I think it's only the clock to do now, 3R3 resistors to remove for wire links, nicer RCA sockets and just experiment with output coupling cap values and their quality.
My new frame / case has stopped in the production department till ' Pay Day ' but once that comes it's another test but this time of my woodworking skills.
My new frame / case has stopped in the production department till ' Pay Day ' but once that comes it's another test but this time of my woodworking skills.
Nice job again Andrew!!
and yes the external I/V is on board since yesterday! It worked at once like a charm. No issues of distortion, noises , clipping etc. The buffer opamp feeds the outputs of the internal opamp with a voltage of 2,49V which almost offsets any current between the inverting input and it's output. So as, the DAC current signal is now transfered to an external fet inputs opamp and from there to the output buffer. After a re-distribution of loads to the various power supplies now is working very nice!! It gave more body to the reproduction, a lot lot of separation in the sound stage and the more important it removed any metalic element left from the previous version...Fisrt I tried a bipolar I/V opamp (NE5532) which was a complete failure
then I put on my beloved AD8066 and get full of pleasure 
This opamp always wins by far. Then I tried the LME 49720 at the voltage offset buffer circuit and matched a better bass response and accurate transients. Then I created a dual regulator stage to drive the 2 signal opamps(external I/V and output buffer) from the tube supply at +-10V , while the offset buffer opamp is powered from the main PCB volages. It's still ongoing ..I will soon report any brake in news. As a first influence I can say that original internal I/V converters of 1549 are good ones!! The difference is not like day and night. But the mode gets the player to another level (probably to an endless route..)
Cheers
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...and again OMG !
I love looking inside your player.....but I don't understand anything that I'm seeing !!
It's just fantastic.
Your new boards look like precision made items and your work is just astonishing.
You say the difference between old and new i/v stage is not like night and day ?
But If I was in your house now would I hear the difference straight away ?
I'm already in a different direction to you but my work is basic stuff.
You on the other hand love valves and you know what you are doing.
If you can think of anything I need to do that is simple do let me know ...
se ef̱charistó̱ fíle mou
I love looking inside your player.....but I don't understand anything that I'm seeing !!
It's just fantastic.
Your new boards look like precision made items and your work is just astonishing.
You say the difference between old and new i/v stage is not like night and day ?
But If I was in your house now would I hear the difference straight away ?
I'm already in a different direction to you but my work is basic stuff.
You on the other hand love valves and you know what you are doing.
If you can think of anything I need to do that is simple do let me know ...
se ef̱charistó̱ fíle mou
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Morning Pete
Yes they did and were a lower value than the ones that I originally used.
I had 10uf at first and the Clarity Caps are 2.2uf.
I expected a drop in bass for some reason but that didn't happen.
The sound of cymbals and percussion instruments changed more to my liking, separation seemed to improve and female vocal shrillness seemed to dissapear.
I refer to Eva Cassidy in particular - if your a fan.
I'm going to try other values and brands eventually but hey, you know how it is.
Money Money Money - and my wife is also very wise to this now....damn
Yes they did and were a lower value than the ones that I originally used.
I had 10uf at first and the Clarity Caps are 2.2uf.
I expected a drop in bass for some reason but that didn't happen.
The sound of cymbals and percussion instruments changed more to my liking, separation seemed to improve and female vocal shrillness seemed to dissapear.
I refer to Eva Cassidy in particular - if your a fan.
I'm going to try other values and brands eventually but hey, you know how it is.
Money Money Money - and my wife is also very wise to this now....damn
...and again OMG !
I love looking inside your player.....but I don't understand anything that I'm seeing !!
It's just fantastic.
Your new boards look like precision made items and your work is just astonishing.
You say the difference between old and new i/v stage is not like night and day ?
But If I was in your house now would I hear the difference straight away ?
I'm already in a different direction to you but my work is basic stuff.
You on the other hand love valves and you know what you are doing.
