NAD M33 phono stage question for owners

[JDRCapeCod]

Hi,

I recently set up my NAD M33 and I am very impressed with it, but I have a question regarding the phono stage. I am driving a pair of KEF LS-50 Meta speakers, with a KC-62 subwoofer and the output is excellent with everything except the phono input. I have a B&O TX-2 turntable with a MMC-3 cartridge which has output of 2.12mV and I can turn the volume all the way up and it is not what I would call loud by any means. I have looked at the input level adjustment on the M33 and it looks like you can cut it back, but not boost it. I also tried it in both ADC settings in the M33 with the same result. The MMC-3 is moving iron, but is compatible with the MM input, although I tried it on MC just to see what would happen.

I am not sure if this is a result of the LS-50 Meta speakers being somewhat inefficient and the cartridge not having a really high output. I turned off both Dirac and the tone controls just to set everything as level as possible. Has anyone else had this experience with the phono input? Is anyone having a good result with it? It seems silly to either add a line level gain stage to the phono input, or an outboard phono stage to fix this. Any input will be appreciated!

 

[MaxwellsEq]

It might be that the cartridge output is low. The only result google offers is "Output mV/cm/s RMS 0,6" Soundsmith make a copy which is 2.2mv. My cartridge is 5 mV at 5cm/sec.

I don't think it's right to blame the speakers. It just could be a low output from the cartridge. How did it sound via the MC input? Did that sound overloaded?

 

[JDRCapeCod]

It might be that the cartridge output is low. The only result google offers is "Output mV/cm/s RMS 0,6" Soundsmith make a copy which is 2.2mv. My cartridge is 5 mV at 5cm/sec.

I don't think it's right to blame the speakers. It just could be a low output from the cartridge. How did it sound via the MC input? Did that sound overloaded?

It is 2.2mv, I have the documentation. With the MC input the tonal balance is way off. I am not blaming the speakers,, but I think it's the combination of the two (low output and low efficiency), it all works great with anything but phono. I have an output phono stage with gain control that I might experiment with, I may buy a new TT/cartridge combo but didn't want to do it until I heard others have had success with the phono stage. I came over from a c 658 preamp that had no issue at all. Thanks for your insight!

 

[Tom C]

Typical for the phono sections I have had would be an input sensitivity of 4 or 5 mV for the moving magnet input. So 2.2mV would be kind of low. But that doesn’t explain the results you’re getting with the MC selected, which would probably have a lower rated input sensitivity level. You say it all works great except for phono, so the system does have enough power for your needs, and your speakers are not in any way responsible for the disappointing results from phono. I think it has to be the phono section (BTW, I’m not holding myself out as an expert. I’m just an enthusiastic amateur).
A quick look at customer reviews on the Crutchfield website show complaints similar to yours with regard to the phono section, so I’m thinking it’s related to the design choices made by the NAD folks. It could be that keeping the gain low for the phono section helped keep noise under control.
‘One option for you would be to add a dedicated outboard phono stage, and feed it into one of the NAD’s inputs. They are available in high quality for a few hundred dollars or less. Amir has reviewed several here on ASR, so you wouldn’t be buying blind. The other two options would be to live with it as is, vs. replacing the whole thing.
‘There is some chance that adding a step up transformer could help, but they tend to be not super cheap, and have to be selected with some care to be properly matched for gain and loading . Do you have specs for impedance for your cartridge, and input impedance and input sensitivity for MM and MC for your unit? I couldn’t find a download copy of the owner manual on the NAD web site.

 

[JDRCapeCod]

Typical for the phono sections I have had would be an input sensitivity of 4 or 5 mV for the moving magnet input. So 2.2mV would be kind of low. But that doesn’t explain the results you’re getting with the MC selected, which would probably have a lower rated input sensitivity level. You say it all works great except for phono, so the system does have enough power for your needs, and your speakers are not in any way responsible for the disappointing results from phono. I think it has to be the phono section (BTW, I’m not holding myself out as an expert. I’m just an enthusiastic amateur).
A quick look at customer reviews on the Crutchfield website show complaints similar to yours with regard to the phono section, so I’m thinking it’s related to the design choices made by the NAD folks. It could be that keeping the gain low for the phono section helped keep noise under control.
‘One option for you would be to add a dedicated outboard phono stage, and feed it into one of the NAD’s inputs. They are available in high quality for a few hundred dollars or less. Amir has reviewed several here on ASR, so you wouldn’t be buying blind. The other two options would be to live with it as is, vs. replacing the whole thing.
‘There is some chance that adding a step up transformer could help, but they tend to be not super cheap, and have to be selected with some care to be properly matched for gain and loading . Do you have specs for impedance for your cartridge, and input impedance and input sensitivity for MM and MC for your unit? I couldn’t find a download copy of the owner manual on the NAD web site.

