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Help with the famous PCM 42 trick, please. Condenser Microphones
Old 1st January 2008
  #1
Help with the famous PCM 42 trick, please.

First off, lemme start by saying "Sorry, Slipperman". I'll spare the specifics of this (not-so) famed "trick" as best I can; I don't wanna give away the good stuff.

OK. So I tried the PCM 42 guitar trick yesterday. The harder I drove the unit, the more it created an unpleasant tremolo-type effect on the return signal. I believe this has something to do with the Feedback control, because as I increased the feedback the tremolo effect became faster and more pronounced. So I set the Mix control to Dry, and it went away. But it didn't really sound that interesting, so my questions are:

1. does the limiter affect the signal when the unit is set to fullly dry
2. if it does, is it really subtle? Cuz I wasn't really hearing anything all the drastic.

I guess I sorta expected it to be one of those "wow" moments....maybe I just need to play with it a little more.

Oh, one last thing: the PT session I opened up was some random thing on our computer, and the tracking was pretty awful. Would it be worth trying to use the trick on better-tracked guitars? My impression of the trick was that it could sorta save a mediocre, boring guitar sound. Maybe it's just not much of a turd-polisher...?

Anyway, thanks in advance for any help.
Old 1st January 2008
  #2
Lives for gear
 
Empire Prod's Avatar
 

It sounds like you either don't know how to control the VCO sweeps, or your unit is having issues. Raising the feedback does not cause any strange modulation effect, however the PCM 42 is capable of modulation (controls are on the right side of the unit).
Old 1st January 2008
  #3
Old 1st January 2008
  #4
Pastor Obviedo
Guest
Quote:
Originally Posted by Empire Prod View Post
It sounds like you either don't know how to control the VCO sweeps, or your unit is having issues. Raising the feedback does not cause any strange modulation effect, however the PCM 42 is capable of modulation (controls are on the right side of the unit).
and...

Quote:
Originally Posted by Led View Post
Keep an eye/ear out for broken units for parts. The ic's in the early models that do the limiting (U14 and U16) are no longer made. If they crap out you can pull them and the delay will still work, just without the input limiter. I'm dropping over to a mate's to open up his 1300s to see if it uses the same ic's as they could be a cheap source (the 1300 is even cheaper) so I will post what I find out.
Cheers
Old 1st January 2008
  #5
Quote:
Originally Posted by Empire Prod View Post
It sounds like you either don't know how to control the VCO sweeps, or your unit is having issues. Raising the feedback does not cause any strange modulation effect, however the PCM 42 is capable of modulation (controls are on the right side of the unit).
My first thought was that it was the VCOs, too, but setting the sweep rate to zero didn't stop the effect. And any other changes (increased rate, sine/square wave, etc) didn't change the sound of the tremolo effect. The only thing that changed the effect's sound was the feedback control.

I guess maybe there's something wrong with the unit, but it operates correctly in every other capacity.

Anyway, do you happen to know if the limiter is still audible when the unit's mix control is set to fully dry?

Also, is the effect subtle? Maybe I just need to try a more dynamic guitar signal.
Old 1st January 2008
  #6
Led
Lives for gear
 
