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In Reply to: RE: best lundahl to use with pcm63 and tda1541a posted by AlexanderKonyarov@yahoo.com on July 01, 2009 at 00:23:20
Sasha, I am using standard configurations, exactly as shown in the old DAC tech papers, you can google it easily, also I can draw a sketch and scan it but I don't know how to send it to you, what is your fax number or email?
I would buy LL1674 for the tube line state output, it is a relatively large transformer with 22 v RMS primary(!!!), also for the current output DAC duties as I-V converter it has relatively low ratio (1:8), the volume will be on a low side, I ended up with another gain stage. While I am completely satisfied with the performance of LL1674 it might be overkill for the current output DAC.
If you insist on metal glass - I heard here that LL1678 for the DAC I-V purpose showed surprisingly good results, the DCR is much better as well, you can go with 1:16 single ended or even try the differential (balanced) configuration 1:16+16 (btw, highly recommended, worth every cent you spend on extra tube, I assume you don't go with passive I-V conversion).
In the past I tried 8347 and found that high ratio is very appropriate for the I-V conversion.
With LL1678 you can always lower resistor value (across primary) if you will feel overloading or realize a DC offset. With LL1678 the cost will be much lower too.
It will be a great investment for future transition to vinyl record player with MC cartridge (no kidding).
Actually I was lucky with absence of DC offset in both of my pcm63-based dacs. In case of tda1541- I have 4 DACs running in parallel, the (possible) DC offset can be closer to zero because of averaging.
HL
thx humless
my E-mail Is my nickname
I would like to use only step up transformer with resistor I/V - no output buffers, lamps and etc
do you have a schematic with only resistor and maybe capacitator and step up transformer which you tried with pcm63 and tda1541
OK, I will send it, you can use passive I-V conversion but transformers must be installed in the amp (not in the DAC :) then you can run long cables, also there is a caveat - the transformer approach works best with no-feedback tube amps, in general with simple circuit (=poor filtering) one can get interference noise in feedback amps, it will be unbearable if you use DAC like tda1541 in a non-oversampling mode. The latter works surprisingly good with NFB SET amp,
Effect of transformer-based I-V conversion on sound can be marginal, the I-V conversion might be not the weakest point in the chain, let us move discussion of your setup off the web
HL
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