PCM1704 with Lundahl LL1588?

spavleski · 10th February 2006, 09:58 AM

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 · 15th February 2006, 02:05 PM

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

I hope help you!

ciao

Francis_Vaughan · 16th February 2006, 01:04 AM

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 · 22nd February 2006, 12:19 PM

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 · 22nd February 2006, 05:36 PM

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

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

spavleski · 23rd February 2006, 07:52 AM

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 · 24th February 2006, 11:48 AM

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 · 27th February 2006, 11:59 AM

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

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15th February 2006, 02:05 PM	#2
nicoch58 diyAudio Member Join Date: Oct 2004	http://www.audiodesignguide.com/cdplayer/dac.html I hope help you! ciao

16th February 2006, 01:04 AM	#3
Francis_Vaughan diyAudio Member Join Date: Feb 2005 Location: Adelaide	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.

22nd February 2006, 12:19 PM	#4
spavleski diyAudio Member Join Date: Aug 2005 Location: Belgrade	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 ?

22nd February 2006, 05:36 PM	#5
nicoch58 diyAudio Member Join Date: Oct 2004	http://digilander.libero.it/paeng/magnetics_frame.htm is possible complete passive out stage ...hope.... r i/v and trafo

23rd February 2006, 07:52 AM	#6
spavleski diyAudio Member Join Date: Aug 2005 Location: Belgrade	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) ...

24th February 2006, 11:48 AM	#7
Francis_Vaughan diyAudio Member Join Date: Feb 2005 Location: Adelaide	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.

27th February 2006, 11:59 AM	#8
spavleski diyAudio Member Join Date: Aug 2005 Location: Belgrade	Thanks Francis - great idea! I'll try that.

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