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In Reply to: RE: Lundahl 1931 and 1933 cost posted by 4142 on February 23, 2013 at 08:51:32
Interesting... Kevin, does Lundahl offer equivalents to the 1931 and 1933 without the special Cardas wire?I'm working on a project requiring a 1:7 or 1:8 ratio step-up transformers utilized in a direct line output application, driven from mono configured PCM1794A DACs. Yes, similar in application to the RAKK DAC's passive LL1674 output, but having lower parasitic impedance contribution from the winding resistances than is offered in the 1674. The total differential I/V circuit source resistance - via passive resistors connected from the DAC current outputs to ground, not via the RAKK DAC style reflected DAC loading - would be 25 ohms, 12.5 ohms per output phase. The target full-scale output amplitude from the secondary is around 1VRMS, from a primary side maximum differential signal amplitude of around 140mVRMS.
Given this application, the D.C. resistance of the windings, as you know, can become a very significant parasitic factor in increasing the effective output impedance presented by the secondary. The 1931 and 1933 seem the Lundahl transformers closest to my target performance requirements (approx. 1:8 ratio, sufficient primary inductance for use with a 25 ohm source impedance with low distortion @ 1VRMS out, low primary and secondary winding resistances so to minimize parasitic inflation the output impedance), but their $200+ cost is a major deterrent. It could make the difference, if sufficient savings might be had utilizing standard Lundahl magnet wire, such as is presumably used in the 1674 and 1922, rather than the nice but evidently costly, Cardas wire.
Please advise, thanks.
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Ken Newton
Edits: 02/23/13 02/23/13 02/23/13 02/23/13 02/23/13Follow Ups:
These transformers are not produced with "standard" copper wire. You might be able to convince Lundahl to make a run of coils with standard wire, but you would have to buy the whole run's worth of transformers. You'd need to contact Per Lundahl (per@lundahl.se) directly to see if this was feasible.
Kevin Carter
K&K Audio
www.kandkaudio.com
Okay, thanks. Out of curiosity, how many units constitute a run?
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Ken Newton
That would be a question for Per, as I have no idea how many coils are deemed a minimum practical batch.
Kevin Carter
K&K Audio
www.kandkaudio.com
You think the cost for the Cardas copper wire is steep, look at the price of a 1931AG with silver wire!
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