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Project Specific Discussions => Dynamic Processors => Topic started by: dustbro on February 02, 2006, 12:07:58 AM

Title: Roger Mayer RM57 build?
Post by: dustbro on February 02, 2006, 12:07:58 AM
I was playing around with the RM57 the other day, and it blew my mind... It's the instant "smash 'em up" compressor. I pulled the top off and was shocked when I saw how basic the thing was.
Does anyone have a schematic / part list / kit for one of these? I'd love to build one.
thanks
Dan
Title: Roger Mayer RM57 build?
Post by: pucho812 on February 02, 2006, 12:11:18 AM
newbie asking for stuff :evil:  :mad:  :evil:

reverse engineer it. we can help you... nothing is free
Title: Starters
Post by: northsiderap on February 02, 2006, 02:21:26 AM
How about a picture of the 'guts?' :thumb:
Title: Roger Mayer RM57 build?
Post by: dustbro on February 02, 2006, 02:40:58 PM
Quote from: "pucho812"
newbie asking for stuff :evil:  :mad:  :evil:

Uh... you never asked for a schematic or help before?
Quote from: "pucho812"
... nothing is free

Really? There sure does seem to be a lot of FREE and HELPFUL information floating around this forum. I wasn't expecting someone to track one down and reverse engineer it for me. I was wondering if it had already been done so I dont have to reinvent the wheel.

Maybe you're just in a bad mood after breathing in solder fumes all day?
Title: Re: Starters
Post by: dustbro on February 02, 2006, 02:42:57 PM
Quote from: "northsiderap"
How about a picture of the 'guts?' :thumb:

That would be the next step I guess... Thanks.
Dan
Title: Roger Mayer RM57 build?
Post by: JustinS on February 02, 2006, 04:49:33 PM
Quote from: "pucho812"
we can help you


Note this part of the post...

If you have a try and start the process there are many cool people (including Pucho) who'll help you along the way!

Justin

Ohh yeah... and if you haven't already... have a look at the Meta's - so much useful info (see the Meta-Meta link above the board).
Title: Roger Mayer RM57 build?
Post by: pucho812 on February 02, 2006, 05:48:09 PM
sorry to come off so harh dan. have a  :guinness:  :guinness:

It's just lately  lots of newbies come on right away and without little intro are asking for stuff without even a hint of thanks or whatever.  I have asked for schemos and info before don't get me wrong but took me  lil while before I started getting into it.  anyway I didn't mean to jump on you so quickly.  :cool:  :guinness:
lets pop that puppy open and get started. I along with others love to share info. I help out where I can but have much to learn as well.

Quote
Maybe you're just in a bad mood after breathing in solder fumes all day?
yeah I was but mainly from the migrain combined with solder fumes...
Title: Roger Mayer RM57 build?
Post by: dustbro on February 02, 2006, 05:56:36 PM
Quote from: "pucho812"
sorry to come off so harh dan. have a  :guinness:  :guinness:

Its cool... We're in the audio business and I'm well aware that everyone in this business is a dick (including me  :grin: )
Schematics are hard to come by on this unit. As a matter of fact, I'm not even sure that one exists. My issue is that I do not own this compressor and kind of popped it open when the assistant at the studio was sleeping in the lounge. I saw one for sale on ebay for $350... I guess I'll have to pick one up and rip it apart.
Title: Roger Mayer RM57 build?
Post by: pucho812 on February 02, 2006, 05:58:57 PM
Quote from: "dustbro"
Quote from: "pucho812"
sorry to come off so harh dan. have a  :guinness:  :guinness:

Its cool... We're in the audio business and I'm well aware that everyone in this business is a dick (including me  :grin: )
Schematics are hard to come by on this unit. As a matter of fact, I'm not even sure that one exists. My issue is that I do not own this compressor and kind of popped it open when the assistant at the studio was sleeping in the lounge. I saw one for sale on ebay for $350... I guess I'll have to pick one up and rip it apart.


I try not to be a dick but as you can see I got my moments. so it was a rackmount? balanced I/O? got a link to that e-bay sale?
Title: Roger Mayer RM57 build?
Post by: dustbro on February 02, 2006, 11:38:38 PM
http://cgi.ebay.com/Roger-Mayer-RM58-Stereo-Compressor-NEEDS-REPAIR_W0QQitemZ7385618234QQcategoryZ23793QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


When I popped it open, there were like 2 pcb's and a LOT of open space. Im going to see if anyone at pro.audio.rec has a schematic that can get me started.
I'm totally excited about starting to build my own gear... if you can suggest a good starter compressor that's easy to build to get my chops up, i'd appreciate it!
thanks
Dan
Title: Roger Mayer RM57 build?
Post by: pucho812 on February 03, 2006, 02:13:55 AM
hmmm a mastering studio :?
compressor to build? hmmm well lots folks around these parts building 1176's and la2a's. if your crazy could go after that pice of shyte 670 no one ever uses thoses. :green:
Title: Roger Mayer RM57 build?
Post by: dustbro on August 07, 2006, 01:21:21 PM
OK.... It's been 6 months since I got the idea to work on this comp. I'm almost finished my Gssl, built a Fuzzface, Big Muff, and Phase 90... Now I think it's time to tackle this guy.
Since no schematics exist for these things, I've had to test every part to get the parts list. I'm still unsure of what transistors are used since only 2 of them are actually marked. I'm also not sure what trim pots are used.
If anyone has ever reversed engineered a piece of gear, any help would be greatly appreciated on getting me started.
The PCB layout is very inefficient since the cards had to slide into a big connector. Should be pretty easy to redesign?
(http://ftp://myspace:[email protected]:667/DIY/RM57/rm57-pics.jpg)
Title: Roger Mayer RM57 build?
Post by: dustbro on August 07, 2006, 07:26:16 PM
Wow!! Thanks to another member, I now have a schematic to the RM58. This makes my life a whole lot easier.

I guess my first step is to get the parts list going.
Can someone please share their wisdom on how to approach the redesign of the PCB? What to do first?
thanks all
Title: Roger Mayer RM57 build?
Post by: Flatpicker on August 07, 2006, 07:48:40 PM
Look's cool, kind of like the old Neve stuff. Can someone host the schematic and link it to the meta?
Title: Roger Mayer RM57 build?
Post by: dustbro on August 07, 2006, 07:52:31 PM
Trying to get a schematic now... I have one in a manual that is very hard to read, so I'm trying to track down a better one now.
Title: Roger Mayer RM57 build?
Post by: dustbro on August 20, 2006, 10:12:08 PM
Would anybody like to help out with the PCB redesign? I am not experienced enough to do it on my own... even a nudge in the right direction with what software and what specs the pcb should be would help a ton.
Title: Roger Mayer RM57 build?
Post by: rafafredd on August 20, 2006, 11:52:09 PM
Hey, can you post the RM58 schematics? with all that utc iron I got curious...
Title: Roger Mayer RM57 build?
Post by: kvintus on August 21, 2006, 05:15:05 AM
I could volounteer to help you with this project. Could you send me the 58 schematics and good close up pictures of the PCBs?

/Anders
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 09, 2009, 09:26:07 AM
I have been researching this unit and was very fortunate to get some help from dustbro.
There are some undocumented trims on the PCB and components without designations, so I emailed Roger Mayer to ask him. (He lives in South London).
He was extremly unhelpful and showed no interest in giving any kind of support at all.
His reply:

we do not support this Model anymore and yourdetailed questions would require us to go into the archives to revisitthis old design from the 1970's. Many of the parts in this design areobsolete now and new substitutes would have to be chosen. All in allthis would be very time consuming and our current work load negates thisoption. We have had certain interest for these two old models butinsufficient to consider a new reissue.