If you can think of anything I need to do that is simple do let me know ...
se ef̱charistó̱ fíle mou
Thank you Andrew for you kind thanks in Greek language
I was expecting a tremendous improvement due to the following 3 reasons: 1) independent package power supply , which confirmed with more space and instruments separation for the external IV in comparison with the kinda rounding and flat sound stage of the internal one. The dynamics In conjunction with the music body also improved a lot. I credit both improvements to the indepedent PS and probably the more voltage +-10 DC Vs 5V single voltage .
2) Bad habit of Philips to incorporate chippy I/V opamps into their DAC chips (eg TDA1547) , NOT confirmed. The 1549 has a relible, decent IV converter that gives it's tonal signature to the chip, translated to musicality and entertainment but a bit ringing in high frequencies. It does have the above limitations in sound stage.
3) Releasing loads from DAC chip (thermal & other) should affect to more linear performance to it's primary work load, means the switching..
Summing up the diference is straight away audible and by making a review of targets set , for sure it's completely succesfull. Not to mention the flexibility for several opamps trials and best match.
It's just the risk of the project that generated expectations for "revolutionary subversion"
Never the mind: cost+ labours< benefits. I hope giving you an impartial review
Andreas - I've applied an inductor and 1800uf Pan fc to the internal i/v op amp power supply and put 1uf and .022uf bypass caps on the main capacitor to this supply and it's transformed the hf brightness.
I'm going to do the same on all the others after this gain.
I've no more inductors and no 1R resistors lying around so I have to wait but I'm very surprised by this step in quality.
The balance is so much better now.
Thanks for this excellent tip
I'm going to do the same on all the others after this gain.
I've no more inductors and no 1R resistors lying around so I have to wait but I'm very surprised by this step in quality.
The balance is so much better now.
Thanks for this excellent tip
That's great news Andrew!!Andreas - I've applied an inductor and 1800uf Pan fc to the internal i/v op amp power supply and put 1uf and .022uf bypass caps on the main capacitor to this supply and it's transformed the hf brightness.
I'm going to do the same on all the others after this gain.
I've no more inductors and no 1R resistors lying around so I have to wait but I'm very surprised by this step in quality.
The balance is so much better now.
Thanks for this excellent tip
keep experiment...What I say , the good day is shinning early in the morning. Whatever change does not suit your tastes from the first audio session, in most cases would not tremendously improve later. Trust your ear. One of the last "analog sensors" still in service
Keep in touch
Andeas
A 'heads-up' for followers of this thread.
Cheap Philips CD-753 here.
~ Much Under-Rated Philips CD-753. Clean and Reliable ~ | eBay
Cheap Philips CD-753 here.
~ Much Under-Rated Philips CD-753. Clean and Reliable ~ | eBay
Well, it's not like mine but the DAC chip is the same at least and I guess will sound mighty - as noted in the Lampizator site.
I've not stopped and my new case is coming on OK. It's just been far trickier than I hoped.
So many things to think about, obstacles and wiring headaches but I'm a few weeks away at least.
Someone should snap that 753 up and get it modded...
I've just added a 6v x2 toiroidal in my CD48 to power the DAC with it's own regulator, I did have a cathode follower valve circuit in place but I don't think it really added much... I also have 5 brand new TDA1549 DAC chips, just bought them as they are so damn good I might need to replace one
Has anyone done the same mods to a Marantz PDM320? It has a completely different board (larger, more complex - think for transport control as I think it has pitch control as a studio machine) with front styling like the CD63/7 but of course with TDA1549.
Bought one ages ago on the back of Lukas Fikus' TDA1549 enthusiasm .
Bought one ages ago on the back of Lukas Fikus' TDA1549 enthusiasm .
CD5000
I spent my redundancy money on some mundorfs.
Also added a new 4v reg for the servo circuit.
It's brought back a lot if the bass that I felt was missing a bit before. Very happy with it now.
I don't think I'll do any more to this now, just adding the new feed to the servo circuit ended up with me having to add 2 jumper connections due to the fragility of the tracks. Don't want to risk any more damage.
@AndrewGM - Any updates on your progress?
Pete
I spent my redundancy money on some mundorfs.
