eh 12ay7 is clipping/distorting!

analoghacker · Post by **analoghacker** » Tue Jul 17, 2007 1:46 pm

just stopping by, the problem does not sound at all like it is the pre... let me repeat the setup rountine, which would be a good rountine for any mic/pre arrangement.

connect the mic. if its a condensor mic, turn on the phantom supply. connect the output (either the XLR or the TRS) to a balanced input on a recorder or mixer or interface. turn the input gain level of said device OFF. turn the input gain of the 12AY7 pre up enough to get the amber led blinking softly with your program. this insures a level in the range of +4dBu. if you are recording drums with a close mic, you will want an inline pad after the mic. if you are using the buffered output, ALLWAYS start with the buffer level OFF. set the gain with the main input levelpot. turn to your recorder/mixer/interface. set the input for UNITY gain (ie. line level or +4dBu). if you are using the buffered output, now you turn the level up until you get unity out. you are ready to record. the stress i am putting on the amber led is very helpful because that will give you the best signal to noise ratio. always important with ANY pre. setting the input level low and turning up the gain at the recorder/interface/mixer is a sure bet to make lots of NOISE.

once again, do the math... if your snare makes 115dB of SPL and your mic puts out a volt at 115dB of SPL, and your pre has 40dB of gain (a gain of 100), you are officially clipping the crap out of the poor equipment you are connected to, as well as the pre. with the right input level, the 12AY7 will put out 16 - 18 VRMS before clipping. that's way more than any common digital interface can handle wide open. you will most definitely be attenuating BEFORE the interface. but not at the 12AY7. if the mic puts out 3 mVRMS with your program, you will want the pre wide open. then you can add a little gain at the mixer/interface/recorder.

punkrockdude · Post by **punkrockdude** » Tue Jul 17, 2007 4:05 pm

but i am not clipping my MOTU 828mkII interface. Check the mp3 file in an audio editor. Regards

kayagum · Post by **kayagum** » Tue Jul 17, 2007 7:44 pm

Punkrockdude: Why don't you try following the directions of THE DESIGNER OF YOUR PREAMP (who happens to be analoghacker- search on his threads)? Then if it's still messed up, send it back to EHX and not waste any more of your time and the board's time.

I still am betting on user error of some sort.... lower overall level doesn't necessarily mean that it's not clipping. Give you an example: you can ruin speakers with an underpowered amp that's maxed out and distorting (i.e. clipping). It still may be relatively "quiet", but the clipped signal can shred tweeters pretty quickly.

Describe your chain (including every jack and chord and hardware setting [yes, including your guitar amp and rig] and software setting), and maybe we can help. If you're not willing to do that, then none of us can help you. Sell it off, move on, call it a day.

Don't let this thread devolve into this classic: http://messageboard.tapeop.com/viewtopic.php?t=45529

(edited for bad punctuation and expletives

)

Jeff White · Post by **Jeff White** » Tue Jul 17, 2007 9:04 pm

Bad cable?

punkrockdude · Post by **punkrockdude** » Wed Jul 18, 2007 6:46 am

Ok, I'll tell you my whole chain...

punkrockdude -> pick -> strings -> some electronics in the gtr -> cordial high quality gtr cable -> marshall 8240 -> sm57 -> mogami cable -> he12ay7 and gain at around 10 -> xlr out with gotham gac-3 cable -> motu 828mkII usb 2 interface -> tapco monitors (the 8" version) -> my ears -> my humble brain picks up some things.

Is that enough kayagum or should I stop posting on this board right away?
Regards and to kayagum too if I misunderstood his way of expressing himself.

Jeff White · Post by **Jeff White** » Wed Jul 18, 2007 6:55 am

I also own an 828mk2. My question is, how is the metering on the 828mk2? In the software (using something like FreeG)?

Have you tried switching tubes?

You mentioned that you are recording at bedroom level, so I am certain that there is no way that you are clipping the mic. Have you switched in another preamp for the 12AY7 to make sure that it is nothing else in your chain?

Sorry if I am being redundant, just trying to help.

