 2013, 12:05 PM   #5
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This is how I implemented it on my DAC. I used SE output circuit but it can be balanced if you want.
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Old 20th September 2013, 12:14 PM   #6
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Thanks Pete,

I was thinking of doing that too. But I reckon my load might be a bit heavy. So not sure if will overload the dac...

That is why I thought of using the fet buffer...

Oon
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Old 20th September 2013, 12:22 PM   #7
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Correction. There is no connection to ground on the RCA output.
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Old 20th September 2013, 01:25 PM   #8
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Why did you choose this particular transformer. All the Jensen stuff looks so identical..
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Old 20th September 2013, 02:11 PM   #9
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FYI - Nearly all amorphous core, or nickel alloy core transformer will require that you ensure there is essentially no (less than 1mV) D.C. offset applied to their primaries. If you will be utilizing a B1 style balanced JFET buffer, there will be too much D.C. offset at their outputs, necessitating either a hand trimmed compensation network or a D.C. blocking capacitor.
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Old 20th September 2013, 02:16 PM   #10
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Quote:
Originally Posted by Ken Newton View Post
FYI - Nearly all amorphous core, or nickel alloy core transformer will require that you ensure there is essentially no (less than 1mV) D.C. offset applied to their primaries. If you will be utilizing a B1 style balanced JFET buffer, there will be too much D.C. offset at their outputs, necessitating either a hand trimmed compensation network or a D.C. blocking capacitor.
Per previous testing, as been established that there is no DC offset at the output of AKM-439x DAC so it is optional to put a DC blocking cap before the transformer in this application.

Last edited by petefrontiers; 20th September 2013 at 02:29 PM.
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