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Grace 901 replacement: Grace m902 - Page 2

post #16 of 209
Quote:
Originally Posted by Iron_Dreamer
Seriously?!?! Well this will be fun indeed. I love that it has a USB input option built right in, though like Neil said, too bad no balanced outputs for a total solution, but then again it is supposed to be "just" a headphone amp. I guess with this you could ditch you remaining RME, eh Ed?
Well as long as it's not priced insanely.

I like the unbalanced output part at least. I could use it as a preamp for my home theater receiver in case I want to listen to speakers.

Well, no balanced output is not too big a deal for me. I wouldn't be using this thing as a DAC only. Well, I would hope the headphone amp section sounds better than the 901.

-Ed
post #17 of 209
MSRP is $1695.

The m902 should be alot better than the Benchmark, as it's nearly twice the price.

-Ed
post #18 of 209

...

Quote:
The m902 should be alot better than the Benchmark, as it's nearly twice the price.
...And we all know price has a direct relationship with sound quality...
post #19 of 209
this is a real winner if the dac is (almost) as good as the apogee / benchmark.
post #20 of 209
Quote:
Originally Posted by NeilPeart
...And we all know price has a direct relationship with sound quality...
Well it's supposed to, goddammit!
post #21 of 209
Hi All,
I thought I would shed a little light on the m902. The m902 replaces the 901 in our lineup (although we still have a few 901s left!). It has the same headphone output amplifier as the 901 which is based on a high current, high speed transimpedance amplifier (AD815). This is where the similarities end though.
The first important difference is in the level attenuator. The m902 uses a digitally controlled analog attenuator which provides 95dB of attenuation with precision .5dB steps. I think there are several advantages to this type of control. First off there are no contacts to become contaminated, there is no switch capacitance that varies from setting to setting, and there is no wire or connectors to color the sound. Also, the digitally controlled attenuator has a very wide volume range which makes the m902 handle a variety of headphones from super sensitive types like the Shure E5 to the not-so-sensitive types like the HD600 or K1000. Anywhere in the entire range you can find the exact listening level with .5dB steps. (final firmware might switch to 1dB steps at attenuation levels of –85dB and below). The attenuator IC that had the best transparency and musicality also happened to have four channels so we hooked up the extra two channels to a line output so that you could use the m902 to control speakers or use it as a DAC.

Speaking of DACs, the m902 contains our “second generation” DACs which have some notable improvements over the DACs in the 901. While the 901 used a very high performance chip (CS43122) we chose the Burr Brown PCM1730 for the m902. This DAC is one of the few that has current outputs and allows us to use our own current to voltage converter. The current to voltage converter uses very high speed transimpedance amplifiers which assures that reconstruction of the analog signal is done without the non-linear slew rate limiting of regular op amps. While you won’t see the benefits of this type of topology in the measured performance I think it makes a significant improvement in the clarity and resolving power of the DAC. The m902 also employs a second PLL which we call s-Lock. The s-Lock PLL re-clocks the recovered clock from the digital inputs (including the USB) using super stable crystal oscillators and delivers a sample clock to the DAC with very low intrinsic (self generated) jitter and well over 100 times attenuation of incoming jitter from external sources. Call me old fashioned but I’m just not a believer in sample rate converters. While the 901 DAC is capable of fine performance with a low jitter source the clock recovery circuitry is not capable of attenuating incoming jitter so its performance degrades with long cables and jittery sources.

Like the 901, there are no electrolytic capacitors in the signal path. The inputs to the volume control are capacitor coupled with metalized polymer capacitors while the output amplifier is controlled with a DC servo. I think that a coupling capacitor sounds better than a servo since, when using a servo, you are not only listening to the integrator capacitor but you are also listening to the servo amplifier as its output is summed into the audio signal. However, in the case of the output amplifier we would need a very large value output capacitor to protect the headphones from DC offset so a servo is necessary here. (to keep the low frequency roll off below 10Hz while using 32 Ohm phones we would need around 5000uF which would only be available in an electrolytic type.)

