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The Channel Islands VDA-1 is a fine-sounding, musical DAC, especially with some modest mods like soft-recovery or Schottky recitifer diodes and better caps.However, it does NOT do de-emphasis of CDs recorded with pre-emphasis. True, the number of such discs is low (<1% ?), and new CDs will not have pre-emphasis. However the Glenn Gould (1980) Goldberg Variations does, as do a fair number of CDs from Hyperion, Sheffield Labs, etc.
Not having de-emphasis is NOT like not having HDCD. Listening to a CD with pre-emphasis but no de-emphasis is horrible -- totally unlistenable. It's +10.4dB at 10kKz!
Good news for the risk-takers: I've found that the receiver and DAC on the VDA-1 do support very accurate digital de-emphasis. All it takes is one connection from the receiver (DIR1701) to the DAC (PCM1716). Tricky because they're surface mount, but possible at home. I'm listening to the Gould Golberg as I type... at last! I won't be posting technical details until this mod is verified and proves stable.
Follow Ups:
I'm wondering if later VDA-1s may have this problem fixed. I tried some of my old CDs (Sony's, Sheffields, and others), and none have that overly-bright sound. (I'd figure to check inside, but I don't like opening up anything that I otherwise have no problem with.)Are all Sheffield CD pre-emphasized or just some? I have "Growing Up in Hollywood Town", "Prime Cuts", and the Sheffield/XLO Burn-In/Test CD.
I put in "Growing Up in Hollywood Town", and the emphasis LED lit up on my old Proceed DAC. Yes, it has pre-emphasis.I'd be surprised that there's a new version with de-emphasis enabled -- Dusty really did not seem bothered about this, and he said on his email to me that "The VDA-1 does not has digital de-emphasis as this recording practice was done away with several years ago. Most current DAC IC's (like the Burr Brown PCM1716) do not have a provision for this.". It's a little puzzling, because the 1716 certainly does have provision for it; it fact it does de-emp for 32, 44.1 and 48kHz -- pretty neat.
All you need to do is to remove the 4 rear screws, and see if the 1716 has any connection to pin 27 (2nd last pin), or pin 26. I'd be very interested to know if it's implemented. My VDA-1 arrived in Aug 2002.
"I put in 'Growing Up in Hollywood Town', and the emphasis LED lit up on my old Proceed DAC. Yes, it has pre-emphasis."Just played the entire album. Sounds great on the VDA-1!!
If I come across a CD that sounds "pre-emphasized" without decoding (or if I get some time to investigate the internal connections), you'll be the first to know.
Original:DIR1701 Emphasis Flag, EMFLG (Pin 17) -> N/C
PCM1716 DM1, Gnd --> DM1 (Pin 27) (one of the emphasis pins, used when the DAC is in hardware mode)Mod:
DIR1701 EMFLG -> PCM1716 DM1
When a CD has pre-emphasis, EMFLG goes high. When DM1 is brought high, 44.1kHz digital de-emphasis is applied.
No guarantees! YMMV! Read the datasheets before you proceed. I was not careful with soldering, and pulled the entire leg off the PCM1716. It took *very* fine soldering to connect a fine wire almost directly on the remaining stump of the leg!
Enjoy. Also look into soft recovery diodes and better electrolytic caps for the board. I didn't touch the op-amp or or anything else. Channel Islands have done a very nice job in voicing the op-amp (class-A bias).
would it add more pace perhaps?
How much of drastic change in its overall presentation?
.. so that CDs recorded with pre-emphasis sound correct. Otherwise they sound *very* bright. Few CDs ( < 1%?) were produced with pre-emphasis, but they are quite un-listenable without correct de-emphasis.Without correct de-emphasis, the sound will be around +3dB at 3kHz, +6 at 7kHz, and +9 at 10kHz (these are approximate). I believe that pre-emphasis was added in analog recordings so that the subsequent de-emphasis would reduce tape hiss, and improved HF headroom.
Some CDs I own with pre-emphasis:
(Sony) Glenn Gould 1980 Goldberg
(Hyperion) Emma Kirkby collection
(Sheffield Labs) Various
(Stereophile) Some tracks on Test CD 2 (organ trio sonata)I've not checked my library extensively. I have more than the expected 1%. I think anyone who has AAD and ADD recordings may have them. Sony apparently believed that pre-emphasis helped in days when DACs could really only do 14 bits of conversion.
i must not own any of those *pre-emphasised* CDs since they don't sound *bright* in my system.
You may want to post a sketch of the mod. I'd be interested in doing this myself.Your findings are much-appreciated.
Hi Todd,Sent you an email on this. I can't verify the mod longer-term because I've just broken a leg on the DAC chip(!!), and I'm back to no de-emphasis, and little chance of fixing this. Sigh... If you try it out, and find it reliable, feel free to post it. No magic at all, I was just using the emphasis flag on the DIR1701 into the emphasis select (DM1) of the PCM1716.
mb
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