The differential offset is approx 40mV, and since it's a circuit under test, I didn't want to risk it with transformers. I have similar offset with BiDAT and actually I found it to sound better with V-Cap in coupling (capacitor on one side only), kinda smoother.
I thought you people must have known already about playing the unit with top cover off, but it was pretty interesting to see the laser light penetrating the disk through. I'm pretty much aware that I'm approaching that project some 5-6 years late.
And I can see that this player has quite a big potential, although it's gonna be a lot of work.
I thought you people must have known already about playing the unit with top cover off, but it was pretty interesting to see the laser light penetrating the disk through. I'm pretty much aware that I'm approaching that project some 5-6 years late.
And I can see that this player has quite a big potential, although it's gonna be a lot of work.
Peter Daniel said:
Hi Peter,
I've still got a virgin 777 and I'm getting ready to do some mods.
First off on my list was the op amps, just because its easy.
I see you went with 6172's. Mine has 2604's, and I was pondering putting in LM4562's.
Have you tried anything else besides stock and 6172's?
Have you tried LM4562's?
I was also thinking of bumping up the gain of the I/V to 1k vs 470R. Better distortion numbers, and the LM4562 has twice the gain of the 2604 already with 20dB better THD.
More signal doesn't seem to be a bad thing and the 4562's, as well as most op amps seem to work better at about 4VRMS, distortion and noise wise.
Any comments?
Are there any thoughts on servo's vs coupling caps?
Thanks
Portlandmike
I've been listening to such modified player for some time now, and while bypassing the output stage with S&B transformers provided much more resolution, space and immediacy, somehow I'm loosing the sense of music as the whole. I mean, I'm getting nice sounds, but it is not as musical as with the original Sony output stage, it seems more mechanical and less involving, although very clean. I didn't use the same interconnects for comparison, so maybe the problem is here, I will check again as soon as my new cables arrive.
I will install LM4562 as well, I just ordered some yesterday. Was also thinking about 1k feedback resistors, especially when I have some Vishay S102 in that particular value.
On Audio Asylum there is a lot of posts by jhietbrink, check them all as they guide through very interesting modification process, completely different than all usual modders do. Here are some links (pasted directly from AA post):
"Other SCD-1/777ES Mods and Information:
Analog Signal Path
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
Replaced AD712s in the output buffer stage with hi-spec OPA2132s
http://www.audioasylum.com/forums/hirez/messages/78259.html
Replaced resistors and capacitors in I/V conversion stage
http://www.audioasylum.com/forums/hirez/messages/93363.html
Replaced OPA2604’s in the I/V conversion stage with LM6172’s
http://www.audioasylum.com/forums/hirez/messages/156269.html
Set filters to “custom”
Power Supplies
Revised capacitors on Audio Board digital power supplies and AC Board http://www.audioasylum.com/forums/hirez/messages/155617.html
Revised grounding, AC polarity, analog supply bypassing
http://www.audioasylum.com/forums/hirez/messages/107304.html
Removed choke on analog power supply
http://www.audioasylum.com/forums/hirez/messages/32357.html
Transport
Added capacitance to the “Digital” (Transport) Power Supplies
http://www.audioasylum.com/forums/hirez/messages/133431.html
Separated data and clock cables between Main (Transport) and Audio Boards
http://www.audioasylum.com/forums/hirez/messages/166048.html
Added a new 5V regulator to serve the RF Board
This post
Clock
Improved power supplies to oscillator and S-TACT chip and quieted ground plane
http://www.audioasylum.com/forums/hirez/messages/137033.html
General Description
Analog Signal Path
http://www.audioasylum.com/forums/hirez/messages/33130.html
""
I will install LM4562 as well, I just ordered some yesterday. Was also thinking about 1k feedback resistors, especially when I have some Vishay S102 in that particular value.