So there you go. I guess we're on our own!
Title: Re: Roger Mayer RM57 build?
Post by: peterc on June 09, 2009, 09:59:06 AM
This looks really cool, any pics? I loved the "voodoo" (no pun...) of this unit, keen to build one.

If I can help, let me know.

::GUINESS::

Peter
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 10, 2009, 08:43:02 PM
Still trying to gather info for this unit.
Some of the circuitry is similar to the RM68 noise gate and if I remember rightly there was some service data with this gate about measuring attack time and component selection.
Anybody have it ?
(I've got the schematic - it's the rest of the stuff I'm after).
Title: Re: Roger Mayer RM57 build?
Post by: hobiesound on June 11, 2009, 04:51:54 AM
hiya,

for all that don't have the roger mayer RM68 schematic :
http://www.schematicheaven.com/effects/rogermayer_rm68_noisegate.pdf (http://www.schematicheaven.com/effects/rogermayer_rm68_noisegate.pdf)

greetings,

Thomas
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on June 11, 2009, 11:01:32 AM
I'm searching now for a unit to dissect.. the RM57 and rm58 I have access to cant really be poked and prodded like I want to do cause they are in use every day. Anyone have a line to one they are willing to let go?
Working on a layout ATM cause it's quite possible to slap it together and tweak around till I figure out what some of the mysterious trimmers do.
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 11, 2009, 11:24:35 AM
Quote
for all that don't have the roger mayer RM68 schematic :
http://www.schematicheaven.com/effects/rogermayer_rm68_noisegate.pdf
greetings, Thomas

Hi Thomas. Thanks very much for the link.
The actual information I'm looking for is the extra pages that came with the gate. The stuff about attack time and which components to change to drive a 600 ohm load etc etc.
Does anyone have that ?
It will actually be useful in trying to piece together the info for the RM57.
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on June 11, 2009, 01:33:54 PM
I used to have 2 or 3 diagrams for the RM58, but can't seem to find them.   I was trying to put it together on veroboard aboutg 5 years ago, but never got it finished.   I'll have a dig round if they are of use to you Martyn ?
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 11, 2009, 02:28:58 PM
Yeah. It's the stuff about attack time and component selection I'm after Rob.
I've got the RM68 noise gate schematic.
I used to have some of those gates but sold them a few years back.
Now the compressor, that's a different story.
Somebody has just told me that one sold recently for over $6,000 (!)
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on June 11, 2009, 03:48:09 PM

Somebody has just told me that one sold recently for over $6,000 (!)
yup
perfect candidate for a clone.
Title: Re: Roger Mayer RM57 build?
Post by: Biasrocks on June 11, 2009, 06:15:16 PM
Somebody has just told me that one sold recently for over $6,000 (!)

I'm not sure if it actually sold for that amount but they were asking 6.6K for one.

Ridiculous.

But, you can ask anything you want. :)

I agree, another character compressor in the arsenal would indeed be sweet.

Mark
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 11, 2009, 10:25:28 PM
Quote
I'm searching now for a unit to dissect.. the RM57 and rm58 I have access to cant really be poked and prodded like I want to do cause they are in use every day.

Dan. Is it at all possible to check some of the transistors on one of those units?
(Might mean pulling out a card or two).
I think I've got a line of what most of them are, but maybe if I give you a list of what to look for....
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on June 12, 2009, 02:17:10 AM
maybe if I give you a list of what to look for....
Send away! I'll definitely check it out
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 14, 2009, 05:21:32 AM
To bump this...
Dan (dustbro) - can you please PM me your email so I can send you the schematic with the data I have so far.
Peter (peterc) - can you do the same. I would appreciate your help.
If you PM me an address I will send you the info I have.
Thanks.
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 14, 2009, 05:00:33 PM
Quote
Quote from: barclaycon on June 11, 2009, 10:25:28 pm
maybe if I give you a list of what to look for....
dustbro wrote:
Quote
Send away! I'll definitely check it out

Dan, can you PM me an email address to send it to.
Title: Re: Roger Mayer RM57 build?
Post by: analogguru on June 25, 2009, 06:08:05 AM
So what about we are talking here now ?
The RM57, the RM58 (Compressors) or the RM68 (Noise Gate) ?

Looking at the guts of the RM57 presented here:
http://www.flickr.com/photos/daveygee/2918090546/in/set-72157607776991626/
there appears no big difference to the RM58 maybe a different transformer 120V/240V.

The driver-card design in the RM58 is definitely stolen from the HELIOS-console which itself is very well documented here:
http://recforums.prosoundweb.com/index.php/mv/msg/16023/0/928/0/
the same circuit was used by roger mayer in his octavio too.

I can´t see a big problem to figure out everything needed to build a clone of the RM58 with all of the available infos.  RM68 shoudn´t be a problem too.  A much better pcb including the driver can be easily done on a single-sided eurocard (160mm x 100mm) when there is enough interest.  Even the (insane) release switch can be replaced by a 10M potentiometer (I have enough of them).

@barclaycon
I´ll send you PM with my e-mail adress, maybe I can be of help.

analogguru
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 25, 2009, 09:50:50 AM
Well, we are talking about the RM57 and RM58 Compressors which, as you say, are essentially the same beast. The RM68 noise gate is mentioned because it has some similar circuitry and we are trying to find out the components used.
As has already been mentioned, Roger Mayer refuses to help in any way and I would not recommend contacting him as it is a very unrewarding experience!
The schematics available don't give any clues as to line-up, and some of the transistors are not identified.
So that is where we are right now.
Hopefully Dan can have a look at his unit and identify some of the parts.

Thanks for the RM57 pictures link - very helpful.
I notice that one of the 2N3820 FETs has a red mark painted on it which would seem to suggest it is a selected part. What the criteria is for that I don't know. It is the same FET as used on the noise gate and I remember some detail being given in the RM68 literature. That's why I was asking about it.

I think the release 'switch' was only used on the RM58. On the RM57 it was a 2M2 pot.
I didn't find the HELIOS  driver circuit you described.
Can't say that I see the similarity with the Octavia circuit (?).
Thanks for your help.
Title: Re: Roger Mayer RM57 build?
Post by: analogguru on June 25, 2009, 10:50:02 AM
For more info on the Roger Mayer Octavio read this:
Octavia History - Truth revealed ? (http://www.diystompboxes.com/smfforum/index.php?topic=52731.0)
this:
Octavia Evolution courtesy of Roger Mayer (http://www.diystompboxes.com/smfforum/index.php?topic=53494.0)
and this:
Roger Mayer Octavia Octavio (http://www.diystompboxes.com/smfforum/index.php?topic=54285.0)
and look at the:
Tycobrahe Octavia schematic (http://analogguru.an.ohost.de/001/schematics/Tycobrahe_Octavia.gif)
and the
Roger Mayer Octavia schematic (http://analogguru.an.ohost.de/001/schematics/RogerMayer_Octavia.gif)

This is the wrong Helios schematic where all came from:
http://vintageking.com/site/files/images/schem_V69-1973-2-Var-1.jpg

Here is the proof of my theory (scroll down for the handdrawn trace of the Tyco-enginieers):
http://wc6w.50webs.com/wc6wvint/index.html?fr411.html

(At least) during this period of time RM was nothing more than a solder-jockey.

I will try to find some time to draw a readable schematic of the RM58.

analogguru
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on June 25, 2009, 12:18:56 PM
Should be getting the RM58 in the mail today. I'll give you an update shortly.
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 25, 2009, 12:30:01 PM
Thanks for all the info fellahs!

I can see the similarities with the Helios Line Driver - albeit opposite polarity.