Thanks for your reply. Since listening to records is not my main choice I will probably not invest a lot in addressing the issue. I just hear such great things about the phono stage on this unit that it seems crazy not to enjoy it. I might buy the NAD 588 turntable, which should work! Output voltage on the included Ortofon Red is 5.5mv, over double the B & O!

 

[MaxwellsEq]

I think the NAD M33 digitises the phono input. If this is the case, there will be bad audio impacts if the ADC is overloaded, so the designers probably set the gain of the input "buffer" quite low so that high output cartridges playing "hot" 12" 45rpm singles never overload the ADC. There's probably a table somewhere or some of the people submitting data into the Cartridge Measurement Library might be able to tell us, but I think 5 to 6mV are the highest output MM devices. They would have needed to design for this corner case. Your 2.2mV is perhaps 1/2 or even 1/3 of the loudest cartridges.

Something like the Art DJ Pre II may be ideal, since it allows you to trim the gain.

 

[JDRCapeCod]

I think the NAD M33 digitises the phono input. If this is the case, there will be bad audio impacts if the ADC is overloaded, so the designers probably set the gain of the input "buffer" quite low so that high output cartridges playing "hot" 12" 45rpm singles never overload the ADC. There's probably a table somewhere or some of the people submitting data into the Cartridge Measurement Library might be able to tell us, but I think 5 to 6mV are the highest output MM devices. They would have needed to design for this corner case. Your 2.2mV is perhaps 1/2 or even 1/3 of the loudest cartridges.

Something like the Art DJ Pre II may be ideal, since it allows you to trim the gain.

I was looking at this between the TT output and the phono input since I can trim it to ensure it doesn't overload: https://www.amazon.com/ATNEDCVH-pre...b7-9d7191c5fad0&ref_=pd_gw_ci_mcx_mr_hp_atf_m

I also have an outboard phono stage with variable gain, but it seems strange to use it on a line input on a device with a built in phono stage.

 

[MaxwellsEq]

I was looking at this between the TT output and the phono input since I can trim it to ensure it doesn't overload: https://www.amazon.com/ATNEDCVH-preamplifier-Headphone-amplifier-phonograph/dp/B0945RFJ6Z/?_encoding=UTF8&pd_rd_w=tJp0y&content-id=amzn1.sym.5f7e0a27-49c0-47d3-80b2-fd9271d863ca:amzn1.symc.e5c80209-769f-4ade-a325-2eaec14b8e0e&pf_rd_p=5f7e0a27-49c0-47d3-80b2-fd9271d863ca&pf_rd_r=SYDPZPR7NZSV5VZTE8N1&pd_rd_wg=oDVEo&pd_rd_r=deb5085a-a7ae-4b65-aeb7-9d7191c5fad0&ref_=pd_gw_ci_mcx_mr_hp_atf_m

I've no idea how good that pre-amp is; the user reviews are positive. I mentioned the Art, because Amir has reviewed it

I also have an outboard phono stage with variable gain, but it seems strange to use it on a line input on a device with a built in phono stage.

It's not that uncommon. I had a lovely preamplifier, but it's phono stage became too unreliable after 30 years, so I bought the cheap Rega Fono 2AD plugged into a line input, which covered LP playback whilst I decided what to do next.

 

[pogo]

Here is a short report about my pickup systems on the M33:
The AT 312 EP (MC) fits the M33 probably from the level optimally, since with loud records to almost 0dB is levelled.
All MM systems (Ortofon OMP10, Sony P33 & AT3474EP) are about 5-6dB quieter output, but can be compensated for me by the normal volume increase.
The best way to evaluate the level at the inputs is via the digital VU meter of the M33.
What is the maximum level in the MC position?

 

[JDRCapeCod]

Here is a short report about my pickup systems on the M33:
The AT 312 EP (MC) fits the M33 probably from the level optimally, since with loud records to almost 0dB is levelled.
All MM systems (Ortofon OMP10, Sony P33 & AT3474EP) are about 5-6dB quieter output, but can be compensated for me by the normal volume increase.
The best way to evaluate the level at the inputs is via the digital VU meter of the M33.
What is the maximum level in the MC position?

View attachment 308273

Good observation. I just changed over to a different turntable (now a Thorens TD-126 MkIII with a Grado Green cartridge) and the output is great. The Grado have 5mv of output, which is a lot better than the 2.2mv from the B&O MMC3. I was thinking about experimenting with an MC cartridge. It looks like yours is a P-Mount, is that correct? Thanks for the info!

 

[pogo]

This is a T4P and this is identical in build to a KENWOOD V-57.
A special feature is the interchangeability of the needle cartridge of an MC system.