I made som mods on a friend's NADC542 with great results:
Lower grain
More resolution
Better transparency
Cleaner sound
Better bass
(quote: Tentlabs.com)
BUT, there has come an adverse effect, that I did not notice in my own setup:
With power on the CDP but not playing a CD, and volume turned to MAX on the preamp, a noisy, crackling hiss comes from the tweeters in my friends setup
. This did not happen before the mod, it was totally silent.
The mods are:
Coupling caps from the DAC to the opamps
C375 parallel with C377/C376 parallel with C378
replaced with cupperfoil paper-in-oil caps. They are quite large and are suspended in foam to avoid that they touch any components on the PCB.
The M302A crystal and the ceramics C328-339 removed and a Tentlabs XO2 clock is applied with a dedicated PSU (transformer, rectifier, smoothing elcap in parallel with a small 100nF MKT).
Muting transistors Q301,302,303,304 removed.
I do not understand why the sound has improved so much but at the same time this noise has been added to the system?
Well... what can I have done wrong ?? What can the noise be, RF pollution, digital noise picked up by the large PIO caps??
Appreciate some ideas to get rid of the noise
Lower grain
More resolution
Better transparency
Cleaner sound
Better bass
(quote: Tentlabs.com)
BUT, there has come an adverse effect, that I did not notice in my own setup:
With power on the CDP but not playing a CD, and volume turned to MAX on the preamp, a noisy, crackling hiss comes from the tweeters in my friends setup
. This did not happen before the mod, it was totally silent.The mods are:
Coupling caps from the DAC to the opamps
C375 parallel with C377/C376 parallel with C378
replaced with cupperfoil paper-in-oil caps. They are quite large and are suspended in foam to avoid that they touch any components on the PCB.
The M302A crystal and the ceramics C328-339 removed and a Tentlabs XO2 clock is applied with a dedicated PSU (transformer, rectifier, smoothing elcap in parallel with a small 100nF MKT).
Muting transistors Q301,302,303,304 removed.
I do not understand why the sound has improved so much but at the same time this noise has been added to the system?
Well... what can I have done wrong ?? What can the noise be, RF pollution, digital noise picked up by the large PIO caps??
Appreciate some ideas to get rid of the noise
2 things:
1. Re-install the muting transistors. Is the problem gone? If YES, consider relays - shorting the output to ground. Or, leave the muting transistors installed.
2. Try recording a wav file, but without any signal (silence) - like white noise. Transfer to CD-R and play it in the CD player. Is the crackling hiss / noise still there? If YES, it could be "something else" you did, or even a bad original design (yes, yes, I know - it's NAD!!). You see, the problem is noticeable only without muting transistors - you can not be 100% positive if the crackling noise problem was there BEFORE you started the mods, because the sound being played / reproduced could've masked the problem....
Extreme_Boky
mlloyd1 said:
Probably the only way to identify exactly what caused the problem, it is possible. I never burn any bridges behind me!
To Extreme_Boky I can say that it is 100% sure that the bad sound was NOT there before the mods, whether there is a CD in the tray or not.
thank you for helping!
Extreme_Boky said:
In another thread is is recommended to bypass the transistors at the output (muting transistors??)
http://www.diyaudio.com/forums/showthread.php?s=&threadid=56185&highlight=
How would this be recommendable if it causes problems?
I did remove (not bypass) Q301-304 shown in attachment.
What is the purpose and the function of these transistors?
Why could their absence cause the noise?
And once more to avoid misunderstandings: The noise is there if I turn up the volume to max. at the preamp without playing a CD.
Before the mods I could turn up the volume to max. without any noise, only a weak hiss if I place my ear 1 inch from the tweeters.
Attachments
Well, sometimes if you remove the muting transistors the noise can creep in. Muting transistors are there to mute (short the output to ground) when the CD player is in stop or in pause mode. They also mute the output, more or less - depending on design, during forward and reverse search. By removing them, you are leaving analog stage output always "active", even when in stop mode. This wasn't the case before the mods were done - the analog stage output used to be shorted to ground if the player was in stop mode.