On Audio Asylum there is a lot of posts by jhietbrink, check them all as they guide through very interesting modification process, completely different than all usual modders do. Here are some links (pasted directly from AA post):
"Other SCD-1/777ES Mods and Information:
Analog Signal Path
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
Replaced AD712s in the output buffer stage with hi-spec OPA2132s
http://www.audioasylum.com/forums/hirez/messages/78259.html
Replaced resistors and capacitors in I/V conversion stage
http://www.audioasylum.com/forums/hirez/messages/93363.html
Replaced OPA2604’s in the I/V conversion stage with LM6172’s
http://www.audioasylum.com/forums/hirez/messages/156269.html
Set filters to “custom”
Power Supplies
Revised capacitors on Audio Board digital power supplies and AC Board http://www.audioasylum.com/forums/hirez/messages/155617.html
Revised grounding, AC polarity, analog supply bypassing
http://www.audioasylum.com/forums/hirez/messages/107304.html
Removed choke on analog power supply
http://www.audioasylum.com/forums/hirez/messages/32357.html
Transport
Added capacitance to the “Digital” (Transport) Power Supplies
http://www.audioasylum.com/forums/hirez/messages/133431.html
Separated data and clock cables between Main (Transport) and Audio Boards
http://www.audioasylum.com/forums/hirez/messages/166048.html
Added a new 5V regulator to serve the RF Board
This post
Clock
Improved power supplies to oscillator and S-TACT chip and quieted ground plane
http://www.audioasylum.com/forums/hirez/messages/137033.html
General Description
Analog Signal Path
http://www.audioasylum.com/forums/hirez/messages/33130.html
""
Transformers & grounding
Do the S&Bs have gain? I think you need at least 1:2 step-up trannies in this application. Also, if the lack of involvement you're hearing owes to slightly sluggish dynamics and shapeless bass, then this can be improved with a simple SS buffer after the trannies. Also, bypassing the I/V and attaching the trannies directly to the S-TACT is more natural & less synthetic & mechanical sounding than putting them after the I/V stage. But to do so requires additional series resistors on the primaries.
I did all of the grounding mods in jhiebrink's posts and they do make a difference. I made a star ground post at IEC earth and eliminated as many chassis ground loops as possible. For example, you can do this with the Main Board as follows: (1) remove the standup beneath the center ground tab to break chassis ground & run a wire from the ground tab to IEC earth, (2) break all other chassis grounds by putting nylon washers under the head of each PCB mounting screw.
Do the S&Bs have gain? I think you need at least 1:2 step-up trannies in this application. Also, if the lack of involvement you're hearing owes to slightly sluggish dynamics and shapeless bass, then this can be improved with a simple SS buffer after the trannies. Also, bypassing the I/V and attaching the trannies directly to the S-TACT is more natural & less synthetic & mechanical sounding than putting them after the I/V stage. But to do so requires additional series resistors on the primaries.
I did all of the grounding mods in jhiebrink's posts and they do make a difference. I made a star ground post at IEC earth and eliminated as many chassis ground loops as possible. For example, you can do this with the Main Board as follows: (1) remove the standup beneath the center ground tab to break chassis ground & run a wire from the ground tab to IEC earth, (2) break all other chassis grounds by putting nylon washers under the head of each PCB mounting screw.
What's IC107 doing?
Hi guys,
I've been staring at the schematics after reading about some of the 777 mods.
I look at IC107 and 207, along with Q109 and 209, on the analog board, and I can't figure out what the heck the circuit is doing. (It seems like it should be a negative regulator, but its not that, is it?
Its saying its making -4.7V going into the current pulse chip, but as I look at the circuit, it makes no sense.
I simulated it, just in case I was confused, and the output does not make -4.7V.
I traced out the ref manual board artwork, and it seems to agree with the schematic.
I'm curious now. Is this a sony cover up of some key item, or what.
Could this be setting the current in the current pulse chip CSX8042?
If so, how critical could that be, and with a AD712 doing it?
Thanks for you help and insights!
Portlandmike
Hi guys,
I've been staring at the schematics after reading about some of the 777 mods.
I look at IC107 and 207, along with Q109 and 209, on the analog board, and I can't figure out what the heck the circuit is doing. (It seems like it should be a negative regulator, but its not that, is it?
Its saying its making -4.7V going into the current pulse chip, but as I look at the circuit, it makes no sense.
I simulated it, just in case I was confused, and the output does not make -4.7V.
I traced out the ref manual board artwork, and it seems to agree with the schematic.
I'm curious now. Is this a sony cover up of some key item, or what.
Could this be setting the current in the current pulse chip CSX8042?
If so, how critical could that be, and with a AD712 doing it?
Thanks for you help and insights!
Portlandmike
Current Pulse Converter
The STACT is a voltage DAC monolithic op amps, so the current pulse Converters puts the signal back into current mode and the "second" I/V stage back into voltage. More info here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=42441&perpage=10&pagenumber=1
The STACT is a voltage DAC monolithic op amps, so the current pulse Converters puts the signal back into current mode and the "second" I/V stage back into voltage. More info here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=42441&perpage=10&pagenumber=1
Re: Current Pulse Converter
Thanks David. I'm not quite ready to toss the current pulse under the bus yet.
