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grace audio 901 - words from the designer

post #1 of 4
Thread Starter 
i contacted designer and owner of the firm himself... ull see what quality this machine have and how customer support should look like...

one best thing is the he use hd600 with this amphimself like bob ludwig from gateway mastering studios (but i guess u know him well).

its like 1400 $ but hellish tamptetion

michael grace words>

Hello Matej,
Thank you for your inquiry. I think you will find the 901 to be
everything that you need. It is absolutely the highest quality
headphone amplifier we can make. I use the HD600 headphones myself and
they work beautifully with the 901.
Of course Bob Ludwig is our most famous 901 user. He has 5 901s and
uses them for his final quality control listening. Also we have 901s at
Airshow Mastering, Oberlin College, Skywalker Sound, Dolby Labs,
DigiDesign and others. I am confident that you will hear more music and
detail with the 901/HD600 combination than any other setup.


Here is some more info on the components in the 901

Precision level control
This control is a dual ganged 24 position gold contact
rotary switch, not a continuously variable potentiometer.
The switch uses precision metal film resistors which
provide better than .05dB channel matching even at 60dB
of attenuation. This is critical for evaluating channel
balance in a recording. Most potentiometers will have
channel balance error of more than 1dB at the 12 o'clock
position and as much as 3-4dB at the 9 o'clock position. I
have found that this is the range of the level control that I
use most often. The attenuator switch in the 901 is made
by Elma in Switzerland and has a wonderful feel and will
last a very long time.

25 Watt toroidal power transformer
The transformer is the heart of the power supply and
should be able to deliver power at a good margin above
what will be called for in the worst case. Also, it should not
radiate noise into the audio circuits. A toroidal transformer
is significantly quieter than a stacked iron transformer but
costs about three times more. This is definitely overkill for
a headphone amplifier but when it comes driving low
impedance phones you don't want any power supply
modulation.

Balanced RFI power line filter
The last thing you want in a high performance audio device
module that has voltage switching for international use as
well as a balanced RFI filter. Power lines are becoming
more and more contaminated with all sorts of high speed
signals. High frequency noise components can modulate
with the internal clocks in the DA section of the 901
causing subtle sonic anomalies.

Scientific Conversions AES3 input transformer
Scientific Conversions arguably makes the finest AES input
transformers. They have very low primary to secondary
capacitance and very high common mode rejection. These
qualities improve jitter performance in the receiver. You
can build a DA without an input transformer and save a fair
amount of money but I think our DA sounds better with
the transformer than without.

Sealed gold contact relays
We could have just sent the audio
signals through the front panel switches (which, by the
way, are also very high quality Swiss made EAO switches)
but this would require longer signal path runs to the switch.
These relays will last forever.

Metalized film capacitors
Film caps sound better (or have less sound) than
electrolytic capacitors. We use coupling capacitors in the
901 to protect the output amplifiers (and subsequently your
headphones) from any possible DC current.

Ultra low noise transimpedance instrumentation input
amplifiers.
These are actually the same amplifiers we use as the front
end for our microphone preamplifiers and help the 901
achieve 115dB of dynamic range.

High current transimpedance output amplifiers
This section of the 901 is absolutely critical. I am a real
believer in transimpedance (current feedback) amplifiers
for audio. They are the most musical and the most
revealing of complex harmonic information.

96KHz, 24Bit DAC
First let us remember that an ideal 24 bit system would
have 144 dB of dynamic range. There are plenty of cheap
"24/96" DACs out there that provide 96dB of dynamic
range. This is theoretical 16 bit performance! (many
marketing bits here) We use the top of the line Cirrus Logic
DAC which they advertise as a 122dB device (still got
some marketing bits in there). We managed net about
115dB in the 901 (this includes the affects of the output
amplifier). Of course, noise and dynamic range are not the
only quantities that affect the sound of a DAC.

I hope this will answer your questions.
I will have Doug Wood, our Director of Sales, contact you about
purchasing options and pricing.
Best regards,
Michael
post #2 of 4
Thread Starter 

bob ludwig on grace 901

here are words from master of mastering lots of audiophile records gone out of his hands... lps also




Dear Mr. Isak,
We own 5 of them and they are great.
The units have a very decent 96kHz D/A and the analog balanced and
unbalanced inputs are a plus!
We use the Sennheiser 580 or 600. Our quality control people wear them
for long periods so comfort is essential.
A better headphone but impossible to find is the original Grado
Signature series (it has a metal case). The present Grado "reference"
woods case headphones sound too bright to me.

I hope this helps!

Bob Ludwig
post #3 of 4
miziq,

Thanks a lot! My conversation with Michael was evidently way too short. I happened to be listening to the 901/325 combination when I was reading your post and I swear as I was reading it was sounding better and better .

So are you going to get one? you know you want one...go ahead...this message from Mr. Subliminal
post #4 of 4
Thread Starter 
jep mr. subliminal is working his way...

well this is hell lot of money for me and i do consider other options but im leaning more and more towards this thing...

we'll se cannot proise nothing. first ill have to find good price on it.

man u have to give some more review over this baby it looks too much the way i like it darn

i know what quality parts mean cos being audiphile for quite some time and starting to sell audiophile product from friend manufacturer again....

man it looks wat too good i only hope it sounds also that good....

if u see u got actually da converter in a box also....

dont u love hd600 with them u heard what ludwig got to say harsssssh hehehe

ok please write more of it...
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