SCD-1/777ES Output Buffer Mod

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If youâ€™ve studied the innards of you SCD-1/777ES, youâ€™ve noticed that there are a pair of AD712 op amps that act as the voltage gain stages of the output buffers and as servos to eliminate DC at the single-ended outputs. If you have an SCD-1, there are two more AD712s on the balanced output board that construct a balanced output from a single-ended input.
You may also know that the AD712 has excellent DC performance â€“ but is mediocre in audio applications. Alleged weaknesses include a thin top and an ample but flabby bottom â€“ problems not unique to op amps. Of the op amps present in the SCD-1/777ES (OPA2604, OPA2132, LM6172 and AD712), the AD712 is the one that most deserves to be sent packing.
So why did Sony use the AD712s? It could be because the 712s are known to perform well in servo applications or because Sony was using AD712s regularly in the era that the SCD-1 was designed. Or maybe Sony didnâ€™t want to pop for the hi-spec version of the OPA2132 needed to match the DC performance of the AD712s.
But I wanted OPA2132s and was willing to pay $8.20 each to get them. There are other choices like the OP249 and the recently released AD8512. Inmate Phopson just installed the AD8512s and reported greater transparency, more bass and a wider and deeper soundstage. But there are some compelling reasons to use the OPA2132:
- The op amps preceding the AD712s are OPA2132s used to combine the positive and negative signals from the I/V conversion stage. Consistency is sometimes a good thing.
- The OPA2132 is known to have excellent audio performance â€“ better than the OP249. The AD8512 is a brand new op amp â€“ and I wasnâ€™t really in the mood to venture into the unknown. Maybe Iâ€™m just getting old.
- The OPA2132 is available in a hi-spec version that has even better dc performance than the AD712 and OP249 â€“ helping to ensure good servo performance.
- Sony uses the OPA2132s in the highly regarded XA-777ES for all of the analog chores.
Doing this mod is a bit of a bother unless you happen to have the skills and equipment to deal with surface mount devices. I donâ€™t, so I had to take the board out to a place that does prototyping and repair work and pay the $50 minimum charge for the 20 minute swap job.
I must say that this mod is far more effective than I ever dreamed that it might be. If I had to use one word to describe its effects, I would say â€œMOREâ€. There is just more of everything. More body, more bass, more articulation, more dynamics, a more extended treble and more clarity.
My SCD-777ES has always sounded very musical and refined â€“ but itâ€™s been polite to the point of being uninvolving. Now thatâ€™s changed. Organ pedal notes send shivers up my spine for the first time with the 777ES. And my feet have started to move with the music. This mod is absolutely worth doing!
I suspect that SCD-1 owners who are using their balanced outputs would also benefit from replacing the AD712s on the balanced output board. And consider doing something with the output coupling caps as well.
By the way, if youâ€™ve been blaming that music-obscuring fog on the Riken resistors â€“ the fog lifts when the AD712s are replaced. The big, slightly warm sound of the Rikens remains.

Other SCD-1/777ES Mods and Information
AC Board:
Removed choke on analog power supply
http://www.audioasylum.com/forums/hirez/messages/32357.html
Reversed AC polarity
(Not posted)
Output Board
Replaced RCA jacks with Vampire OFC jacks
Replaced output wire with Kimber AGSS
Revised grounding creating a star ground for audio board
http://www.audioasylum.com/forums/hirez/messages/41691.html
Audio Board
Replaced AD712s in the output buffer with hi-spec OPA2132s
(This post)
Set filters to â€œcustomâ€
General Description
Analog Signal Path
http://www.audioasylum.com/forums/hirez/messages/33130.html
Accessories
Electraglide Reference Glide power cord
Chang Lightspeed HT1000 power conditioner (w/upgraded capacitors)
AudioDesk Systeme CD Lathe

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Schiit Audio

Topic - SCD-1/777ES Output Buffer Mod - jhietbrink 19:01:49 06/10/02 (5)

Try current loading also... - PhopsonNY 05:50:04 06/11/02 (0)

Re: SCD-1/777ES Output Buffer Mod - fmak 23:26:45 06/10/02 (0)

Re: SCD-1/777ES Output Buffer Mod - musicluver 22:15:33 06/10/02 (0)

Great post! - NGeorge 19:22:58 06/10/02 (1)

Re: Other Mods - jhietbrink 19:48:39 06/11/02 (0)

You can not post to an archived thread.