88Sound
500+ Head-Fier
- Joined
- Dec 14, 2001
- Posts
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The usual disclaimers first: Because of my lack of experience with state of the art solid state headphone amp's I am far from the ideal reviewer. I have never heard a Headroom amp or a Sugden or anything better than a RA-1 until now. From an engineering standpoint, look, feel, operation, this amp strikes me as incredible. Like that line in the Jerry McGuire movie "you had me at hello". So these are my impressions. I have included the initial list of features available in the manual and on the Grace Website because I have added information (italicized) that was gleaned from my conversation with the 901's designer and founder of the company Michael Grace.
The Grace Design Model 901 Reference Headphone Amplifier, is a product marketed to the Pro Studio and not to the audiophile community at all. The 901 is the only headphone amp I know of that contains all of these features in one unit:
- Balanced XLR analog inputs
- Unbalanced RCA analog inputs
- AES, SPDIF and TOS LINK digital inputs
- High current output amplifier drives 8 Ohm loads easily
- 24 position gold contact stepped metal film resistor level attenuator with .05dB channel matching
- Internal linear power supply
- High current , low noise torroidal power transformer
- No electrolytic capacitors in signal path
- Highest quality metal film resistors
- Ultra low distortion 24 bit DAC accepts sample rates up to 96kHz (this is a Cirrus CS43122 DAC)
- Automatic digital de-emphasis filter
- 10dB gain boost switch for –10 sources
- Fast, musical transimpedance output amplifiers
- Precision instrumentation balanced input amplifiers
- Sealed gold contact relays for input select and gain boost switching
I am using a Pioneer DV-47A DVD/SACD/CD player with the 901 hooked up via analog RCA inputs and digital TOS LINK optical inputs. The 901 allows you to instantly switch between the analog input (utilizing the DAC in your player) and the digital input (utilizing the 901's DAC) from the front panel. The DV-47A also has a second set of analog outputs that I have hooked up to an EarMax Pro.
The 901 pushes about every button I have to push. Small Company, very nice on the phone, when I had technical questions about the 901 I was immediately put on the phone with Michael Grace. Turns out he's an HP-1000 owner & fan, also likes the HD600 and made a point to say the 901 will drive the K1000 to satisfactory if not earsplitting levels. Very customer oriented, 5 year parts and labor warranty that's transferable to any subsequent owner. Build quality......Oh My! Steel chassis, solid faceplate, stepped metal film resistor volume control, switches are sealed gold contact... I am an absolute sucker for great engineering design. Weighs in at nearly 8 lbs., which is quite heavy for a half rack unit.
The switches are absolutely silent. While playing music I can instantly compare the DV-47A and it's DAC, associated settings, and interconnects with the 901's DAC. The sample rate on the 901 is not user selectable (like it is on the ART DI/O); it is determined by a frequency comparator, not by the sample rate bits in the digital data. This ensures that the proper DAC filter settings are used even if there are erroneous sample rate bits in the signal (can't tell that was directly out of the manual can you?). So far it seems that CD's always sync at 44.1 kHz and DVD's always sync at 48 kHz. The digital output from the DV47A is muted for SACD's, Sony has evidently learned nothing from their Beta experience years ago, so for SACD's I must go analog to the 901.
There is a High/Low range button next to the Digital/Analog button that you will need to take note of. The High setting boosts the signal 10 dB. If you are listening at a fairly loud level with the low setting and accidentally push this button you will at least be startled! Try as I may I haven’t damaged anything yet.
In every instance I’ve tried so far I prefer the sound of the 901's DAC to the DV-47A's DAC & interconnect. The 901's DAC sounds more 3D, the soundstage has more depth and the instruments sound more realistic and lively than the DV47A's, I have decent but not fancy interconnects so eliminating those when optically connected to the 901 may also contribute to my preference.
A side benefit of having two analog outputs from your source hooked to two different amps makes comparison between amps easy. The switch can be made in the time it takes to unplug and plug in. When I first got the unit I was frantically plugging in phones to the 901, listening, then plugging into the EMP, back to the 901, press the analog to digital button and back…..It made me crazy, scratch that… more crazy!
