EHX 12AY7 Mic Pre - Hum Problem Solved

J

jerfo

Member
Folks,

I just received my EHX 12AY7 mic pre today. As it so happened, I had the same hum issue that Ben Logan and others have had with it. Initially, I had used an XLR to 1/4" TS cable from the output jack. When I used that, there was a significant low frequency electrical hum (60 Hz, I assume) from the audio output. When I switched to a standard 1/4" TS "guitar" cable, the hum was even worse. I don't typically have any grounding issues in this house, so this was extremely worrisome.

However, just for the heck of it, I went ahead and tried a 1/4" TRS to 1/4" TRS cable. Lo and behold, the hum was completely gone and the output was nice and clean. Then, I tried an XLR to 1/4" TRS cable; this also worked well, and there was significantly more gain.

So, if you happen to get one of these preamps and you have a hum problem, try changing your cabling to 1/4" to 1/4" TRS or XLR to 1/4" TRS.

I'll try to post some sound clips soon.

- Jerfo
 
Thanks for posting this Jefro. I'm almost embarrassed to ask this, but what exactly does a TRS cable look like?

TRS = Tip, Ring, Sleeve? Is that right? If I picture this in my mind, I get what looks like a guitar cable. How is a TRS cable different?

Looking forward to hearing those clips of yours...
 
A guitar cable is mono unbalanced, TS (tip, sleeve). It has only 1 plastic band, where a TRS cable has 2 plastic bands.
 
Halion said:
A guitar cable is mono unbalanced, TS (tip, sleeve). It has only 1 plastic band, where a TRS cable has 2 plastic bands.
Click to expand...

Thanks Halion! I'm looking at a picture of one right now in the Sweetwater catalog. I see 'em: two rings.
 
jerfo said:
However, just for the heck of it, I went ahead and tried a 1/4" TRS to 1/4" TRS cable. Lo and behold, the hum was completely gone and the output was nice and clean. Then, I tried an XLR to 1/4" TRS cable; this also worked well, and there was significantly more gain.

- Jerfo
Click to expand...

Jerfo,

I just ran out to my garage and checked. I'm already using XLR to 1/4 TRS. Damn! I still get a little hum - about 40 percent of what I got using the unbalanced guitar cable I was previously using, but hum's still issue enough for me to keep this Furman power conditioner thingy (which I can't really afford right now) on order.

I'm wondering, does 1/4" TRS to 1/4" TRS work any better hum-cancellation-wise than the XLR to 1/4" TRS?

Oh, BTW, I recently discovered that my garage IS grounded afterall.
 
Ben Logan said:
I'm wondering, does 1/4" TRS to 1/4" TRS work any better hum-cancellation-wise than the XLR to 1/4" TRS?
Click to expand...

No, it's the same thing electrically.

You might want to check your other cabling and make sure everything is properly wired through *all* your signal path.

What Furman unit do you have on order?
 
maestro_dmc said:
But is the TRS plugged into a balanced or unbalanced input?
Click to expand...

Those were my thoughts exactly. My guess is that your TRS cable is plugged into an unbalanced input. It looks like the electrical grounding on the EHX preamp requires a completely balanced signal chain. That might explain why I had roughly twice as much hum when I went TS to TS as when I went XLR to TS. I'm only a novice when it comes to audio electronics circuits, but this strikes me as being a rather "unique" design.

Do you have a mixer or soundcard with balanced inputs? If so, try that and see if you have any better luck.

- Jerfo
 
Ben Logan said:
Jerfo,

I just ran out to my garage and checked. I'm already using XLR to 1/4 TRS. Damn! I still get a little hum - about 40 percent of what I got using the unbalanced guitar cable I was previously using, but hum's still issue enough for me to keep this Furman power conditioner thingy (which I can't really afford right now) on order.

I'm wondering, does 1/4" TRS to 1/4" TRS work any better hum-cancellation-wise than the XLR to 1/4" TRS?

Oh, BTW, I recently discovered that my garage IS grounded afterall.
Click to expand...


Ben: Do you know someone, or a music store, where you can bring this unit in, with your gear, and plug it all in and see what happens. You must have a bad something in your chain of things. My garage, where my studio is, isn't grounded, and I am using regular guitar cables from the EH to the delta 66 soundcard, and I have no hum. Walter
 
SonicAlbert said:
No, it's the same thing electrically.

You might want to check your other cabling and make sure everything is properly wired through *all* your signal path.

What Furman unit do you have on order?
Click to expand...

Thanks for asking Albert. I ordered the PL-8 II. Know anything about these? I'm new to all things "electrical," although I've been recording for about 4 years. This EHX pre has rocketed me into a real learning experience. I like the sound so much, it's worth all the fussiness to try to get mine as clear sounding as Walter's seems to be.
 
