[gpalmer]

The buzz appears with the 650s when I have the high gain kicked in and the headphones set to around 2 O'Clock. It is not noticeable with the high gain off. With low impedence headphones and low gain, I find that the hum can be heard starting at about 1 O'Clock on the attenuator. With low impedence phones and high gain the hum can be heard starting at about 9 O'Clock on the dial. This seems a bit too much to me.

 

[Edwood]

I'm listening with my Ety's.
With the Ety's there is absolutely no buzz. In fact with the high gain switch on, volume all the way up, there is no difference between digital and analog. Basically it's like there's nothing connected. But there is.

However, the R10's are much more efficient, sensitve, and detailed, and I can hear a weird hum when I hit the gain switch. It's a constant hum. No matter how high I crank it, I hear the usual hiss at the maximum, but the buzz is constant. It sounds like a soft "wharrrrrrrrrrrrrrrrrrrrrrrr..." Again, I would never want to listen with the High Gain switch on. But this is weird.

Is this like the sound you had before, Dean?

BTW, I can't hear it with the K1000's. Even with the room really quiet. I turned off all but one computer for this test.

I guess Grace didn't spend as much time with the unbalanced inputs. I suppose that could be expected with a company aimed towards Pro Audio.

Well, another reason to go with balanced inputs. I'm ready for Blockhead comparisons now. A little over two months away and counting.

-Ed

 

[Orpheus]

gpalmer:

well, that's not the same problem i had. with phones like the senn's, i can't hear ANY noise at all, hum, hiss, whatever.... it's dead silent at any setting with senn phones, even before i sent it to the factory. well... until the last bit of rotation on high gain, then i can hear a little hissing.

your problem isn't the same thing. however, i have had problems like yours, several times, in many different types of components. and it's always system related. even dirty power can cause buzzing.

the hum i was complaining about was present even with the volume turned to 0. it's caused by amplification of the radiation from the transformer. the hum does not increase in level as i turn up the volume.

anyway, gpalmer, do you hear anything with no inputs, or with the inputs shorted to ground?

if not, well, then it's probably also because of some interaction with your system, or dirty power. although, the tech told me that the Grace has heavy power filtering, so dirty power shouldn't affect it too much.

 

[Orpheus]

Quote:

I guess Grace didn't spend as much time with the unbalanced inputs. I suppose that could be expected with a company aimed towards Pro Audio.

i believe the RCA's are parralleled with the XLR inputs. so, they use the same signal path. the reason you don't get hum with balanced inputs has nothing to do with the Grace's design. it's because one of the benefits of running balanced lines is the reduction of hum--the signal no longer travels along the same wire as the ground/shield.

 

[Edwood]

Quote:

However, the R10's are much more efficient, sensitve, and detailed, and I can hear a weird hum when I hit the gain switch. It's a constant hum. No matter how high I crank it, I hear the usual hiss at the maximum, but the buzz is constant. It sounds like a soft "wharrrrrrrrrrrrrrrrrrrrrrrr..." Again, I would never want to listen with the High Gain switch on. But this is weird.

Does this sound like the problem you had at first, Dean?

It happens regardless whether or not anything is plugged in. Even with the volume turned all the way down. This happens only with the gain switch on.

The only thing left to test is another power cord. The position I have the amp in is precarious, and that stiff ass power cord (PS Audio xStream) won't fit in that location. The quick and dirty XLR cables are too short. I'll have to make another longer one.

But I doubt it will make a difference. The cord I am using is shielded, just not as thick and fancy as the PS Audio xStream.

-Ed

 

[Wodgy]

Ed, it's the ground loop!! Use a cheater plug and be done with it. Honestly, the sound will improve if you do this (perhaps inaudibly, but perceptibly), even using the balanced connection. In any audio system, you should only have one component with an Earth ground. In this case, it's your computer. Any other arrangement will lower sound quality.

 

[Edwood]

Quote:

It happens regardless whether or not anything is plugged in. Even with the volume turned all the way down. This happens only with the gain switch on.

Nope. It's definitely not ground loop. I tried with a cheater plug too. It does not change between a grounded plug and a cheater.

And the hum is there with the volume all the way down. It only happens with the High Gain switch is on. Perhaps it's a different problem.

I wasn't hearing it with other phones. The R10 is just that much more sensitive. I couldn't even hear it with my Ety's.

-Ed

 

[Wodgy]

In that case, it's probably similar to Orpheus' problem. (Glad you tried the cheater plug thing though.)

