New development on old project: Roger Mayer RM58

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soapfoot

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Dec 27, 2010
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382
Cool to see so many people interested in this!

Yes, just about any serviceable 1:1 should do the job. You could even make the compressor unbalanced and omit the transformers--that's actually the original design. By the book, there are probably "better" choices than the UTC A-21 or A-20.

I was trying to replicate a specific example that had been modded by Roy Cicala at the Record plant.

I do think AMI will have more UTC transformer models available soon, if not already (so it might be worth an inquiry if you want something to fit the holes in my Protocase enclosure file)

The UTC iron does "a thing," and that may be why I like it in this device. It's much more audible transformer coloration than modern Lundahls or Sowters or whatever. In the RM58 (which is very much a "character piece" for me), that's a feature, not a bug.

Many surplus suppliers seem to have 2N3820 stock (I got a bunch from tedss.com)

I may buy some more soon, as I'm thinking about whipping up a couple more of these for personal use (they really sound great, and my business partner would never let me take the one from our mix room as he uses it on every single mix now).
 

richiyobs

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Apr 29, 2010
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Hi you all,
i m Richi and thanx to this great forum i was able to rebuild the RM57 to.
special thanx to Spencer for his old prototype and to Ruud for his new version...
the modern one is smoother and cheaper to realize.
i d like to share my info about Gain Reduction, since it s a lot i m experinting on...
tried different schems and solution, but the best tracking is to use the original schem part
 
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richiyobs

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not reversing the Vu and limiting the needle to the zero. adding a diode bridge will give a Log movement.
the balistic improoved, also 1/2dB is tracked. i use the meter only to monitoring the Time constant of course!
 

richiyobs

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i used this for TN73 Vu type ... it works from 0 to -20...
but prefer the original way... less components
 

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richiyobs

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this one instead was usefull with standard small Vu ... track from 0 to -20 to
 

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richiyobs

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here is a test running Rm57, using J175 instead of 2n5461... it s a mono unit
i had the impression that setting the threshold higher i got a less spanky machine or maybe it s J175... i really don t know
compared with other self build units running 2n5461 and 3820
sorry for poor quality audio phone
 

grid_stopper

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Mar 2, 2016
Messages
84
here is a test running Rm57, using J175 instead of 2n5461... it s a mono unit
i had the impression that setting the threshold higher i got a less spanky machine or maybe it s J175... i really don t know
compared with other self build units running 2n5461 and 3820
sorry for poor quality audio phone
i made a quick demo of my unit, which uses 2n5461, and 3820's, if your curious to see if theres much of a difference. The input is cranked, but i figure thats mainly how im going to be using it
 

richiyobs

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Apr 29, 2010
Messages
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Location
italy
i made a quick demo of my unit, which uses 2n5461, and 3820's, if your curious to see if theres much of a difference. The input is cranked, but i figure thats mainly how im going to be using it
hi Grid stopper,
thanks for your reply and for your demo....
i ve got 6 ch of rm limiter, cause i experimented a lot on this design.... also thanx to the modern version of Ruud... 3 ch discrete and the other modern ones, so i know the sound of my replicas only, and from what i can listen on the web and records
 

richiyobs

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Apr 29, 2010
Messages
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Location
italy
For shure the discrete version is punchier and rich in sound but also hard to calibrate for my knowledge... It was my first use of oscilloscope!
 

ashdot

Member
Joined
Nov 23, 2019
Messages
5
Cool to see so many people interested in this!

Yes, just about any serviceable 1:1 should do the job. You could even make the compressor unbalanced and omit the transformers--that's actually the original design. By the book, there are probably "better" choices than the UTC A-21 or A-20.

I was trying to replicate a specific example that had been modded by Roy Cicala at the Record plant.

I do think AMI will have more UTC transformer models available soon, if not already (so it might be worth an inquiry if you want something to fit the holes in my Protocase enclosure file)

The UTC iron does "a thing," and that may be why I like it in this device. It's much more audible transformer coloration than modern Lundahls or Sowters or whatever. In the RM58 (which is very much a "character piece" for me), that's a feature, not a bug.

Many surplus suppliers seem to have 2N3820 stock (I got a bunch from tedss.com)

I may buy some more soon, as I'm thinking about whipping up a couple more of these for personal use (they really sound great, and my business partner would never let me take the one from our mix room as he uses it on every single mix now).
Hi,
I’d love to build one of these.
please email me the files.
many thanks!
Izhar
izash @ me com
 

grid_stopper

Well-known member
Joined
Mar 2, 2016
Messages
84
Curious if anyone could provide any sort of insight as to where one might go about adding a hpf filter to the side chain on this circuit? I was able to do that relatively easily on an 1176, but the answer on the RM58 isn't jumping out to me as quickly in this case!
 

richiyobs

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Joined
Apr 29, 2010
Messages
16
Location
italy
Curious if anyone could provide any sort of insight as to where one might go about adding a hpf filter to the side chain on this circuit? I was able to do that relatively easily on an 1176, but the answer on the RM58 isn't jumping out to me as quickly in this case!
maybe something like this, but not shure.... i d like to know too
 

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