I'm interested in what the AD712 op amp and pnp circuit is suppose to do. I don't see how this is making -4.7 and it goes to a pin called C1ref.
The op amp is running OPEN LOOP. I see no feedback to the inverting input, and the non-inverting input goes to ground.
I'm talking about IC107 and IC207 on the analog board of the SACD-1/777ES
People might be tossing the current pulse under the bus when perhaps a very critical part of the circuit is a AD712 lame duck.
Thanks
Mike
David Garretson said:
Thanks David. I'm not quite ready to toss the current pulse under the bus yet.
I'm interested in what the AD712 op amp and pnp circuit is suppose to do. I don't see how this is making -4.7 and it goes to a pin called C1ref.
The op amp is running OPEN LOOP. I see no feedback to the inverting input, and the non-inverting input goes to ground.
I'm talking about IC107 and IC207 on the analog board of the SACD-1/777ES
People might be tossing the current pulse under the bus when perhaps a very critical part of the circuit is a AD712 lame duck.
Thanks
Mike
I/V op amps
Mike,
Prior to bypassing the I/V stage, I first put dual OPA627s on Brown Dog into the DIP socket, and later replaced the adjacent SOIC AD712 with an OPA2132. I can't remember what was originally in the DIP position. I half recall there may have been some running changes made by Sony in the parts chosen for these positions. In any case, I tested both changes sequentially, & replacing both op amps does makes a nice improvement in sound. There are other SOIC AD712s downstream in the analog section and in the balance board (SCD-1 only) that should be replaced as well.
Regards,
Dave
Mike,
Prior to bypassing the I/V stage, I first put dual OPA627s on Brown Dog into the DIP socket, and later replaced the adjacent SOIC AD712 with an OPA2132. I can't remember what was originally in the DIP position. I half recall there may have been some running changes made by Sony in the parts chosen for these positions. In any case, I tested both changes sequentially, & replacing both op amps does makes a nice improvement in sound. There are other SOIC AD712s downstream in the analog section and in the balance board (SCD-1 only) that should be replaced as well.
Regards,
Dave
I/V op amps
Mike,
Prior to bypassing the I/V stage, I first put dual OPA627s on Brown Dog into the DIP socket, and later replaced the adjacent SOIC AD712 with an OPA2132. I can't remember what was originally in the DIP position. I half recall there may have been some running changes made by Sony in the parts chosen for these positions. In any case, I tested both changes sequentially, & replacing both op amps does makes a nice improvement in sound. There are other SOIC AD712s downstream in the analog section and in the balance board (SCD-1 only) that should be replaced as well.
Regards,
Dave
Mike,
Prior to bypassing the I/V stage, I first put dual OPA627s on Brown Dog into the DIP socket, and later replaced the adjacent SOIC AD712 with an OPA2132. I can't remember what was originally in the DIP position. I half recall there may have been some running changes made by Sony in the parts chosen for these positions. In any case, I tested both changes sequentially, & replacing both op amps does makes a nice improvement in sound. There are other SOIC AD712s downstream in the analog section and in the balance board (SCD-1 only) that should be replaced as well.
Regards,
Dave
Regulation
Yes, the key to improving the stock circuit is to get rid of those 3-pin regulators (both through-hole and SMD). +5V IC304, IC308, IC309 on the Audio Board & IC 401 on the Power Board can all be removed and replaced by one high-quality +5V discrete regulator on the Audio Board near all those +5V applications.
Also, if you bypass the I/V stage to a tranformer output, you can simply remove +/-7V IC105, IC106, IC205, IC206 from the Audio Board, and also remove +/-9V IC402 & IC403 from the Power Board.
Yes, the key to improving the stock circuit is to get rid of those 3-pin regulators (both through-hole and SMD). +5V IC304, IC308, IC309 on the Audio Board & IC 401 on the Power Board can all be removed and replaced by one high-quality +5V discrete regulator on the Audio Board near all those +5V applications.
Also, if you bypass the I/V stage to a tranformer output, you can simply remove +/-7V IC105, IC106, IC205, IC206 from the Audio Board, and also remove +/-9V IC402 & IC403 from the Power Board.
Re: Laser Light
Yup, but what about all those dead laser units and main boards ?
My own experience with Sony has been not that good - the old TV (CRT) keeps plodding away (now not really in use, replaced by plasma unit) but I had to fix their "SOTA" video recorder (also '777') several times and in the end the (hermetically enclosed) switching power supply strarted playing up and that was the last straw.
Shame as it was by far the best looking VCR with a decent audio recording capability.