I am only going to provide some initial impressions of the sound since I’ve only had the unit for slightly over a week and have selfishly been listening to music with abandon, not taking notes or anything. The sound of the 901 is very detailed but not harsh at all with plenty of power to spare, effortless. The phones I have that benefit most are the Grado 325 & RS1. I had no Idea you could play either of these phones that loud without a hint of distortion, positively frightening. The 901 takes control of whatever you plug into it and would be an excellent tool for evaluating other devices i.e. headphones, DAC's, interconnects etc……
With the W100's & W2002's there are times I prefer the EMP and times I prefer the 901, with the Grado's the nod usually goes to the 901. I had always felt the 325 was a little harsh on vocals, female or male, when compared with my other phones. With the 901 that harshness is gone, the RS1’s however have shown the most improvement. I now believe my poor 325 & RS1 were crying out for more current all the time, I just didn’t know it until now.
It is my opinion that the 901 has met its design goals. As much as I like the EMP it would have no place in a project studio, its pleasing tubey goodness (distortion) could have disastrous results when used to make decisions that would effect the outcome of a CD or DVD. The 901 on the other hand is perfect for this application, showing clearly without comment exactly what it is being fed with authority.
There is very little information currently on the Web about the 901. One snippet that carries some weight is Bob Ludwig (President of Gateway Mastering) after hearing a pre production prototype of the 901 ordered 5 for his facility in Maine. By the way if you have a lot of CD’s and you haven’t heard of Bob Ludwig, you don't read liner notes. I would be curious to know how many thousands of albums this man has mastered.
Here are some updates as of 6-24-02:
The switches on the 901 are not absolutely silent all the time, I sometimes hear a very slight transient when engaging or disengaging the digital/analog, high/low switch, or operating the volume control, still quite acceptable.
So far I can get the 901 to sync at 96kHz with DAD discs (DVD-V) only (thanks to Dusty Chalk for the DAD's info!). I have a Bucky Pizzarelli DVD-A put out by Chesky that on the DVD menu you can select 2 channel 24 bit/96kHz output, the DV47-A displays DVD-A V, but it still only outputs 48kHz to the digital out. In my 901 review I stated that the 901 DAC sounded better to me in all cases, I am now finding that on DVD-A discs I like the DV47A DAC better. Somehow I think the DV47A is artificially crippling the digital out down to 48kHz on DVD-A discs but the internal DAC is operating at 96kHz.
Based on some interconnect education I received at this very site I have changed my digital connection between the DV47A and the 901 from TOS LINK (optical) to Coax.
If you want to take a closer look at the 901:
http://www.gracedesign.com/products/...t_frameset.htm
The Grace Design Model 901 Reference Headphone Amplifier, is a product marketed to the Pro Studio and not to the audiophile community at all. The 901 is the only headphone amp I know of that contains all of these features in one unit:
- Balanced XLR analog inputs
- Unbalanced RCA analog inputs
- AES, SPDIF and TOS LINK digital inputs
- High current output amplifier drives 8 Ohm loads easily
- 24 position gold contact stepped metal film resistor level attenuator with .05dB channel matching
- Internal linear power supply
- High current , low noise torroidal power transformer
- No electrolytic capacitors in signal path
- Highest quality metal film resistors
- Ultra low distortion 24 bit DAC accepts sample rates up to 96kHz (this is a Cirrus CS43122 DAC)
- Automatic digital de-emphasis filter
- 10dB gain boost switch for –10 sources
- Fast, musical transimpedance output amplifiers
- Precision instrumentation balanced input amplifiers
- Sealed gold contact relays for input select and gain boost switching
I am using a Pioneer DV-47A DVD/SACD/CD player with the 901 hooked up via analog RCA inputs and digital TOS LINK optical inputs. The 901 allows you to instantly switch between the analog input (utilizing the DAC in your player) and the digital input (utilizing the 901's DAC) from the front panel. The DV-47A also has a second set of analog outputs that I have hooked up to an EarMax Pro.
The 901 pushes about every button I have to push. Small Company, very nice on the phone, when I had technical questions about the 901 I was immediately put on the phone with Michael Grace. Turns out he's an HP-1000 owner & fan, also likes the HD600 and made a point to say the 901 will drive the K1000 to satisfactory if not earsplitting levels. Very customer oriented, 5 year parts and labor warranty that's transferable to any subsequent owner. Build quality......Oh My! Steel chassis, solid faceplate, stepped metal film resistor volume control, switches are sealed gold contact... I am an absolute sucker for great engineering design. Weighs in at nearly 8 lbs., which is quite heavy for a half rack unit.