Jeff

darjama · Post by **darjama** » Wed Jul 18, 2007 7:14 am

are you going into the mic pre input of the 828? 2 mic pres in a row could cause some unpredictable behaviour. If so, you may want to try going into one of the line inputs with an xlr to 1/4" trs cable.

punkrockdude · Post by **punkrockdude** » Wed Jul 18, 2007 7:34 am

Thanks for your responses!

ipressrecords:
I am using the FreeG, VintageMeter and MOTU's meters. MOTU's Cue Mix meters are quite bad in the upper dB's so I rarely check those. All my other preamps (MOTU, Studio Projects, The Brick and Line Audio OMP) don't clip at all. The 12AY7 is completely different sadly. Thanks for staying and helping out!

darjama:
I use the line ins on the back of the MOTU with a XLR to TRS cable so I don't go through one more preamp before conversion.

Everyone! After some minor electric chocks, I found a trim pot inside the 12AY7 which seemed to help out alot. The level is now lower out from the preamp BUT I can have my guitar amp really loud going in to the 12AY7 and I can use full gain without nasty clipping. I guess I have to use this pre on mics and sources that have higher output levels than the SM57 or sources that are very loud in most applications.

Here is an mp3 sample after I turned the trim pot from 5 o'clock (full) to around 11 to 12 o'clock:
http://www.interfearingsounds.com/eh_12 ... l_sm57.mp3
The recording is not normalized and it peaks around -4.4dBFS and FreeG shows about -17 dBFS RMS.
Regards!

Jeff White · Post by **Jeff White** » Wed Jul 18, 2007 7:45 am

punkrockdude wrote: Everyone! After some minor electric chocks, I found a trim pot inside the 12AY7 which seemed to help out alot. The level is now lower out from the preamp BUT I can have my guitar amp really loud going in to the 12AY7 and I can use full gain without nasty clipping. I guess I have to use this pre on mics and sources that have higher output levels than the SM57 or sources that are very loud in most applications.

Not sure where that internal trim pot is located in the chain, but if it's immediately before the XLR output, then it's like a built-in ATTY.

Glad that you resolved the problem.

Jeff

darjama · Post by **darjama** » Wed Jul 18, 2007 7:48 am

yup, the track sounds pretty nice.

First I've heard of the internal trim pot that I recall, hopefully this helps some people who have similar problems. Makes me curious where mine is set, but since I'm not having problems with it, I'm not going to crack it open and find out

Recycled_Brains · Post by **Recycled_Brains** » Wed Jul 18, 2007 8:12 am

darjama wrote:I'm not going to crack it open and find out

has anybody? i'm curious. i don't get the clipping, but i do get tons of hiss and wonder if that would have an impact.

-ryan

analoghacker · Post by **analoghacker** » Wed Jul 18, 2007 9:13 am

the trim pot is the current source set. it does not effect the gain until it is almost off or insanely on. it is most definitely NOT user adjustable. you would need a scope and voltmeter to set it. there is always the possibility of a mistake at the factory. but every preamp is tested here with a mackie mixer and a cheap-ass marshall mic and a SM-57, AFTER set up on the production line. if it works here, it is boxed and eventually shipped.

if there is a lot of noise in your setup, it is most likely the way it is being used. please re-read my comments on the use of the amber LED.

if its still not for you, there are a great many other affordable mic pres on the market.

once again, with the gain on the main level set to 10 (o'clock?), which was your comment, does the amber LED light up?

trodden · Post by **trodden** » Wed Jul 18, 2007 2:22 pm

kayagum wrote:
(edited for bad punctuation and expletives )

ahahah grumpy.

I'd like to see punk rock dude and everyone else get theirs to work..

cause honestly, i've had similiar problems some days, but then its worked just fine on other days... mystery box!! but when its working good, its GOOD!!

punkrockdude · Post by **punkrockdude** » Wed Jul 18, 2007 2:22 pm

The amber LED didn't light up when I had the clipping and gain at 10 o'clock. After I lowered the gain/volume/or what is it at the trim pot I didn't have clipping and I could use full gain without clippinf. Regards

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eh 12ay7 is clipping/distorting!

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