Yeah, it seemed strange to me too Andy.
Maybe I'll double check to make sure there wasn't something wrong elsewhere. Especially seeing as the player attempted to self-destruct not long after these experiments.
Cheers, Lee.
Maybe I'll double check to make sure there wasn't something wrong elsewhere. Especially seeing as the player attempted to self-destruct not long after these experiments.
Cheers, Lee.
Consider keeping C580 - without that, my opamp gets hot and drops out due to oscillation
- you can get lucky though.So the DOS is still doing the 4th order filtering?
I use the 3rd order passive filtering that Ray used after his DOS, but straight after my opamp IV instead, I think it sounds alright. I have a limited frame of reference though.
Yes, without C580 you will be getting greater distortion from this IV stage, whatever it sounds like. And as Phil notes, you may need a certain minimum capacitance to ensure stability (this actually depends on the opamp used, since it compensates for the intrinsic capcitance at the dacs output - often 30pF or so IIRC)
Interesting stuff chaps. I'll not tinker with this area until I understand it better or someone can post a "definitive" / über output stage. If that doesn't happen, laziness will set in and I'll leave it be but with a Burson discrete op-amp. It sounds great that way.
Unlike many people on this forum I'm not clever enough to "design" output stages with pieces of glowing glass etc. but I find good results just separating power rails and leaving the audio circuit as-is. A lot of people seem to miss this important step when improving a player.
Tubee,
I got your delivery today, thanks! I'll make good use 😀
Simon
Unlike many people on this forum I'm not clever enough to "design" output stages with pieces of glowing glass etc. but I find good results just separating power rails and leaving the audio circuit as-is. A lot of people seem to miss this important step when improving a player.
Tubee,
I got your delivery today, thanks! I'll make good use 😀
Simon
Hi SimonSimontY said:
It seems this TDA1541 DAC is much more difficult ot tame than the version in a "normal" Marantz.... I am glad I do not own one of those, otherwise I would surelly be following your ideas.
keep pushing
Ricardo
Hi Ricardo - good to see you trawling around here hehe.
Old TDA1541 players may require a little more work than others (e.g. CD17KI mk1 - as Lee and Brent know) but they can offer a cheap starting base for wonderfully coherent, musical sound. Maybe a bit like a turntable, but without the noises
And how much do you have to spend on a turntable setup to approach good TDA1541 sound? I'd not like to find out...
Simon
Old TDA1541 players may require a little more work than others (e.g. CD17KI mk1 - as Lee and Brent know) but they can offer a cheap starting base for wonderfully coherent, musical sound. Maybe a bit like a turntable, but without the noises
And how much do you have to spend on a turntable setup to approach good TDA1541 sound? I'd not like to find out...
Simon
philpoole said:
Consider keeping C580 - without that, my opamp gets hot and drops out due to oscillation
So the DOS is still doing the 4th order filtering?
I use the 3rd order passive filtering that Ray used after his DOS, but straight after my opamp IV instead, I think it sounds alright. I have a limited frame of reference though.
OP Amps definately not getting hot. They are LM47910. With respect to the filter, I've only got whatever is on the input side of the DOS supplied by Brent based on Rays design. I'm also using Mundorf Supreme 4.7uf as DC decoupling.
Maybe Brent could comment??
martin clark said:
Is there a way to calculate what value should be used here? Assuming its to stop oscillation, can I filter it above the audio band so I don't interfere with sound I'm now acheiving (or am I missing the point??)
I'd be greatful for some guidance/education in this area (its been 20 years since I was a college!)
Thanks
Ian
Sounds not too disimilar to my setup - except I don't have the DOS stage as a buffer (I don't have a buffer).
Does the DOS buffer make much difference? How is it with just the Opamp IV?
(I ask because I wonder if a buffer would improve my setup)
Cheers,
Phil
Curiosity got the better of me and I pulled out the CDM2 and took it apart. I studied the circuit and Googled the ICs for datasheets (TDA5708 and 5709 and two others) and checked out what the caps were all doing. Most seem to be "scary" caps involved in frequency timing or decoupling, which I left well alone. They're mainly mylar/polyester apart from a couple of interesting Philips 2n2 - polystyrene? Those were on the Radial Error Processor IIRC.