Also added a new 4v reg for the servo circuit.
It's brought back a lot if the bass that I felt was missing a bit before. Very happy with it now.
I don't think I'll do any more to this now, just adding the new feed to the servo circuit ended up with me having to add 2 jumper connections due to the fragility of the tracks. Don't want to risk any more damage.
@AndrewGM - Any updates on your progress?
Pete
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A little bit of a thread revival, but it would be good to hear if Andrew is still modding the CD48.
I finally found my CD48, a house move, boxes and a storage container really didn't help working out where it was!
I have a modded CD5000 that's been recapped (Silmics, Panasonics), removed the muting circuitry and optical out, installed Schottky diodes and an op-amp replacement. I've dampened it with generic Dynamat and plasticine all over the case and transport (probably added a good 1.5 kilos to it)
Further things to do will be phonos, PSU mods, although the bypassing the op-amp does sound quite appealing.
I finally found my CD48, a house move, boxes and a storage container really didn't help working out where it was!
I have a modded CD5000 that's been recapped (Silmics, Panasonics), removed the muting circuitry and optical out, installed Schottky diodes and an op-amp replacement. I've dampened it with generic Dynamat and plasticine all over the case and transport (probably added a good 1.5 kilos to it)
Further things to do will be phonos, PSU mods, although the bypassing the op-amp does sound quite appealing.
I thought I'd update this thread with my mods.
As mentioned above I've pretty much replaced and removed most of the extraneous components from the basic CD5000 board.
I've separated the power supplies for the digital and analogue requirements, regulating the analogue side with a toroidal transformer, LM317/337 combination providing the +/- 10v needed for the Cerafine/LM4562NA. The digital side is still using the standard transformer but with a Dexa NewClassD 7805 super regulator replacement after the Schottky diodes with a Nichicon 10000uf reservoir capacitor replacing the 4700uf. I've removed the 3300uf capacitor as the separate analogue supply makes that redundant.
On the TDA1549 side I've removed the filter loopback capacitors and jumped the pure output to the signal bypassing the internal op-amp.
Additional mods have introduced a IEC power socket feeding a power filter before connecting to the transformers.
Next I hope to install a few more regulators but the NewClassDs are a little expensive, I might move the existing one but will need to work which ones are more important.
As mentioned above I've pretty much replaced and removed most of the extraneous components from the basic CD5000 board.
I've separated the power supplies for the digital and analogue requirements, regulating the analogue side with a toroidal transformer, LM317/337 combination providing the +/- 10v needed for the Cerafine/LM4562NA. The digital side is still using the standard transformer but with a Dexa NewClassD 7805 super regulator replacement after the Schottky diodes with a Nichicon 10000uf reservoir capacitor replacing the 4700uf. I've removed the 3300uf capacitor as the separate analogue supply makes that redundant.
On the TDA1549 side I've removed the filter loopback capacitors and jumped the pure output to the signal bypassing the internal op-amp.
Additional mods have introduced a IEC power socket feeding a power filter before connecting to the transformers.
Next I hope to install a few more regulators but the NewClassDs are a little expensive, I might move the existing one but will need to work which ones are more important.
I know this thread is very old, but did anybody completely replace the stock transformer? I've been fiddling this evening as I've got a 0v - 9v and a 0 - 25v kicking about so they both should do the job (I already have a separate 6v transformer in there) - my question is regarding what seems to be a strange centre tap arrangement on the stock transformer and how I'd retrofit the above mentioned transformers in it's place (virtual centre tap?)
Hi damiangt, from what you described you have just bypassed the signal buffer op-amp. It is still a voltage output signal this one you handle, but more weak (in terms of current and voltage capability. Your signal needs buffering, unless your receiver / amp input does have one.
On the other hand, you still have in use the DAC intergraded internal I/V converter op-amp which has it's limitation.
Good try anyway!
Cheers
Hello,
I have read the whole of this thread and must say I have enjoyed it very much. Thanks Andrew and all.
The reason I found this thread was through searching for TDA1305 which is used in my much abused Naim CD3.5. It is very similar to the TDA1549 although it has more pins (28).
