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NAD M66 - finally someone makes a decent 2-channel preamp!

What is the best source of information about how Dirac works in practice and how to use it most effectively? I do not need introduction to concepts of room correction; rather, information on using the Dirac software (including BC) specifically. I am evaluating an M66, and what I've found online is superficial and not enough for me to use the software effectively and efficiently.

For example, I have not yet found information on many of the controls of the software . . . by clicking around on the right side, things change, but it's not clear what's happening or what the little squiggly control are meant to do. I can change from control points to handles for the target, but I'm never sure how I did this, how to change back, and whether it's possible to combine changes in the two modes. How is headroom handled? Is there any feature (like Anthem's Quick Measure) that would allow me to view measurements with Dirac, so I can position and adjust speakers before running a correction? Or is it absolutely necessary to use an external tool like REW?
 
Mike-48 said:
What is the best source of information about how Dirac works in practice and how to use it most effectively? I do not need introduction to concepts of room correction; rather, information on using the Dirac software (including BC) specifically. I am evaluating an M66, and what I've found online is superficial and not enough for me to use the software effectively and efficiently.

For example, I have not yet found information on many of the controls of the software . . . by clicking around on the right side, things change, but it's not clear what's happening or what the little squiggly control are meant to do. I can change from control points to handles for the target, but I'm never sure how I did this, how to change back, and whether it's possible to combine changes in the two modes. How is headroom handled? Is there any feature (like Anthem's Quick Measure) that would allow me to view measurements with Dirac, so I can position and adjust speakers before running a correction? Or is it absolutely necessary to use an external tool like REW?
Click to expand...
I also have the STR preamp; tried the M66 last fall. Besides the ridiculous "feet" on the M66 there were bugs galore and simple things like volume at start up are not available. And Dirac was a PITA compared to ARC. Just my two cents but I returned the M66 with a feeling of "good riddance" and gained newfound affection for the STR.
 
Another BluOS update of minor importance.

4.8.21

WHAT’S NEW​

  • DSD Playback on Bluesound NODE (N130), NODE X (N131), POWERNODE (N330), POWERNODE EDGE (N230) and PSB Speakers Alpha IQs with MQA QRONO dsd
  • Resolved issue with Pandora Users in US skipping tracks while forming group playback
  • Resolved time zone not selected properly when starting a NODE ICON
 
love the preamp but I may have to return. The gain level for the amp outputs, both xlr and rca are just too low and waaaay below spec. it has been mentioned in a couple of reviews but I didn't know how bad it would be. my speakers are 84 db sensitivity, so that does not help but it do not believe it will drive most amps to their full potential. Volume is roughly the same for internal sources like tidal or external optical. phono doesn't seem to be different either and I wonder if that is why they are limiting the digital side.
 
It relates to what the amp is expecting. From the tests I've seen the max output at 100% is around half or less of other preamps. If your amp is expecting lets say 5v for max the m66 is only giving 2.6. if you have high efficiency speaker, not a real problem. if they are low, you need to have enough gain range on your amps input to make up the difference and drive you amp more towards it maximum output range . I've tried three amp, an older classee amp, a myrad amp and just plugged in a la90 because it had high/low gain. at max volume the amp never gets near clipping or breathing hard meaning the preamp does not have enough voltage to drive the output stage to max. I have a pair of buckeyes on the way which have even more gain. There is an article in soundstage which mentions the ADC clipping a relatively low output using the mm input and I'm wondering if that is why they limited the entire output. Shereophile measurements allows show the low output.
 
I believe the gain limitation is most likely to be a problem when Dirac is engaged and the preamp sets aside some digital headroom. When the tone controls are engaged (even if set to flat), another chunk of headroom is lost. The result is that some quiet recordings can't be played at sufficiently loud volumes, unless one has a high-gain amplifier and/or efficient speakers. I have used other DRC preamps that had more gain than the M66.
 
tomstir said:
volume control at 100
Click to expand...
Switch to the dB display and turn up to 0dB. Set the tone controls to off beforehand. If you are using Dirac Live, you can get back the unused headroom adapting the target curve.
What is the result if you go analog direct?
 
thanks for the feedback
few measurements, no tone, 0db, volume at 100 percent amp input gain set to high using bridged input. 9 ft from speakers.
phone
analog direct max spl 91-93 db
Dirac max spa 91-93
no Dirac 97-100
digital optical
Dirac 91-93
no Dirac 97-100

plugged the Classe back in using the rca inputs and got nearly identical readings
I tried upping the gain by creating a hand filter. you can add some gain but if I remember correctly your limited on gain available(not sure on this it was a passing experiment) I added 4 db to the curve and still have it loaded. output is still below the no Dirac curve.
 