Led's Avatar
Hi, wow this old thing has reared it's head again...
The 'tremelo' effect you are getting is because one or both of your limiter IC's is faulty. There are 2 stages to the limiting. If the mix is set to dry you are only hearing one chip, not both, so if your unit doesn't tremelo with the mix set to dry then it's most likely only one chip, probably U16 that's gone. You would need to check the schematic but from memory they are chips positioned at U14 and U16, I think. They are a chip model number 'CLM50' and are about $10 each nowdays but you can usually only find them at some sort of obsolete electronic components broker. I got some a few years back from a place called "Cheaper Electronics" in the US. Maybe google CLM50. There's usually a minimum order of about 10 chips so it's handy to find a few others with 42's and do a group buy. The CLM50 blowing is a pretty common problem so it's worth getting a couple of spares to keep in the cupboard as the 42's are getiing older nowdays and the chips will get harder to source. Make sure you put them in the same way as the old ones.
Good luck.
Old 2nd January 2008
  #7
Quote:
Originally Posted by Led View Post
Hi, wow this old thing has reared it's head again...
The 'tremelo' effect you are getting is because one or both of your limiter IC's is faulty. There are 2 stages to the limiting. If the mix is set to dry you are only hearing one chip, not both, so if your unit doesn't tremelo with the mix set to dry then it's most likely only one chip, probably U16 that's gone. You would need to check the schematic but from memory they are chips positioned at U14 and U16, I think. They are a chip model number 'CLM50' and are about $10 each nowdays but you can usually only find them at some sort of obsolete electronic components broker. I got some a few years back from a place called "Cheaper Electronics" in the US. Maybe google CLM50. There's usually a minimum order of about 10 chips so it's handy to find a few others with 42's and do a group buy. The CLM50 blowing is a pretty common problem so it's worth getting a couple of spares to keep in the cupboard as the 42's are getiing older nowdays and the chips will get harder to source. Make sure you put them in the same way as the old ones.
Good luck.
Thank you so much, Led! I'll ask our tech to look into it!
Old 7th January 2008
  #8
Quote:
Originally Posted by embrionic View Post
As far as I was taught it is 100% wet, otherwise, theoretically, it would not matter what the delay times is set to right?

At 100% on the 42 the limiter would still be in effect if you had 100% wet because the signal is passing through the device. I don't have a block diagram for either at hand so I can't verify exactly what happens to the signal at 100% dry, but I would guess it is limiter only, no a/d/a. Hope that helps.
I have 2 PCM42 that I bought from Vintage King.
When I use 100% wet I get this tremolo sound that "bgrotto" have experienced, when I use 100% dry I get a great sound and yes, there's a limiter in that mode too.


Quote:
Originally Posted by Led View Post
Hi, wow this old thing has reared it's head again...
The 'tremelo' effect you are getting is because one or both of your limiter IC's is faulty. There are 2 stages to the limiting. If the mix is set to dry you are only hearing one chip, not both, so if your unit doesn't tremelo with the mix set to dry then it's most likely only one chip, probably U16 that's gone. You would need to check the schematic but from memory they are chips positioned at U14 and U16, I think. They are a chip model number 'CLM50' and are about $10 each nowdays but you can usually only find them at some sort of obsolete electronic components broker. I got some a few years back from a place called "Cheaper Electronics" in the US. Maybe google CLM50. There's usually a minimum order of about 10 chips so it's handy to find a few others with 42's and do a group buy. The CLM50 blowing is a pretty common problem so it's worth getting a couple of spares to keep in the cupboard as the 42's are getiing older nowdays and the chips will get harder to source. Make sure you put them in the same way as the old ones.
Good luck.
Well, if this is true, I find really weird that my 2 PCM42 were failling.
Anyway I have ordered those CLM50 in case mine's are broken.



Best regards.

delcosmos.
Old 7th January 2008
  #9
Led
Lives for gear
 
Led's Avatar
Hi Armando, as you have seen Mike and the boys at VK are good at testing stuff before they send it, but this problem is only obvious when you set it to full wet mix and drive the unit way into the red. If you are sending it normal operating levels it isn't obvious that there is anything wrong. As driving the unit so hot is not what would be considered normal, maybe they just didn't pick it up. In any event, the CLM50's are socketed on the main board so it's an easy fix to open the lid and swap them for new ones.
All the best.
Led
Old 7th January 2008
  #10
Quote:
Originally Posted by Led View Post
Hi Armando, as you have seen Mike and the boys at VK are good at testing stuff before they send it, but this problem is only obvious when you set it to full wet mix and drive the unit way into the red. If you are sending it normal operating levels it isn't obvious that there is anything wrong. As driving the unit so hot is not what would be considered normal, maybe thet just didn't pick it up. In any event, the CLM50's are socketed on the main board so it's an easy fic to open the lid and swap them for new ones.
All the best.
Led
Thank's Led, you rules!
After your advice, 2 CLM50 on the way!

