Preamplifier Specifications
alucididea
Posts: 113
in Electronics
So I’m trying to figure out why certain preamplifier specs are the way they are, particularly the output voltages. I’m looking at the NAD M12 and it lists these specs:
Output
Maximum Output Level
>8Vrms into 600 Ohms
THD (CCIF IMD, DIM 100)
>0.005% (ref. 20Hz-20kHz, 2V out)
Balanced
>2Vrms
What I don’t understand is why NAD is rating the single-ended outputs with a maximum level and the balanced with a minimum level. Does this make sense to anyone else?
Output
Maximum Output Level
>8Vrms into 600 Ohms
THD (CCIF IMD, DIM 100)
>0.005% (ref. 20Hz-20kHz, 2V out)
Balanced
>2Vrms
What I don’t understand is why NAD is rating the single-ended outputs with a maximum level and the balanced with a minimum level. Does this make sense to anyone else?
Comments
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How are you making the determination that the balanced output specs are the "minimum"?
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Per NAD:How are you making the determination that the balanced output specs are the "minimum"?
“Thank you for contacting the NAD Electronics Support Center regarding the M12 Balanced Output Level. It is rated to output at least 2V. ”
“The unbalanced outputs Maximum Output Level is greater than (>) 8Vrms into 600 Ohms.” -
Interesting. Depending on the way that you asked your question to their support team, they definitely seem to have given you answers with two different ranges mentioned.
The unbalanced output hitting a full 8V would probably be unlikely under normal use cases. That's really high. -
They just decided to regurgitate the specs I can clearly read without any further explanation. I thought that maybe because it’s balanced they measure it differently for the specs.Interesting. Depending on the way that you asked your question to their support team, they definitely seem to have given you answers with two different ranges mentioned.
The unbalanced output hitting a full 8V would probably be unlikely under normal use cases. That's really high.
8v does sound halfway ludicrous, right?
Either way, I’m going to demo the M12. I’ve only got RCA cables at the moment (Kimber Hero). I wish I didn’t have to spend another $200 just to demo it with some decent XLR cables. I suppose I could always return those too. -
Monoprice XLRs baby! Boom!
I also had a less than pleasant experience interacting with NAD support about 6 months ago. I think they farmed out all their support overseas now. -
You think Monoprice XLRs would do me better than the Kimber Hero RCAs?Monoprice XLRs baby! Boom!
They’ve actually given me some decent information in the very recent past. Seems like a hit or miss situation depending on who’s answering.I also had a less than pleasant experience interacting with NAD support about 6 months ago. I think they farmed out all their support overseas now.
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If I were you I'd absolutely stay balanced between your nice NAD master series components.
I've used Monoprice balanced cables for my studio monitors and observed nothing but exceptional performance. I would think that they would do just fine for your application, imo.
I'm sure that others will disagree, but I think that for balanced interconnects, the overall quality of the cable doesn't need to be as high. The inherent design benefit of the fact that they are balanced will cancel out any potential interference/noise issues. As long as the cable is not a complete piece of crap, I would wager that it would sound just fine.
*braces for impact*alucididea wrote: »You think Monoprice XLRs would do me better than the Kimber Hero RCAs?
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Sez unbalanced is greater than 8 AC volts RMS into 600 ohms.
Sez balanced is greater than 2 AC volts RMS, but the load's not specified.
2 V RMS ought to drive any decent power amplifier pretty well.
The classic "line level" standard was, as I recall, 1V RMS into 600 ohms, back in the day when the "line" was -- well -- a line. A telephone line, which was how remote broadcasts got back to the studio from the remote location
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If you look at the M12's service manual the output is given as:
Output Level 2V (ref. input 0dBFS)
"0dBFS" is 0dB Full Scale which means the preamp will deliver 2Volts with the maximum digital input. There's not a separate output for single ended and another for balanced given.
The difference in the two outputs in your specifications could be related to the load impedance the measurements are taken with. -
Yeah, there seems to be quite of bit of convoluted information contained in the specs and manual. It’s not really a bit deal. I’m just trying to figure out why it’s described as such.KennethSwauger wrote: »If you look at the M12's service manual the output is given as:
Output Level 2V (ref. input 0dBFS)
"0dBFS" is 0dB Full Scale which means the preamp will deliver 2Volts with the maximum digital input. There's not a separate output for single ended and another for balanced given.