Look forward to your findings Dan
Title: Re: Roger Mayer RM57 build?
Post by: Biasrocks on June 25, 2009, 12:41:41 PM
I came across this while searching for Mayer schematics

http://analogguru.an.ohost.de/193/schematics/RogerMayer_RM58-Driver.gif

Mark
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 25, 2009, 01:14:48 PM
Excellent stuff Mark.
Thanks
Title: Re: Roger Mayer RM57 build?
Post by: analogguru on June 25, 2009, 01:17:40 PM
I came across this while searching for Mayer schematics

http://analogguru.an.ohost.de/193/schematics/RogerMayer_RM58-Driver.gif

Mark
Ooops.... I really forgot that I put this already online..... I think that I am getting old.

analogguru
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 25, 2009, 01:22:01 PM
Yes. Now you are found out Gottfried !!
Title: Re: Roger Mayer RM57 build?
Post by: mr coffee on June 29, 2009, 12:56:55 AM
Did I miss something, or has the RM57\RM58 schematic (for the compressor part of the circuit) never been posted?

I'd be glad to help with the clone process.

Bart
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on June 29, 2009, 11:14:25 AM
We are still collating info on this.
analogguru says he might draw out the limiter board when he has time.
dustbro has actually aquired an RM58 and will be looking inside for more clues.
Title: Re: Roger Mayer RM57 build?
Post by: hobiesound on June 29, 2009, 02:38:17 PM
i'm not sure if it's ok but i can email the schematic for the RM58 to the Gdiy email account.

greetings,

Thomas
Title: Re: Roger Mayer RM57 build?
Post by: shuchoco on October 14, 2009, 10:50:34 PM
anyone made progress on DIYing the RM57 or RM58?  i would love to build one if it's doable.

is the schematic for the RM57 posted anywhere for public consumption?

thanks
 
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on October 15, 2009, 12:22:35 AM
Hey guys!
My day job (making records) has gotten in the way of my hobby, so I havent had much time to put towards cloning this thing. I could probably bang it out in a weekend if I had some spare time.
I'll keep everyone updated when something happens.
Dan
Title: Re: Roger Mayer RM57 build?
Post by: shuchoco on October 15, 2009, 12:24:33 AM
thanks dan!
Title: Re: Roger Mayer RM57 build?
Post by: axisbold on February 09, 2010, 11:46:39 AM
Doe's anyone know what became of all of this? I would like to see a good schem of this thing and see what is going on with it. I have identified some different values used with these for those interested.  Thanks, Axisbold.
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on September 09, 2010, 11:50:18 AM
Just in case anyone missed it..

http://www.roger-mayer.co.uk/rm58.htm

Title: Re: Roger Mayer RM57 build?
Post by: volker on September 09, 2010, 12:05:56 PM
The manual/schematic is attached in the first post here (http://freestompboxes.org/viewtopic.php?f=1&t=10369).
Not sure if you can see or download it without being logged in.


If you read the last post, you can see that it actually originated from somebody here.
Title: Re: Roger Mayer RM57 build?
Post by: kato on September 09, 2010, 09:48:49 PM
Just in case anyone missed it..

http://www.roger-mayer.co.uk/rm58.htm


Jeez what a tool. He sure changed his tune quite a bit since June 2009 (http://www.groupdiy.com/index.php?topic=13287.msg415958#msg415958).
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on September 10, 2010, 11:22:44 AM
Unbelievable huh ?!

I'm tempted to email him back.
What do you think ?


Can anybody login to that forum and grab the schematics/ technical info ?
There's something about the FET that might be useful.
Title: Re: Roger Mayer RM57 build?
Post by: kato on September 10, 2010, 11:42:51 AM

I'll put it in the google account.
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on September 10, 2010, 01:07:20 PM
Thanks very much for the Roger Mayer pdf.
Somebody on that stompboxes forum (Hotrats) said something about choice of FET (2N3820).

the schematic was lent to me by an extremely generous chap over at ProdigyPro who basically gave me the password to his huge ftp site - I haven't even gone through half of it yet ... says he, some of the first RM58 clones are supposed to be making their way out shortly ... interesting data about that 2n3820 jFET, it has Idss lying between 0.3mA and 15mA ... what a spread !

Can't find that info anywhere (!)
Any clues ?
Title: Re: Roger Mayer RM57 build?
Post by: kato on September 10, 2010, 07:39:59 PM
ftp.thehouseofloud.com
user:  schematics
password:  [email protected]#$
Title: Re: Roger Mayer RM57 build?
Post by: thomasdf on December 09, 2011, 06:42:08 PM
Hi folks, any news about this drawing? I'm really dying to build up that beauty. Lemme know if I can be of any help...

Thomas
Title: Re: Roger Mayer RM57 build?
Post by: pedroplanet on December 09, 2011, 09:00:03 PM
Quote
ftp.thehouseofloud.com
user:  schematics
password:  [email protected]#$

I couldn't find the schematics there...  :-\
Title: Re: Roger Mayer RM57 build?
Post by: dustbro on December 10, 2011, 10:02:12 PM
I have a pcb etched and ready to go... just waiting on some rare transistors to make their way to my shop.
Title: Re: Roger Mayer RM57 build?
Post by: pedroplanet on December 10, 2011, 11:24:19 PM
Quote
I have a pcb etched and ready to go... just waiting on some rare transistors to make their way to my shop.

Could you possibly share it with us?  :D
Title: Re: Roger Mayer RM57 build?
Post by: ChrisPbass on December 16, 2011, 06:00:17 AM
I've placed an 11 page pdf in the groupdiy email account regarding the rm58. I'm sure it is the same as the one previously mentioned, but in case anyone has missed it, then there it is. It includes schematics and connections although it doesn't list every transistor type unfortunately!
Chris
Title: Re: Roger Mayer RM57 build?
Post by: jstuart on January 05, 2012, 10:28:01 AM
Hey all, I have an rm57 , originally from the Record Plant ( it has some attack and release mods done for them), and the manual. It has the parts list, at least the caps/resistors/ VRs etc.  I scanned it for someone a couple of years ago, so it should be on one of my drives, and If it would be helpful, I'll be glad to send the scans to anyone who would like them.

Of course, if you would like to pay me an insane amount of $, you can have the thing.......( just kidding. I read through the posts, and saw that someone was asking 6K for one........ seems sort of nuts......, but hey, I can dream. can't I?
j
Title: Re: Roger Mayer RM57 build?
Post by: smallbutfine on January 05, 2012, 12:40:04 PM
Hey guys,
How about to take a look at this Document I just found .... looks a bit clearer, but I'm unsure about the handwritten information, it's not mine....
Nevertheless, it's a good scan.
http://www.technicalaudio.com/pdf/Roger_Mayer/RogerMayer_RM58_Stereo_Limiter.pdf (http://www.technicalaudio.com/pdf/Roger_Mayer/RogerMayer_RM58_Stereo_Limiter.pdf)

Kind regards,
Martin

(PS Contains unverified RM-57 schem.....)
Title: Re: Roger Mayer RM57 build?
Post by: Biasrocks on February 02, 2013, 10:07:03 AM
It looks like we're close to solving this, including PCB etching.

Would love to build this.

Anyone make progress on this guy?


Regards,
Mark
Title: Re: Roger Mayer RM57 build?
Post by: barclaycon on February 02, 2013, 02:06:06 PM
Hi Mark.
I gathered a fair bit of information on this unit - including the very useful stuff you had.
I still didn't find out about FET selection though.
I'm sure there must be some specific criteria for correct operation. (Pinch off voltage etc.)
As you know, the man himself turned out to be very rude obnoxious type who wasn't prepared to help in any way, and tried to make out that this unit couldn't be built these days - then went and revived the unit as a stomp box product! (check his website).

