Hi all,
I have two Sony CD players with almost identical audio output stage using something called LA9215 IC as audio buffer and mute control. I have modded other cd players with discrete op-amp audio stage before without problems. But this combo multi function IC is a bit pain in the back to work with.
My main goal is to replace the electrolytic caps along the signal path to MKT type. I have already jumped the output cap since the offset measured is minimal. This has improved the sound somewhat but there is another 100 uF electrolytic cap in the signal path.
I have included that part of the schematic. It is the cap from the output of internal op-amp A to the input of the internal op-amp B. Op-amp C acts as mute control.
Now my questions are (1) Can I take the output from internal op-amp A directly to the RCA jack bypassing the the craps such as op-amp B and C, mute circuit etc ?
(2) The group of R & Cs between the output of op-amp A and the input of the op-amp B (the 2x1.5k and the 0.0047 uF) serve any LPF function ? (I want to try replacing the 100uF coupling cap to MKT type but MKT do not have such a big value)
(3) Am I better off build my own audio stage using something like opa2134 taking the diff signal and totally bypassing the IC LA9215 ?
Thanks.
I have two Sony CD players with almost identical audio output stage using something called LA9215 IC as audio buffer and mute control. I have modded other cd players with discrete op-amp audio stage before without problems. But this combo multi function IC is a bit pain in the back to work with.
My main goal is to replace the electrolytic caps along the signal path to MKT type. I have already jumped the output cap since the offset measured is minimal. This has improved the sound somewhat but there is another 100 uF electrolytic cap in the signal path.
I have included that part of the schematic. It is the cap from the output of internal op-amp A to the input of the internal op-amp B. Op-amp C acts as mute control.
Now my questions are (1) Can I take the output from internal op-amp A directly to the RCA jack bypassing the the craps such as op-amp B and C, mute circuit etc ?
(2) The group of R & Cs between the output of op-amp A and the input of the op-amp B (the 2x1.5k and the 0.0047 uF) serve any LPF function ? (I want to try replacing the 100uF coupling cap to MKT type but MKT do not have such a big value)
(3) Am I better off build my own audio stage using something like opa2134 taking the diff signal and totally bypassing the IC LA9215 ?
Thanks.
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The LA9215 is a Sanyo integrated circuit. It was discussed here:
Sanyo LA9215 upgrade
It is actually quite a good sounding integrated circuit. I also have two Sony players with them, one with the LA9215 and another with the LA9216, I seem to recall the manufacturer Rega spoke very highly of them.
The attached datasheet reveals some very impressive spec's
Sanyo LA9215 upgrade
It is actually quite a good sounding integrated circuit. I also have two Sony players with them, one with the LA9215 and another with the LA9216, I seem to recall the manufacturer Rega spoke very highly of them.
The attached datasheet reveals some very impressive spec's
Opamp B appears to be a low pass filter.
100uF feeding 10k will rolloff at 0.16Hz, therefore it is extremely unlikely that even a very poor capacitor could introduce any distortion here. However, if you want to make a wholly unnecessary change, you may be pleased to hear that a film cap in the same position need not be 100uF. 2.2uF or 4.7uF would be fine.
100uF feeding 10k will rolloff at 0.16Hz, therefore it is extremely unlikely that even a very poor capacitor could introduce any distortion here. However, if you want to make a wholly unnecessary change, you may be pleased to hear that a film cap in the same position need not be 100uF. 2.2uF or 4.7uF would be fine.
Thanks for replies. I saw that short discussion and I have downloaded the datasheet but it doesn't tell much only to give a test and a sample schematic.
I also thought op-amp B is the LPF but I noticed its output feeds to the + input via a 0.0047uF cap into the two 1.5k resistors so I think with little positive feedback, it boosts treble, right ?
I have replaced other CD player's big signal path caps (such as 50uF or bigger) with 2.2uF film caps and I really like it. I personally do not like the electrolytic cap sound. I think I'm going to give it a try and see what kind of result I'm getting by replacing the 100uF to a 2.2uF film cap.
I also thought op-amp B is the LPF but I noticed its output feeds to the + input via a 0.0047uF cap into the two 1.5k resistors so I think with little positive feedback, it boosts treble, right ?
I have replaced other CD player's big signal path caps (such as 50uF or bigger) with 2.2uF film caps and I really like it. I personally do not like the electrolytic cap sound. I think I'm going to give it a try and see what kind of result I'm getting by replacing the 100uF to a 2.2uF film cap.
I have corrected the schematic but the system won't let me replace the original upload....so I put it here.
The film is ERO MKT1813 2.2uF 100v. The original caps were regular Elna electrolytic type. After the change and some burning in, the CD player sounds wonderful. The LA9215 does sound good.
Impression: The sound stage is much bigger and the singers appear they are up at the front. Prior to the change, the sound stage was small and the sound quality was not appealing but tiring after listening for a few minutes. The decrease in value of the coupling cap from 100uF to 2.2uF does not really makes me feel a lack of bass. The cut off freq may be higher but I do not notice it. I played few CDs after the mod and the music is so smooth and I like the "roundness" of the sound. I fell asleep on the 3rd CD.... Usually if music is bad, it irritates me and I won't fall asleep. This mod is good and I'm happy with it.
The film is ERO MKT1813 2.2uF 100v. The original caps were regular Elna electrolytic type. After the change and some burning in, the CD player sounds wonderful. The LA9215 does sound good.
Impression: The sound stage is much bigger and the singers appear they are up at the front. Prior to the change, the sound stage was small and the sound quality was not appealing but tiring after listening for a few minutes. The decrease in value of the coupling cap from 100uF to 2.2uF does not really makes me feel a lack of bass. The cut off freq may be higher but I do not notice it. I played few CDs after the mod and the music is so smooth and I like the "roundness" of the sound. I fell asleep on the 3rd CD.... Usually if music is bad, it irritates me and I won't fall asleep. This mod is good and I'm happy with it.
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