I have decided to update my old Magnavox CDB650 CDP taking the advice of Kuei Yang Wang (KYW). This entails the analog I/V stage, clock, and PSU. And have divided it on those three sections. This one is the first and covers the I/V section.
The CDP has a SAA7210 Decoder, SAA7220P/A Digital Filter and a TDA1541A S1 DAC.
After pondering the different I/V stages that have been posted on this forum I centered my attention two designs, the one shown by rbroer and the other by KYW and both were kind enough to awnser some questions by private mail regarding their designs.
Even though selecting the KYW OPA660 I/V - Buffer meant a bigger effort in the implementation I decided for this one.
The end result paid back many times the effort I put to build the stage and took me by surprise.
I'm not a High End reviwer so let me say on simple words my appreciation of the sound. Excellent macro and micro transients details, very clean and balanced and very good bass slam.
In short a very worthwhile stage to try and I think it will run with the best ones though I cannot compare.
Here is a pic of the implementation,
The CDP has a SAA7210 Decoder, SAA7220P/A Digital Filter and a TDA1541A S1 DAC.
After pondering the different I/V stages that have been posted on this forum I centered my attention two designs, the one shown by rbroer and the other by KYW and both were kind enough to awnser some questions by private mail regarding their designs.
Even though selecting the KYW OPA660 I/V - Buffer meant a bigger effort in the implementation I decided for this one.
The end result paid back many times the effort I put to build the stage and took me by surprise.
I'm not a High End reviwer so let me say on simple words my appreciation of the sound. Excellent macro and micro transients details, very clean and balanced and very good bass slam.
In short a very worthwhile stage to try and I think it will run with the best ones though I cannot compare.
Here is a pic of the implementation,
Attachments
Is there 39u coupling cap at the output? Should it be that big? Also, where do you get your +/- 8V from?
Pedja,
AD844 won't do as common base I/V since the bias currents for the AD844 input stage are way below the fullscale current of your dac.
Apassgear,
did you manage to find a DIP package
AD844 won't do as common base I/V since the bias currents for the AD844 input stage are way below the fullscale current of your dac.
Apassgear,
did you manage to find a DIP package
Peter Daniel said:
Sorry that the schematic does not read too well but output cap is now set at 3.9u.
The output buffer even though it has a 7 Ohms output impedance does not like heavy loads. So you must limit it to the smaller cap you can get away with. I have tryed up to 15u but the sound degrades with this.
I have a load of 50K on the line amp so I think I can use even a smaller cap, something in the order of 3u but don't have a good cap on that range. BTY it seems that it doesent like much // caps. The sound is very dependant on size and quality of this cap, so for the ones that would like to experiment with this stage be prepared to test several options.
One more thing regarding sound, the response of this I/V stage is such that you will find yourself tweaking the speakers to get the most out of it. To put this in perspective I tryed taking away the only Zobel I have on the system and was amazed to find out the tremendous impact that this seemingly inofensive circuit has on the overall sound (a first for me). I also closed the vent duct of the full range speaker to get rid of reflections from the inside of the box and limit somewhat the LF excursion.
Soundwise it will pay to have a very clean amp (and pre if you use one) and a very simple XOver or none if possible, I'm using only one element and that is a low pass inductor for the bass speaker and this is a very special one which I call a high performance.
Coming to the +-8V preregulated supply you can find details of this at the thread "5V PSU question for analog" from recent days. They were finaly set at 8V instead of 10V.
Peter Daniel said:
That's correct.
I use to have a Jung type reg for analog at the CDP but decided to do the present type arangement.
apassgear said:
Well... with only 15ma output current that's not a surprise.
Maby it should be buffered with a good op-amp.
BTW, there's a DIP version.
At least it's in the datasheet.
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