[size=large]Introduction.[/size]
So far, the DAC in the m902 is a definite improvement over the one in the 901. Better than my RME 96/8 PAD as well. (this was to be a minimum requirement for me. )
I will save sound quality impressions for later, after I've lived with the m902 for awhile.

Til then, enjoy the pr0*.







Little foot can be removed by simpy unscrewing. My unit came with the feet not installed. There are little rubber feet included, but if you can, use the bigger feet, they look better and allow more clearance for cooling the bottom of the case.


Attention to detail, one area where the screwed in top meets the frame has the anodization stripped off to make conductive contact.




The Toroid has grown considerably since the 901.

Take a look at the Grace 901 for comparison.




Notice that the unbalanced inputs are now separately wired (and switched) from the balanced inputs.









Notice that the Bottom of the case, in fact the whole case acts as a heatsink now. The m902 operates more warmly, but not uncomfortably hot. This is due to the better heat dissipation.



[size=large]Possible Issues.[/size]
One thing about the USB input. I can hear a slight "click" sometimes when switching applications. Also right before music starts playing and the m902 locks the signal and the "S-Lock" lights up. But after it has a lock, no more clicks. Mind you, this is a very quiet sound. Occassionally I've seen the S Lock lose it's lock, the light went off, and there was a small "skip" in the music. This was quite rare. I only saw it once, so it may be a fluke, or perhaps an error in the encoded file. I'll have to check again.

For the DIY, you may be interested that the m902 uses the Switchcraft 1/4" Panel Mount jacks (Digikey# SC1107-ND).






While Grace Design claims them to be an upgrade from the previous jacks used before, I personally think they were picked mainly for their compact size, rather then purely for quality. While they are decent, their contact pressure is almost too weak. But at least it's not the death grip of the 901's jacks before (Neutrik Jacks?). So personal preferences abounds here, and will probably not bother anybody unless they open up their m902. Of course, I only find this an issue with my ridiculous silver K1000 adapter cable.

Also, the power button is not recessed like the 901. This means that it is entirely possible to accidentally turn the power on or off. Not something you'd expect to see for a piece of pro audio equipment. But it's a minor issue. Just watch your hands. A thinner bezel matching the ones on the headphone outputs could solve this "problem", but I like the cleaner look.

Of course everything else is impressively sourced and assembled.


Measuring DC Offset.

0.001VDC DC for both Left and Right Outputs. Nice.

-0.001VDC for Grace 901.

So basically they're off the scale for my wimpy DMM.



[size=large]Interesting features.[/size]
You can loop out unbalanced output AND headphone at the same time. By toggling the rotary encoder (volume knob), you can adjust the volume of the preamp output separately. So, you can have another amp hooked up and control the volume independantly from the m902's built in headphone amp.

Because the m902 does not use a stepped attenuator like the 901, the microprocessor controlled volume has much finer steps than the 24 (+hi gain, so, sort of like 48 steps) that the 901 has. There is an option to increase the gain to be able to ramp up the volume faster. (This is a must for the K1000's).
The benefit with extremely sensitive headphones like the Sony R10's is that no longer am I stuck with 4-5 levels of volume adjustment.

Using the m902 as a Preamp will also have benefits of having much finer volume control with a more powerful amp like say a Dynahi.

And last but not least, a little m902 and 901 comparison pics.








-Ed

It's a good start to the impressions, get that little hammie back to work generating some more info for us junkies!

Great post and impressions, Ed, and the pics are terrific as usual.

No do what Greg says, and get those hammies ears to work.

Is it better than the stock or modded RME?

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This amp sure isn't shy in front of the camera. Looks tight in all the right places, if you know what I mean.

Found something else interesting.

At 86 I can hear something inside the amp click (not through the headphones). Like it's switching something. Perhaps it switches to extend the gain in hi gain mode.

I prefer Hi Gain mode even for my R10's, it just takes so long for the volume to ramp up otherwise.

I guess the switching is to keep the noise levels down for the lower dBL levels. Otherwise, hitting the gain switch in the 901 adds noise, but only because it is increasing the gain across the board.

-Ed

Oh, yeah. Did I mention that the m902 is immune to the ground loop the 901 was vulnerable to?