The crackling noise problem usually means something else (other than analog stage) might be wrong with the CD player. It could be even impedance mismatch between analog out and pre-amp analog in impedances + high capacitance interconnect cables. You can trace the problem backwards if you follow the crackling noise backwards, starting at RCA's, with a CRO (have one? - you ought to get yourself one if you are serious about mods!).
First step would be to re-install the muting transistors. See if that fixes the problem. People suggest their removal, but usually warn of the popping side-effects during track search, or reading the TOC, loading the disk, during turning the unit ON-OFF and similar... These side-effects are minor and should disappear after a week or 2 (joke, lame one though!)
Good luck
Extreme_Boky
The crackling noise problem usually means something else (other than analog stage) might be wrong with the CD player. It could be even impedance mismatch between analog out and pre-amp analog in impedances + high capacitance interconnect cables. You can trace the problem backwards if you follow the crackling noise backwards, starting at RCA's, with a CRO (have one? - you ought to get yourself one if you are serious about mods!).
First step would be to re-install the muting transistors. See if that fixes the problem. People suggest their removal, but usually warn of the popping side-effects during track search, or reading the TOC, loading the disk, during turning the unit ON-OFF and similar... These side-effects are minor and should disappear after a week or 2 (joke, lame one though!)
Good luck
Extreme_Boky
I have also removed the muting transistors from my 521i. In addition there are two 150 ohm resistors in the signal path for the muting operation. I removed those as well and there is no problem.
I have taken the output directly from the opamp pins without an output coupling cap (the paralleled set of caps). No adverse effects and only 3 mV offset so I'm assuming I'm doing OK.
Haven't touched the caps between DAC and opamps.
I have taken the output directly from the opamp pins without an output coupling cap (the paralleled set of caps). No adverse effects and only 3 mV offset so I'm assuming I'm doing OK.
Haven't touched the caps between DAC and opamps.
The way I read the circuit seems wrong, then.
I thought the first prevents the opamp output from shorting to ground when the muting transistor switches in, the second to prevent shorting out the preamp input.
They do help driving capacitive loads, too, but my guess was the bulk of their job is for muting.
I thought the first prevents the opamp output from shorting to ground when the muting transistor switches in, the second to prevent shorting out the preamp input.
They do help driving capacitive loads, too, but my guess was the bulk of their job is for muting.
Hi,
My modded NAD542 sounds very good indeed and I have done an A/B test in which it comfortably destroyed my friend's top of the range brand new CEC CD player recently bought for AUD$3,500.00. The difference was so obvious and we could make a conclusion within a minute. Note that the CEC player sounds very good - it weights over 10kg, very solidly built, top loading, very impressive PSU capacitor bank, using servo to trim DC offset without using output cap, using relay instead of output muting transistors, using Elna Cerafine capacitors throughout the analogue section, etc. Indeed, if I were given the CEC player I would not know what to mod because it is very good already. Yet the mod NAD542 is again much better.
It is interesting that most people don't buy the NAD players and the NAD player is never in people's mod list. Of course the stock items sound pretty rough.
This was how I got started. Long time ago my friend modded a NAD512 player and brought it to me. The sound was very impressive indeed. At the time I used a Marantz CD67Se MKII as the transport and the Meridian 565 digital processor (20 bits) as the DAC. The modded NAD512 beat my Meridian in musicality with the only drawback of having lower resolution (with its 16 bit DAC). A friend of mine also brought in another dedicated Meridian Transport and DAC (can't remember the model number) and I still preferred the modded NAD512 for the overall sweet, musical sound. There was more life in the music.
So I commissioned my friend to mod a NAD for me. Since at the time the NAD541i became available, I asked him to mod the NAD541i for me because it had a 24bit DAC.
The result of the mod in the NAD541i - I thought it was OK. I don't think my friend did enough to it although Elna Cerefine was used throughout and the PSU was much strengthened. The details were substantially better than the modded NAD512 but I thought musicality was not as good.
I bought a NAD542 to be used in another room. Comparing with the modded NAD541i, the sound of the stock NAD542 was un-listenable - too harsh while the modded NAD541i is much cleaner and smoother.
Then I started DIY.
