Transformer I/V& OP stage w/AD1862 - Worth the trouble? - diyAudio
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Old 13th October 2006, 02:23 AM   #1
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Default Transformer I/V& OP stage w/AD1862 - Worth the trouble?

I have a Denon DCD-2560 player , which , amoung other things uses 4 AD1862N-D Dac chips. 2 per channel. I'm ready to upgrade the output stage with better(?) op-amps(8 of them) , but somehow this player begs for more. I am very much interested in transformer based I/V conversion AND output stage. It seems GOOD transformers are expensive , but the total cost would be reasonable if that's the complete circuit . This, provided I purchase the correct ones(2) and implement them properly. Anyone have experience with either this DAC(AD1862) or transformer I/V(or both ). Help in this direction , regarding components and outcome are very much appreciated. Thanks
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Old 13th October 2006, 12:45 PM   #2
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Prehaps someone could tell me the transformer specs I should be looking for; Pri. & Sec. impedence , turns ratio , inductance??). I have to believe that this would be a very simple and elegant solution , provided it is done correctly. I think the datasheet states the AD1862 outputs 1ma. There are 2 of these dacs per channel(push-pull?)
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Old 13th October 2006, 02:50 PM   #3
poobah is offline poobah  United States
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A resistor will always be the best I to V convertor.

Tranformers are problematic... why good ones are expensive.

What is your purpose in doing this? That would help you get more replies. Are you looking to achieve a balanced output? If so, what are you driving?

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Old 13th October 2006, 03:15 PM   #4
phn is offline phn  Sweden
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Isn't better sounding a good enough reason?

I expect two 600:600 balancing transformers next week for my PlayStation.

Correct me if I'm wrong here. But as I understand it, you will need gain for the I/V. That invariably means higher output impedance. So tubes (like the Russian 6S45PE) and interstage (step-down) transformers could be an alternative. Just a thought.

Edit: For the tube output stage I'm thinking something like the Euridice line stage.
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Old 13th October 2006, 04:23 PM   #5
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Yes , I do understand that the I/V conversion will be accomplished with a resistor , which is how I would like to replace the original op-amp(s). My frame of reference is something along the lines of K&K Audio's (AA) Rakk Dac Transformer based Passive Output Stage. He (Kevin) is currently out of stock on these for another month , so I was hoping for GOOD alternatives , as well as some additional advice on adjacent circuitry(resistor values and placement, ie. pri or sec. side) for this particular dac set-up (2 AD1862's per channel).
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Old 13th October 2006, 04:32 PM   #6
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After reading my own posts , and the replies , I guess I'm asking for the appropriate resistor value for the dac arrangement , and then the proper transformer for what amounts to step-up for useful output(single ended RCA). My pre-amp is tube based with an input imped of 300k. Can the output , from the dac(s) after I/V conversion ,be associated with the output from a MC phono cartridge?
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