Review and Measurements of Grace Design m900 DAC & Amp

[Blumlein 88]

I wonder if they have a fixed 8 or 10 db gain block that gets activated and when it goes on the drop the digital portion to provide the fine control? If that were the case as you raise volume you'd regain some of the lost SINAD as you move toward 99.

 

[amirm]

I wonder if they have a fixed 8 or 10 db gain block that gets activated and when it goes on the drop the digital portion to provide the fine control? If that were the case as you raise volume you'd regain some of the lost SINAD as you move toward 99.

You only get a couple of dB of that back at max volume:

 

[Blumlein 88]

"F4" ("= slow roll off, minimum phase Not linear phase in the pass band. Best for acoustic music without compression and artificially high levels of treble. Will have very low level of ringing caused by transients and ringing will be shifted to after the transient. )

So the slow roll off lets enough imaging occur to replace the hashiness of compression on music that doesn't have it yet. And naturally the post transient filtering (which imaging tones along for the ride) are so much nicer. I believe it is J-J that always calls this a broken design or a broken DAC. Wished they (and all the others) would just leave this off.

 

[Blumlein 88]

You only get a couple of dB of that back at max volume:

View attachment 21000

Thanks for checking Amir.

Looks like the higher signal level pushes up the second harmonic which is keeping the SINAD number low. The noise portion doesn't look so bad.

 

[HammerSandwich]

Well researched, Amir.

This filter situation reminds me of something Bruno Putzeys said about digital filters, in his Engineer's Survival Guide:

2 common impementation problems were identified
• Aliasing and Pre-Echo
• Audible deficiencies are linked to compromising.
• Solved by better adhering to theory, not deviating further.

The guy's not just a solid EE, he's a world-class smart-ass!

 

[Jimster480]

The DX3 Pro is in my measurement templates so it is always there. I also use it for listening tests so for new data, I don't use it. Music comes first, measurements second.

So you are saying that you primarily use the D50 vs the DX3 Pro?

Also now that you figured out what the filter problem was, shouldn't you re-run the multi-tone test?

 

[amirm]

So you are saying that you primarily use the D50 vs the DX3 Pro?

The DX3 Pro. The AP analyzer has a loud fan and I can't think straight listening to it. So I am always wearing headphones, listening to music through the Topping DX3 Pro. As such, taking it out of that role and test is painful. I don't use the D50 except for testing.

 

[amirm]

Also now that you figured out what the filter problem was, shouldn't you re-run the multi-tone test?

I did. It was in the same post: https://www.audiosciencereview.com/...of-grace-design-m900-dac-amp.6470/post-144171

It made no difference there. The harmonic distortion is simply higher in Grace Design m900 than other DACs we have tested like d50.

 

[restorer-john]

...The AP analyzer has a loud fan and I can't think straight listening to it...

Oh the irony. Digging 140dB below for dynamic range tests on D/A converters when the test equipment is making so much background noise you need earmuffs or headphones.

Maybe a firmware update to ramp up and down the fan speed according to load like a PC? Or does Amir stress the poor AP so hard its fan is running flat out all the time?

 

[Jimster480]

The DX3 Pro. The AP analyzer has a loud fan and I can't think straight listening to it. So I am always wearing headphones, listening to music through the Topping DX3 Pro. As such, taking it out of that role and test is painful. I don't use the D50 except for testing.

Alright, makes sense.
I know that the DX3 Pro has been a favorite for you so I was surprised when you mentioned the D50. Especially considering that you always talk about balanced connectors.

 

[amirm]

Maybe a firmware update to ramp up and down the fan speed according to load like a PC? Or does Amir stress the poor AP so hard its fan is running flat out all the time?

It is not a variable fan unfortunately. So it whales from power on until finished. I have it at near chest level so that it is easy to plug things in and out of it so the sound transmits even more. Seeing how much I paid for it, I put up with it running cooler this way so that it lasts as long as it can.

 

[gvl]

It is not a variable fan unfortunately. So it whales from power on until finished. I have it at near chest level so that it is easy to plug things in and out of it so the sound transmits even more. Seeing how much I paid for it, I put up with it running cooler this way so that it lasts as long as it can.

For the kind of money they charge it should be liquid nitrogen cooled with complete silence.

 

[rajapruk]

Can’t wait to see the Massdrop Grace Balanced SDAC to be measured, when it ships in late May.
I think that one is my next dac.

 

[pii75]

@amirm sorry if from time to time I go back with the same question, but I don't understand the linearity test results in general... For instance here the linearity test is superb, while in DX3-PRO is no so good (dominated by noise floor starting at 90 db), though DX3 has a lower noise level than m900 as shown in this review in the intermodulation test. Can you help me in understanding?
Thanks

 

[m8o]

Summary: using the F4 filter was causing severe aliasing due to not getting rid of out of band components.

Glad to see you found the reason for this aberration. I know about the filters, but it didnt come to mind to suggest it. Glad it's in no way related to the internal processing of the DAC which did come to mind.

Reminded of the filter selection (had forgotten about this; have not used my M9xx seriously for about a year) , I will say that I've tried F4 many times and each time it doesn't take me long to conclude something is 'not right' with the playback of the music. If a gun was to my head I could still not qualify what 'not right' is. But I dont like it, and always switch to another filter.

 

[MZKM]

Maybe it’s the “spurious tones”, but for the J-Test, are you using the +/- 250Hz LSB sidebands?

 

[graz_lag]

I have a M9xx which I picked up for roughly half price. It's great with HD6xx phones.

I can get one @ $280 (EUR), is it fair as a second hand price ? (A 2017's MassDrop unit.)

 

[Ron Texas]

I can get one @ $280 (EUR), is it fair as a second hand price ? (A 2017's MassDrop unit.)

I suppose so, if it is complete and not scratched up. The best use for this item is with headphones. As a standalone DAC, there are better deals.

 

[Biblob]

I can get one @ $280 (EUR), is it fair as a second hand price ? (A 2017's MassDrop unit.)

As I look at your set-up beneath every post, I notice you are not easily satisfied.

 

[Bliman]

Maybe it would be interesting to contact Grace Design and ask why these measurements are what they are.
The weird ones. Maybe they could say what is going on.
Most of the time they are pretty open.