The switches are absolutely silent. While playing music I can instantly compare the DV-47A and it's DAC, associated settings, and interconnects with the 901's DAC. The sample rate on the 901 is not user selectable (like it is on the ART DI/O); it is determined by a frequency comparator, not by the sample rate bits in the digital data. This ensures that the proper DAC filter settings are used even if there are erroneous sample rate bits in the signal (can't tell that was directly out of the manual can you?). So far it seems that CD's always sync at 44.1 kHz and DVD's always sync at 48 kHz. The digital output from the DV47A is muted for SACD's, Sony has evidently learned nothing from their Beta experience years ago, so for SACD's I must go analog to the 901.
There is a High/Low range button next to the Digital/Analog button that you will need to take note of. The High setting boosts the signal 10 dB. If you are listening at a fairly loud level with the low setting and accidentally push this button you will at least be startled! Try as I may I haven’t damaged anything yet.
In every instance I’ve tried so far I prefer the sound of the 901's DAC to the DV-47A's DAC & interconnect. The 901's DAC sounds more 3D, the soundstage has more depth and the instruments sound more realistic and lively than the DV47A's, I have decent but not fancy interconnects so eliminating those when optically connected to the 901 may also contribute to my preference.
A side benefit of having two analog outputs from your source hooked to two different amps makes comparison between amps easy. The switch can be made in the time it takes to unplug and plug in. When I first got the unit I was frantically plugging in phones to the 901, listening, then plugging into the EMP, back to the 901, press the analog to digital button and back…..It made me crazy, scratch that… more crazy!
I am only going to provide some initial impressions of the sound since I’ve only had the unit for slightly over a week and have selfishly been listening to music with abandon, not taking notes or anything. The sound of the 901 is very detailed but not harsh at all with plenty of power to spare, effortless. The phones I have that benefit most are the Grado 325 & RS1. I had no Idea you could play either of these phones that loud without a hint of distortion, positively frightening. The 901 takes control of whatever you plug into it and would be an excellent tool for evaluating other devices i.e. headphones, DAC's, interconnects etc……
With the W100's & W2002's there are times I prefer the EMP and times I prefer the 901, with the Grado's the nod usually goes to the 901. I had always felt the 325 was a little harsh on vocals, female or male, when compared with my other phones. With the 901 that harshness is gone, the RS1’s however have shown the most improvement. I now believe my poor 325 & RS1 were crying out for more current all the time, I just didn’t know it until now.
It is my opinion that the 901 has met its design goals. As much as I like the EMP it would have no place in a project studio, its pleasing tubey goodness (distortion) could have disastrous results when used to make decisions that would effect the outcome of a CD or DVD. The 901 on the other hand is perfect for this application, showing clearly without comment exactly what it is being fed with authority.
There is very little information currently on the Web about the 901. One snippet that carries some weight is Bob Ludwig (President of Gateway Mastering) after hearing a pre production prototype of the 901 ordered 5 for his facility in Maine. By the way if you have a lot of CD’s and you haven’t heard of Bob Ludwig, you don't read liner notes. I would be curious to know how many thousands of albums this man has mastered.
Here are some updates as of 6-24-02:
The switches on the 901 are not absolutely silent all the time, I sometimes hear a very slight transient when engaging or disengaging the digital/analog, high/low switch, or operating the volume control, still quite acceptable.
So far I can get the 901 to sync at 96kHz with DAD discs (DVD-V) only (thanks to Dusty Chalk for the DAD's info!). I have a Bucky Pizzarelli DVD-A put out by Chesky that on the DVD menu you can select 2 channel 24 bit/96kHz output, the DV47-A displays DVD-A V, but it still only outputs 48kHz to the digital out. In my 901 review I stated that the 901 DAC sounded better to me in all cases, I am now finding that on DVD-A discs I like the DV47A DAC better. Somehow I think the DV47A is artificially crippling the digital out down to 48kHz on DVD-A discs but the internal DAC is operating at 96kHz.
Based on some interconnect education I received at this very site I have changed my digital connection between the DV47A and the 901 from TOS LINK (optical) to Coax.
If you want to take a closer look at the 901:
http://www.gracedesign.com/products/...t_frameset.htm