Anyway, I'll be very interested to see how you've got on with this.
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 01, 2018, 11:49:06 AM
Do we have any news on this project?
This is really high up on my whish list :)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 05, 2018, 05:28:04 AM
I’m very interested in building this as anything Eddie Kramer uses or used I’m mad on!!
I built stereo version of the pie compressor and it turned out pretty good, I use it on over heads and acoustic guitar and it sounds fat and thick.
This could also be a great compressor for my studio.
I’ll take a look at the schematic and see if I can eagle something up and also track down what values are missing.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 05, 2018, 09:11:13 PM
If we could get some photos of a working unit perhaps please?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 04:26:36 AM
how does anyone feel about me making a parts list and as long as it can be done on single layer pcb, i can make the pcb and populate, bearing in mind i would need some support from people who can check through what ive done so i havent made any mistakes.

thoughts?
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 06, 2018, 06:54:41 AM
Well count me in of course.

There's this Italian company Side-B Studio in Italy (https://sidebstudio.it (https://sidebstudio.it))
They've apparently managed to clone the RM57.
Looks like a single sided PCB too.
So it must be feasible.

Also the part count is so low and no transformers are involved.
This could be such  a fun project while being super affordable :)
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 06, 2018, 06:55:17 AM
Gut shot of the "b-side studio" clone.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 07:28:29 AM
thats great stuff could you also detail the power supply please and value of the VU meter?

also any higher res closer photos always help, need some values on a few things but let me go through it for a few hours and then i can put up a list of things to find.
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 06, 2018, 07:30:09 AM
No - that's all I could find on their HP.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 08:02:22 AM
ok well the first problem is that the first schematic is quite different form the last (scribbled) drawn schematic.
they share a few similarities but i'm going to stick with the first one for the time being, its on page 5 of the pdf.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 08:12:00 AM
Ok so far from page of the pdf I'm missing or not sure of the following values:

R34 is it 2.21 ohm or 2.21k?
C4 ?
Q6, Q7, Q8, Q9 transistor?
Q10 and Q14 fets?
Q15 ?

i can see the release is a lorlin with resistors for set release times, this should be fairly easy to work out.
Im going to check on the available parts for transistor equivalents and diodes, if someone could take best guess or check on a working unit perhaps?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 08:32:20 AM
here is the parts list so far
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on November 06, 2018, 09:29:25 AM
Good luck you guys ! too busy to help right now.. but i'm very interested in this project
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 03:26:18 PM
yeah, i just downloaded the other pdf from freestompboxes so i'll take a look through that and see what gives.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 07:03:41 PM
right i've put the schematic in eagle and i will play around with layouts, just need to verify what transistors to use and what two JFET's are used or equivalents.

I have all the other information now i think.

regards

Spence.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 06, 2018, 09:28:30 PM
this is the list i've put together, if everyone could check it and let me know any errors please.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 07, 2018, 05:29:25 AM
here is a screen shot of the schematic laid out as per the picture of the insides, please let me know if you spot and issues or mistakes.
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 07, 2018, 06:10:32 AM
Looks like you're on a mission - cool!
Will take a closer look at the schematic.

In the meantime, here are a couple more gut shots of actual units.

It's probably noteworthy that styroflex capacitors were used in some places.
Also some metal transistors transistors are different in the L/R channel cards of the very same unit.

Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 07, 2018, 06:12:05 AM
Card 1:
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 07, 2018, 06:13:17 AM
Card 2 of the same unit:
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 07, 2018, 07:13:20 AM
great stuff, i've abandoned eagle and i'm learning and using easyEDA now so a little learning curve but will get there, thanks for the new gut picks!!! looks great
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 07, 2018, 03:15:26 PM
have to ask, but is there anyway i could get a picture of the back of those pcbs please?
Title: Re: Roger Mayer RM57 build?
Post by: thomasdf on November 07, 2018, 03:39:47 PM
A huge THANKS to you for getting seriously into this. Can't wait to see where it goes, this puppy has been on my which list for years. I don't know how I can help, and I don't have much time but let me know if there are things I can do. Can be prototyping, stuff like that.
Best from Paris,
Thomas
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 08, 2018, 04:45:02 AM
I’ve put together a circuit from the first picture but will see if I can do the card one first over the weekend
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 08, 2018, 12:16:19 PM
Only thing I’m missing is what are all the transistors and jfets?

I think we could use 2N2222 and BD139 and Jfet is J201?

Could anyone find out please?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 08, 2018, 04:44:36 PM
Thought id do a rough version!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 08, 2018, 05:46:18 PM
I’m going to use 2N2222 in replacement of the 2N3391 from the originals, the 2N697 I will replace with BD139 or try a 2N3053 as per 1176 output transistor and use J201 for the jfets.
I’ll make a few pcbs and populate with 0.5W resistors not sure yet if I could get away with 1/4w?
Pretty sure I have most of the bits here to mock up, hopefully this will turn into a nice project!!!
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on November 09, 2018, 05:40:04 AM
This is great, keep it up !
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 09, 2018, 06:41:24 AM
Other replacements are diodes to1N4001, 50uf/40v to 47uf/35v
200uf to 220uf/25v.

I notice one card has D1 and the other just uses a jumper.

Everything else so far I’ll keep the same.
Corrected a couple of things from the original documents as well as there was some mistakes.
Have tidied it up a bit and will print off a pcb, then drill and populate!!!
Title: -
Post by: mig27 on November 09, 2018, 06:51:15 AM
Biiig thumbs up - your efforts are much appreciated!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 09, 2018, 09:45:42 AM
Let’s get the circuit working first then see how it sounds, for drums I’ve read it’s fantastic, bit of a one trick pony but all the albums it’s been used on I love so it’s a must for the studio.

Running it parallel on kick, snare overheads and getting it pumpin!!
Title: Re: Roger Mayer RM57 build?
Post by: jarvis on November 09, 2018, 01:23:56 PM
Thanks so much for all your work on this, excited to hear how you like it!

Best
Jannis
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 10, 2018, 07:30:23 AM
have done both pcbs now, the main pcb and the driver amp pcb, will now print off and make!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 10, 2018, 11:40:02 AM
Will finish pcbs tomorrow, getting parts together.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 10, 2018, 11:40:50 AM
Few more bits I’ve found I can use!!!
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 10, 2018, 12:37:37 PM
Old school baby, love those PCBs!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 10, 2018, 12:56:02 PM
GARBAGE COMPRESSION
One of the not-so-secret pieces of outboard that has helped define Garbage’s sound is the Roger Mayer RM58 compressor. Butch and Billy swear by it for drums.

Butch: “If you listen to the drums on the end of Amends, they’re hammered through the Roger Mayer, which blows them out in a cool way. Whenever the drums get really loud, like on Empty, it’s probably mixed in 50% on one of the buses.

“I found it when I was producing Sonic Youth’s album Dirty in New York City. The engineer, John Siket, knew this gear broker who had a bunch of weird gear out in Brooklyn. I went out to his pad and he said, ‘You should try out this compressor, man.’ It was a $500 solid state compressor. I took it to the studio, plugged it in, and to me, it made everything sound like early The Who records. It had this wild, but cool, crunchy out of control sound. So I bought it. I’ve used it on so many records, but it’s got a specific sound, so you either have to embrace it or not.”

Billy: “Roger Mayer made these compressors in the late ’60s when he was making a bunch of console parts around New York. They’re super fast solid state compressors that admittedly don’t really sound great. I called Roger Mayer up about it and he said, ‘Why would you want to use that?’ When you put it in the most extreme settings, it’s got the most glorious drum sound. We scoured the planet for these things and we’ve got three of them now, Butch has got one and I’ve got two. They’re beat to hell, the VU meters don’t work, and it only ever works when everything’s cranked to 10. If you run it as a parallel compressor on the kick, snare and toms, and a little bit of room mic, it creates this sound I haven’t heard on anything else.”
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 10, 2018, 07:15:05 PM
Ive just done a new pcb which includes both boards more like the Italian studio pictured pcb, looks much better and has a smaller foot print, looking like i'll probably make quite a few of these!!!
Just missing some pots and we should be good to go ahead and start testing.