Not missing it at all now, (b#tt ugly) Panasonic PVR/DVR works like a charm for an occassional recording from FM (not to forget digital radio which is supposedly around the corner for my favourite ABC Classical).
Bratislav
David Garretson said:
Yup, but what about all those dead laser units and main boards ?
My own experience with Sony has been not that good - the old TV (CRT) keeps plodding away (now not really in use, replaced by plasma unit) but I had to fix their "SOTA" video recorder (also '777') several times and in the end the (hermetically enclosed) switching power supply strarted playing up and that was the last straw.
Shame as it was by far the best looking VCR with a decent audio recording capability.
Not missing it at all now, (b#tt ugly) Panasonic PVR/DVR works like a charm for an occassional recording from FM (not to forget digital radio which is supposedly around the corner for my favourite ABC Classical).
Bratislav
Sony
Bratislav,
Yeah I hear you. I have an old XBR TV from 1980 (the golden age of Sony) that still works great. But one should be cautious mucking about with an SCD-1/777ES, as some parts have already been discountinued as per Sony policy of withdrawing support after 7-10 years from date of first production. I have purchased a spare laser and motors to keep mine rolling along. D
Bratislav,
Yeah I hear you. I have an old XBR TV from 1980 (the golden age of Sony) that still works great. But one should be cautious mucking about with an SCD-1/777ES, as some parts have already been discountinued as per Sony policy of withdrawing support after 7-10 years from date of first production. I have purchased a spare laser and motors to keep mine rolling along. D
Re: Regulation
David,
Could be, yet lots of that might be of little importance.
I think the clock needs to have clean power, but not so much the DAC. Not if its only being used as a a zero crossing generator into the current pulse generator. Its way more critical if your actually using it as you are to drive your transformers. Extra so since that's a significant load and all that....
I think the concept is interesting and I want to see what it has.
I think the current pulse chip is actually really really simple, and one could build a really good one very easy.
It just seems insane to me that the whole accuracy of the output is directly proportional to a 3 pin regulator setting the current pulses. Its another perfect case of were two cents would really make a vast improvement and two dollars a huge improvement.
They used a regulator where a reference was called for, or at least another R and C to filter the noise!
I'm not tossing Sony under the bus though. Besides a 100 dollar VCR, I've never had a sony thing to bad on me. Maybe just lucky I guess.
Best Regards,
portlandmike
David Garretson said:
David,
Could be, yet lots of that might be of little importance.
I think the clock needs to have clean power, but not so much the DAC. Not if its only being used as a a zero crossing generator into the current pulse generator. Its way more critical if your actually using it as you are to drive your transformers. Extra so since that's a significant load and all that....
I think the concept is interesting and I want to see what it has.
I think the current pulse chip is actually really really simple, and one could build a really good one very easy.
It just seems insane to me that the whole accuracy of the output is directly proportional to a 3 pin regulator setting the current pulses. Its another perfect case of were two cents would really make a vast improvement and two dollars a huge improvement.
They used a regulator where a reference was called for, or at least another R and C to filter the noise!
I'm not tossing Sony under the bus though. Besides a 100 dollar VCR, I've never had a sony thing to bad on me. Maybe just lucky I guess.
Best Regards,
portlandmike
S-TACT
Mike, you have a better grasp of the technology than I do. I'm just a country boy with the empirical results of my ear on this. I & several others found that improving power to the S-TACT makes a big sonic improvement, whether with the stock analog section or the traffos, both for RBCD & SACD. For further improvement to SACD, you can actually bypass the S-TACT completely (as done by Allen Wright in his VSE L5+ mod). But in this scenario you need a switch, as RBCD still needs to be decoded by the S-TACT.
Mike, you have a better grasp of the technology than I do. I'm just a country boy with the empirical results of my ear on this. I & several others found that improving power to the S-TACT makes a big sonic improvement, whether with the stock analog section or the traffos, both for RBCD & SACD. For further improvement to SACD, you can actually bypass the S-TACT completely (as done by Allen Wright in his VSE L5+ mod). But in this scenario you need a switch, as RBCD still needs to be decoded by the S-TACT.
Re: S-TACT
Ears rule in my book!
I don't doubt that better supplies almost anywhere will improve things. The question I ponder is where is the biggest single improvement had, then where is the next biggest one.
My player is still stock. I want to go in and do a few things to the stock design before I start bypassing everything.
I've noted some things I'd like to do. Like better op amps, better R's and C's. I think the diff to single ended converter 10k resistors are way to large.
I think the current source that sets the reference for the current pulse is weak.
The 10ohm and 68,000pF should change too.
