New development on old project: Roger Mayer RM58
« on: February 09, 2021, 09:51:19 PM »
Starting a new thread here for a few reasons:

1) The previous RM57 thread had evolved more into a discussion of the RM58

2) That thread had turned into quite a journey, and this seemed tidier.

Using Spencerleehorton's great work in that thread as a starting point, I decided I'd like to make a version of this circuit that incorporated Roy Cicala's modifications to include UTC transformers on the input and output.

Using Spencer's schematic (which is accurate) combined with original documentation and some old photos, I laid out the circuit on three separate PCBs, separating the booster and the limiter into separate cards as the original had done, as well as a small board for a very simple +18v regulated DC supply.

I've got Gerber files of each that I'll attach below (sorry; format not supported by forum software); JLCPCB did a great job on them and turned them around quickly. Pleased to say that everything worked more-or-less properly the first time, with only a few kinks to iron out.

The one change I made to the circuit: I lowered R31 to 6k8, which, combined with connecting the VU meters in reverse, allowed me to set the zero point at 0VU and have it swing to the left under gain reduction, which is more conventional and more to my liking (the original showed gain reduction starting from far left and swinging toward the right under GR).

Finally, I also designed an enclosure in Protocase Designer which I had them make up for me, and it turned out quite well!

I'll upload the Protocase Designer file as well as the Gerber files below in case anyone else wants to have a go. The PCBs are laid out for the specific components I chose... I never put together a full BOM with part numbers, but if there's interest I'd be happy to take the time to do so.

I've gotten a lot of help on this forum on other projects, so I'm happy to share this if it's useful to someone.
« Last Edit: February 09, 2021, 10:02:29 PM by soapfoot »


Re: New development on old project: Roger Mayer RM58
« Reply #1 on: February 09, 2021, 09:56:50 PM »
Well, I made a .zip archive with Gerber files of the PCBs and a Protocase Designer file for the chassis, but neither .zip archives nor the associated file types are acceptable attachment types for this forum. I don't always check PMs super-regularly, but feel free to try me with an e-mail address and I'll send to you if needed!

I'll get to work on at least a partial BOM to include in the folder as well.

Happy to share photos of my completed build if anyone is interested. One thing I did was to include the resistors for the stepped release time control on the limiter PCB itself (instead of hanging them off the rotary switch like the original)

Whereas the Record Plant RM57/58 had UTC A21s on input and output, I used A21s on input and A20s on output.
« Last Edit: February 09, 2021, 10:03:17 PM by soapfoot »

Re: New development on old project: Roger Mayer RM58
« Reply #2 on: February 09, 2021, 11:06:05 PM »
Wow, good work and neat build! Thanks!

EmRR

Re: New development on old project: Roger Mayer RM58
« Reply #3 on: February 09, 2021, 11:56:32 PM »
Looks great
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

Rocinante

Re: New development on old project: Roger Mayer RM58
« Reply #4 on: February 10, 2021, 11:42:25 PM »
Looks great man. I might consider giving it s whirl
If there's a harder way to do this, I haven't found it yet.

Re: New development on old project: Roger Mayer RM58
« Reply #5 on: February 11, 2021, 10:16:31 AM »
Looks great man. I might consider giving it s whirl

If you do, send me a PM with your e-mail address and I'll forward all files and documents I have.

I kept all of the Gerber files and the Protocase Designer file current and revised as I made tweaks, so everything should be quite ready to go.

One thing I did--instead of hanging the release time resistors off of the rotary switch like in the original, I added them in their own section of the Limiter Board PCB. I labeled it up and color-coded it so it's easy to connect (the pole of the rotary switch connects to point "B" as in the originals).

Re: New development on old project: Roger Mayer RM58
« Reply #6 on: February 12, 2021, 02:54:42 PM »
Brought this by the studio today. Didn't have much time to play around, but did have time to do this:

"All faders at unity" super-rough drum submix, attack and release both at maximum-fast (both of which are still pretty slow!), and a healthy amount of input level, quite a bit of squish happening.

I just recorded the output of the compressor, but it's really nice in parallel.

I find it to be impressively smooth considering how much compression is happening, and really nice and thick, too.

https://www.youtube.com/watch?v=9q5b_qT6oWs&feature=youtu.be


 

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