The difference in the two outputs in your specifications could be related to the load impedance the measurements are taken with.
Just for reference, my amp is in the same line of products, the NAD M22. I’m not really worried about it at all. Just trying to figure out all the ins and outs.mhardy6647 wrote: »Sez unbalanced is greater than 8 AC volts RMS into 600 ohms.
Sez balanced is greater than 2 AC volts RMS, but the load's not specified.
2 V RMS ought to drive any decent power amplifier pretty well.
The classic "line level" standard was, as I recall, 1V RMS into 600 ohms, back in the day when the "line" was -- well -- a line. A telephone line, which was how remote broadcasts got back to the studio from the remote location
Unbalanced MAXIMUM Output Level is >8v
But the way the support guy made it sound is the MINIMUM balanced output level is 2v. -
I doubt that's what the meant -- the minimum would be 0 volts (RMS).
AC volts do get a little confusing -- at least to folks like me.
2 AC volts RMS is equivalent to about a peak voltage of 2.8 volts or a peak to peak voltage of 5.6 volts.
I mention this mostly because the concept here is sort of a "maximum average value", which sort of makes one's brain hurt if one thinks too hard about it
I am guessing, then that the 8V maximum presumably means the maximum "undistorted" RMS voltage output specification, i.e., before clipping sets in.
I reckon the 2V does too - irrespective of tech support.
That being said -- I reckon that they're both probably guaranteed "minimum specifications" (i.e., any given example of the preamp in question might be capable of more output than that -- but those levels are "guaranteed").
Just musing wildly here, though
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My understanding is that the volts only indicate the strength of the signal, not the contents. So the preamp could easily send 2 minimum volts with no contents. The idea here is that no matter what gain the preamp is set to, the amp is always utilizing its full potential (since the input sensitivity on the amp is 1.6v).mhardy6647 wrote: »I doubt that's what the meant -- the minimum would be 0 volts (RMS). -
No that is not true (or, at least, it's misleading) -- other than the fact that the preamp could, if its circuitry allowed, pass a 2 volt DC signal. That would have no AC content (i.e., no "signal" in the sense of a musical waveform) but it has "content". 2 volts DC with respect to ground.
An amplifier that had no DC blocking components (e.g., a capacitor or transformer) on its input or its output, and if it had adequate bandwidth, would happily amplify 2 V DC to, say, 20 VDC and pass it along to the poor loudspeakers.
A DC voltage applied to the voicecoil of a woofer makes an electromagnet and a lot of heat. The woofer will most likely burn out quite quickly.
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I'm liking all the tech talk, but I will kindly remind you to post up a few (a lot) of photos of it once it arrives!
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I guess I'm thinking of the 2v as the quality of signal, rather than the signal itself. So if there is no musical contents, the amplifier is not sending any sound to the loudspeakers because there is no actual signal to interpret and pass along, no matter the quality of the connection.mhardy6647 wrote: »No that is not true (or, at least, it's misleading) -- other than the fact that the preamp could, if its circuitry allowed, pass a 2 volt DC signal. That would have no AC content (i.e., no "signal" in the sense of a musical waveform) but it has "content". 2 volts DC with respect to ground.
An amplifier that had no DC blocking components (e.g., a capacitor or transformer) on its input or its output, and if it had adequate bandwidth, would happily amplify 2 V DC to, say, 20 VDC and pass it along to the poor loudspeakers.
A DC voltage applied to the voicecoil of a woofer makes an electromagnet and a lot of heat. The woofer will most likely burn out quite quickly.
There will absolutely be plenty of pictures when its all set up on Thursday!I'm liking all the tech talk, but I will kindly remind you to post up a few (a lot) of photos of it once it arrives!
Will be the M12+M22+LSiM707s.
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@Clipdat I also ordered some balanced mono price XLRs that will be here Thursday also. (Thank you amazon prime.) But if/when I decide to keep this beauty, I'll probably just order some Kimber Heros or a Pangea XLR. I definitely want to do a comparative listen between Monoprice and something a supposed step up.
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The output stage uses an opamp based DC servo to keep the output DC to zero. The single end output is direct coupled (no blocking capacitor). The balanced output is produced by another opamp and has a series capacitor before the input to the opamp.