I changed about 5 electrolytics of varying types all for ZLH 330uF/35V one one to 100uF/16V ZA (Rubycon). The exception was a 1.5uF Nichicon MUSE bipolar cap - I changed this for a 1uF polyester box cap.
I've just put it back together, and whilst it plays, I'm not sure it's ok
It sounds "weird" - very phasey!!! I don't know if the upgraded caps have improved the sound SO MUCH that this CD sounds unfamiliar or I've created an odd effect by tampering too much....
I'll try another disc.
Simon
I changed about 5 electrolytics of varying types all for ZLH 330uF/35V one one to 100uF/16V ZA (Rubycon). The exception was a 1.5uF Nichicon MUSE bipolar cap - I changed this for a 1uF polyester box cap.
I've just put it back together, and whilst it plays, I'm not sure it's ok
It sounds "weird" - very phasey!!! I don't know if the upgraded caps have improved the sound SO MUCH that this CD sounds unfamiliar or I've created an odd effect by tampering too much....
I'll try another disc.
Simon
Ok, off with JJ Cale & Eric Clapton and on with Carol Kidd.... it's not broken!!! It's just revealing spatial cues (and therefore highlighting artificial stereo effects) better. With real music the sound is more enveloping (wider stage), tighter, more detailed, more open, crisper. Treble is better I think, but I'm listening more quietly than normal and I find that hard to judge at night time levels...
Simon
Simon
philpoole said:
I'll give it a try later this week and let you know what I find. The DOS did sound very good on the 63. I'm pretty certain Brent said it was a 1.1:1 so I see no reason why I can't drive into the DC decoupling caps from the I/V stage. Incidentaly, that Mundorf made a huge difference as well!
SimontY said:
Simon, I changed the 5 caps on my CDM1. It completely cured my lazy laser! I didn't change the values, 33uf 10v, I just put os-cons in there. Again it was a very early change I made and didn't compare the sound, I was just racing to try and catch up with the 63!
Ian
Replacement Caps
All those caps take a considerable time to "come good" - The Ruby ZAs take over 100hrs operating time, the Muse about 50 hrs and ZLH should be okay in about 20 or so, from memory - the polyester, don't know. Try a CD with lots of overdubs like "Enya" or Live-echo, Blues Alley (Cassidy) or even Friday Night in SF(DiMeola) When it does "come good", suggest upgrading the other poly caps too - you can replace them if not satisfied. I did the similar thing with my CDM-4 + chipset, and it took a few weeks (continuous use)to stop changing. There was also some mention at the time of adding a small series resistor in series with the digital path to reduce "reflections" but I didn't get around to it. The shortage of info about these transport mods still suprises me considering how the simple non tech mods have quite noticeable effects - just how much improvement can be attained by a systematic project/investigation is tantalising - I'm contemplating a seperate suspended & inert platform for my next player and it'll save quite some time if somebody knows if this sort of thing has been successfully done before and what sort of results. The design details about the Esoterics and CECs are pretty sketchie, at best. No doubt about the prices, tho! I did dampen the transport body and support frame to isolate mech feedback, too - don't use "bluetack" type goo but proper elastomer damping material, and just enough so the mech assembly springs move at about 1 - 2Hz (not too much). To complete this, add some panel damping sheet material (not stick on filter foam used in computer cases) to the base plate / bottom of case and in general, deaden the whole chassis.This is a general purpose cheap, simple action to help with any electronic device with resonant sensitive components.
