[Orpheus]

hi.

well, i was so looking forward to this amp, as it seemed almost perfect. and i was most looking forward to its ultra-low noise floor.

well, in low gain mode, yes, it's basically totally silent in any volume less than 3/4 max of the volume knob, with any headphones (the lowest impedance, most sensative phones i've tried are the 32 ohm Sony CD3000's.) however, in high gain mode, it seems there's some hum being amplified, even with the volume turned all the way down! even when the input is selected to digital, with no digital input connected, one can still hear a very small amount of buzzing with the CD3000's. with any other headphones, it's unaudible. with the analog inputs shorted, with analog input selected, same thing.

so..........is there anything wrong with my unit?--i got mine used, so there's always that 5% chance something's wrong. or is this to be expected?

i'm a little nervous about this, cause it's a hecka expensive amp... and from all the reviews written, it sounded like it would have no audible noise floor...

any other grado or sony cd3k users out there with the grace 901?

 

[gpalmer]

I'm a Grado user, I can't remember every hearing a hum or buzz with them. It might be limited to the CD3K because of its higher sensitivity though.

BTW - Why would you want to use high gain mode with the CD3K anyways? Afraid you might leave some of your hearing intact?

 

[kartik]

What power filtration are you using? Maybe that's your problem.
My SR-325s seem to pick up a volume independent hiss on my Sharp Digital amplifier when powered by the speaker output. Doesn't do this on the Unico power amp with a 4kva servo power regenerator.

 

[kartik]

Quote:

Originally posted by gpalmer Afraid you might leave some of your hearing intact?

LOL

As an informal member of Team Stealthy!

 

[gsferrari]

I find the Grace to be extremely sensitive to power supply quality and cables...

Try using the Optical connection (unless you are listening to SACD's in which case there will not be any signal through the optical output) and see if using the internal DAC eliminates the noise - in which case your source could be at fault...

Troubleshoot

Always think that the amp is the last thing that can fail and work towards the causes that might point to an amplifier failure...this way you can confirm that you have a faulty Grace...

 

[Music Fanatic]

Quote:

Originally posted by Orpheus hi. well, i was so looking forward to this amp, as it seemed almost perfect. and i was most looking forward to its ultra-low noise floor. well, in low gain mode, yes, it's basically totally silent in any volume less than 3/4 max of the volume knob, with any headphones (the lowest impedance, most sensative phones i've tried are the 32 ohm Sony CD3000's.) however, in high gain mode, it seems there's some hum being amplified, even with the volume turned all the way down! even when the input is selected to digital, with no digital input connected, one can still hear a very small amount of buzzing with the CD3000's. with any other headphones, it's unaudible. with the analog inputs shorted, with analog input selected, same thing. so..........is there anything wrong with my unit?--i got mine used, so there's always that 5% chance something's wrong. or is this to be expected? i'm a little nervous about this, cause it's a hecka expensive amp... and from all the reviews written, it sounded like it would have no audible noise floor... any other grado or sony cd3k users out there with the grace 901?

I have that combination, and have just tried the CD3000 on digital input with volume on maximum. I hear a slight amount of background hiss, but absolutely no hum. I think you should send your unit back to Grace for repair.

 

[Orpheus]

Quote:

BTW - Why would you want to use high gain mode with the CD3K anyways? Afraid you might leave some of your hearing intact?

heh he, no, i wouldn't actually. but i was testing for noise.... that's all.
Quote:

What power filtration are you using? Maybe that's your problem.

sometimes yes, that's the problem. but i've tried on my cleanest outlet, which usually would produce no noise.
Quote:

Try using the Optical connection (unless you are listening to SACD's in which case there will not be any signal through the optical output) and see if using the internal DAC eliminates the noise - in which case your source could be at fault...

thanks, but it doesn't have anything to do with the connection type. it had no digital ins connected... just the analog. and i was selecting digital input. therefore, it should not have any signal. any noise/hum is picked up from the circuitry itself, or of noise cycling through the DAC itself, not from any outside signal.
Quote:

I hear a slight amount of background hiss, but absolutely no hum.

yeah, the hum isn't amplified. it's present at no volume. a background hum.

but yes, i just got off the phone with Grace, and they verified that the hum is higher than it should be. (they do recognize there is hum, but it's very low level.) ....they have a transformer "turning" procedure that might help. ....so, anyway, they offered to do the work, despite it being a used unit... and gave me a RA number. pretty cool. i like companies that don't bitch. i'm definitely going to buy some Grace mic preamps in the future!

thanks for all the suggestions guys..........

 

[Music Fanatic]

Quote:

Originally posted by Orpheus but yes, i just got off the phone with Grace, and they verified that the hum is higher than it should be. (they do recognize there is hum, but it's very low level.) ....they have a transformer "turning" procedure that might help. ....so, anyway, they offered to do the work, despite it being a used unit... and gave me a RA number. pretty cool. i like companies that don't bitch. i'm definitely going to buy some Grace mic preamps in the future!

Wonderful! Yet another positive point for the Grace amp -- good customer service.

 

[Edwood]

I have noticed a small amount of "ground loop" buzz when connecting analog to a computer sound card of any kind. Really bad with Iron_Dreamer's and barely noticeable with my RME PAD. It's worse with analog outputs of my Audigy 2.

No buzz whatsoever with digital inputs or when I have the analog cable plugged into the Grace, but the cable is not plugged into the source.

I noticed that I only get this problem with sound cards, perhaps there is a ground loop issue with sound cards only? (and don't tell me to abandon PC based source, smart @sses.

)

I'm going to test it again.....

BTW, the buzz is only noticeable when I turn the volume all the way up (without anything playing, of course). I can only hear it if it is dead quiet in the room with my K1000's. And I can hear it more easily with my Ety's. With and without Gain.

-Ed

 

[Edwood]

What is this "transformer tuning" that you did?

Can you post pics of where this is?

-Ed

 

[Orpheus]

oh, you know what.... i have another question:

i opened the unit, and attached to the heatsink are three chips: the big opamp, and 2 buffers?. i dunno.... i dunno much about these things, but i think that's what those are right?

anyway... one of the buffers looks different from the other--one is rectangular, and the other has notches on the side. it's supposed to be like that right?--one's different from the other? it's not a one-per-channel kind of configuration right?

 

[Music Fanatic]

Quote:

Originally posted by Edwood What is this "transformer tuning" that you did? Can you post pics of where this is?

Orpheus said this was being done by Grace service.

 

[Edwood]

Well, I just got off the phone with Grace Design.

They say it's probably a ground loop, and to try a cheater plug on the 901. (or the computer).

Audio Ground is connected to earth ground in the 901.

Question:

Is the Audio Ground is connected to earth ground in the Gilmore V1? Because I didn't hear any buzzing/hum there.

For anyone have a multi meter or ohm meter, measure the continuity between the third prong (ground of the IEC) to audio ground (touch the other prong to the outside of your RCA jack. 0 - 1 ohm = Grounded to earth ground. A larger number means no ground.

I guess I'll try the cheater plug and see if it works.

-Ed

 

[Orpheus]

hey ed, can you open your unit really fast and describe to me the chips attached to the heatsink? there should be 2 small ones and one huge chip. are the two small ones different from each other?

thanks.

 

[gerG]

oooooh....
We need pics of ampguts!

I wasn't sure from the description, but did you try it with no inputs connected? Also may want try another room with no inputs.

Have you tested the ground circuits in your house? Just checking

I will check tonight, but I don't recall hum. There is background noise with very high sensitivity headphones (like Shure E3c). The CD3000 and the E5 have the worst S/N of anything I have owned to date, so they are the acid test for noise floor.

gerG