Basics on transformer-coupling dacs ?

[rc30geir]

The loadresistor is 36 Ohm as per Doedes instructions. (180 Ohm/ dacboards) I have no clue what output impedance it has. I'm just thinkering and has implementied an idea I've had for a long time. The transformers are connected in a 1:2 configuration. Per Lundahl advised against connecting the secondaries in parallell. This gives me a little bit high output voltage, but my preamp doesn't seem to mind.

Geir

[Bill Fuss]

Didn't they recommend a resistor load for the trafo? That's surprising if they didn't.

[rc30geir]

When used as an input transformer they recommend a source impedance of 600 Ohm and load impedance of 10KOhm.
I didn't think much about that because I used it mostly to be able to use balanced cables and thought that when used in a parafeedconfiguration that would be irrelevant. The loadresistor is placed across the primaries and not the secondaries as I've seen in other implementations.

Geir

[Bill Fuss]

I think the issue would be taming the resonance of the trafo at elevated frequencies. You might want to experiment with a secondary load with an added resistor of 10k or so. Just a thought.

[paulb]

Originally Posted by intermittent

-- guess I'm basically asking for a FAQ on tx-coupled-dac-output. Please presume a standard 2V dac output signal, and thanks for any of the requested info.

intermitten t

I guess my question is, if you don't know much about this, what made you decide to pursue it? Not criticizing, just asking.
I think this forum's Steve Eddy is a big transformer fan. You might want to search around for some of his posts.

[intermittent]

Originally Posted by paulb

I guess my question is, if you don't know much about this, what made you decide to pursue it? Not criticizing, just asking.
I think this forum's Steve Eddy is a big transformer fan. You might want to search around for some of his posts.

Why not pursue.. ? Reading-up, learning, looking into new approaches, asking questions, doing mods, etc.. uhm, isn't that the theme of this board ?

What strikes me across all the different 'neighborhoods' of audio, whether moving-coil-stepups, tube-amp-outputs, etc --- is that a properly calculated Tx is often worlds better than other approaches. This is from listening; in reference to tx-coupling dac outputs, as you remark, no, I don't know much, but I notice it's not a completely unknown or undiscovered strategy.

So thanks, I'll try searching some SEddy posts.

[topround]

My friend is going to mod my Lector cd player with the Superclock 4 and transformer coupling with Lundhal transformers. I am dropping it off to him today, I will post my impressions of what has happened to the sound.

He has turned me on to transformer coupling, he does not like caps, his preamp is transformer coupled 26 tubes and my God that thing is glorious!.
Also Reference Audio Mods is now doing mods that include transformer coupling with either copper or silver transformers. He uses Audio Consulting transformers, which may be his own brand.

There definitely is something to transformer coupling that I love, of course all the transformers I have heard used in this way were either, Tango or Black Art, all very high end trannies, cheap trannies might do more harm than good. All I know is that I was a changed man when I heard what transformer coupling does!


Mike