Two months ago, my friend bought the CEC player. I had an A/B test comparing with the modded NAD541i. The CEC player killed the modded NAD541i instantly. There was no contest. At the time, I regretted buying the NAD542 and thought I would have paid the AUD$3,500.00 to get the CEC.
Fortunately, I modded the NAD542 about a month ago. After the A/B test with the CEC, I was over the moon. Again there was no contest. My modded NAD542 won!
I bought my stock NAD542 for about $AUD680.00. The total part costs for the upgrade were possibly no more than AUD$70. So spending only $AUD750.00 and got a CD player that beats the $3,500 player by far, I have got to be happy.
More to follow below...
My modded NAD542 sounds very good indeed and I have done an A/B test in which it comfortably destroyed my friend's top of the range brand new CEC CD player recently bought for AUD$3,500.00. The difference was so obvious and we could make a conclusion within a minute. Note that the CEC player sounds very good - it weights over 10kg, very solidly built, top loading, very impressive PSU capacitor bank, using servo to trim DC offset without using output cap, using relay instead of output muting transistors, using Elna Cerafine capacitors throughout the analogue section, etc. Indeed, if I were given the CEC player I would not know what to mod because it is very good already. Yet the mod NAD542 is again much better.
It is interesting that most people don't buy the NAD players and the NAD player is never in people's mod list. Of course the stock items sound pretty rough.
This was how I got started. Long time ago my friend modded a NAD512 player and brought it to me. The sound was very impressive indeed. At the time I used a Marantz CD67Se MKII as the transport and the Meridian 565 digital processor (20 bits) as the DAC. The modded NAD512 beat my Meridian in musicality with the only drawback of having lower resolution (with its 16 bit DAC). A friend of mine also brought in another dedicated Meridian Transport and DAC (can't remember the model number) and I still preferred the modded NAD512 for the overall sweet, musical sound. There was more life in the music.
So I commissioned my friend to mod a NAD for me. Since at the time the NAD541i became available, I asked him to mod the NAD541i for me because it had a 24bit DAC.
The result of the mod in the NAD541i - I thought it was OK. I don't think my friend did enough to it although Elna Cerefine was used throughout and the PSU was much strengthened. The details were substantially better than the modded NAD512 but I thought musicality was not as good.
I bought a NAD542 to be used in another room. Comparing with the modded NAD541i, the sound of the stock NAD542 was un-listenable - too harsh while the modded NAD541i is much cleaner and smoother.
Then I started DIY.
Two months ago, my friend bought the CEC player. I had an A/B test comparing with the modded NAD541i. The CEC player killed the modded NAD541i instantly. There was no contest. At the time, I regretted buying the NAD542 and thought I would have paid the AUD$3,500.00 to get the CEC.
Fortunately, I modded the NAD542 about a month ago. After the A/B test with the CEC, I was over the moon. Again there was no contest. My modded NAD542 won!
I bought my stock NAD542 for about $AUD680.00. The total part costs for the upgrade were possibly no more than AUD$70. So spending only $AUD750.00 and got a CD player that beats the $3,500 player by far, I have got to be happy.
More to follow below...
How did I do the mod?
First I spent nearly 3 months searching the internet and studying CD mods. This forum has a vast amount of valuable information and some can be found at the Asylum. I did a very substantial amount of reading (hours and hours on a daily basis) before I started planning the CD mod.
I then obtained the NAD542 service manual. For about 3 weeks I stared at the schematics (hours a day again) and tried to figure out what need to be modded. I then derived a plan and wrote down the list of all the mods I would like to do.
I learned so much from studying the NAD542 schematics. I wondered how the NAD542 sounded so harsh and uninspiring with already pretty good components in the stock player, e.g. Nichicon Muse is used in coupling caps, Nichicon Fine Gold is used throughout the analogue supply, and Schottky diodes are used in the analogue power rectification.
I found the NAD542 circuit board design was very good indeed. This is the base that a modded NAD542 can be modded to be at a reference level. Each individual IC has its own ground return and local supply caps. Grounds and power supplies are very well separated. The digital supply (D5+) regulator is placed quite closed to the digital chips and the analogue regulator is closed to the analogue section. There are 4 regulators in total, i.e. 4 power supplies in a way. The D5+ and A5+ are after two regulators. What more can we expect from a cheap to mid-price player like the NAD542!