Other enhancements to the m902 include:

All audio signal path resistors are 0.5% tolerance thin film surface mount types. Thin film resistors use the same type of metalic material used in thruough hole metal film types but have no lead inductance.

Improved capacitors in the output amplifier compensation network.

Larger power transformer with separate winding for digital circuitry. (the 901 derived digital supplies from the +analog supply)

Improved headphone jacks

4 layer pcb (this allows a continuous, low impedance ground plane and low inductance power supply distribution)

Separate power supply regulators for analog amplifiers, digital reciever PLL, DAC digital supply, DAC analog supply. 7 regulators in the m902!

Passive cross feed circuit.

Optional IR remote control. I wanted to be able to sit on my couch and have the m902 in my stereo cabinet so I could have it hooked into my loudspeaker system as a DAC…


Yup, there is more stuff in the m902 than in the 901…and it costs more. No cut corners. Just nice rounded ones on the outside.

Cheers,
Michael

PS. The little I-river IHP player is a nice low jitter device for playing wav files. No laser pickup error correction…
post #22 of 209
Wow! A post by the man himself, Michael Grace.

Thank you very much for sharing directly with us, Michael. As you can see, there is much anticipation here for your new baby.

Welcome to Head-Fi, and in this case, I will reverse the normal greeting and say, "Sorry for our wallets"

Thanks again, and hope we see more of you around these parts.
post #23 of 209
now if only if it had a remote option............................sweet
post #24 of 209
Quote:
Originally Posted by GoRedwings19
now if only if it had a remote option............................sweet
It actually does! Check his quote -

"Optional IR remote control. I wanted to be able to sit on my couch and have the m902 in my stereo cabinet so I could have it hooked into my loudspeaker system as a DAC…
"
post #25 of 209
Holy cow dudes, A remote option now this should be standard with all headphone amps. Okay who's gonna be the first to pick one up and find out what's it like???? Edwood???????Ayt999???? Come on people
post #26 of 209
Quote:
Originally Posted by GoRedwings19
Okay who's gonna be the first to pick one up and find out what's it like???? Edwood???????Ayt999???? Come on people
how did my name come up? I haven't posted in this thread yet. I'm trying to limit the number of amps I have around, and you want me to get another? lol
post #27 of 209
Well how many 901's have you got????? And if grace does his homework and make the DAC better than the competition then he is on to a winner. I got another headfier to order me one about a few weeks ago. But now that I have got the DCS delius/upsampler I don't need the grace 901 anymore and it's brand new!!!!!! But it doesn't mean I would say no to the new 902. And with the remote option I am totally there dude.
post #28 of 209
Quote:
Originally Posted by GoRedwings19
Well how many 901's have you got?????
I only have one 901... which I may sell soon since I never use it. besides, my Accuphase DP-85 SACD player has a better DAC section than the 902m (it better have a better one at least)... and I have many headphone amps that are better than the 901, which apparently shares the same amp section as the m902, so there's no need for that either.

the DP-85 has digital volume controls via the remote too.
post #29 of 209
Quote:
Originally Posted by ayt999
I only have one 901... which I may sell soon since I never use it. besides, my Accuphase DP-85 SACD player has a better DAC section than the 902m (it better have a better one at least)... and I have many headphone amps that are better than the 901, which apparently shares the same amp section as the m902, so there's no need for that either.

the DP-85 has digital volume controls via the remote too.
Well I originally bought the 901 to handle all my digital gear e.g playstation 2 and my dvd player, sat box so I would benefit from better sound and being able to use headphones with them. But with the DCS multiple digital inputs and upsampling technolgy the grace 901 is redundant already. I haven't even recieved it let alone open it. It's somewhere in the atlantic ocean coming my way. Damn I will probably have to sell it now.
post #30 of 209
the is the all-in-one 'sound box' for people using their computers as the source...it isn't that expensive (no IC needed, 1 power cord for dac + amp) either, nice...
gee ayt999 you KNOW you want it, right?
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