Best regards.

delcosmos.
Old 7th January 2008
  #11
outofphase
Guest
100% WET OR DRY?
Old 6th October 2009
  #12
Gear Nut
 

Has anybody else had this tremolo problem that Delcosmos and a few others mentioned. I just got a 42 and when I dime the input I'm getting a tremolo effect with the feedback turned up a little. Don't know if this is normal or not? Or if I too need this chip that Led mentioned.

This thread won't die.
Old 7th October 2009
  #13
Lives for gear
Quote:
Originally Posted by bgrotto View Post
First off, lemme start by saying "Sorry, Slipperman". I'll spare the specifics of this (not-so) famed "trick" as best I can; I don't wanna give away the good stuff.

OK. So I tried the PCM 42 guitar trick yesterday. The harder I drove the unit, the more it created an unpleasant tremolo-type effect on the return signal. I believe this has something to do with the Feedback control, because as I increased the feedback the tremolo effect became faster and more pronounced. So I set the Mix control to Dry, and it went away. But it didn't really sound that interesting, so my questions are:

1. does the limiter affect the signal when the unit is set to fullly dry
2. if it does, is it really subtle? Cuz I wasn't really hearing anything all the drastic.

I guess I sorta expected it to be one of those "wow" moments....maybe I just need to play with it a little more.

Oh, one last thing: the PT session I opened up was some random thing on our computer, and the tracking was pretty awful. Would it be worth trying to use the trick on better-tracked guitars? My impression of the trick was that it could sorta save a mediocre, boring guitar sound. Maybe it's just not much of a turd-polisher...?

Anyway, thanks in advance for any help.
just pin it. Was slipperman around in 1982? I think anyone and everyone who owned a 42 invented that technique
no one can take claim. That makes about 10,000 of us. I think they shipped about that many. I remember recording at a little rathole studio in Revere MA in 82 and the engineer turned us on to that . Andy wallace did not invent that
he discovered it probably the same time everyone else did in 82 or 83 if he was even recording then or even owned one. We always got first dips in the Waltham area as beta testers on early units. It was no secret the input had a limiter it was stated in the original documentation. Just cuz it was an 'effect' in it's own right did not make it rare archeological discovery or anything. That trick was never a secret from day 1. Most folks early on were afraid of it
since it was so aggressive on gtrs and other sources.. I played death metal then so we loved it. We wanted the most in your face gtr tone possible. Back then we were scooping out all the mids with pultecs, the engineers would cringe. They didn't get it. They were still listening to Neil Young and Ten years after................

But remember that made 80's gtr tone 'classic' who wants to sound like that now? Motley? Venom?
I suppose it works for extreme metal still though. Now why they took that out of later lexi units boggles the mind.
Gary Hall from the Beaver road days was a genius.
Old 20th October 2009
  #14
Gear Nut
 

Hi guys-

Experimenting with the PCM 42 limiter trick, and wanted to sanity check the results I'm getting, which do not on the surface sound right. Because an mp3 is worth 1000 posts, here are two quick audio clips: Clip 1 original guitar track. Clip 2, through the 42's input limiter at max gain, in the red without blinking, with the "output" knob on the rear reduced to compensate.

What I'm hearing is choppy, like a cheap soft-limit circuit fighting for its life. Nevertheless, is this the faulty IC tremolo effect or something else?

Thanks!
Attached Files

42-unprocessed.mp3 (224.4 KB, 4870 views)

42-limited.mp3 (224.4 KB, 4914 views)

Old 22nd October 2009
  #15
Gear Nut
 

I've got two units doing the same thing. Don't know if it's normal either.

