Home » R/E/P » Whatever Works » The EMT 140 Stereo Plate (Plus Chamber) Thread
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #400168 is a reply to message #295601 ] |
Mon, 26 January 2009 14:21   |
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 Billy Yates
Messages: 980
Registered: August 2007
Location: Venice California |
Gold Member |
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Well now...
The thread has been revitalized, thanks in part to Terry for posting the link to this thread, which I believ is the official EMT Plate Thread.
It has been awhile since I posted here due to various reasons, none of which have anything to do with lack of interest on my part...just busy as hell.
I am going to get back to the plate in our studio soon as client needs outweighed the time I need to finish the EMT 140 stereo tube plate project and I surely will post all of my efforts in detail so that those who who are less informed on the subject may gain some useful insight.
When I left off, I had finished reworking the electronics which had been totally stock with blistered electrolytic caps and a very bad case of previous tech mistakes which I corrected.
Some observations:
DC filament supply is of utmost importance and fresh electrolytics are an absolute must for reducing all filament nosie issues from entering the audio chain.
Good tubes:
As most of you know, the tubes used in the 140 are expensive and I highly recommend buying what stock you can while it is available and somewhat affordable. These units can be modified for more current tube types but I do not advise this unless you really know what you are doing.
Tensioning:
This, in the truest sense of the term, is an art...a delicate sense of user mechanical feedback, skill with tools and a good ear, all of which are a balancing act of sorts. Trust me, it is so worth the effort and patience is a virtue here, but the payoff is big, especially when you see the smile on the clients face...something I look forward to in our own studio.
There is nothing, as I have said before, that comes close to a well tuned plate, unless you have Terry's amazing chamber or something on that scale and magnitude.
The 140, for the money and effort, is one of mankind's amazing inventions that still hold acoustic strengths that is hardly rivaled.
Pictures and commentary relating to isolation, adjustment, calibration and dampening will be shared by me soon.
Thanks Terry, for getting me back into the fold and augmenting my enthusiasm for finishing my project.
Long live the plate reverb....
Billy Yates
Billy Yates
Venice Amplifier Co
310 425 2566
AES Member 72975
"Mix? What mix? Oh, that mix...it's easy!
Because it's all Digital, the only thing you have to do is pour a bunch of zero's and one's into a blender and push "mix". Then, you pray."
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436604 is a reply to message #295601 ] |
Mon, 27 July 2009 09:48 |
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Billy Yates
Messages: 980
Registered: August 2007
Location: Venice California |
Gold Member |
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Finally.
After many months of procrastination, I mustered the troops and we wheeled the EMT 140 ST out into the main room and removed the panels and got to work.
At the last writing on powering the plate up, I had mentioned that the motor would not budge. Screw it, I followed Terry's advice and disconnected the thing. The connector arm from the motor bell crank was disengaged and viola! Manual decay time is now adjustable. All I have to do now is machine the pointer handle that mounts on the damper shaft and calibrate the markings with actual decay time...easy.
But....
The fly in the ointment always occurs when you are most excited about making something work, but in this case, the process of fixing something revealed a secret that was unbeknown to me.
Most of you recall, the process of tuning the plate, right? This is a tedious task that requires patience and nerves of steel, well in a manner of sorts...if you break a tension clip, you are semi screwed. This did not happen, but what I did find was very interesting. Please read on.
I ran some cabling to the 140, one send and two returns from the console. I launched a Protools session and looped a snare track so that it would play quarter notes forever, at a medium tempo.
I powered the EMT up and allowed the tubes to get warm. I slowly heard signal emitting through the monitors. I turned up the return channels and what I heard sounded awful. Puny, metallic whispers that sounded like a fly banging a mallet on tin foil.
I thought, well, here I go...I had previously rebuilt the electronics with fresh electrolytic capacitors, and the voltages were right etc...no, that's not it, it's a mechanical thing.
I observed the tension of the plate and it felt rather tight and not flimsy at all, except for the exact center which I will get to later. So, I pulled up a chair and sat down to inspect the driver. The coil was seated properly because the magnet mounting plate and magnet are self centering. By chance, I took my two pointer fingers and pushed the plate away from me, thus exposing more of the coil windings...HELLO! BIG PLATE REVERB!