I've settled on either the 2N2222 or 2N3053 for the NPN transistors, 2N3906 for PNP and 2N3819 for the JFETs.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 12, 2018, 06:23:31 AM
before putting this together i just wanted to ask a couple of thing, as all the schematics are slightly different and some show points that are connected and others at the same place don't.

Q9 crossroads junction or does Q9 connect only to VR5?
Q8 Emitter junction connection only to R12 or to C6 and R10 as well?
Q7 to V+ or connection to C4 and Q6 emitter and R9?

I have gone with Q9 connects to VR5
Q8 emitter to R12
Q7 to V+

just wanted conformation on this incase of mistake?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 12, 2018, 12:41:06 PM
Done a couple of boards today and populating now but just seen part of the schematic which I haven’t included!!!
Will make up the extra part!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 12, 2018, 01:37:29 PM
My mistake I’m just missing the 18v regulator, I can do this another way.
Will try and build Psu tomorrow then finish populating , then I will test!!!
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 13, 2018, 05:52:01 AM
Just took a closer look at this and it seems that you got it just right.
Keep up the good work!



before putting this together i just wanted to ask a couple of thing, as all the schematics are slightly different and some show points that are connected and others at the same place don't.

Q9 crossroads junction or does Q9 connect only to VR5?
Q8 Emitter junction connection only to R12 or to C6 and R10 as well?
Q7 to V+ or connection to C4 and Q6 emitter and R9?

I have gone with Q9 connects to VR5
Q8 emitter to R12
Q7 to V+

just wanted conformation on this incase of mistake?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 13, 2018, 08:53:13 AM
Still getting parts together but getting there.
Edge of the pcb I will tidy up.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 13, 2018, 10:34:20 AM
Just missing some 0.47uf tantalum caps and gotta build Psu and case tomorrow.
Hopefully by the weekend should be putting some sound through it!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 15, 2018, 12:46:20 AM
Need to finish 18v Psu and missing a couple of pots.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 15, 2018, 10:17:21 AM
Just out of interest what’s the s/n like on these compressors?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 06:22:53 AM
Have powered up , no smoke but signal doesn’t pass yet!!!
Will go through and see if I can find what the problem is.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 08:09:46 AM
So far I can’t get signal past C19!!
Just goes horrible after Q11?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 08:28:03 AM
Right first problem, I need p channel jfets!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 10:25:18 AM
would appreciate some help if anyone can.
here is my pcb with values, could you guys check this please?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 11:51:40 AM
now looking at the drawing of the schematic, R16 and R17 are connected to Q9 base and it gives a voltage of 3.64v at that point
and it connects C6 +side to Q8, R12 and R10

Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on November 16, 2018, 01:42:24 PM
The junction of R16 and R17 is going nowhere on your PCB...
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 02:52:55 PM
Yeah sorry I rubbed that bit off but on the pcb it’s there along with the other connections I’ve just said
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 03:06:26 PM
Sorry Ian, try this one, if you can find my mistakes i would be very grateful.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 03:14:01 PM
this is the drawing schematic which i'm taking it off
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 16, 2018, 03:21:38 PM
and heres the other.

i've used 2n2222 for the NPN general transistors and a 2n3906 for the PNP, the Jfets ive used J201 but not got any signal past Q11 yet?
Ive got some 2N5088 which could be used which are quite similar to the 2N3707 which you can see on the schematic.

From what i've seen the JFET used was a 2N5461 which is a P-channel which maybe different from the N-channel one i've used?

If anyone could explain why one would work and one wouldn't i would appreciate it.

Just need to clarify the circuit first and make sure i've done the connection correctly, then i can start messing around with slightly different transistors.

any help on this is much appreciated.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 02:36:06 AM
My findings first are that the Jfet's are are not letting the audio pass as when i take the Jfet J201 out i do get audio to Q11.
I have tried J201, 2N5457, i have 2N5952 and K118, but im pretty sure they are all n-channel?

How have some people got this working with J201?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 03:19:37 AM
Also NTE326 seems replacement for 2n5461.
As far as I can see I should be able to take out q10 (J201) and get signal through to at least q13 emitter, but nothing on either collector or emitter of q11 yet?
Might change the 2N2222 for 2N5088 and see.
Any comments yet?
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on November 17, 2018, 05:35:21 AM
Some thoughts:

It might be useful if you drew out a clear diagram of what you used to design your board.  It's difficult for anyone to check your board when it is not to clear which diagram you based it on, & also that some of the diagrams are little more than a hand sketch.  So your interpretation may be different to mine , for example.

WIth regards to the fet selection.  I'm not sure you can just shove any old n channel fet in there.   If you go back and look at some of Barclaycons posts on pages 3 & 4 of this thread it has a little bit of info.   When you use a fet for compression they use a very small area of the transfer curve of the fet.  Therefore if the fets you are using don't have the right transfer curve compared to what the circuit was designed for you may find that the fet is fully turned on & just shunting your audio signal totally to ground.

Keep up the good work !
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 09:00:13 AM
I have detailed how I’ve done the pcb in a few posts earlier.
But I will put together a new one within some software so it’s easier to read and correct.
The main bones of contention is a few areas in the schematic which are not clear, as you say I may have I interpreted it differently from you!!!
I have ordered some p channel fets so I’ll see how they go but a good bit of discussion about a correct schematic is in order so we are all on the same page
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 10:40:38 AM
Ok, i have redrawn schematic, please check and let me know of any errors, i have gone by the hand drawn schematic off the 11 page pdf that was posted.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 11:24:55 AM
could someone explain why if i take out the first Jfet (Q10) why i cant get any signal past Q11?
Am i right in saying that signal should appear at Q13 emitter? and branch off at this point to C7 and out to L to go into the Driver Amp section.
I dont understand why the signal ends at the base of Q11? all i see on the scope is a weird shark fin waveform?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 12:04:16 PM
Finally progress, I have signal through the first part of circuit!!
Changed 2n2222 for 2n3391, bingo!!
Title: Re: Roger Mayer RM57 build?
Post by: volker on November 17, 2018, 12:42:49 PM
I dont understand why the signal ends at the base of Q11? all i see on the scope is a weird shark fin waveform?

Because Q12 collector isn't connected to R27.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 03:58:48 PM
Lol! Mistake on my drawing!!!
It is connected, will adjust, thanks for spotting that, any other errors?
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on November 17, 2018, 09:24:08 PM
could someone explain why if i take out the first Jfet (Q10) why i cant get any signal past Q11?
Am i right in saying that signal should appear at Q13 emitter? and branch off at this point to C7 and out to L to go into the Driver Amp section.
I dont understand why the signal ends at the base of Q11? all i see on the scope is a weird shark fin waveform?

Unlikely you'll get much on Q13 emitter becauset here is no way for the signal to appear here because the signal isn't connected to the base of the Q13.  Its base is tied to what I think is +v therefore the transistor is switched on hard.   
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 17, 2018, 11:39:35 PM
As I said previously that is a mistake, I have corrected, q13 base is connected to q12 collector and R27

see new version below.

