yet another EH 12ay7 thread

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vsr600
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Post by vsr600 » Tue Sep 05, 2006 9:17 am

KennyLusk wrote: 1st let me say you can't do what I did without voiding your warranty. Having said that, all I did was remove the black tube guard, then remove the four screws that lock down the top section of the metal case and remove the top section (or cover as you might call it). What I'm calling the "power cord saddle" is just the socket on the side of the box where you actually connect the ac power adapter. Just remove the 2 screws that attach it to the side of the case. Then you'll have it free from the top section of the case which can act as an antennae for RF interference. For me, this helped eliminate the shielding problem.

The next step will obviously have to be further disassembly to properly rackmount the unit and make sure it's shielded. The hum problems were compounded by having it in proximity to my computer monitors, my HD and other audio gear. But again, it's just kind of unacceptable that this wonderful EHX box was the only box in my little studio that had this problem, you know? I just hope the crackling sound doesn't come down to a bad cap or 2...or more because I'm not THAT much of a solder head.
Hmm I just opened mine up and I don't see how that can be the problem. The connector (on mine at least) is completely covered in plastic and not connected to the case at all it apears. I've been having humm and hiss problems for a while now (on no I am using balanced connections and not the trs output). An interesting side note: printed on the board is "Listen to elvisbeatlesgod"... hmmm...

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Post by vsr600 » Tue Sep 05, 2006 9:32 am

ah-hah figured it out,

http://www.myspace.com/elvisbeatlesgod

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Post by cities » Tue Sep 05, 2006 10:48 am

KennyLusk wrote: 1st let me say you can't do what I did without voiding your warranty. Having said that, all I did was remove the black tube guard, then remove the four screws that lock down the top section of the metal case and remove the top section (or cover as you might call it). What I'm calling the "power cord saddle" is just the socket on the side of the box where you actually connect the ac power adapter. Just remove the 2 screws that attach it to the side of the case. Then you'll have it free from the top section of the case which can act as an antennae for RF interference. For me, this helped eliminate the shielding problem.
Thanks for the info Kenny -- I haven't had any time to crack mine open yet but hope to do so in the next couple of days.

cheers
Han

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Post by KennyLusk » Tue Sep 05, 2006 11:56 am

New tubes didn't help it and I tried (as I've done before) all of my best tubes. But what finally ended the crackling problem was isolating the pc board from it's own power supply.

Yep, believe it or not the units power supply seems to have been the culprit for the crackling, so I guess that was just another form of RF interference. So far, so good today - it's performing really well and just as quietly as anything else in my humble arsenal. Sorry for taking so long. So try moving it as far from the power supply as you can with some form of shielding between it and the supply.
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2121TrumbullAve
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crack-a-lackin'

Post by 2121TrumbullAve » Tue Sep 05, 2006 1:17 pm

It'd be nice to have analoghacker himself chime in regarding this crackling issue and potential remedy.
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Post by bounce » Wed Sep 06, 2006 5:58 pm

cities wrote:
KennyLusk wrote:
I get the crackling also. I was able to tame the 60 cycle hum issue by removing the casing, disconnecting the power saddle from the casing and setting up what was left. The unit is not shielded properly and picks up every available RF interference in it's immediate radius. That's the humming issue. (Keep in mind this is the only piece of gear I own that hums like this - so it's not my setup, my power, or my cables.) In any event, removing the casing seems to correct the shielding problems.
Hope this isn't hijacking the thread, but I'm having the same hum problem with my 12AY7 and I'm curious to hear the details about the surgery you performed to fix the hum issue. Did you permanently remove the casing? And what's a power saddle?

cheers!
I had the hum problem on the XLR out and fixed it by lifting the shield (disconnecting the sleeve wire) on the XLR cable going out. Now she's nice and quiet :-)
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Post by KennyLusk » Wed Sep 06, 2006 7:49 pm

Bounce, did you disconnect the shield wire on the cable you're using for the output? Or did you actually cut the shield lead connected to the output jack from the pc board?
"The mushroom states its own position very clearly. It says, "I require the nervous system of a mammal. Do you have one handy?" Terrence McKenna

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Post by bounce » Wed Sep 06, 2006 9:31 pm

I usually keep a small xlr cable or 2 around with the shield lifted so I tried that first. Worked great. I can actually use this pre now! I racked mine up and it's meaty :-)
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Post by spacelabstudio » Sat Sep 09, 2006 9:56 am

How are guys racking this up? Got any pictures?

Got mine this week, haven't played with it too much yet. Is dead quiet. No hum or crackles. Tried it on a electric guitar track: vibrochamp->m69->12ay7. Sounded good mixed, but soloed you could hear it was kind of, uhm, fizzy in the top end. Not sure how to describe the sound. Will probably buy a few different tubes and experiement with that at some point.

chris

PS kind of digging elvisbeatlesgod. Weirdest way to find out about a band ever.