I have a couple nodes that take a lot of gain (1 around 10 db if I remember) that Dirac is filling in to get me to flat. That may have been the limiting factor, but I'm not 100 percent sure. ill give it a try
 
tomstir said:
thanks for the feedback
few measurements, no tone, 0db, volume at 100 percent amp input gain set to high using bridged input. 9 ft from speakers.
phone
analog direct max spl 91-93 db
Dirac max spa 91-93
no Dirac 97-100
digital optical
Dirac 91-93
no Dirac 97-100

plugged the Classe back in using the rca inputs and got nearly identical readings
I tried upping the gain by creating a hand filter. you can add some gain but if I remember correctly your limited on gain available(not sure on this it was a passing experiment) I added 4 db to the curve and still have it loaded. output is still below the no Dirac curve.
Click to expand...
The massive difference between Dirac on and Dirac off tends to suggest you have not set up your speakers as well as they should be, or that your speakers' response if far from ideal.

If you notice a drop in volume when a Dirac filter is engaged, that's a bad sign and you need to get the speakers changed or set up much better - sorry to be blunt! This is because (in layman's terms as I understand them) Dirac has detected deep dips in the frequency response and needs to lower much of the response plot to compensate for these dips, so that you hear a flatter overall response. It may sound better, but it's not good practice to allow Dirac to work so hard.

It would appear that you are asking Dirac to do fundamental jobs that should be done long before you resort to Dirac. A well set up system using carefully chosen full-range speakers of good quality, should result in a Dirac filter that causes an inaudible drop in perceived volume when a filter is engaged. I hope you can resolve the problems, but I am almost certain that the M66 is not to blame for a perceived low output.
 
Dirac drops the level compared to the peaks by -6dB, that’s how it works, the room dominates even the finest loudspeakers in the low bass.
Keith
 
Purité Audio said:
the room dominates even the finest loudspeakers in the low bass.
Click to expand...
Certainly it does -- and in some situations, room effects will be more severe. Sonically leakier rooms will exhibit less severe room effects; those that are very tight will develop more severe peaks and nulls. One could argue that a DRC (digital room correction) system should be able to deal with either situation, whether by limiting corrections or by providing extra gain, or by some other work-around readily available to the user.
 
thanks again for the feedback
The room is actually very flat till below 85 or so. In fact I was considering not using dirac above 500 or so but now it looks like I will be using it for boost and analog direct will be on hold. Hopefully this gets better with the new higher gain amps I have coming. Neeldess to say I wish the preamp output closer to its stated spec.that would more than likely make the Dirac gain penalty a moot point soundstagenetworks does a good job of highlighting the output difference even without Dirac. I love the preamp, I have not seen another one with its combination of feature but Dirac is what made me pick it over others. I am hoping they will be able to a software update which will get them closer to the majority of preamps I've seen on the market.
 
Purité Audio said:
Dirac drops the level compared to the peaks by -6dB, that’s how it works, the room dominates even the finest loudspeakers in the low bass.
Keith
Click to expand...
One still has to question why well chosen (with regard to the room) speakers that are well set up need Dirac at all. If speakers are well chosen, are well set up and consideration has been given to room furnishings, carpeting, curtains, etc, is there really a need to mess with a nice flat signal to compensate for other wrongs? Were our systems rubbish before DSP was available in domestic systems?

If Dirac filters result in a significant reduction in perceived volume level, there is definitely something seriously wrong that needs to be fixed before chucking Dirac at a problem that it is not designed to do. I have Dirac Live in my own system and filters make no difference to the apparent volume because my speakers are full-range, were chosen to suit my room's peculiarities and I've set them up reasonably well. In fact, the sound without DSP is noticeably better in terms of excitement factor because the precious signal has been kept away from "processing" as much as possible. I'd prefer this than loose the excitement factor for a slightly flatter bass response any day.
 
Standing waves in the room completely dominate , if your loudspeakers have enough bass extension to excite them, EQ makes absolute sense.
Have you ever acoustically measured your room, perhaps you should.
Keith
 
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