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In Reply to: RE: For starters, because I am thinking I can do better, and... posted by Frihed89 on February 18, 2009 at 10:44:36
Check out "components" in Audio Note website ... you just might find the transformer you're looking for. OTOH ... there are a lot of winders out there and Sowter is one of the oldest, I think (i think old man Sowter wrote some papers on transformer theory ... somewhere in AES files). If your DAC does not use it now, then look for a unity gain 1:1 transformer. They will attenuate high frequencies waaay above 20kHz, thereby eliminating it from your tube circuit.
1. PQ says he doesn't sell the part, also
2. Hifi Collective has a bunch of AN interstage transformers (none of which look like the one in the kit). and
3. Because of my confusion about whether I really want an interstage transformer (which I usually associate with an amplifier) or an a Dac-Grid transformer. However, I can't find a Sowter that is 1:1.
"Live free or die"
Dear Mac,
It is correct that we have stopped selling the components directly, but they are still sold via our distribution network, Anders at Audio Consult sells them all, although he rarely holds stock, neither do we for that matter, they are generally made to order or for internal production.
The I/V interface transformers you are looking for are the TRANS-496 and 497, we are redesigning the versions used in the other DACs at the moment to fit metric bobbins (the old imperial types are getting too hard to find), so expect to see revised versions for sale within the next 3 - 4 months.
Sincerely,
Peter Qvortrup
NT
"Live free or die"
one : measure AC voltage out from your DAC chip, say at 100Hz, 500Hz, 2kHz and 10kHz(from a test CDs. stereophile, chesky, etc...) (use an o-scope. most DMMs are frequency selective). two, measure AC voltage at the grid of your first triode (again use o-scope). three, measure AC voltage out of the unit, at the RCA output. Let us start from there ... BTW, what is/are your tube/s and how is/are they configured? Let's get the voltages and then we ask the guys at tube diy. For all we know, you already have the best there could ever be ... A transformer could provide magical mids, but soft lows and highs. You'd probably need, assuming you need a pair at all, a very small transformer. Get one encased in what is known as mu-metal shield (metal cylinders) like the ones used in microphones or just a little bit bigger. But transformer specs has to conform to your specific circuit. Another btw, a bigger "improvement" could be achieved by building a better and separate power supply for both the digital board and the output tube/s. Cheers
Thanks very much for the detailed information. I see where you are going. I don't have access to an O-scope, but i do have access to a local technician who upgrades AN equipment.
The DAC and output circuits (and parts) look identical to the AN Dac 1.1x/II Sig. I say this not as result of measuring anything, but poking around under the hood. Th tube output is 2xECC88s. It looks like a cathode follower. Is that possible?
I think you are right about new power supplies, but this looked like the easiest, cheapest first thing to do, but it may not be as easy as it looks. Maybe I was wrong. I have decided to stay away from the jitter issue. It's too complicated for me.
"Live free or die"
i started reading on digital-jitter, etc...I am afraid that by the time I would have a vague understanding, I wouldn't be able to handle a soldering iron anymore ...the great digital divide... hehehe. k-follower is possible, low Zout for dynamics. But you'd get "gain" of around 0.9. That means a voltage amp BEFORE the k-follower. I did see some AN stand-alone DACs and they used what they called an SRPP configuration, producing around 2V peak-to-peak output. Sitting down with a qualified tech would be the way to go. Enjoy the weekend.
I've been talking with a local guy and Lukasz Ficus, a polish guy who is called "The Lampizator". He has a home page that's fun under the last "name". He comes highly recommended by the chief designer at deHavilland whose name I will not drop, but i respect her openness and products a lot.
"Live free or die"
ya ... Lucas not only knows a lot, but more importantly, has had long experience with many digital circuits
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