Electro-harmonix 12ay7 preamp. Hmmmmm.... Hum.

[nag hammadi]

I can get eh stuff wholesale, so I ordered a pair of the 12ay7 pre's, figuring they would be usEful for SOMEthing.

They both hum ridiculously. I called my rep, and he said "oh yeah- those things sound great. You just have to rePlace the tubes".

I pointed out that they ship with eh branded tubes. AND the eh tubes are what we carry at the shop... A little odd.

Has anyone been able to use these guys without the world of hum?

[KennyLusk]

I just saw this and laughed myself silly. Welcome to the world of the EHX pre. Those things are an absolute PIA man. I have 2 of them, can't sell them because they hum but there is also a factor of "man, they sound so great".

A few things you can do, yeah:

Remove the tubes and take the case top off (which isn't easy either), look on the PCB for the internal Gain component. It's a PCB mounted component that has a tiny slot in it. Turn that slot counterclockwise[?] about a quarter of a turn. Put the tubes back in, don't put the case top back on yet and see how that sounds. If you're satisfied, then reassemble everything. And yeah, that stupid harness for the power supply socket is a real peach, huh? (sorry, had to add that in there).

Also, if you're connecting it to a mixer, make sure you're mixers gain is turned down and that your volume is coming from the faders instead of the Gain/Trim pot.

Another thing you can do is insert one of those Whirlwind Little IMP thingy's at the end of your xlr cable.

And IME replacing the stock tubes doesn't help at all. If I didn't love the way those boxes sound I would have taken a hammer to mine a long time ago.

[Recycled_Brains]

I use mine to amplify the talk back in the control room.

Totally awesome for that. The players in the other room are contantly commenting on how warm and tubey my voice sounds.

[Snarl 12/8]

I just did a little search here on TOMB. Are you sure you've got a true balanced connection from the output of the EH to wherever you're sticking it?

[trodden]

You could also use the search function and read the many threads with many pages in regards to this.

Mine does not hum. It is stock and has worked well for me for years.

[roygbiv]

yes, what Snarl, trodden and Kenney just said.

I've used one for about 3 years, and the key (at least in mine) for minimizing hum is:

1. DONT use the 1/4'' out for recording, use the XLR.

2. Use a pretty hot source going in: loud signal-> GT MD1a , soft signal -> SM7B

3. Pay close attention to possible ground loops/power source (i.e., try to plug everything into the same grounded receptacle)

4. RF/shielding issues - to deal with this, try moving your unit around - I was having hum problems until I realized my unit was setting on top of a rack which has my old Studiomaster 8X4 mixer - when I moved the EH preamp off of that, hum went away.

[agrpap]

One of mine used to hum. Honestly, I whacked it on the logo and it hasn't hummed in over two years.

[joel hamilton]

I love the 12AY7. Its a great mic pre. Nthing in its price range even comes close at ALL.
There is not one mic pre that is an all discrete audio path from input to output (XLR) that I have ever seen for a price even close to the inexpensive tag on the 12AY7.

The concession made in the design phase was to NOT have transformers in the pre at all.

That means the pre is very sensitive to whatever is downstream of the output XLR.

I beta tested the prototype for this pre, and I still have the prototype, and a couple more of the production models. All of them work really well. just put something properly balanced between the pre and whatever thingy you are using to record.

[chris harris]

Both of mine hum. Always have. I'm using the balanced XLR output, to a TT patchbay, to SSL Alphalink converters. Balanced properly all the way. Both units still hum. I'm in the third studio location since I bought them. And, in each studio, I've tried placing them in multiple places in the control room. Both units still hum.

I like the sound of these, too. But, the hum means that they hardly ever get plugged in.

The hum in mine is the same, regardless of the gain level. I recognize that some people have experienced problems with these because of user error. I just wish the people who always point that out would recognize that there are also just a lot of bum 12ay7 units out there, being used properly, that still have a hum.

It's kind of mind blowing that they haven't fixed this. It must be a limitation of the affordable design. Some will hum.

[terryb]

maybe it's that unfiltered Okie lektricitay.

I've always wanted to try one of these pres. Would any of you portlanders be willing to loan yours out for a couple of days? I promise not to throw it, even if it hums.

[Recycled_Brains]

The hum in mine is the same, regardless of the gain level. I recognize that some people have experienced problems with these because of user error. I just wish the people who always point that out would recognize that there are also just a lot of bum 12ay7 units out there, being used properly, that still have a hum.

+1.

I've contacted EH and PM'd the designer on this forum, and every response was the same... basically, I'm doing it wrong.

Nope.

Oh, and mine is much quieter if I use the 1/4" output.

I understand it's extremely low cost, and at its core, a nice preamp. But QC is clearly piss-poor, and I can't get behind them because of that.

[trodden]

Oh, and mine is much quieter if I use the 1/4" output.

Isn't the 1/4" output completely void of the tube aspect of the pre since it's main purpose is for monitoring?

[Recycled_Brains]

Oh, and mine is much quieter if I use the 1/4" output.

Isn't the 1/4" output completely void of the tube aspect of the pre since it's main purpose is for monitoring?

I have no clue. Last year, I emailed someone at EH, who told me that using the 1/4" out with a TRS cable is exactly the same as using hte XLR out, just with an extra gain stage.

[trodden]

Dammit Ryan. Look at what we've done. We've brought another living EHX tooob pre thread into the world. Another to continue on with the many others filled with problems, hums, hearsay, mis-information, and continually repeated questions of it's reasons for existence. I feel the heavy burden of responsibility upon my shoulders. I shall have a few drinks during my lunch to help lighten this load of regret and shame.

[roygbiv]

All's I know is I really dig mine, minor hum and all. Sounds fabulous.

Seriously, just a few days ago, I was recording some vocals for our band, using a GT MD1a mic (thanks again Joel for that tip).

For expediency, I was just using the Onyx mic pres in my Mackie 1620 board (pretty good, serviceable clean pre's).

Out of curiosity, I decided to swap in my EH 12AY preamp, since I usually use that with the MD1a for vocals (great combo, BTW).

The before and after recordings were NOTICEABLY different, and the takes using the EH12AY were way better (at least I thought).

What was nice - the difference was so obvious that even our singer was impressed, and he is usually skeptical of my gear-gearheadness. He was all like "wow, that tube preamp thing sounds so much better - it's more interesting and live sounding - we have to re-record my previous takes"

Anyway, back to the hum - my hum is minor, but I've noticed in the past it can change when I move around the power-supply - could a bad batch of power supplies/wall warts be contributing to some peoples humming issues?