Also i now have good signal going through unit to Q1 so the 2N3391 transistors seem good, just need to look at the amp driver section.
My 2N3906 could be duff as i've reused it, waiting on some other info on transistors so hopefully within the next few days will get p-channel jfets and know what transistors to use, so far circuits looks like its close.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 19, 2018, 03:16:21 AM
I have all the transistor values now and some little corrections.
Will test this morning and feedback.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 19, 2018, 05:21:07 AM
right, just tested and getting good signal through the circuit, i don't have the Jfets in yet so im assuming the waveform looks a bit all over the place due to this?
I replaced all 2N2222 for 2N3391 and replaced the PNP for a BC560C, these are not the correct transistors but what i had to hand just to test the circuit.
Im not out of the woods yet as i wait for the p-channel jfets to install and see what happens with the waveform and the VU meter.
I will update schematic with correct transistor values and post.
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 19, 2018, 05:24:00 AM
Again, thanks so much for sharing your findings!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 19, 2018, 05:31:48 AM
here we go, so far this seems to be correct, i'll know more like i said once i get those p-channel jfets in there!!!
Title: Re: Roger Mayer RM57 build?
Post by: pvision on November 19, 2018, 08:00:01 PM
Watching with interest but not really competent to help! Good work so far, I'd say

It might just serve to confuse but, if you want something to compare against, the Orban 418A is a very well thought-through piece of kit

https://archive.org/details/orban_418A_Manual

Nick Froome
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 20, 2018, 05:57:37 AM
from what i've read about N-channel vs P-channel Jfet's, the N-channel jfets's are cutting the signal due to positive voltage so closing the gate, if the drain is more positive than the source it turns the jfet on (shuts the gate, cutting signal)

This circuit needs P-channel jfets so if the drain is more negative than the source it will shut the gate, i dont really understand how it goes more negative yet, but perhaps someone could explain?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 20, 2018, 06:39:39 AM
Also just to note that I get good signal up till Q1 base, after that it goes screw wiff!!!

Also whenever i connect A100k pot for threshold control waveform comes and goes? when i touch pin 2 the waveform comes back?
Ive checked GND connection and are fine, then when i bypass the A100k pot and connected the wires together it fine?

dodgy pot? i thought so so i tried a couple more, same problem?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 20, 2018, 08:11:26 AM
ok i have found one problem!! 3.3k at R62 rather than 330R, now i get great waveform at output.

Just need to sort threshold pot and hopefully get these p-channel jfets soon!!

update:

sorted pot problem, must have either been a dodgy wire or could have been my scope playing up!!!
seems fine now apart from i need a new probe!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 22, 2018, 07:45:55 AM
well i seem to have a working compressor!!!

If i can sort out this dodgy batch of A100k pots i should be in business.

I'll start putting in a case now and then test, then take in the studio and do some recording!!!
Title: Re: Roger Mayer RM57 build?
Post by: mig27 on November 22, 2018, 08:45:37 AM
Congrats!
Please do share some sound samples!
Title: Re: Roger Mayer RM57 build?
Post by: thomasdf on November 22, 2018, 09:56:51 AM
Great news ! Kudos !
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 22, 2018, 12:00:36 PM
I've done a little video but before i show you the first test, i do need to look at my PSU i think.

I am getting noise and haven't used screened leads for input and output!!

my PSU is really simple so i think i need to put a bit more filtering in!!

at the moment its just IEC into switch, pilot light into 18v TXF, into bridge diodes (1N4007) then 1000uf/50v electrolytic, then 7818 regulator then 470uf/50v electrolytic. I had diode from input to output for protection and that it!!
should probably up the 1000uf to 2200uf? and then have a 330nf cap before input to regulator then after output of regulator put 100nf cap.

whats your thoughts PSU wise for 18v dc nice and clean?
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on November 22, 2018, 12:23:36 PM
There shouldn't be any problem with using the PSU as is.    An old boy radio engineer once said to me use 1000uF per amp, I normally have several times that per amp on the PSU's I make.  You won't be drawing anything even close to an amp.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 22, 2018, 12:34:12 PM
Ah ok, thanks Rob, i'll try and use the screen leads on input and output and see if the noise improves.

Meanwhile here is where i'm at!!!


https://www.youtube.com/watch?v=c4ZHW6nZwtA
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on November 22, 2018, 07:11:00 PM
That's sounding FAT !
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 12:47:12 AM
My jfet choice for q10 and q14 is 2N5461 and I have BC560C in Q1 , q2 and q3 are 2N5088.
All others are 2N3391, I’m checking with Dan that my transistor choices are ok.
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on November 23, 2018, 04:43:57 AM
Thanks for your hard work!!! It looks like there is R19 22K in your schematic insted of 220K (value from original schematic). Values of R8 and R9 are reversed. R38 should be 3K3. R35 = 5K6 in original schematic. R27 = 47K. R24 = 1K2.

Pleas can you update your schematic with final choice of jfets and transistors?
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on November 23, 2018, 05:49:19 AM
wooooohohoh !! I like that !
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 06:31:00 AM
Vac11, nice one for spotting those, I’m changing them now and will update!!
Thank you.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 07:09:49 AM
here is updated schematic,

will see what changes have improved and report back, thanks again for all your input.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 07:35:26 AM
mmmm. now it doesnt work, waveform all over the place and vu meter all the way to right with only adjust more to the right!!!

back to the drawing board!!
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on November 23, 2018, 09:25:40 AM
I think it will be difficult to obtain correct left/right tracking for stereo, since there is no adjustment to get the tracking right.
So: it only depends on the parameters of the FETs.
Ideally, you should have 4 exactly matched FETs, if you want the meters to indicate the effective gain reduction.
(My experience is that you need something like 25 FETs, to obtain a matched quad.)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 09:43:05 AM
I’m not that interested in stereo unit yet, just want to get this working correctly, but thanks for that info, well worth matching some FETS eventually once the unit is working correctly.

It was working but I had a few mistakes of different value resistors.
Now I have corrected them all it doesn’t work again!!!
The first part of the circuit which I’m thinking is the preamp I don’t get clear waveform at q13 emitter so I’m going to disconnect and go through each section again!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 09:44:53 AM
One quick question, these p channel jfets, should source go to gnd or drain?
Drain to gnd right?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 23, 2018, 03:46:14 PM
Well, would be glad help to this thread ;)

One quick question, these p channel jfets, should source go to gnd or drain?
Drain to gnd right?
Should be source to gnd.

Made a quick test in LTspice with RM input chain. It also shows P-channel fet principle.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 07:08:27 PM
ok, well i'm completely foxed with this at the moment, i'm getting signal through but the signal just seems to move and wobble, no compression, release and attack do not function but i can measure the 5v at B (with release at slowest) going into both the attack and release pots and the trim pot works to adjust this voltage.
maybe I have blown the 2N5461?, not sure but the VU meter just sits too much to the right? Q4 and Q5 have -0.4v and -2.8v on base? and 0v on collectors?
Im not measuring any voltages on jfets?

the weird thing is that before i changed the following it was kind of working!!??

R19 was 22k changed for 220k
R8 was 12k changed to 1.2k
R9 was 1.2k changed to 12k
R38 was 2.2k changed to 3.3k
R35 was 8.2k changed to 5.6k
R27 was 22k changed to 47k
R24 was 12k changed to 1.2k

And i think  i had FETs drain to gnd!!
Meanwhile i wait on some more jfets!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 23, 2018, 07:14:49 PM
Q11
E - 2.4v
B - 2.9v
C - 3.8v

Q12
E - 3.2v
B - 2.9v
C - 5.8v

Q13
E - 5.2v
B - 5.9v
C - 18.6v

Q9
E - 0.9v
B - 1.5v
C - 2.1v

Q8
E - 2.0v
B - 2.1v
C10.7v

Q7
E - 1.4v
B - 2v
C - 18.8v

Q6
E - 12v
B - 10.8v
C - 18.7v

Q5
E - 0v
B - –0.4v
C - 0v

Q4
E - 0v
B - –2.8v
C - 0v

Q1
E - 7.9v
B - 7.1v
C - 5.6v

Q2
E - 5.1v
B - 5.7v
C - 18.4v

Q3
E - 4.4v
B - 5.1v
C - 10.7v

Q15
E - 2.2v
B - 2.8v
C - 15.3v
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on November 26, 2018, 05:46:07 AM
Normally speaking you should be expecting to see around 0.6-0.7v between the base and emitter.  This could be + or - depending on whether it;s an NPN or PNP.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 26, 2018, 06:58:59 AM
Yes I’ve used that rule before to fault find,  thanks for reminding me!!
Looks like I have problems with Q1, q4, q5, q6, q8 and q12.
Q4 and q5 seem worst off?
Along with q4?
Q8 not good either!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 27, 2018, 07:53:27 AM
well i've taken out the fet's to just look at signal and replaced Q4 and Q5 for 2N2222 this is the waveform i get at output.