Anybody care to respond. Curious minds want to know
Old 22nd October 2009
  #16
Gear Nut
 

Is this taboo? There's a ton of PCM 42 users, no?
Old 24th February 2014
  #17
Does anybody know if atari800's problem is the actual toasted CLM50 problem?
Old 25th February 2014
  #18
Old 25th February 2014
  #19
Lives for gear
 

Sometimes PM's work best.....Don't want to see another cmp-06 scenario from hexigon!
Old 18th March 2014
  #20
Really? Nobody?
Old 18th March 2014
  #21
Quote:
Originally Posted by Thomas.Gloor View Post
Really? Nobody?
You might have better luck posting this question in the Geekslutz forum. Lotta wicked smaht dweebs hangin' round over there.
Old 18th March 2014
  #22
Bgrotto, did you find out if your units were fine?

What i'm dreaming about is a sample of a processed signal thru a working unit... Any chance you have time? ??
Old 18th March 2014
  #23
Quote:
Originally Posted by Thomas.Gloor View Post
Bgrotto, did you find out if your units were fine?

What i'm dreaming about is a sample of a processed signal thru a working unit... Any chance you have time? ??
Sadly, we never replaced the limiter's IC, so we're still getting that funky sound. But there's a very, very detailed article or blog somewhere on the web (might even be here on GS) that makes multiple comparisons between processed and unprocessed sounds on several instruments (but with a focus on guitars) using the PCM42 limiter trick. I wish I could remember the URL, but I know I was able to track it down through a web search. It was a couple years ago that I saw it, but hopefully, it's still kicking around somewhere.
Old 18th March 2014
  #24
Thanks a lot bgrotto, will try to find it! Thank you for your time!
Old 19th March 2014
  #25
Lives for gear
 

i've tried googling but anyone know where I can find a pair of the clm50 chips???
Old 19th March 2014
  #26
On ebay a seller sells some for 25usd. Search CLAIREX CLM50 Opto isolator
Old 19th March 2014
  #27
Lives for gear
 

Can't someone just pick up a used Lexicon 1300 or 1300S for $100 and use it for this trick and as a pre delay (it doesn't have the feedback & modulation sections of the PCM 42)? I thought it had the same input circuit to overdrive into soft limiting. Input and output gain are set from the front plate with set screws.
Old 19th March 2014
  #28
Lives for gear
 

Quote:
Originally Posted by Thomas.Gloor View Post
On ebay a seller sells some for 25usd. Search CLAIREX CLM50 Opto isolator
cool thanks. question: on the ebay one it says that they are real old, is this not made anymore? if not then i guess this is the best as long as they work.
Old 20th March 2014
  #29
Lives for gear
 

Quote:
Originally Posted by Bassmankr View Post
Can't someone just pick up a used Lexicon 1300 or 1300S for $100 and use it for this trick and as a pre delay (it doesn't have the feedback & modulation sections of the PCM 42)? I thought it had the same input circuit to overdrive into soft limiting. Input and output gain are set from the front plate with set screws.
Actually, the limiting is even more extensive in a 1300 and the AD/DA is 16 Bit all the way, the cost around $6000 Bucks for a 1300S in 1983/4, the pre-delay is brilliant, and you can lock to T/Code via TTL, (They were Broadcast Units) though you could also buy a moogerfooger and throw that in front, and get near the same result! No talking of price though as eBay buyers will suck the life out of like they did with the PCM-60

TLB
Old 9th May 2015
  #30
Lives for gear
 

Quote:
Originally Posted by TheLastByte View Post
Actually, the limiting is even more extensive in a 1300 and the AD/DA is 16 Bit all the way, the cost around $6000 Bucks for a 1300S in 1983/4, the pre-delay is brilliant, and you can lock to T/Code via TTL, (They were Broadcast Units) though you could also buy a moogerfooger and throw that in front, and get near the same result! No talking of price though as eBay buyers will suck the life out of like they did with the PCM-60

TLB
Though to qualify that post the 1300 has no opto CLM-50's in the unit whatsoever! Just so people know!
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