Closer inspection of the driver plate revealed spacer washers behind the plate on the mounting studs with more room to spare for added spacers. I figured 3 washers per stud should work for starters. I removed the nuts, pulled the plate off and inserted the washers. I reinstalled the plate but the sound wasn't right. So, I removed one washer from each stud leaving 2 per stud. I reinstalled the plate again, and bingo. There was that marvelous sound often copied but never duplicated. I had arrived at that place where I had always wanted to be in my studio owner experience...that realization of knowing that I had a functioning EMT 140 Plate reverb in my studio. A real reverberation device that I had always dreamed of was working at my hands. Unbelievable.
The story doesn't stop here folks. Some additional info is needed.
I had mentioned earlier that the middle of the plate is a bit flimsy. This seems natural to me in that the physics involved point to this as being normal. Hence the spacers for the magnet so that the proper adjustment can be made for optimum performance. But seeing how the voice coil is mounted in the center of the plate, this adjustment becomes even more crucial.
Just like a speaker, a voice coil must be positioned in the area of maximum magnetic flux for best performance. This is what I did in the procedure I just described.
So far, in all of the discussions pertaining to the EMT Plate, I don't recall anyone describing this adjustment, only the tension adjustment has been discussed. This is probably due to the fact that once the plate had been setup at it's final destination, this would no longer be an issue. Once the plate is moved from one location to another, the torsional effect of physical movement would not only require readjustment of the tension nuts, but the magnet depth too.
Owners of these wonderful devices should take this into consideration if you haven't done so already. Then again, if it sounds good don't screw with it.
Later on, I will delve into setting up the amplifiers for minimum hum.
Billy Yates
Venice Amplifier Co
310 425 2566
AES Member 72975
"Mix? What mix? Oh, that mix...it's easy!
Because it's all Digital, the only thing you have to do is pour a bunch of zero's and one's into a blender and push "mix". Then, you pray."
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436630 is a reply to message #295601 ] |
Mon, 27 July 2009 11:21 |
RMoore
Messages: 4406
Registered: May 2004
Location: Spaceship Earth |
Platinum Member |
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Right on, great post...
Funnily enough I was just looking into storage today for my EMT 140 mono - a rainy day project I've had sitting around for years... hearing stories like the above sure is encouraging..
People's Republic of Ryan
http://www.myspace.com/twilightcircus
http://www.youtube.com/user/Ryonik
By the end of today, another day is gone forever. You will never get it back.
We must never let up for a second. Work harder at every single thing - Terry Manning
You miss 100 percent of the shots you never take - Wayne Gretzky
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436640 is a reply to message #295601 ] |
Mon, 27 July 2009 11:40 |
RMoore
Messages: 4406
Registered: May 2004
Location: Spaceship Earth |
Platinum Member |
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With the spray on liquid oil mentioned a few pages back - does one leave this on the plate? Does this affect the sound? Just out of curiosity, what does one do with a rusty plate? I seem to recall John Klett saying something years ago about polishing with steel wool & applying / leaving on a thin coating of light oil (??)..
People's Republic of Ryan
http://www.myspace.com/twilightcircus
http://www.youtube.com/user/Ryonik
By the end of today, another day is gone forever. You will never get it back.
We must never let up for a second. Work harder at every single thing - Terry Manning
You miss 100 percent of the shots you never take - Wayne Gretzky
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436654 is a reply to message #436640 ] |
Mon, 27 July 2009 12:17 |
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Billy Yates
Messages: 980
Registered: August 2007
Location: Venice California |
Gold Member |
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| RMoore wrote on Mon, 27 July 2009 11:40 |
With the spray on liquid oil mentioned a few pages back - does one leave this on the plate? Does this affect the sound? Just out of curiosity, what does one do with a rusty plate? I seem to recall John Klett saying something years ago about polishing with steel wool & applying / leaving on a thin coating of light oil (??)..