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2121TrumbullAve
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fizzy?

Post by 2121TrumbullAve » Sat Sep 09, 2006 3:52 pm

So, is the 'fizz' you hear almost a clipping, unhealthy static type noise, stronger w/ the transients?

I'm going to try the earlier suggestion of keeping the box as far away from the wall wart as possible, but have doubts that it will make a difference.

I think it might be that this thing just can't take much spl, and that the clip light is not accurate. There are a handful of folks on this forum with the same issue.

What u describe may be different...
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figured it out

Post by 2121TrumbullAve » Sat Sep 09, 2006 7:10 pm

I've diagnosed the static problem.

Its an SPL thing. With a louder source, and particularly distorted guitar, record meters (Sonar, in my case) cannot read above -12, or else this static occurs. -12 is a healthy level anyway - it's like a built in punishment for hitting the converters too hot, I 'spose.

On my EH pre, this means the input pot when recording a not-very-loud guitar amp is at 9-10 o'clock. There's that tiny area in the throw of the pot at around 8 o'clock that most of the gain is at - so on a really loud source, it'll be tuff to set a level. I still don't know why this doesn't happen when I record vox really hot - but I'm glad I figured it out for elec-guit.

This doesn't mean the gentleman up-thread's diagnosis did not work for him - but keeping the unit away from the power supply didn't affect anything in my experiments.

So folks who are bummed about this - back off on the input gain; oughtta do the trick.
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Post by spacelabstudio » Tue Sep 12, 2006 8:41 pm

Okay, just to give some reference, rather than trying to describe the sound in words, here's a (not the best) guitar part recorded through a 12ay7 and again through a more or less home built (not by me) IC op amp based pre with a Jensen input transformer:

http://spacelabstudio.com/guitar_12ay7.mp3
http://spacelabstudio.com/guitar_ic.mp3

Performance is different, but nothing else was changed between takes except the preamp.

Les Paul Studio->Vibrochamp->M69->Preamp->Apogee Rosetta

Without the second amp as a reference, I don't think you would know that you're getting any distortion out of the 12ay7, but compared to the opamp based pre you can tell that the 12ay7 is adding some distortion that I would describe as, oh, I dunno, glassy?

Anyway, I'm still interested in knowing how you guys who have racked them up have gone about doing that. Also, has anyone who's done some tube swapping care to share any recommendations/insights?

Thanks!
Chris

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2121TrumbullAve
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thanks for that

Post by 2121TrumbullAve » Tue Sep 12, 2006 10:09 pm

I didn't really detect any of the crackling noise in the 12ay7 clip you provided - the stuff I experience is not musical; not cool.

I'd like to hear how your clip sounds recorded a bit hotter, to see if that would cause the static myself and others have been getting.

The only tube swapping I've done was trying a 12ax7 in the right-hand slot. The unit had less gain and the sound was more compressed - I didn't care for it. The crackling phenomenon disappeared w/ the 12ax7, however.

There's one thread where the moderator all but guarantees a multichannel rackmount version will come out, but it's been like 6 months and still no dice.
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Re: thanks for that

Post by spacelabstudio » Wed Sep 13, 2006 8:46 am

2121TrumbullAve wrote:I didn't really detect any of the crackling noise in the 12ay7 clip you provided - the stuff I experience is not musical; not cool.
Yeah, I suspected we hearing different things. Easier to demonstrate with actual examples.
2121TrumbullAve wrote:I'd like to hear how your clip sounds recorded a bit hotter, to see if that would cause the static myself and others have been getting.
Well, if I crank it up much more I'm going to get clipping on the converters. They're set at +4 so I should be getting a nice hot signal out of it. If just turning the thing down solves your problem, are you sure it's actually the 12ay7, or are you just getting something that comes after it to clip on transients?

2121TrumbullAve wrote:There's one thread where the moderator all but guarantees a multichannel rackmount version will come out, but it's been like 6 months and still no dice.
Which I'm fully expecting to cost about $2k. ;) Have you looked at their big tube compressor?

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cracka-lackin'

Post by 2121TrumbullAve » Wed Sep 13, 2006 9:22 am

I'm pretty sure it's the eh pre - it does not happen with any other pre I have with the same gain staging. In fact, with my other pre's I can slam them really hot and it does not occur.

for instance, the signal path for my last round of troubleshooting was:

57 in front of classic 30, lead channel, not very loud > eh 12ay7 > (fully balanced, of course) rme fireface analog in @+4.

As long as I don't send a signal hotter than -12 to my sonar record meters, I'm fine. Any hotter, this crackling occurs.

with all my other pre's, i can slam the record meters into the red wthout issue (not that i make it a habit...)

No idea what the cause is.
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