After much thread searching , I'm going to try resistor based i-v conversion in lieu of op-amp , in my Denon DCD-2560 player. The player uses the AD1862N-D dac chip , with 2 per channel. Appears to be in differential mode. I'm having a difficult time determining which transformer to use for step-up. I would like to be able to use the trans as the output stage also. The AD1862 datasheet states ouput current as +-1ma. I'm thinking I should begin with a 100ohm resistor(?). My thought is , since this voltage out will be in millivolts , can I look at this output as stepping up the voltage of a MC phono cartridge? I would seem a lot easier to determine which transformer to use. Are there other considerations I should be aware of? What transformer specs should I look for when chosing one for I-V step-up (pri imped, sec imped)?
Thank-you
Paul
Thank-you
Paul
sreten said:Hi,
it sounds like it will not be able to drive the output cable capacitance.
The higher the output voltage, the longer the cable, the worse it will get.
/sreten.
Is there a practicle way of doing this resistor i-v with a passive(transformer step-up) output stage? Is itthe AD1862 DAC chip(s) or is this the usual problem with transformer based output?
An "easy" way is to use a tube stage and step-down transformers.
How much of a problem is step-up transformers? People are using passive transformer attenuators seemingly without problem.
Since you will end up with something like 5kOhms with step-up transformers, your pre/amp will need to have higher input impedance than that. That should be no problem.
How much of a problem is step-up transformers? People are using passive transformer attenuators seemingly without problem.
Since you will end up with something like 5kOhms with step-up transformers, your pre/amp will need to have higher input impedance than that. That should be no problem.
My tube pre-amp has an input imped of 300k. At this point , I need some help in chosing a transformer . Do I want very low pri. imped.(<100ohm)? Does it need to be center-taped? And does this whole thing become more problematic as I increase the ,turns-ratio'? I'm willing to purchase good(expensive) transformers for this , but I would really like to do that just once .
.
I hear you. I'm planning to build a SET with interstage transformers. Once the transformers are bought, it's final.
I think 250-Ohms primary will do it. Something like these: http://www.lundahl.se/pdfs/datash/1538_8xl.pdf But this is nothing I know. I don't even know what kind of gain you need.
Hopefully somebody else will jump in. I think you do the right thing. But most people tend to shun transformers for reasons I don't understand.
I think 250-Ohms primary will do it. Something like these: http://www.lundahl.se/pdfs/datash/1538_8xl.pdf But this is nothing I know. I don't even know what kind of gain you need.
Hopefully somebody else will jump in. I think you do the right thing. But most people tend to shun transformers for reasons I don't understand.
look at sowter:
http://www.sowter.co.uk/
search for the dac page on the left
and than the 9762. Specially built for the 186* family.
I have the 9545 with the PCM 1704 sounds very nice
Good luck
http://www.sowter.co.uk/
search for the dac page on the left
and than the 9762. Specially built for the 186* family.
I have the 9545 with the PCM 1704 sounds very nice
Good luck
Dear Wobbly,
nice to give a new life to the discussion.
i used the Caddock MK132 on the primary side of the transformer, 100 ohm's to start with. It will give a low output of about 600 mV in avarage, if I remember well. Later I doubled the resistor to get 50 ohm, it sounded better but the output was twice as low.
Now I use a AudioNote tantalum resistor of 100 ohm and it sounds more natural than the MK132.
I heard that it was possible to put the resistor on the secondary side only a few weeks ago, when I checked the sowter site I read it. At the time that I build my player it was not known so i never experimented with the secondairy resistor.
i can not tell you what the effect will be. But this is the nice world of DIY, try and see, it will not destroy your transformers so,...
I would like to hear the results though.
Good luck
Rob
nice to give a new life to the discussion.
i used the Caddock MK132 on the primary side of the transformer, 100 ohm's to start with. It will give a low output of about 600 mV in avarage, if I remember well. Later I doubled the resistor to get 50 ohm, it sounded better but the output was twice as low.
Now I use a AudioNote tantalum resistor of 100 ohm and it sounds more natural than the MK132.
I heard that it was possible to put the resistor on the secondary side only a few weeks ago, when I checked the sowter site I read it. At the time that I build my player it was not known so i never experimented with the secondairy resistor.
i can not tell you what the effect will be. But this is the nice world of DIY, try and see, it will not destroy your transformers so,...
I would like to hear the results though.
Good luck
Rob
also check out the RAKK DAC using the Lundahl LL1674
http://www.raleighaudio.com/passive_output.htm
http://www.raleighaudio.com/passive_output.htm
You can also adapt my transformer/tube solution that avoids the I/V resistor entirely, it is differential mode:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100297
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100297
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