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That would make sense, in that the environment the plate is being used would dictate the use of a protective film of a rust inhibitor. I doubt very seriously that the light film of oil or other medium would make a difference. Being that the plate is mounted vertically, any fluid of significant mass would drain off leaving only the thinnest film. I noticed yesterday that when I stumbled upon moving the plate away from the magnet, that my fingers made very little difference in the sound of the plate.
Here is some out loud thinking....
Perhaps oil would accumulate dust on the surface of the plate. Keeping the plate stored in a clean environment would help.
Silicone spray instead of oil. It's viscosity is lighter and would likely penetrate and stick better. Silicone would also not become gummy like oil.
Depending on location, the use of a dehumidifier might be in order.
Billy Yates
Venice Amplifier Co
310 425 2566
AES Member 72975
"Mix? What mix? Oh, that mix...it's easy!
Because it's all Digital, the only thing you have to do is pour a bunch of zero's and one's into a blender and push "mix". Then, you pray."
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436694 is a reply to message #295601 ] |
Mon, 27 July 2009 14:41 |
Philip Shaw Bova
Messages: 81
Registered: July 2005
Location: Ottawa, ON Canada |
Member |
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This is a great thread. I'm a serious EMT plate enthusiast and I use mine everyday. For the longest time I had my plate tensioned up fairly tightly using Jim's (Cunningham) tuning gauge. The plate sounded great, shimmery, bright, .... Recently though I wanted to try bringing down the tension, which increases the low frequency decay. I've always loved the reverb sounds that are on records done at Trident Studios in the early 70's. I always assumed that they had real echo chambers over there because that reverb is much darker than the sound I associate with EMT's, but it turns out that they never had chambers, only one or two plates. I wanted that sound so a couple of weeks ago I opened up the old matress box for the first time in about 3 years and had a go at trying to make my plate sound more "Trident" like. In the end the tension had to be brought down a very substantial amount to get into the ballpark. The only problem now was that I still had too much high end decay time... Maybe it's just that my piece of metal has a more inherently brighter than some other plates, who knows. Finally I attached little pieces of foam on two edges of the plate. and now I'm a very happy man. Maybe I should have just found a rusty dull out of tune plate in the first place, who knows, but now I have the plate sound that I like. Warm, and I can still get it to shimmer, but not too much.
Philip
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436747 is a reply to message #295601 ] |
Mon, 27 July 2009 20:03 |
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Billy Yates
Messages: 980
Registered: August 2007
Location: Venice California |
Gold Member |
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Some shots of the interior.
This one is of the Mag Mount.
Note the washers behind the plate, these set the space to allow proper coil depth into the magnet core.
Attachment: Mag mount.jpg
(Size: 115.68KB, Downloaded 541 time(s))
Billy Yates
Venice Amplifier Co
310 425 2566
AES Member 72975
"Mix? What mix? Oh, that mix...it's easy!
Because it's all Digital, the only thing you have to do is pour a bunch of zero's and one's into a blender and push "mix". Then, you pray."
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436748 is a reply to message #295601 ] |
Mon, 27 July 2009 20:05 |
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Billy Yates
Messages: 980
Registered: August 2007
Location: Venice California |
Gold Member |
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I disconnected the control arm from the Bell Crank assembly. The damper plate is now manually operated.
Attachment: Motor arm.jpg
(Size: 129.99KB, Downloaded 540 time(s))
Billy Yates
Venice Amplifier Co
310 425 2566
AES Member 72975
"Mix? What mix? Oh, that mix...it's easy!
Because it's all Digital, the only thing you have to do is pour a bunch of zero's and one's into a blender and push "mix". Then, you pray."
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| Re: The EMT 140 Stereo Plate (Plus Chamber) Thread [message #436750 is a reply to message #295601 ] |
Mon, 27 July 2009 20:08 |
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Billy Yates
Messages: 980
Registered: August 2007
Location: Venice California |
Gold Member |
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Interior shot of the plate, showing the driver and pickups.
Attachment: Interior.jpg
(Size: 138.63KB, Downloaded 530 time(s))
Billy Yates
Venice Amplifier Co
310 425 2566
AES Member 72975
"Mix? What mix? Oh, that mix...it's easy!
Because it's all Digital, the only thing you have to do is pour a bunch of zero's and one's into a blender and push "mix". Then, you pray."
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