The waveform seems chopped? on the scope at Q12 it looks this way so i'm going to poke around and see if i can see anything, but if anyones got any ideas?

Also would a J175 P-channel work? seems to have a slightly higher rating than the others?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 27, 2018, 09:45:33 AM
Here is my quick LTspice emulation. I used 2N3391A spice model for all NPN's.
Less sidechain control voltage (Vsc)  = more compression.
So... in theory compressor compress 8)
Output 200Hz sinus looks pretty distorted, so may be not ideal transistor models +  same model everywhere, what could be non optimal.
 
 
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 27, 2018, 02:09:07 PM
Are you able to try q2-q3 to  2n5088
All other NPNs to 2n3707, see how it looks then?

Also was there a reason you used 200hz rather than 1k?

Some of those voltages might come in useful.

I’ll try a bc550c for the VU meter, I’m on version 2 now so will check everything tomorrow.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 27, 2018, 04:29:13 PM
Are you able to try q2-q3 to  2n5088
All other NPNs to 2n3707, see how it looks then?
I need to check  2N5088 spice model, same as 2N3707.

Also was there a reason you used 200hz rather than 1k?
I'm using 200Hz for emulation compressions because that's necessary to check time characteristics (100ms at minimum) and in the same time it's necessary to check whats going on with wave shape and 1kHz becomes too frequent on 100ms.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 12:39:44 AM
Also your attack and release looks different.
I was getting 5v at slowest release so at 10meg.
I’ve got attack as 100k log and release says 2.2M lin but is Lorlin starting at 470k up to 10meg in 11 steps.
Could you also include the driver amp?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 02:29:56 AM
Also q11 to 2n5088
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 03:42:24 AM
Im trying BC184C today as they seem to have about the right HFE 350-400.

getting similar voltages as per LTspice but different on emitter of your Q4, I'm getting 6.8v there, all other voltages are virtually the same in that part of the circuit.
Will test other voltages and see where it differs.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 03:43:41 AM
here is an output amp.
15dB gain, headroom up to 6.8Vrms = 18dBu
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 04:11:17 AM
second emulation with corrected VT's.
preamp have pretty low headroom.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 04:18:54 AM
interesting that your getting flat bottom half of waveform as well, as that is what I'm getting?

could you post a picture of Q4 emitter waveform please.

also could you try submitting 2N3391 for BC184C see how it looks as bit different HFE on BC184C
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 04:22:09 AM
and here is corrected preamp for better headroom. R18 changed from 47K to 33K
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 04:23:21 AM
interesting that your getting flat bottom half of waveform as well, as that is what I'm getting?
see preview image.

could you post a picture of Q4 emitter waveform please.
also could you try submitting 2N3391 for BC184C see how it looks as bit different HFE on BC184C
give me a couple minutes)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 05:20:11 AM
ah ha!!, R18 i knew something was wrong here, just didnt know which way to go!!, will change and look at waveform!!!
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 05:21:08 AM
also could you try submitting 2N3391 for BC184C see how it looks as bit different HFE on BC184C
Swaped 2N3391A to BC550C (witch is close to BC184C). Absolutely the same result, same voltages.

Found that changing detector input pot from 100K to 1R improve RM output waveform and make it more symmetrical.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 05:31:03 AM
changed R18 from 47k to 50k trim then trimmed down and have lovely symmetrical waveform now!!
just need to wait for some FETs to arrive then i can get some compression going!!!
thanks for all your help so far dude.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 05:32:00 AM
are you able to test with 2N5461 FET or other p channel FETs? J175?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 06:33:30 AM
One pcb i have trimmed R18 (47k) to 15k and the other pcb i have trimmed to 20K, might be better to leave it as trimmer in case of tuning later.
PCB A with 15k as R18 has BC184C as the 3 transistors for the preamp, PCB B has 20k and has 2N5088 as the 3 transistors.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 08:03:45 AM
changed R18 from 47k to 50k trim then trimmed down and have lovely symmetrical waveform now!!
thanks for all your help so far dude.
yap, yap, yap! glad to hear that!)

are you able to test with 2N5461 FET or other p channel FETs? J175?
it all depends on the availability of their models, will check

Additionally I can say that I've tried to replace all NPN's (preamp and detector) to BC550 and... no significant changes occurred. So you can try BC184/BC550 everywhere.

Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 08:09:51 AM
Here is 2N5461 emulation. It has a significant lover threshold, start to compress at much lover levels.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 08:54:11 AM
Yes I found the 2n5461 compressed at lower levels and ended up squashing it to nothing!!
I’ll wait for some 2n3820 to arrive!!!

Is there a way to adjust for the compressing of the 2n5461 at lower levels?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 08:56:59 AM
Could you try a J175?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 28, 2018, 09:44:38 AM
Could you try a J175?
J175 smashing even more)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 10:20:03 AM
Could you try a NTE460, don’t worry, I think it’s safe to say the 2n3820 is the one to go for.
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on November 28, 2018, 10:42:52 AM
Where to buy 2N3820? Is there a modern standard available equivalent ?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 01:02:43 PM
There seems to be loads on eBay, don’t think there is an equivalent?
Anyone got any other info on this?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 28, 2018, 09:12:57 PM
Quick question about putting a bypass switch on here.
As this circuit is basically a 1176 rev d can I add a switch into the GR control amp circuit as per the 1176 to bypass compression?
What I mean is, is this the best way to bypass the compression?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 29, 2018, 01:17:31 AM
Quick question about putting a bypass switch on here.
As this circuit is basically a 1176 rev d can I add a switch into the GR control amp circuit as per the 1176 to bypass compression?
What I mean is, is this the best way to bypass the compression?
Best way to add “active” bypass, when signal will pass thouth preamp/amp is ground detector input. Same principle as in 1176, yes. That mode will allow to distort preamp (as it has headroom just about 2.5Vrms) for additional coloration.
Better way - true bypass with in/out relays.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 29, 2018, 03:59:42 AM
Also I’ve found a P1086 p channel jfet is this any good compared with 2n3820?

Are you able to simulate Gary?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 29, 2018, 05:24:02 AM
Also I’ve found a P1086 p channel jfet is this any good compared with 2n3820?

Are you able to simulate Gary?

Okey, I will :-\  ;D
you have all of them on hands?)
2N3820 looks good and used in original.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 29, 2018, 07:13:33 AM
just trying to cover every base, and you never know we might come across one that good for a certain thing? people might want to build one for instance with the 2N5461 as it really smashes it, they might want that effect.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 29, 2018, 08:21:56 AM
Here is P1086 emulation.
Looks like 3820 the softest one ;D
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 29, 2018, 08:27:38 AM
yep, always good to check!!
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on November 29, 2018, 10:26:07 AM
Thanks dirty1_1garry!!! It is nice info.