I think I'll increase the gain out of the I/V stage one way or another. Either increasing the reference or changing the 470R's, 10R's and 68,000pF accordingly.
I wouldn't be supprised if the anti aliasing filters wouldn't actaully be better as total passives.
The attenuation at 1Mhz is 180dB by simulation. I think it could be still 150dB and be passive.
Change the R's to metal film, RN65's is what I'd likely use.
The grounding is also a huge issue.
So I'm just getting my thoughts in order before I do this "stock" change.
David Garretson said:
Ears rule in my book!
I don't doubt that better supplies almost anywhere will improve things. The question I ponder is where is the biggest single improvement had, then where is the next biggest one.
My player is still stock. I want to go in and do a few things to the stock design before I start bypassing everything.
I've noted some things I'd like to do. Like better op amps, better R's and C's. I think the diff to single ended converter 10k resistors are way to large.
I think the current source that sets the reference for the current pulse is weak.
The 10ohm and 68,000pF should change too.
I think I'll increase the gain out of the I/V stage one way or another. Either increasing the reference or changing the 470R's, 10R's and 68,000pF accordingly.
I wouldn't be supprised if the anti aliasing filters wouldn't actaully be better as total passives.
The attenuation at 1Mhz is 180dB by simulation. I think it could be still 150dB and be passive.
Change the R's to metal film, RN65's is what I'd likely use.
The grounding is also a huge issue.
So I'm just getting my thoughts in order before I do this "stock" change.
Re: Transformers & grounding
S&B offers 6dB gain, and the output level is approx the same as with Sony stage. The bass is fine too, actually it is better defined, my only complain was that sounds were missing musical purpose, but it seems to be improving now.
I tried LM4562 today, in place of LM6172, but I'm not impressed yet.
The new chips are certainly "cleaner" with more punch, however, the highs seem to be excessively etched, and I'm missing "musical purpose" even more
I'm currently back to LM6172 and I'm still waiting for better interconnects (KS1130).
David Garretson said:
S&B offers 6dB gain, and the output level is approx the same as with Sony stage. The bass is fine too, actually it is better defined, my only complain was that sounds were missing musical purpose, but it seems to be improving now.
I tried LM4562 today, in place of LM6172, but I'm not impressed yet.
The new chips are certainly "cleaner" with more punch, however, the highs seem to be excessively etched, and I'm missing "musical purpose" even more
I'm currently back to LM6172 and I'm still waiting for better interconnects (KS1130).
Resistors
Peter,
You would probably be OK with 220R, but be cautious, as I overloaded & destroyed an S-TACT by experimenting down to zero R when directly attaching my transformers. No fun replacing that 64 pin chip!
I used Caddock MK132 radials in the 330R positions & Caddock flipchips in the 10R positions. If I were doing it over again, I would use SMDs like Vishay vsm1206 (3.81x1.57mm) in place of the large MELFs on the bottom of the PCB, and smaller 0805 (2.03x1.27mm) on the top between the VC24 & the S-TACT. These SMDs have very low TCR of +/-2ppm as compared to 50ppm for the MK132s. But the Caddock radials significantly better the stock SMDs and I have also used them in signal path in the digital section.
Initially I replaced the through-hole Rikens with Vishay VSR4, but these sections of the circuit were later obsoleted by the transformers.
I don't know where Allen Wright taps the SACD bitstream in his S-TACT bypass mod. I suspect he combines the differential phases coming off the 330Rs between the VC24 & S-TACT. If you can figure this out please comment.
Dave
Peter,
You would probably be OK with 220R, but be cautious, as I overloaded & destroyed an S-TACT by experimenting down to zero R when directly attaching my transformers. No fun replacing that 64 pin chip!
I used Caddock MK132 radials in the 330R positions & Caddock flipchips in the 10R positions. If I were doing it over again, I would use SMDs like Vishay vsm1206 (3.81x1.57mm) in place of the large MELFs on the bottom of the PCB, and smaller 0805 (2.03x1.27mm) on the top between the VC24 & the S-TACT. These SMDs have very low TCR of +/-2ppm as compared to 50ppm for the MK132s. But the Caddock radials significantly better the stock SMDs and I have also used them in signal path in the digital section.
Initially I replaced the through-hole Rikens with Vishay VSR4, but these sections of the circuit were later obsoleted by the transformers.
I don't know where Allen Wright taps the SACD bitstream in his S-TACT bypass mod. I suspect he combines the differential phases coming off the 330Rs between the VC24 & S-TACT. If you can figure this out please comment.
Dave
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