All those caps take a considerable time to "come good" - The Ruby ZAs take over 100hrs operating time, the Muse about 50 hrs and ZLH should be okay in about 20 or so, from memory - the polyester, don't know. Try a CD with lots of overdubs like "Enya" or Live-echo, Blues Alley (Cassidy) or even Friday Night in SF(DiMeola) When it does "come good", suggest upgrading the other poly caps too - you can replace them if not satisfied. I did the similar thing with my CDM-4 + chipset, and it took a few weeks (continuous use)to stop changing. There was also some mention at the time of adding a small series resistor in series with the digital path to reduce "reflections" but I didn't get around to it. The shortage of info about these transport mods still suprises me considering how the simple non tech mods have quite noticeable effects - just how much improvement can be attained by a systematic project/investigation is tantalising - I'm contemplating a seperate suspended & inert platform for my next player and it'll save quite some time if somebody knows if this sort of thing has been successfully done before and what sort of results. The design details about the Esoterics and CECs are pretty sketchie, at best. No doubt about the prices, tho! I did dampen the transport body and support frame to isolate mech feedback, too - don't use "bluetack" type goo but proper elastomer damping material, and just enough so the mech assembly springs move at about 1 - 2Hz (not too much). To complete this, add some panel damping sheet material (not stick on filter foam used in computer cases) to the base plate / bottom of case and in general, deaden the whole chassis.This is a general purpose cheap, simple action to help with any electronic device with resonant sensitive components.
Re: Replacement Caps
Hi Ian,
You may not have noticed at the time but you probably scored big points there. I played some Dire Straits (On Every Street) this morning before work and it sounds wonderful. Knopfler's vocals are sweeter and more present; drums and cymbals are tight and the sound has more space than I'm used to. Best value modification so far I think - especially as Jean-Paul Dude gave me the ZLH caps for free when he sent me my N2 TDA1541!
These Dutch guys are nice aren't they?! 😀
The MUSE was standard (weird choice?) and I changed it for a film cap. I look forward to the others improving!
I agree it's incredible you don't hear about this sort of "tweak" more often, when it has such profound effects on sound quality.. or at least it can on a 1986-designed Philips CD650. I may measure the old caps to see if any have lost capacitance.
What about the filter caps on there? There are some through-hole mylar caps that could be changed to polystyrene or silvered mica.
I also want to know more about the "L212M" IC, or is it L232M or L222M? It's hard to tell because the print is so bad. There's also what looks like a JRC op-amp - 8 pin through-hole. I wonder if this can be upgraded.
Tracking sounds more noisy, more "purposeful" now. It's as if it's really keen to play the CD 😉 😀
I'll post a pic when I get home later so everyone can see what I'm talking about.
Simon
UV101 said:
Hi Ian,
You may not have noticed at the time but you probably scored big points there. I played some Dire Straits (On Every Street) this morning before work and it sounds wonderful. Knopfler's vocals are sweeter and more present; drums and cymbals are tight and the sound has more space than I'm used to. Best value modification so far I think - especially as Jean-Paul Dude gave me the ZLH caps for free when he sent me my N2 TDA1541!
These Dutch guys are nice aren't they?! 😀
jameshillj said:
The MUSE was standard (weird choice?) and I changed it for a film cap. I look forward to the others improving!
I agree it's incredible you don't hear about this sort of "tweak" more often, when it has such profound effects on sound quality.. or at least it can on a 1986-designed Philips CD650. I may measure the old caps to see if any have lost capacitance.
What about the filter caps on there? There are some through-hole mylar caps that could be changed to polystyrene or silvered mica.
I also want to know more about the "L212M" IC, or is it L232M or L222M? It's hard to tell because the print is so bad. There's also what looks like a JRC op-amp - 8 pin through-hole. I wonder if this can be upgraded.
Tracking sounds more noisy, more "purposeful" now. It's as if it's really keen to play the CD 😉 😀
I'll post a pic when I get home later so everyone can see what I'm talking about.
Simon
Hi all,
Glad you've made further improvements.
I wonder too about the transport. Perhaps a lot of this is improving decoupling to suppress interference on power rails?
On my CDM9 board, there is a JRC opamp, if its like yours, I think it is used to provide PWM to drive the motor speed (I could be very wrong there! Its been a couple of years since I studied the transport schematics). It did ponder upon upgrading it, but never bothered. Also, I was surprised to see the servo circuitry on these Philips boards is very rarely regulated at all. If I recall, Martin pointed out that it was most likely because, being a servo, it PSRR was rather high and it was often deemed unnecessary. I've no idea if the CD650 is similar. If I recall, my CD624 was similar in some ways to my CD940.
