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-   -   Output transformers for DACs (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs.html)

analog_sa 4th December 2018 01:10 PM

Well done and well presented BR & Ivan

Such a low step-up ratio will certainly exceed the voltage compliance range of many dac chips. Do you find this to be the lesser evil compared to the compromises associated with higher ratio transformers?

bisesik 4th December 2018 03:06 PM

Quote:

Originally Posted by schultzsch (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5621717.html#post5621717)
Very nice work you did there. Congratulations!

Thank you!

Quote:

Originally Posted by analog_sa (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5621726.html#post5621726)
Well done and well presented BR & Ivan

Thanks guys.

Quote:

Originally Posted by analog_sa (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5621726.html#post5621726)
Such a low step-up ratio will certainly exceed the voltage compliance range of many dac chips. Do you find this to be the lesser evil compared to the compromises associated with higher ratio transformers?

In my understanding step-up transformers are for current output DACs mostly. I think, that the main problem of many other step-up transformers on market is that they have simultaneously too low inductance (LF losses) and too high DC impedance of primary coil (undesirable voltage presence attached to the output during "signal generation") , that make bad impact on the output of the curent type DAC.

In case of Voltage Type DAC like AK4490 it is better to use 1:1 with high primary inductance and DCR. But I do not recommend use such 1:1 with its 450 Ohm DCR with PCM63 for example, because to the output will be attached (as I said earlier) undesirable voltage presence that will degrade the whole SQ.

Regarding step-up vs step-down transformers. It is always better to use step-down transformer to store the load capability (current) of the source and FR. But in case of the curent type DAC it is hard to get simultaneously the high enough signal and flat FR from 20 to 20k. If 0.5 V (p-p) instead of 2 V is enough for the next device input, then to save output current of the DAC is better to use 1:1 instead of 1:4. But my practice say that is is better to get as high signal as possible straight from the DAC, instead of make futher amplification of lowlevel signal, because you are limited on the "bottom" by PSU noises and no amplification will returns the beaten\lost signal.
So my opinion is for Current DACs is better to use step-up transformers, for Voltage DACs - step-down transformers (1:1).

gabdx 4th December 2018 03:15 PM

Must sound superb with tda1541.

Great work there.

analog_sa 4th December 2018 03:53 PM

Quote:

Originally Posted by bisesik (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5621828.html#post5621828)
So my opinion is for Current DACs is better to use step-up transformers, for Voltage DACs - step-down transformers (1:1).


I assumed mentioning voltage compliance will make it clear my question concerns only current output dacs...

bisesik 4th December 2018 04:07 PM

Thanks. TDA154x has DC-offset on the output, that is why one extra compensative (2mA) coil is used in addition to the primary coil.

nounouchet 4th December 2018 05:14 PM

Hi bisesik,


Your transformers look good.
I tested a Jensen JT-11-DM with a DAC AK4490 and it works really well.
If your transformers work as well then it's wonderful because the price is more interesting!
I'm going into active tri-amplification and I'll be interested in getting you a pair.
What is the delivery time and price for France?

Is it possible to have a picture of the inside of the box?


nounouchet

bisesik 4th December 2018 05:54 PM

1 Attachment(s)
Quote:

Originally Posted by nounouchet (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5621965.html#post5621965)
What is the delivery time and price for France?
nounouchet

Last time delivery to Germany was 2 weeks (registered air), but Christmas is coming soon, may be will longer. $10

Quote:

Originally Posted by nounouchet (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5621965.html#post5621965)
Is it possible to have a picture of the inside of the box?
nounouchet

Transformer is made on this nanocrystalline core
Attachment 719910

after winding the transformer, it is filling with epoxy inside the screen

nounouchet 10th December 2018 08:52 AM

Hi bisesik,


Dimensions for DAC voltage transformers are the same ? : OD=47mm, H=24mm

analog_sa 10th December 2018 09:27 AM

Still, very dubious these will work well with pure current output dacs. Whether the loading resistor is applied to the primary or secondary the effective load seen at the dac output is way too high for any reasonable voltage compliance. With voltage output dacs, these seem perfect but unless SE>BAL or BAL>SE conversion is required i cannot quite see the purpose of a transformer. Is it to act as a low pass?

Not arguing at all with the excellence of the transformers, just the application.

bisesik 10th December 2018 10:02 AM

Quote:

Originally Posted by nounouchet (https://www.diyaudio.com/forums/vendor-s-bazaar/327794-output-transformers-dacs-post5627921.html#post5627921)
Hi bisesik,


Dimensions for DAC voltage transformers are the same ? : OD=47mm, H=24mm

Yes


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