[joelongwood]

I'm hoping someone has an explanation for what I'm hearing out of this $350 RA-1 amp. I first noticed the hiss when I plugged in the Sony CD3000s. It was very noticeable, and appeared at all volume settings, but did not get any louder. It also seemed to be predominantly in the right channel, and was audible even with the RA-1 totally disconnected from the system. With music playing, the hiss was masked and inaudible. I then plugged the 'phones into the MG Head.....no hiss until about 2 O:clock on the volume control. Then the Creek......no hiss until almost full volume. Then the TA.....hiss, about the same as the RA-1, except it does get louder with an increase in the volume control. Then the Penguin CHA47.....no hiss at all.
What gives here? A $350 amp which exhibits the same noise level as the TA, and more hiss than the Penguin? Granted, none of my Grados have any hiss when plugged into the RA-1, nor does the AKG or Sennheiser, but I'm assuming that is because the Sonys have such tremendous efficiency.
Is the RA-1 defective, or is this normal? I hope it's defective, because that thing should be dead silent with any headphones. Any help here would be appreciated. Thanks.

 

[Odeen]

High-efficiency low-impendance CLOSED headphones are the absolute worst torture test you can invent for hiss testing. I'm surprised the CHA47 was that quiet, actually..

 

[blr]

joelongwood.
In a review article about the RA1 amp (forgot the link, sorry) the authors commented on RA1 not having a ground on the volume pot which can make it noisy. Such ground wire can be easily added. Another comment from the same article was that due to its construction RA1 is prone to RF interference more than some other amps, which can also rise the noise floor and also deteriorate the sound.
Is your amp under guarantee? If yes you can try to return it, if no just open it and add a volume pot grounding.
Yet another thing, are your interconnects shielded? If no, try to use some heavily shilded interconnects.

 

[Beagle]

My RA-1 has a very very slight even hiss that is only audible when I plug in the SR325 and with the source idle. It is not audible with the HD600. I didn't actually even notice the hiss until someone at Headwize mentioned it a while back. But again, I can only hear it in a very quiet environment and only realize it is there after I unplug the phones. And it is not effected by turning the volume up.

 

[joelongwood]

Thanks for the replies and suggestions, guys. The hiss is audible without the interconnects as well. I tried it outside, away from any interference, and the hiss is still there.
I can understand the high-efficiency, closed can explanation, but how come there is no hiss on any of my other amps, except the TA?.....and that hiss increases with the volume control. And the fact that it's predominantly in the right channel has me concerned. To make a long story short.....I spoke to Grado (GRAY-DO) Labs and it's going back today. They said they would either repair it, or send a replacement. I hope they don't tell me it's normal to have that hiss. For $350 that thing should be DEAD silent!!!!!!!

 

[coolvij]

joelongwood: I hope you get this resolved. For the kind of money you pay for the RA-1, it SHOULD be dead silent. Hopefully your's was defective...and you'll get a nice new one soon from Grado Labs.

 

[Beagle]

Sounds great. Or may be you could get a hairdryer and loosen all that potting compound around the opamps and fix it yourself

DON'T YOU DARE!!

 

[Redwoood]

Hehe, if the hair dryer doesn't work, there's still the butter knife...

 

[dhwilkin]

Weird, sounds like it's broken. Something like that happened w/ my MG Head, but I wasn't too surprised since it was inexpensive tube equipment. Personally, I would blame it on evil demons from Bose!

 

[KR...]

Hum, I tried to get my amp to hiss with my SR-60 and HP-2 and HD600, and my earbuds and I couldn't hear a thing (I have really good ears). I don't have the Sonys, so I can't say anything about them. I turned the volume all the way up, dead silence. I couldn't recreate what you are hearing.

E-mail Grado, that's all I can tell you.

 

[joelongwood]

KR, the RA-1 is on it's way to Grado as I type this, and should be there Wednesday. There has got to be something wrong with it. For that price, I won't accept hiss with any headphones!

 

[Tim D]

My JMT CHA47 is indeed dead quiet. Not only that but it has very balanced L/R channels from ANY volume level, which I couldn't say for many of the more expensive commercial amps I've heard. It drives Grados aplomb, and my Ety's as well.

After having JMT's amp...lets just say one really begins to expect a lot from commercial amps that are multitudes more expensive. Hopefully the fixed RA1 fulfills your expectations joelongwood!

 

[markl]

Hi joelongwood,
I think the "problem" may be the Sonys. With my MicroZOTL and CD3000s, I, too, can hear a teeny-tiny buzzing sound that is unaffected by volume. I can't hear it when music plays, though.

It also disappeared when I plugged in my HD600s.

I think it's an artifact of the high-efficiency Sonys.

markl

 

[joelongwood]

Quote:

I think it's an artifact of the high-efficiency Sonys.

I agree with you, markl, that the high-efficiency plays a part. But this hiss (definitely not a buzz) is not present on the MG Head, unless the volume is at 2 O'clock, nor on the Creek, nor on any of the four JMT CHA47 amps......all dead silent.
That's why I'm concerned. As I said, for that money I expect silence. I'm anxious to see what Grado says when they get it.

 

[flashbak]

Joelongwood,
Since the Grado circuit board has a covering all over the components (so no one can get component values used) I'm betting they don't fix it and will just give you another one.