Mod/upgrade NAD C 541i

[arlekin]

I got it! Thank you!

[HiFiNutNut]

Here is my new report.

Over the weekend I did another upgrade to my NAD542.

To reduce the risk of getting possible resonance I added a 1 ohm resistor in series with the LM317 / LM337 and installed some large value low impedance capacitors. It sounded very different but eventually I decided to ditch it. Definitely no resistors after the regulators. The lower the impedance the better the sound. I will let it resonate if it does.

The new capacitors have an impedance of only 0.012R at 100kHz. I thought that was pretty low and took out the 0.01uF polystyrene bypass caps. It sounded bad. The were back on.

I never thought that the capacitors before the regulators 317/337 are important. The NAD has the 1000uF Nichicon Fine Gold that is supposed to be a good capacitor. I thought using lower value capacitors would reduce the conduction angle during the charge cycle. That might be right. But as far as sonic is concerned, I was wrong. Putting on the Panasonic 4,700uF made a huge improvement.

Finally, I replaced the OPA2134 with the OPA627. By the way, I bought 2 pairs of "dual" OPA627 mounted on browndogs from eBay (seller: ca2832) and another pairs of single AD825 on browndogs. Chris is the guy selling them. They are the cheapest I found. Most important of all, they are genuine products and Chris shipped them in no time. I am very happy with the purchase and can highly recommend Chris.

When the OPA627 was plugged in, I found basically no difference at the time. Perhaps I was still getting used to the much improved sound from the big Panasonic FC before the regulators. The next day, I unplugged the OPA627 and plugged in the OPA2134, I heard the difference immediately. The sound was less clear. I then put the OPA627 back on. It sounded clearer.

Basically, both have the same sound character and presentation. Both are nice. The OPA2134 is more coloured making the tone slightly warmer. The OPA627 is more transparent as if it does not have its own sound, and more detailed. They are more similar than different, unlike the AD825. The OPA627 is overall better than the OPA2134.

I have learnt a lesson here. It all depends. If you look at the datasheet, you can find that the OPA627 has much better PSRR than the OPA2134. So when used in a noisier PSU, I presume, the OPA627 will outperform the OPA2134 by a large margin. If used in a very quiet PSU, the OPA627 only has slightly higher bandwidth and higher slew rate so it would give you better details but not a "night and day" difference. If you hear people saying the OPA627 being substantially better than the OPA2134. That may probably be right. The other way may also be true - if you hear people saying the OPA627 being no difference to the OPA2134. It all depends on many other factors.

I would think replacing the PSU capacitors makes bigger difference than replacing the opamps. On my system, all the major caps are replaced. So the OPA627 stay. They are definitely better.

But if you have not replaced anything yet, spending $30 on capacitors may give you 80% sonic improvement, spending $100 on the opamps may give you 20% improvement.

I also helped my friend with his Aragon DAC. It had NE5534s in it. We first replaced it with OPA2134. The sound was a lot better. Then we replaced the OPA2134 with AD825. The difference was huge. It immediately gave a high-end feeling. Much better resolution, high frequency details, etc. But after 10 minutes, we both agreed that the sound was a bit cold comparing to the OPA2134, and vocals might not be as sweet as the OPA2134. My friend then took it back. After one week, he told me the AD825 is definitely better than the OPA2134. Either he is now used to the new sound, or in his warm system the AD825 simply sounds a lot better. He believes that the AD825 is not lesser than the OPA2134 in the mid range. It is because the high and low frequency extremes now sound better it makes the midrange appears to be less sweet.

In any case, my NAD542 now sounds really nice with the latest round of upgrade, so nice that I really have no intension to do anything else on it. I have lost the interests in installing new clocks on it.

Regards,
Bill

[SimontY]

Very interesting insights Bill, thanks.

I think you might like to reconsider reclocking at some point down the line. The difference in my player was larger than op-amps or changing most caps to Black Gate.

Having said that, Marantz players are jittery, how about the Nads?

Simon

[HiFiNutNut]

Simon,

Well, when the NAD542 was released, in NAD's literature it said that they paid a lot of attention to reducing jitters and they achieved it. Of course that is NAD's statement.

My NAD now sounds very good - dynamic, open, transparent, musical and reasonably detailed. It is not as accurate or as high-end as the Marantz SA11 I have, but it does give the same level of musical enjoyment. As said, I have compared it to many players and it only lost to the Meridian G08, which is the only player I am really happy with.

I do believe that replacing the clocks would help. However, this player costs only AUD$680. My mod (including 4 x OPA627) cost just under AUD$200. Its current level of performance would not be lesser than players up to $5,000. I should be happy. The problem is that for the NAD542 you need to install two clocks according to the TentLab Australian agent GeorgeHiFi. The DIY costs including buying two Tent clocks and buying components to build a dedicated PSU for the two XO clocks would be above AUD$300. Further more, I must find the space within the enclosure to fit in and mount 3 separate boards. If I have not had the Marantz SA11, I would possibly go for it. But my NAD is only my second player so I will leave it. I did seriously consider installing new clocks but now finally decided not to proceed.

I will start modding my Marantz SA11 tonight. You guys wish me good luck?

Regards,
Bill

[SimontY]

My Marantz CD63 also needs two clocks, but in reality they can be fed from the same source, with the use of a divider cicruit. Reclocking the DAC made a huge improvement (timing, detail, imaging etc.), then feeding the servo a new clock signal made another huge improvement (finally really detailed and a more lifelike top end).

I wonder if this would be the case in the Nad.

Good luck with your SA11

[HiFiNutNut]

Simon,

I gave a nearly new CD67se to a friend. I can swap it back with my modified NAD541i, which sounds better than the CD67se. Then I can modify the CD67 just for fun.

Does the CD67se need 1 clock or two clocks?

Regards,
Bill

[SimontY]

Hi Bill,

CD67 just needs the one clock. If you spend time separating supplies for the 5v parts and you reclock you will be stunned. Also change the op-amps to LM4562. You may also like the sound with 'HDAM' bypassed. Just look at all the people doing it on the mammoth thread elsewhere here.

Sorry, this is off-topic.

Simon

[Baka]

Originally posted by HiFiNutNut
The problem is that for the NAD542 you need to install two clocks according to the TentLab Australian agent GeorgeHiFi. Bill

If you want to install a better clock you need to replace only one (labeled M302 on the board) in your NAD542 since I have done the same in mine too.
NAD542 is a bit tricky but it can be upgraded to a significant degree at reasonable cost.
Many tweaks that are generally known work here too.

Regards,
Baka

[haenisch]

Hello all,

since I want to start modifying my C541i I'm looking for a service manual.

Maybe someone of you can help me ;-)

my email is till.haenisch at gmx.de

Greetings till

[Asen]

Can s.b. please send me a C542 service manual?
tutekov@gmail.com
Thanks in advance!

Asen