[Russtafarian]

I’m in the midst of modding my Pioneer 563A by installing Lundahl transformers to replace the analog stage of the left and right audio output.  Thanks to Kevin at K&K Audio for his help in selecting the transformers.

I’ve wired the voltage outputs of the BB DSD1794 DAC to inputs of a pair of LL1527XL transformers.  So DAC pins 12 (R-) and 13 (R+) are going to one transformer and DAC pins 17 (L+) 18 (L-) are going to the other.  I connected each DAC output wire to one side of a surface mount resistor that traces to the DAC pin.  I wired each transformer for 1:2 to give me as much gain as possible.  The transformer outputs are connected to left and right RCA jacks to feed my preamp.

So does it work?  Yes and no.  For PCM playback it works great!  Both CD and DVD-A sound wonderful, though I haven’t done a lot of critical listening yet.  But the results are so far very promising.

SACD is another story.  When I play an SACD I get signal output, but it’s very hissy.  There is a lot of hiss behind the music and the hiss increases in amplitude at a greater rate than the music when I turn up the volume.  So at higher volume levels the hiss overwhelms the music, whereas at moderate levels the hiss stays in the background.  The hiss level also jumps around.  It doesn’t “pump” with the signal like the old DBX noise reduction systems did.  It’s a steady hiss that jumps up a few db for a bit, then jumps back down, then back up again.  I haven’t listened enough to figure out if this jumping corresponds to signal level or modulation.

Also, when I remove an SACD, I get a strong noise/hum like the ground has been broken.  While the player has the SACD initialized the noise is not there.  But once it releases the SACD, the noise hits until another disc is initialized.  Incidentally this does not happen with PCM discs (CD & DVD-A).  I can change discs freely without this noise.  It’s only when I release an SACD that the noise hits.

My understanding is that the DSD1794 processes PCM but merely passes DSD through the DAC.  My guess is that there is some sort of DSD filtering/buffering that I’m missing when I directly tap into the voltage output of the DAC.  Any thoughts, ideas, suggestions?

[randytsuch]

Here is a link to your dac data sheet
http://focus.ti.com/lit/ds/symlink/dsd1794.pdf

Right in the beginning, it says it supports dsd and pcm, so it does the d/a for both CD and SACD.  There seems to be some misinformation out there over how sacd players handle CD and SACD.

A well known feature of SACD is it generates noise that starts around 50KHZ.  Most SACD players incorporate multi pole filters to take care of this noise.  But 50KHZ is pretty high, so I don't know if that's what is causing your hiss, but its the only reason I know of that would cause it.  

When my SACD1000 was working, I had a transformer output on it, and had no problems, but it used a crystal dac, not the TI/BB ones.

The noise you are getting when the disk is removed would probably be taken care of by a muting transistor or relay, which you have bypassed with your mod.  More expensive players use relays.  You might be able to add a relay and connect it to the existing muting circuit.  This would let you have the muting again, without have a muting transistor messing things up.

BTW, russtafarian seems to be a strange handle for someone from OC .

Hope this help a little.

Randy

[Russtafarian]

I just spent some time adjusting the gain on my preamp inputs to account for the different output level of the transformers.  This fixed the hiss problem.  Stupid me, I should have thought of this first.  Looking back on when I heard the hiss, I was using stereo SACDs with comparatively low output (Florestan Trio and Allison Krause) and was pushing my preamp to the edge of its gain capability.  Once I readjusted the gain, the hiss ceased to be an issue.

I still get a pop when I eject an SACD, but that’s a minor irritant I can live with if necessary.  Maybe I’ll explore options for fixing this down the line.

For now, I’m really enjoying the sound.  I don’t have much point of reference for comparing players but I can say this sounds way better than the stock 563A and the DV-45A I used to have.  I had a Sony SCD-C555ES but it's been 18 months since that was in my system.  From what I remember, this is a least as good as that was for SACD and CD, if not better.

[Mike B.]

I did the same thing to a Sony SACD last year. Very musical and the trannies take several hundred hours of break-in, so expect even more. I assume you put a cap between dac and transformer to block DC? This mod bypasses the muting transistors at the output, so you will get some noise when the mechanism is activated. Enjoy.

[Russtafarian]

I just posted a review of this project in the SACD forum of AA.

http://www.audioasylum.com/forums/hirez/messages/173906.html

[gnnett]

Mike

Just wondering which Sony player it was you have carried out this modification on?

Kind Regards

Grant Newby

[Mike B.]

Hello Grant. I modded a Sony SACD 775. If you want help doing this mod, contact Kevin at the K&K forum at the Audio Asylum. He sells the trannies and offers good advise.