There are so many different suggestions to CD mods. I guess that if we blindly take those suggestions then the result would more or less depend on our luck. Each player is different and requires specific treatments. All upgrades should be based on electronic principles and I wouldn't do the mods to the NAD simply because somebody says he got good result with the mod on a Marantz CD63, for example.
The mods I did were relatively simple - removing the muting transistors, upgrading some critical capacitors, replacing some filtering caps with the Rubycon ZL and Panasonic FC. Two OSCON caps were used. A MKP type of cap (2.2uF) replaced the Nichicon Muse. Of course the resistors shunt to ground after the cap had to be increased. Many Nichcon Fine Gold were pulled out / replaced. Filtering was further strengthened by adding appropriate capacitors as well as increasing the values of some filtering caps to appropriate values. It is certainly not the case that bigger is the better. e.g. I put on a Panasonic FC 4700uF/25v after the regulator for the 12V supply and did not like the sound at all. It did require 7 hours labour, but no additional transformers, no additional PSU, not a single board was added, no changes to the existing LM317, LM337, LM1805, LM1808 regulators, no use of any exotic capacitors, i.e. no PIO, no film and foil caps, no Blackgates, no Elna Cerefines or Similics, no clock upgrades, no silver wires, no IC shields, no sand bags, no... That was how the upgrade cost of the parts were a mere AUD$70.00. However, all the mods are there to address the weakness of the well designed NAD542.
Well, I don't mean that some of the above items won't work - they can work very well but I have not got a chance to do them. I am very keen to try some of the above when I have the time. But I am already quite content with its sound.
Anyone in Sydney who has a CD player retailed at higher than $5,000? I would be happy and be very interested in having an A/B test with yours - not to show off the modded NAD but it is fun to compare the sound and I would like to know what other areas / weaknesses of the NAD so that I may improve it further.
Extreme_Boky / Nick,
I am very interested in comparing the modded NAD542 to your professionally modded CD Player with clock upgrade, blackgates, power cord upgrade, etc. I am sincere. Drop me an email if you could please. I will buy you drinks, etc.
Best regards,
Bill
First I spent nearly 3 months searching the internet and studying CD mods. This forum has a vast amount of valuable information and some can be found at the Asylum. I did a very substantial amount of reading (hours and hours on a daily basis) before I started planning the CD mod.
I then obtained the NAD542 service manual. For about 3 weeks I stared at the schematics (hours a day again) and tried to figure out what need to be modded. I then derived a plan and wrote down the list of all the mods I would like to do.
I learned so much from studying the NAD542 schematics. I wondered how the NAD542 sounded so harsh and uninspiring with already pretty good components in the stock player, e.g. Nichicon Muse is used in coupling caps, Nichicon Fine Gold is used throughout the analogue supply, and Schottky diodes are used in the analogue power rectification.
I found the NAD542 circuit board design was very good indeed. This is the base that a modded NAD542 can be modded to be at a reference level. Each individual IC has its own ground return and local supply caps. Grounds and power supplies are very well separated. The digital supply (D5+) regulator is placed quite closed to the digital chips and the analogue regulator is closed to the analogue section. There are 4 regulators in total, i.e. 4 power supplies in a way. The D5+ and A5+ are after two regulators. What more can we expect from a cheap to mid-price player like the NAD542!
There are so many different suggestions to CD mods. I guess that if we blindly take those suggestions then the result would more or less depend on our luck. Each player is different and requires specific treatments. All upgrades should be based on electronic principles and I wouldn't do the mods to the NAD simply because somebody says he got good result with the mod on a Marantz CD63, for example.
