DAC for Studer d730 or d731

[mrtakib]

The internal DAC on the Studer d 730 and d 731 gives a great sound on these machines. I was wondering if anyone had found or used an external more modern DAC that can further improve the sound?

[OneyedK]

Originally posted by mrtakib
The internal DAC on the Studer d 730 and d 731 gives a great sound on these machines. I was wondering if anyone had found or used an external more modern DAC that can further improve the sound?

Yups, I did.
Problem with those machines is that the AES-output has a lot of jitter.
(measurements done on several D731's)
Think improving the clocks would benefit them more than using an external DAC.
(D730's have to be wordclocked or they really run out of spec)

[mrtakib]

Thanks, So there was no improvement with the external DAC or just a little ?
Interesting comment about the clock. How would you go about to improve it ?
Mine is the D731

[OneyedK]

There are several options:

1) simply feed a wordclock signal to the wordclock input. (easy, if you have a wordclock at hand)
2) remove C720, C721, R729 and X701. Connect a decent clock (kwak, tent, ...) to pin 2 of IC707. btw, fequency of that clock is 11.2896MHz

These two options leave every function of the D731 intact.
It's a good idea to change the most important alectrolytic caps while you have the device open.
Best to change D701 (BB212), part of the VCO, they age quickly...

Now the other option is to replace the system clock completely.
Remove IC705 and feed the output of a decent clock to where pin 3 of that chip used to be.
This option certainly the best sounding, but there's no way to use the varispeed again. (wordclocking will also be impossible)

The DAC of the D731 consists of a format converter from Philips transport to Sony format (basically a 16-bit shift register), 8x oversampling filter (SM5803_APT), 3rd order noise shaper (SAA_7350) and finally the TDA1547.

Now after the TDA1547, Studer moves directly to single ended.
By means of NE5532AN (room for improvement there, IC402 and IC452). After those, the industrial part of the D731 begins, nothing you want to see in a high end player, simply do not use it.
L = pin 7 of IC402
R = pin 7 of IC452

When you want to use an external DAC with the D731, you should clean up the digital output portion of the mainboard, not exactly easy to do. (and still have to improve the clock)

[mrtakib]

Thanks, I will see if I can find a decent clock and see what I can do with it.

On the other hand the D731 does sound pretty amazing just the way it is, so I wonder if it is even worth doing now.

I was thinking of connecting it to a DAC because I want to connect my computer to my hi fi system and if I do get a DAC for that, I want it t least to be an improvement for the D731 while I'm at it.

In the end did you keep your Studer "as is" ?

[OneyedK]

Originally posted by mrtakib

On the other hand the D731 does sound pretty amazing just the way it is, so I wonder if it is even worth doing now.

I was thinking of connecting it to a DAC because I want to connect my computer to my hi fi system and if I do get a DAC for that, I want it t least to be an improvement for the D731 while I'm at it.

In the end did you keep your Studer "as is" ?

If you like the sound, don't change anything!

But changing the NE5532's (IC402, IC403, IC452, IC453) won't hurt and is easy to do.
There are also 2 100µF coupling capacitors in the audio path, chage them to 47µF high quality types. (C411 and C461)
Remove the resistors R416 and R466.
Remove Q401, Q402, Q451 and Q452 (BC817, mute transistors)

All thes things are easy to do and have a very audible and positive effect.

I don't own a D731 or D730, but we're using loads of them at work (100+) since they are the only players with a simple serial protocol to read de display info into other systems.
We do have to service them, after all, they are old...

[mrtakib]

Originally posted by OneyedK


If you like the sound, don't change anything!
...

Well, some CD's sound much better then others that could sound a lot better.

But changing the NE5532's (IC402, IC403, IC452, IC453) won't hurt and is easy to do.
There are also 2 100µF coupling capacitors in the audio path, chage them to 47µF high quality types. (C411 and C461)
... [/B]

Thanks for that.

Remove the resistors R416 and R466.
Remove Q401, Q402, Q451 and Q452 (BC817, mute transistors)
... [/B]

Remove and don't replace ??


Thanks a lot for all the information, it's hard to get and not many people know about these.
What did you think of the DAC in them by the way ?


oh and I'm I correct in thinking that the jitter problem is only using the AES-output and not in normal balanced or unbalanced output ?

Again, thanks.

[OneyedK]

Originally posted by mrtakib

Remove and don't replace ??

Yups, you could change the resistors from 10k to 100k, just to fill the empty holes ;-)

Originally posted by mrtakib

What did you think of the DAC in them by the way ?

I think it's one of the best implementations of the TDA1547.
Sounds very natural and neutral.
(It's a matter of taste)

Originally posted by mrtakib

oh and I'm I correct in thinking that the jitter problem is only using the AES-output and not in normal balanced or unbalanced output ?

Partially correct, it depends on the age and the condition of the caps around the clock and in the power supply. The BB212 should be replaced, depending on how many hours the divice has been switched on.

If you can, borrow a DAC from somebody, if it sounds worse connected to the D731 than when connected to another decent player, you'll know your D731 needs to be taken care of.

[mrtakib]

Originally posted by OneyedK



Partially correct, it depends on the age and the condition of the caps around the clock and in the power supply. The BB212 should be replaced, depending on how many hours the divice has been switched on.

If you can, borrow a DAC from somebody, if it sounds worse connected to the D731 than when connected to another decent player, you'll know your D731 needs to be taken care of.

That is a good idea ! I will see what I can find. btw, where is BB212, I don't seem to find that?


earlier you mentioned...

2) remove C720, C721, R729 and X701. Connect a decent clock (kwak, tent, ...) to pin 2 of IC707

If I did go this route what happens to C720, C721, R729 and X701 after I connect a new clock, do they go back on ?


How is it you know this machine so well !

Thanks again for all your valuable information. I do like this player and hope to keep it up as best as possible. As for the future I think I will give a hard drive as a transport for non compressed music a go. There are also a bunch of ipod transports on the way that will bypass the internal dac and offer digital out.

[OneyedK]

Originally posted by mrtakib
btw, where is BB212, I don't seem to find that?

It's close to IC704 and looks like a transistor.

Originally posted by mrtakib

If I did go this route what happens to C720, C721, R729 and X701 after I connect a new clock, do they go back on ?

The parts mentioned there are all part of the original oscillator,
they have to be removed or the new clock will not work properly.

Originally posted by mrtakib

How is it you know this machine so well !

We use a lot (100+) of these machines at work...
They all are end of life (transport nog longer replaceable or serviceable) but we want to keep them as long as possible.

Originally posted by mrtakib
I do like this player and hope to keep it up as best as possible. As for the future I think I will give a hard drive as a transport for non compressed music a go. There are also a bunch of ipod transports on the way that will bypass the internal dac and offer digital out.

It's a great player, but if the transport dies, it's finished
@home, I use Denon CD-players, not the best, but a lot of room for audible improvement. Measurements of my unmodified DCD-1550AR don't differ much from those of a great unmodified sample of the D731. Still working on the DCD-1550AR.
If that's finished, I'll start on a quiet Linuxbox to play uncompressed audiofiles.
I still like the CD as a media format best, not from a audiophile point of view, but I like to have a disc in my hands ;-)

Good luck with the modifications!