Walter Tore said:
Ben: Do you know someone, or a music store, where you can bring this unit in, with your gear, and plug it all in and see what happens. You must have a bad something in your chain of things. My garage, where my studio is, isn't grounded, and I am using regular guitar cables from the EH to the delta 66 soundcard, and I have no hum. Walter
Click to expand...

Hmmm. That's really strange Walter. You're lucky. I'm using the Audiophile 2496. It's an M Audio Card too. Maybe the Delta 66 has balanced inputs (?) whereas the 2496 I have has unbalanced (?)
 
Ben Logan said:
Hmmm. That's really strange Walter. You're lucky. I'm using the Audiophile 2496. It's an M Audio Card too. Maybe the Delta 66 has balanced inputs (?) whereas the 2496 I have has unbalanced (?)
Click to expand...

Ben thats exactly right...the audiophile, as we talked earlier this week, has unblalanced ins..that might be your problem over there...

more on the matter we discussed, i talked to the ppl at Maudio and they said they would support the audiophile 100%, and that drivers for the new upcoming Windows 64 are being developed...with that said, in the end they did say: "you should look at our firewire units" - so what happened to your friend is happening again ;)

instead of gettin electric material, you should really try to realize if the hum is being generated from the audiophile unbalanced ins..if thats so, all the material you're spending money on now will be useless once u upgrade to a better soundcard...that might be the way?

try to use the pre with TRS cabling and with another soundcard..if u can, go to a store and try some stuff out and see for yourself...im going with either the tascam US122 or the new Alesis IO2...if u wanna stick to the 2 1/4" ins aproach like im going for, u might wanna give these two machines a look?

i totally gave up on the audiophile, i really dont think its gonna be good, and i cant imagine why Maudio didnt put balanced ins on the damn thing.. :/

look at soundcards first man..its your best bet ;)
 
Somebody gave me negative REP feedback just for participating in this thread. Weird.

Anyway, Ben, that PL-8 II is really not a power conditioner, it's a rack power strip with some filtering and a surge suppressor. True conditioners actually take the incoming power, clean up the signal, and then output the cleaned up power. The real deals have very heavy transformers in them, which the PL-8 II doesn't.

However, I have several Furman Pl-Plus rack power strip units and they are well built. If you can afford to keep the PL-8 II it's an improvement to have the power outlets in a nice solid rack unit in my opinion. I just don't know how much good it is going to do in solving your hum problem.

I really think the place to start searching for your problem is in the rack cables and how the cables are run. While I realize those hum eliminators can work, I think using them is like putting a bandaid on the problem. Better to really sort out what the root cause of the hum is and then fix it.

You need to test all the cables, try swapping them out. Make sure that every cable in the whole audio chain is the proper cable for the gear on both ends of it. You'll probably have to read the manuals to sort all that out. What's balanced TRS what's unbalanced TS, etc.

Then (or maybe do this first) check to see how your cables are being run. You *must* avoid running audio cables near wall wart or lump in the line power supplies. Those kinds of power supplies are notorious for bleesing huge amounts of hum into audio cables. Keep your audio cables as far from those things as possible! I know this from experience.

Don't buy anything new until you completely troubleshoot your current setup.
 
SonicAlbert said:
Somebody gave me negative REP feedback just for participating in this thread. Weird.
Click to expand...

For the record, I got a negative rep point as well. That's a tad baffling, considering that I've offered a reasonable potential solution to a problem on a popular piece of gear...and I didn't even mention the words "Studio Projects." :-)

Oh well...as long as I have something to offer, I'll continue posting. I hope that I'm at least able to help out a few folks here and there.
 
fellas,

anybody posting on the Electro Harmonix threads will get a bad rep...its the same guy givin them over and over...it got to the point where he cant give me any more bad reps so he just registers as another person and gives it with the new identity, but as he doesnt have any rep points with the new one, so all squares come out grey...pure genious i tell ya...pure genius this guy. he's after everyone here so, guess he has nothing better to do...more power to the wanker, i wish i had that much free time...i pass on the hairy hands though..u can keep those.
 
hey Albert..

probably cause he bought a whole shippment of starved plate pres right before he read these threads ;)

and cause he probably thinks anyone actually gives a shit about the whole reputation thing :rolleyes:
 
I got yet another negative feedback from the person. But this time he left a message explaining why:

"You're part of a shill selling thread."

But I thought this particular thread was about trying to figure out why Ben Logan is getting a hum through is EH tube preamp. There have been several threads regarding hum through these things. I don't see how that is a shill selling thread since what we are talking about is not a necessarily a cool thing about the EHX 12AY7. A shill selling thread is like "everything is golden, go out and buy one now". This thread is not like that.

Well, I suppose I'm going to get slammed with negative feedback now.
 
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