Naim CD3.5 uses Vam 1205 transport & TDA1300 laser amplifier, TDA7073AT power drivers, SAA7376 (combined digital servo processor and decoder) and finally the TDA1305 dac chip. From stock there were already 15 LM317 regs, a 200VA toroid and a 7 pole Bessel filter output stage.
I too have extensively modified the thing over the last 10 years. More transformers, better regs, flea powered tentlabs clock, replaced some caps etc etc. I concur with Andrew about having separate psu's on each of the dac ps pins - awesome. I have a flea reg on the TDA1305 internal opamps and some very little (5VA) pcb EI transformers.
Only very recently have I tried bypassing the output stage (6 opamps & tens of caps and resistors) and have found the sound after doing so to be VERY pleasing and an overall improvement on having the output stage in circuit. I kept some 680pf polystyrene caps providing the 1st order filter on the output and wired in a pair of 10uf wima mks 2xl as coupling caps and 100k ohms to ground.
I am planning on tryng some 1uf Russian paper in oil coupling caps as the 10uf wima's are a bit large in value I think. I too use a 10k shunt volume control (of sorts) and no active preamp. Currently I have no buffer between dac and volume control but don't find it lacking if I am totally honest. Output impedance of TDA1305 is 10 ohms in the data sheet. I have sacrificed 0.5V of signal output though as the output of the 1305 is 1.5 V not 2V as previously when the output stage was in use.
After reading this thread (and lampizator) I began to get curious about tube cathode follower buffers but as yet I am still pondering. Also if there was a way of extracting the current output from the dac and doing IV conversion externally (as andypap has done) I would be very interested in the details of how to do it and what I would need to build.
A couple of threads from another forum about my TDA1305 Naim CD3'5
Naim CD3.5 mods (not on Acoustica) | pink fish media
Bypass cdp anologue output stage | pink fish media
Many thanks, Stu
I have read the whole of this thread and must say I have enjoyed it very much. Thanks Andrew and all.
The reason I found this thread was through searching for TDA1305 which is used in my much abused Naim CD3.5. It is very similar to the TDA1549 although it has more pins (28).
Naim CD3.5 uses Vam 1205 transport & TDA1300 laser amplifier, TDA7073AT power drivers, SAA7376 (combined digital servo processor and decoder) and finally the TDA1305 dac chip. From stock there were already 15 LM317 regs, a 200VA toroid and a 7 pole Bessel filter output stage.
I too have extensively modified the thing over the last 10 years. More transformers, better regs, flea powered tentlabs clock, replaced some caps etc etc. I concur with Andrew about having separate psu's on each of the dac ps pins - awesome. I have a flea reg on the TDA1305 internal opamps and some very little (5VA) pcb EI transformers.
Only very recently have I tried bypassing the output stage (6 opamps & tens of caps and resistors) and have found the sound after doing so to be VERY pleasing and an overall improvement on having the output stage in circuit. I kept some 680pf polystyrene caps providing the 1st order filter on the output and wired in a pair of 10uf wima mks 2xl as coupling caps and 100k ohms to ground.
I am planning on tryng some 1uf Russian paper in oil coupling caps as the 10uf wima's are a bit large in value I think. I too use a 10k shunt volume control (of sorts) and no active preamp. Currently I have no buffer between dac and volume control but don't find it lacking if I am totally honest. Output impedance of TDA1305 is 10 ohms in the data sheet. I have sacrificed 0.5V of signal output though as the output of the 1305 is 1.5 V not 2V as previously when the output stage was in use.
After reading this thread (and lampizator) I began to get curious about tube cathode follower buffers but as yet I am still pondering. Also if there was a way of extracting the current output from the dac and doing IV conversion externally (as andypap has done) I would be very interested in the details of how to do it and what I would need to build.
A couple of threads from another forum about my TDA1305 Naim CD3'5
Naim CD3.5 mods (not on Acoustica) | pink fish media
Bypass cdp anologue output stage | pink fish media
Many thanks, Stu