Glad you've made further improvements.
I wonder too about the transport. Perhaps a lot of this is improving decoupling to suppress interference on power rails?
On my CDM9 board, there is a JRC opamp, if its like yours, I think it is used to provide PWM to drive the motor speed (I could be very wrong there! Its been a couple of years since I studied the transport schematics). It did ponder upon upgrading it, but never bothered. Also, I was surprised to see the servo circuitry on these Philips boards is very rarely regulated at all. If I recall, Martin pointed out that it was most likely because, being a servo, it PSRR was rather high and it was often deemed unnecessary. I've no idea if the CD650 is similar. If I recall, my CD624 was similar in some ways to my CD940.
Hi Phil,
I think it powers the radial motor. There's no decoupling near it, so I may have to mess with this a little more. I'll need my photos to ID the chip to see if it's a standard single or dual opa, then I can work out a replacement. Dedicated regs here may be sweet, but not easy to achieve.
Some of these voltages must be regulated because, for example, the TDA5708 Vdd (+ voltage) has to be 4.5V - 5.5V. This means it's probably sharing the same 7805 that originally fed the DAC, SAA7220 and SAA7210, RAM, and more?! No wonder the '650 sounds so muddled before mods... It might be possible to fit a 7805 on there to power it. I might have a go, but it could get messy! The negative rail can vary a lot (according to the 'sheet), and I've not worked out where that's fed from yet.
Then there's the 5709 that could be messed with more 😉
One thing's for sure here - if I take this board out too many times one or more of those old connectors is going to fail
Simon
I think it powers the radial motor. There's no decoupling near it, so I may have to mess with this a little more. I'll need my photos to ID the chip to see if it's a standard single or dual opa, then I can work out a replacement. Dedicated regs here may be sweet, but not easy to achieve.
Some of these voltages must be regulated because, for example, the TDA5708 Vdd (+ voltage) has to be 4.5V - 5.5V. This means it's probably sharing the same 7805 that originally fed the DAC, SAA7220 and SAA7210, RAM, and more?! No wonder the '650 sounds so muddled before mods... It might be possible to fit a 7805 on there to power it. I might have a go, but it could get messy! The negative rail can vary a lot (according to the 'sheet), and I've not worked out where that's fed from yet.
Then there's the 5709 that could be messed with more 😉
One thing's for sure here - if I take this board out too many times one or more of those old connectors is going to fail
Simon
Phil, you're right, the cdm9 does use the decoder output to drive a local opamp which drives the motor.
I do think that the servos should be indifferent,. and reckon the reason that servo rail regs work so well in the CD63 is because..the rails in that player are an utter mess, all off the one 5v reg and its the reverse isolation which really helps! Added to which some of the chips used have very low psrr IIRC.
The cdm9 in my old CD2 has regulated rails, I have noticed...
I do think that the servos should be indifferent,. and reckon the reason that servo rail regs work so well in the CD63 is because..the rails in that player are an utter mess, all off the one 5v reg and its the reverse isolation which really helps! Added to which some of the chips used have very low psrr IIRC.
The cdm9 in my old CD2 has regulated rails, I have noticed...
martin clark said:
Hello Martin,
Any idea on what parameters to search for in a suitable replacement op-amp? If it's dual, I have: 2132, 2134, 4562, 5532, 6172 and in single I have OPA627BP and some SMT AD825 from memory.
Simon
Your cdm2 mech is not like my player's cdm9 though, sorry, I've no experience there.
Generally though - to drive the motor the opamp only needs to be slow and robust; almost anything will do providing it can output enough current (often these drive external transistors which actually control the motor). Wide bandwidth etc - absolutely not required, in fact not really wanted - it might upset the control loop.
Generally though - to drive the motor the opamp only needs to be slow and robust; almost anything will do providing it can output enough current (often these drive external transistors which actually control the motor). Wide bandwidth etc - absolutely not required, in fact not really wanted - it might upset the control loop.