These are surface mount devices, which some designers find sound better than their larger counterparts. -
That would be a great comparison, looking forward to it if you decide to keep the NAD.alucididea wrote: »@Clipdat I also ordered some balanced mono price XLRs that will be here Thursday also. (Thank you amazon prime.) But if/when I decide to keep this beauty, I'll probably just order some Kimber Heros or a Pangea XLR. I definitely want to do a comparative listen between Monoprice and something a supposed step up.
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Thank you! That helps explain the differences in output voltages and specs. Can you tell me, does this allow the preamp to send a 2v minimum via the balanced output?KennethSwauger wrote: »The output stage uses an opamp based DC servo to keep the output DC to zero. The single end output is direct coupled (no blocking capacitor). The balanced output is produced by another opamp and has a series capacitor before the input to the opamp.
These are surface mount devices, which some designers find sound better than their larger counterparts. -
I don't believe that would be a problem.
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Not to derail the original intent of this thread, but are you planning on using an aftermarket power cord with the NAD? If so, stock first and then switch it to aftermarket? Or just aftermarket from the get go?
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Just stock to start and upgrading eventually. I'm already using a Furman ELITE-15 PF I for my power needs, which should help a bit with any noise in the power lines in the meantime.Not to derail the original intent of this thread, but are you planning on using an aftermarket power cord with the NAD? If so, stock first and then switch it to aftermarket? Or just aftermarket from the get go? -
alucididea wrote: »
Thank you! That helps explain the differences in output voltages and specs. Can you tell me, does this allow the preamp to send a 2v minimum via the balanced output?KennethSwauger wrote: »The output stage uses an opamp based DC servo to keep the output DC to zero. The single end output is direct coupled (no blocking capacitor). The balanced output is produced by another opamp and has a series capacitor before the input to the opamp.
These are surface mount devices, which some designers find sound better than their larger counterparts.KennethSwauger wrote: »I don't believe that would be a problem.
I am clearly out of sync with this discussion so I'll drop out now. -
@KennethSwauger Was just telling me that the information NAD supplied should be accurate, being the minimum 2v output for the balanced outputs.mhardy6647 wrote: »I am clearly out of sync with this discussion so I'll drop out now. -
Next question for their tech support: What is the recommended amount of break in time for the M12 before it sounds it's best?
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Message sent. Although I'm pretty sure their answer will most likely be some sort of nonsense.Next question for their tech support: What is the recommended amount of break in time for the M12 before it sounds it's best? -
From NAD: “The M12 does not have a break in time. It was tested at the factory after manufacturing, so it's "broken in" when you take it out of the box.”Next question for their tech support: What is the recommended amount of break in time for the M12 before it sounds it's best?
Basically what I was expecting. You? -
I did not have any expectation in regards to how they would reply, to answer your question.
However, their response is interesting. It implies that these master series components get additional attention paid to them at the factory during/after production. It sounds like they do a listening test to verify functionality. I'm sure they don't do this to all of their stuff.
I would politely disagree that a listening test at the factory constitutes an acceptable/recommended break-in process though. I would wager that it's going to sound different right out of the box vs 20 hours, 50 hours, and then 100+ hours.alucididea wrote: »From NAD: “The M12 does not have a break in time. It was tested at the factory after manufacturing, so it's "broken in" when you take it out of the box.”
Basically what I was expecting. You?
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I agree about electronics settling in, so to speak. I’m sure the NAD rep was just meaning it’s completely functional, however. I can’t imagine he can come out and say something isn’t 100% coming out of the factory. Though I am buying this refurbished. So I’m positive this unit has had some extra attention. Not to mention the dealer also installed the BluOS 2 card.I did not have any expectation in regards to how they would reply, to answer your question.
However, their response is interesting. It implies that these master series components get additional attention paid to them at the factory during/after production. It sounds like they do a listening test to verify functionality. I'm sure they don't do this to all of their stuff.
I would politely disagree that a listening test at the factory constitutes an acceptable/recommended break-in process though. I would wager that it's going to sound different right out of the box vs 20 hours, 50 hours, and then 100+ hours. -
Nice, this is actually one type of product I wouldn't mind buying a refurb of.
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