 

[ayt999]

you guys seem to be having so much fun I'm joining in.

I have never used the unbalanced connection on my 901 so don't know how that is on mine (I did get some radio shack fusions to test them, they are my most expensive RCA cables for now). with my balanced homegrown silver lace and the L3000, I do hear a hum at higher settings on high gain mode. nothing on low gain. it is only there about six clicks from the maximum level though.

the RCA input is indeed parallel with the XLR. the XLR connector is directly soldered onto the PCB and the RCA is connected to the XLR via some wire. I don't know what the wire is, but it looks like it could use some upgrade. I have some pictures I took when I opened the case so I'll put those up. it may be a bit blurry though since I forgot to use manual mode and focus it myself.

so no RMA for me most likely... I think most of my cans and anything I will get soon (PS-1, maybe the CD3000 and R10) are low ohm so it isn't a problem for me. maybe when I am bored and have another amp to use in the meantime I will call grace and tell them I want to be treated the same as Dean.

UPDATE: pictures posted at photobucket, you can see the RCA and other connector connections quite well I think.

 

[Orpheus]

Quote:

maybe when I am bored and have another amp to use in the meantime I will call grace and tell them I want to be treated the same as Dean.

oh man...... i'm gonna need a body guard, and witness protection services from the FBI (they have my number and address)...

but just so you know, ayt999, my hum is the same level, no matter where the volume knob is. if yours gets louder as you turn up the volume, it's most likely a ground loop, not the problem i had. please make sure it's not a ground loop before you call them, cause i don't want them thinking, "dang, i do something nice once, now i get all this trouble." you know what i mean?

actually....... TO ALL WHO ARE WORRIED ABOUT HUM IN YOUR 901: if you unplug all the inputs, and your problem goes away, it IS NOT the same problem as mine. it is a ground loop most likely, and that's a function of your own environment, not the 901's construction!

you know, there's usually some sort of hum present in all audio systems, even at extremely low levels. the more equipment you have, the more hum you will probably have. now, the 901's high gain mode is REALLY sensitive. match that with ultra sensitive phones, and you are essentially looking at audio with a high magnification microscope! do not be alarmed if you hear hum. it's there. just like if you look at your own skin with a microscope you'll see millions of bugs. they exist all the time. that is not necessarily a problem with the construction. the 901 in high gain mode is more sensitive than any amp i have ever owned.

 

[Edwood]

Do you have that high gain hum now, Dean? The one that is only there with the high gain switch on and using the CD3000's?

-Ed

 

[Orpheus]

no, my unit is DEAD SILENT. on high gain, there is some hiss approaching the maximum amount on the volume dial... but that's normal. even at a noise floor around -110db or whatever it is, even with that much gain you're gonna hear the noise floor.

but no... no hum. and up to any volume setting, at either high or low gain, less than eardrum-melting and with any headphone, there is NO NOISE of any kind at all. dead silent.

my amp's absolutely perfect now.

 

[Edwood]

Quote:

Originally posted by ayt999 UPDATE: pictures posted at photobucket, you can see the RCA and other connector connections quite well I think.

Where'd you get those RCA plugs? Were they cheap? I need a whole bunch of those.

Yeah, look at the wiring on the Coaxial SPDIF jack. The analog input RCA's were definitely an after thought compared to that beautiful wiring.

-Ed

 

[Edwood]

Quote:

Originally posted by Orpheus no, my unit is DEAD SILENT. on high gain, there is some hiss approaching the maximum amount on the volume dial... but that's normal. even at a noise floor around -110db or whatever it is, even with that much gain you're gonna hear the noise floor. but no... no hum. and up to any volume setting less than eardrum-melting and with any headphone, there is NO NOISE of any kind at all. dead silent.

Sh!t.

Time to call Grace again, I guess.

That hum is weird.

Damn the R10's. Why must they be so sensitive! Oh, wait. That's a good thing......

Oh, BTW. Were they really careful not to scratch the bezel at all, Dean? I know I'm being anal, but if they didn't make it so purdy, I wouldn't be so paranoid.

-Ed

 

[ayt999]

of course, I'll be testing the grace more before deciding if I should call them and see if there is a problem that should be fixed. I would like to upgrade my power connections, it is somewhat connected to the same outlet as my computer (which happens to be the source) so that may be it.

did I mention I like audio-technica??
my connector covers. I got them in japan for ~$4, but I think you can get them at audiocubes at a nice premium... or not. they don't carry the model I got, but they offer something similar for $10.