What is "Transformer Coupling" and why does it sou

Hantra · « **on:** 17 Sep 2003, 02:22 pm »

All:

I've been thinking about doing something to upgrade my digital. Being that the only DAC I have heard that I like better than my DAC is the Audio Note DAC 3.1x Balanced, it is going to cost me LOTS of money for a 5-10% improvement.

So. . . I did some reading on the AN Balanced DAC's, and I found that the major difference is that they are transformer coupled. Now. . I know that means they use a transformer to do this "coupling" thing instead of caps. But. . I don't know exactly what the "coupling" thing is, and why the transformer is better.

Can anyone enlighten me on this? And how hard would it be to mod my current DAC making it transformer coupled? Perhaps I could avoid laying out a few grand.

Thanks!

B

eico1 · « **Reply #1 on:** 17 Sep 2003, 05:31 pm »

Handra, transformers can cure a lot of ills. Here are 2 great sources for information and harware, jensen for audio and scientific for digital:

http://www.jensen-transformers.com

http://www.scientificonversion.com

randytsuch · « **Reply #2 on:** 17 Sep 2003, 06:33 pm »

These guys make the transformers Bent uses for his preamp, but they make other transformers as well
http://www.stevens-billington.co.uk/

Audio note makes them (obviously)

Audio consulting makes them, sold by referenceaudiomods.com in the US, I have used them and liked them in my SACD 1000.

Another english company is
http://www.sowter.co.uk/

Transformer coupling is simply feeding the single through a transformer. One nice thing is you could make the transformer output either single ended or balanced easily.

Randy

Raj · « **Reply #3 on:** 17 Sep 2003, 06:52 pm »

Hi Hantra,

Hah!,
Just in the process of getting parts together for a tube output stage (cd enhancer II), nearly there!!!!

www.ultranalog.com

also check

http://hjem.get2net.dk/aaholm_audio

between these 2 sites you should find some good info.......

Thanks
Raja

Hantra · « **Reply #4 on:** 17 Sep 2003, 10:06 pm »

Thanks guys.

Raja: I see on your site a few different options. What about those of use with non-oversampling DAC's? I guess the multi-bit one would fit for that, right? I think mine is an 18 bit DAC. . Not sure. .

B

Raj · « **Reply #5 on:** 18 Sep 2003, 05:21 am »

Hi Hantra,

Well, I do know that cd enhancer II is for voltage ouput dacs, so if yours is current output you need to look at cd enhancer I and III. I would find out which dac chip you specifically have, if you have problems doing this, post on diyaudio forums in the digital section, there's plenty of clued up guys there that should be able to help you out. With regards to your question about non os etc, it doesn't really matter I think, although the end result may be different. Dac chips such as tda 1543, are supposed to have a lower hf rolloff than your typical os dac chips, so the rolloff caps in whichever output stage you wish to use may have to be adjusted to compensate for this. In any case the output stages on ultranalog's site can be adjusted to work with most chips i think........ Again you may be able to squeeze the info for your chip and the values required from diyaudio.....

Thanks
Raja

audioengr · « **Reply #6 on:** 19 Sep 2003, 04:05 pm »

There are two concerns with pulse transformers:
1) impedance matching
2) voltage level shifting

You need to be sure that both of these are addressed if you replace or insert a transformer, particularly at the source end. With digital, the signal voltages are fixed, so you cannot arbitrarily change them. If you use a high-quality transformer, there should be just a little added jitter.

This website will educate you on this:

http://www.epanorama.net/documents/audio/spdif.html

Raj · « **Reply #7 on:** 12 Oct 2003, 09:02 am »

Hi,

Well I finished the cd enhancer II, for my pd-s 703, and the results are terriffic, gives a good 3d image of music, and is the most listenable player I've had. In fact as far as I can recall this beats my Arcam cd92 hands down, and that's no mean feat, as the cd92 was a very well engineered machine....

I suppose dc blocking caps certainly do change musical presentaion somewhat, that's what I like about this design, as everything complementary, passive components are kept to a minimum. I don't know how good a dac feeding a OT directly would sound, but considering the state of modern recording methods I'd say that tubes in the signal path somewhere do help.

Thanks
Raja