PCM1704 with Lundahl LL1588?

[spavleski]

Hi,
I'm waiting delivery of 2 X LL1588 in order to put them as DAC (PCM1704 ) output after first OPA627 - I/V converter.

- Schematic attached.

- Any hint/comments ? (Ok/Not Ok, better ideas?)

Thanks,

S.P.

 

[nicoch58]

http://www.audiodesignguide.com/cdplayer/dac.html

I hope help you!

ciao

 

[Francis_Vaughan]

I assume you are simply looking for a balanced output, but also trying to use the natural high frequency rolloff charateristics of the transformer to replace the reconstruction filter.

Just seems a pity to go to all this trouble and still leave the op-amp I/V in place.

 

[spavleski]

Thanks for your comments.

I've just put transformer after OP I/V and sound is OK.

Could there it be better solution - I don't know - maybe ?

 

[nicoch58]

http://digilander.libero.it/paeng/magnetics_frame.htm

is possible complete passive out stage ...hope.... r i/v and trafo

 

[spavleski]

I've tried to bias I/V OPA627 in class A with 8mA (using BC107B as current source).

And... sound improves gradualy!

Now thinking, is this the best operating point for OPA627 in class A ?

PCM 1704 is giving Iout +, - 1,2mA so, to be able to use passive I/V (resistor) + transformer, transformer have to be step-up type, that I don't have (at the moment) ...

 

[Francis_Vaughan]

There is no reason why you can't add gain after the transformer - with an op-amp if you like. This way around you will avoid the range of issues that may beset using the op-amp as an I/V - and use it for a job to which it is much more suited.

 

[spavleski]

Thanks Francis - great idea! I'll try that.