The mods I did were relatively simple - removing the muting transistors, upgrading some critical capacitors, replacing some filtering caps with the Rubycon ZL and Panasonic FC. Two OSCON caps were used. A MKP type of cap (2.2uF) replaced the Nichicon Muse. Of course the resistors shunt to ground after the cap had to be increased. Many Nichcon Fine Gold were pulled out / replaced. Filtering was further strengthened by adding appropriate capacitors as well as increasing the values of some filtering caps to appropriate values. It is certainly not the case that bigger is the better. e.g. I put on a Panasonic FC 4700uF/25v after the regulator for the 12V supply and did not like the sound at all. It did require 7 hours labour, but no additional transformers, no additional PSU, not a single board was added, no changes to the existing LM317, LM337, LM1805, LM1808 regulators, no use of any exotic capacitors, i.e. no PIO, no film and foil caps, no Blackgates, no Elna Cerefines or Similics, no clock upgrades, no silver wires, no IC shields, no sand bags, no... That was how the upgrade cost of the parts were a mere AUD$70.00. However, all the mods are there to address the weakness of the well designed NAD542.
Well, I don't mean that some of the above items won't work - they can work very well but I have not got a chance to do them. I am very keen to try some of the above when I have the time. But I am already quite content with its sound.
Anyone in Sydney who has a CD player retailed at higher than $5,000? I would be happy and be very interested in having an A/B test with yours - not to show off the modded NAD but it is fun to compare the sound and I would like to know what other areas / weaknesses of the NAD so that I may improve it further.
Extreme_Boky / Nick,
I am very interested in comparing the modded NAD542 to your professionally modded CD Player with clock upgrade, blackgates, power cord upgrade, etc. I am sincere. Drop me an email if you could please. I will buy you drinks, etc.
Best regards,
Bill
Let me give another comparison result.
Two years ago I brought the modded NAD541i (modified by my friend) to Len Wallis to compare it to the expensive Shanline tube CD player. It thought it was a draw. The modded NAD541i was cleaner with more detail and stronger bass while the Shanline was smoother and slightly more musical in some way. I would not say one is better than the other. I thought the Salesman agreed - he was trying hard to convince me that the Shanlin was the best CD player under AUD$10k. Obviously the Shanlin looks very impressive but its sound is only so so.
Since the CEC comfortably beats the modded NAD541i while my modded NAD542 comfortably beats the CEC, I am pretty sure that my modded NAD542 will blow the Shanlin away.
So guys having the NAD542 here in this thread are truly blessed.
I don't have the NAD541i service manual. It looks very much the same as the NAD542 but it is NOT! I bought the parts and tried to do the same mods on the NAD541i. For the most critical part, I failed to upgrade the DC blocking cap because I found that the analogue output is different. The NAD542 uses the OPA2134 non-inverted (I have not upgraded the opamp and apparently the OPA2134 sounds pretty fine with the way I filter the power supply). My modded NAD541i uses the OPA2604 inverted. Without the service manual and schematic, I spent a lot of time reverse engineered it from the PCB. It was too time consuming and I gave it up. Currently, my modded NAD541i has nearly the same mods as my NAD542 but sounds no where near as good. Out of the DAC it connects to a DC blocking capacitor of 100u Cerefine shunt with a Wima MKP then to the OPA2604 inverted. Any lytic in the signal path is a trouble regardless of Cerefine or Muse or not. To modify this part I think I have to put in a small new board. I have the NAD542 so I am not worrying about the NAD541i too much.
I may be interested in trying the OPA627 and possibly a clock upgrade and chassis damping but I have no comfidence they will bring in any audible performance gain.
Regards,
Have Fun in CD mods,
Bill
Two years ago I brought the modded NAD541i (modified by my friend) to Len Wallis to compare it to the expensive Shanline tube CD player. It thought it was a draw. The modded NAD541i was cleaner with more detail and stronger bass while the Shanline was smoother and slightly more musical in some way. I would not say one is better than the other. I thought the Salesman agreed - he was trying hard to convince me that the Shanlin was the best CD player under AUD$10k. Obviously the Shanlin looks very impressive but its sound is only so so.
Since the CEC comfortably beats the modded NAD541i while my modded NAD542 comfortably beats the CEC, I am pretty sure that my modded NAD542 will blow the Shanlin away.
So guys having the NAD542 here in this thread are truly blessed.