I hooked it up to the analog outputs of the RME digi96/8 PAD, and no annoying buzzing. So, I was able to use a fully grounded power cord.

I will test some more. Including hooking it up to the craptacular analog outputs of the Audigy 2.

-Ed

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Finally! eh? Good to have that annoyance out of the way so your uber-snakes can go back to work.

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Heheh, well. It was a moot point, since I was using balanced cables, which eliminated the buzz. And using the DAC eliminated it too.

But it's nice to know that it no longer has that problem.

-Ed

That is a kick-ass looking amp, at the very least. I always loved look if not the sound of the 901. Can't wait for further listening impressions.

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Ed: please tell me that you are NOT listening to R10's at HI gain with level set to 86! That would make my ears bleed. Heck, I don't even get that high with K1000's.

I'm gonna try listening for that switching click myself tonight to see if mine does it too. Are you saying that when you reach an attenuator setting of 86 that you hear it? In both LO and HI gain?

Keep the impressions coming. and I will try to double check what you are experiencing.

One thing that gerG pointed out was that on power down, much of the custom settings are lost, including volume levels. Would be a nice option to keep settings through reset (xfeed, exclusive output, volume levels, etc). Conversely, if remembered settings were too difficult to implement through a power down, Grace has given us the safest options. Wouldn't be nice to turn on in the am after a late night of loud listening to have your head blown off.

With my R10's 40's to 50's with HI (Hi Gain) and 60's to 70's with LO (Low Gain /Default)

But I also have an overall 6dBL attenuation due to a 6dBL 50Hz "bass boost" in Foobar's EQ.

And yes. All settings are lost when I power down. That kind of sucks.

Guess I won't be turning it off often.

-Ed

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At 86 I hear the click (remember to listen to it with your headphones off.) in HI gain. At 96 I hear the click in LO gain.

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Yes, particularly when listening to the K1000's for a while, and then listening to the R10's later. I have always been careful to turn the volume all the way down and turn off Hi gain with the 901 when plugging lower impedance headphones.
I don't really personalize a whole lot of settings, so it's not a big deal for me. Still. Would be nice if Grace would have a firmware update. But unless they included enough non-volatile memory on board the m902, it's not likely.

-Ed

Looking forward to the sound impressions.
Some minor things that bug me though:

1. that screw right smack in the middle of the faceplate... what's up with that?... it looks like a regular old slot-screwdriver screw. Looks very out of place on an almost $2000 headphone amp. Apparently these screws are also used on the sides of the unit, which isn't so bad. A cross/hex or custom screw-head would have looked better I think. But the fact that it's right in the middle of the faceplate... it's sort of annoying.

2. On many of the pics of the m902 that I have seen, the screws (or whatever) on the metal surrounds that are around the headphone jacks, have the screws at 10 o'clock and 4 o'clock on both jacks. But Edwood's unit has the screws in different positions (almost 12 and 6, and 10 and 4)... maybe that's because he took his apart. It's absolutely trivial, but if they don't at least come in the same position, that would bug me... this would fall under the "attention to detail" that was raved about with respect to some other thing earlier. Not sure how those pieces connect to the chassis or the headphone jack behind them mind you, maybe you can just twist them round.

3. I'm stunned that the unit loses all settings when you unplug it. That is really disappointing, maybe if someone is talking to Grace or Michael, you can bring that up. My plan was to take my DAC/amp back and forth pretty much every day. Mind you not sure how many settings I'd really care about if they were lost, but I think that's one of those details that you just expect on a piece that costs this much.


I think someone said the m902 looks better in person, and the m901 photographs better... I sure hope so, because in those pics the m901 really kicks the m902's ass. At least with respect to front-on view of the faceplate. The m901 looks just that much more classier, while the m902 looks more technical.

Anyway, glad you guys are enjoying the new amps, thanks for all the super pics Edwood!

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Just tried mine, and ditto.

Actually the click (you have to really listen for it) happened when going from 86 to 86.5 (86 with decimal point) at LO gain, and from 96 to 96.5 at HI gain.

If I were listening through headphones OR speakers (not likely, those are insanely high levels), I would never notice it. Good catch, Ed. If Michael G. is listening in, maybe he will shed some light on what is going on.