Yamaha CD-S700 Opamp upgrade (OP275) : hints ? - Page 2 - diyAudio
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Old 13th August 2013, 12:59 AM   #11
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Quote:
Originally Posted by marble88 View Post
...how is it (sound-like) compared to AD826 or AD8066 ?
To tell the truth I haven't listened to it. I chose it because for DAC duty opamps need a front-end which is linear at HF, and the usual undegenerated LTPs are particularly poor in this respect. Hence I selected one which avoids the LTP. LM6172 is similar in architecture and sounds very good to my ears in an AD1955 DAC I modded. I didn't suggest this because its bandwidth is such that its a little harder to get stable - the LT1355 is more domesticated.

I haven't listened to AD826 but I do have experience with AD8065 which is the single version of the AD8066. Sounds peculiarly coloured at the top end to me. However this wasn't in a DAC, rather as an integrated amp's input stage.
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Old 13th August 2013, 09:01 AM   #12
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marble88 is it possible to get the service manual from you, for my S700? regards Chris
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Old 13th August 2013, 09:27 AM   #13
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Originally Posted by chris86 View Post
marble88 is it possible to get the service manual from you, for my S700? regards Chris
Chris, you have MP.
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Old 13th August 2013, 12:10 PM   #14
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After long readings, I found DSD1791 should be likely a more or less PCM1793 : design after it is more or less the same in any application so there is plenty written out there. Original design datasheet says NE5532 or OP2134 should be fine... imho, OP275 should better these two given its specs... I think I'll try OPA1662 as suggested and something discrete...
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Old 16th August 2013, 05:11 AM   #15
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The CD-S700 I have uses the LME49723MA that is used in all markets except Japan which uses the OP275GSR.
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Old 16th August 2013, 09:18 AM   #16
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Originally Posted by rabbitz View Post
The CD-S700 I have uses the LME49723MA that is used in all markets except Japan which uses the OP275GSR.
You're luckier than most... I do have OP275GSR in mine.
I did not pay attention to that on service manual... there's big difference in some capacitors aswell. I am glad you gave me info
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Old 16th August 2013, 09:56 AM   #17
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Quote:
Originally Posted by Mooly View Post
I think your just going to have to shortlist a few and try them. An outsider for you would be the OPA2604, probably the most "coloured" sounding of any. Those muting transistors look as though they could usefully be swapped out for small FET's.

Enjoy
The muting transistors only mute so there will be no improvement there.
The Op Amp replacement will not produce much if any improvement as the Op Amp was chosen in the factory. The noise level is excellent unless it is faulty in which case as a retired authorized Yamaha Agent we were advised to fit a low noise 4558. Yamaha supplied a 6558 as they have JFet inputs and are very low noise.
Who listens to a CD player with no CD playing? That is what the muting stage is for.
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Last edited by JonSnell Electronic; 16th August 2013 at 10:02 AM. Reason: More information added
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Old 16th August 2013, 12:03 PM   #18
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Quote:
Originally Posted by JonSnell Electronic View Post
The muting transistors only mute so there will be no improvement there.
Many do seem to claim sonic improvements when this type of muting is removed, but the other very real issue is that they can be a source of trouble if the transistors play up which is surprisingly common in this type of bjt application. For some resaon they fail leaky in this configuration (grounded collector and high negative voltage on the base) which presents a weird non linear load to the opamp so distorting the audio.
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Old 16th August 2013, 12:24 PM   #19
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Quote:
Originally Posted by JonSnell Electronic View Post
The muting transistors only mute so there will be no improvement there...
The perceived problem with muting transistors is that they remain in circuit when not muting.

IMO the rest of the circuit would have to be exceedingly good for replacement to be a worthwhile modification.

edit...unless they're faulty...good point Mooly

Last edited by PlasticIsGood; 16th August 2013 at 12:26 PM.
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Old 19th August 2013, 10:06 PM   #20
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Ok, so first I am going to recap the whole analog board with some Nichicon FG except C53 and C56 of service manual where I will put "something else". I am also going to bypass these with some metalized poly (C54 and C55).
The whole thing came with standard capacitors (Nichicon VR and United Chemi-con SMG).
Next will be replacement of capacitors in power sections with some Panasonic FC.
Last will be Opamp replacement : I think I will start with LME49723MA .
I thank you all for your suggestions
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