I don't have the NAD541i service manual. It looks very much the same as the NAD542 but it is NOT! I bought the parts and tried to do the same mods on the NAD541i. For the most critical part, I failed to upgrade the DC blocking cap because I found that the analogue output is different. The NAD542 uses the OPA2134 non-inverted (I have not upgraded the opamp and apparently the OPA2134 sounds pretty fine with the way I filter the power supply). My modded NAD541i uses the OPA2604 inverted. Without the service manual and schematic, I spent a lot of time reverse engineered it from the PCB. It was too time consuming and I gave it up. Currently, my modded NAD541i has nearly the same mods as my NAD542 but sounds no where near as good. Out of the DAC it connects to a DC blocking capacitor of 100u Cerefine shunt with a Wima MKP then to the OPA2604 inverted. Any lytic in the signal path is a trouble regardless of Cerefine or Muse or not. To modify this part I think I have to put in a small new board. I have the NAD542 so I am not worrying about the NAD541i too much.
I may be interested in trying the OPA627 and possibly a clock upgrade and chassis damping but I have no comfidence they will bring in any audible performance gain.
Regards,
Have Fun in CD mods,
Bill
Extreme_Boky said:
As explained above the problem seems to be solved by re-installing the muting transistors.
However, another problem has appeared and actually started during the first hours of playing with the CDP without the transistors.
The symptom is a scratching sound in both left and right speaker when the volume knob is turned in normal speed. Turning it very slowly does not cause the same degree of scratching, nor is it a problem if the knob is pressed inwards while turning, probably because the slider gets better contact.
The pot is a "Noble" which I believe is conductive plastic.
Could it be that missing the muting transistors has damaged the pot?
klitgt,
maybe some kind of output dc offset coming from your cd player damaged the pot as there has been no output cap & no muting transistors to suppress it before that. dont know exactly...i'm guessing...
bill,
my new nad c542 sound harsh & bright but after burning-in for a few days it sounded better well a lot better than my philips cd player & pioneer dvd player. it sounded more spacious, wider, lows are punchier, more detailed than my philips & pioneer. the sound of instruments like piano sounds so real to me. the slam of drums is amazing! would also love to do some mods
btw is there a possibility you can share the SM give the full details of your mod i mean all the components changes all values?
please?
ricman
maybe some kind of output dc offset coming from your cd player damaged the pot as there has been no output cap & no muting transistors to suppress it before that. dont know exactly...i'm guessing...
bill,
my new nad c542 sound harsh & bright but after burning-in for a few days it sounded better well a lot better than my philips cd player & pioneer dvd player. it sounded more spacious, wider, lows are punchier, more detailed than my philips & pioneer. the sound of instruments like piano sounds so real to me. the slam of drums is amazing! would also love to do some mods
btw is there a possibility you can share the SM give the full details of your mod i mean all the components changes all values?
please?
ricman
There is no doubt that the NAD542 is MUCH better than the Philips and pioneer. I lived in London for 2 years during which time I could not live without music. So I went to Ritchard Sound and bought a cheaper set of HiFi, ended up with a NADT550, Cambridge Audio integrated amp and the Eltax speakers. Prior to that, I had the Musical Fidelity and some hi-end gears back in Australia. I compared all the CD players in the shop at Ritchard Sound, including the highly aclaimed Cambridge Audio and others. I felt that the NAD DVD Player was way better than other dedicated CD players in the shop (this doesn't sound logical to me) in the price range so I bought the NAD DVD player. Later when I compared the NAD DVD player with the NAD 541i, the difference was marginal.
On a lower resolution system or a system with relatively high distortions, the difference between CD players may be subtile. As the distortion of the system is reduced (this is my way of interpretation of hi-end), even subtle problems are revealed clearly. Any components in the audio chain seem to have a major sonic impact on the sound.
I said the stock NAD542 is harsh - of course, when compared to better quality CD players it is very harsh. When compared to the Philips or Pioneer I have no doubt it sounds very musical. It is all relative.
Regards,
Bill
On a lower resolution system or a system with relatively high distortions, the difference between CD players may be subtile. As the distortion of the system is reduced (this is my way of interpretation of hi-end), even subtle problems are revealed clearly. Any components in the audio chain seem to have a major sonic impact on the sound.
I said the stock NAD542 is harsh - of course, when compared to better quality CD players it is very harsh. When compared to the Philips or Pioneer I have no doubt it sounds very musical. It is all relative.
Regards,
Bill
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