Do you think its possible to public full resolution schemo from you LT Spice project? It coul be helpfull for us who will try this circuit...
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 29, 2018, 10:35:23 AM
Thanks dirty1_1garry!!! It is nice info.

Do you think its possible to public full resolution schemo from you LT Spice project? It coul be helpfull for us who will try this circuit...

Here is a print from LTspice's last project.
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on November 29, 2018, 01:09:07 PM
Tnank you very much. Is there any reason to use 2n5088 for q12, q13 and q11 instead of BC550C?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on November 29, 2018, 01:15:57 PM
Only difference will be hfe I reckon.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on November 29, 2018, 01:18:02 PM
Tnank you very much. Is there any reason to use 2n5088 for q12, q13 and q11 instead of BC550C?

In LTspice world there are no significant differences.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 02:45:29 AM
Just to note my only difference in cap values so far is 6.8uf rather than the 4.7uf in the driver amp.
I was told some time ago that as long as your fairly close to the desired value but higher should be fine!?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 03, 2018, 03:10:24 AM
Just to note my only difference in cap values so far is 6.8uf rather than the 4.7uf in the driver amp.
I was told some time ago that as long as your fairly close to the desired value but higher should be fine!?

Better way to know - emulate it! 8)
And... I can say that there is now difference at all in LTspice.
There are a couple important caps:
- coupling capacitors. In theory should be high quality for good sound. But as RM is more on the dirt side, any lytic will work here.
- 0.47uF on the gate of input jfet.  It set time characteristics (attack/release). Better to use tantal cap here for more stable time.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 04:20:33 AM
Yep I’ve used 0.47uf tants for all, hopefully I’ll get a delivery of some fets today!! Defo this week.
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on December 03, 2018, 04:35:33 AM
Thank you for all inputs. Here is my redrawed schematic. I will update it with new values and informations you are saying here. I think there is bad direction of C8 now...

M.

Edit: C8 polarity changed, Some values changed.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 03, 2018, 08:55:09 AM
I would remove T4..T6 and increase the gain of IC2A.
The same goes for Q11..T3. This could be replaced with a single OpAmp stage.
We have better OpAmps nowadays...
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on December 03, 2018, 09:06:54 AM
Yes it is possible of course... I just want to preserve "discrete signal circuit" as is and add balancing und debalancing of compressor in the simplest way from my point of wiev and experience...  ;)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 12:41:57 PM
I see you have added a section after the driver amp?

when i had mine working there was plenty of output, what is the point of this bit that you have added exactly?
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on December 03, 2018, 01:29:39 PM
Pleas check here:
https://groupdiy.com/index.php?topic=29333.0
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 02:27:05 PM
Ah so your going from unbalanced to balanced?
I have a few line balance boards I can use left over from my old ssl 9 k builds.
This will lower noise? But might look at that design as it might me better.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 03, 2018, 02:45:52 PM
Best way to achieve input/output balancing is with the THAT line receivers/transmitters.
In that case your inputs and outputs will behave like transformers.
With the 'OpAmp inverter' circuit, you will always get level differences when connecting inputs/outputs balanced/unbalanced.
When using the THAT chips, you can simply ground the unused 'leg' and maintain the same level.

For example: if you use the output unbalanced in the circuit shown, the level is 6 dB lower than when using the balanced output.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 03:30:54 PM
Yeah, I use the that 1646 chips, have tried quite a few different types but the That1646 seem to be the best.
SSM2142 and DRV134 are others.
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on December 03, 2018, 03:45:06 PM
Best way to achieve input/output balancing is with the THAT line receivers/transmitters.
In that case your inputs and outputs will behave like transformers.
With the 'OpAmp inverter' circuit, you will always get level differences when connecting inputs/outputs balanced/unbalanced.
When using the THAT chips, you can simply ground the unused 'leg' and maintain the same level.

For example: if you use the output unbalanced in the circuit shown, the level is 6 dB lower than when using the balanced output.

So which Thats  could you recommend for input and output balancing to preserve the unity gain?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 10:35:32 PM
That1646

http://www.thatcorp.com/datashts/THAT_1606-1646_Datasheet.pdf

Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 03, 2018, 10:58:33 PM
I got a couple of opa transformers I could use on input and output, will see how they sound, I’ll wire up balanced to unbalanced for input, and opposite for output.
Will use 1:1 ratio.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 04, 2018, 04:33:25 AM
any ideas what meter should be? VU or mA?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 07:12:34 AM
Ive used a couple of VU meters from an old GS3000 meter bridge, Fets just arrived so gonna fire up the iron and get soldering!!

Will post a video once ive got it working, fingers crossed!!!
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 04, 2018, 07:48:26 AM
Ive used a couple of VU meters from an old GS3000 meter bridge, Fets just arrived so gonna fire up the iron and get soldering!!

Will post a video once ive got it working, fingers crossed!!!

Great! Will wait your news!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 10:36:18 AM
Not good news so far , waveform all over the place, seems way to much signal, square wave on output , signs that compression is working but I need to now compare voltages to the spice diagram.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 04, 2018, 11:08:15 AM
Not good news so far , waveform all over the place, seems way to much signal, square wave on output , signs that compression is working but I need to now compare voltages to the spice diagram.

let me know if you need my emulation help
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 11:24:12 AM
The frustrating thing is that without the fets it was working fine.
I’ve used 22k attack pot, 100k threshold pot, Lorlin with 11 stage resistors going from 470k up to 10meg and 10k output pot with 330R down to gnd and 27k on other pin.
Will take a break then look again as I get the square wave on the 3rd transistor of the preamp.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 01:14:04 PM
ok voltages looks like this in preamp, would be easier if you could change all your values for the same as the original so i can be specific.

Q11
E - 4.2v
B - 4.8v
C - 5.5v

Q12
E - 4.9v
B - 5.5v
C - 17v

Q13
E - 17.56v
B - 17.05v
C - 17.82v

for me something strange is happening as Q11 and Q12 emitter voltage is lower than the base voltage which should be 0.6v higher.
Q13 Emitter is 0.6v lower than the base, which is opposite to the others?

any ideas?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 04, 2018, 01:41:25 PM
By the way: doesn't this thing produce a terrible distortion, or is this 'part of the sound'?
I mention this, because in most FET compressors, the gate of the FET is modulated to reduce the distortion.
As far as I see, no attempt is made to reduce distortion in this design.
It might be that distortion is acceptable as long as the voltage over the FET is low, but with a very low  (AC) voltage over the FET,  signal to noise ratio will get worse.
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on December 04, 2018, 03:25:30 PM
ok voltages looks like this in preamp, would be easier if you could change all your values for the same as the original so i can be specific.

Q11
E - 4.2v
B - 4.8v
C - 5.5v

Q12
E - 4.9v
B - 5.5v
C - 17v

Q13
E - 17.56v
B - 17.05v
C - 17.82v

for me something strange is happening as Q11 and Q12 emitter voltage is lower than the base voltage which should be 0.6v higher.
Q13 Emitter is 0.6v lower than the base, which is opposite to the others?

any ideas?

If Q13 is PNP then this is normal.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 03:27:51 PM
ok, nice stuff there, considerations for mods and improvements then!!!

right, my second version is working how it should so far, getting fairly good signal and compression working how i thought it should.
Fair bit of noise present but i haven't used screened leads yet as waiting for delivery of some better thinner stuff than i've got.
Im going to look at voltages on this working one and redo my other one accordingly to the working one.

So far so good!! it really compresses quite well, haven't heard it yet but thats the next stage.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 03:29:07 PM
Q13 is not PNP it NPN!! pretty sure i blew it by putting the switch of cutting of the GR in the wrong place so i'm gonna change a few bits and power up again.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 04:24:52 PM
nice one Robb, you called it!!, it was a BC560C!!! a rogue transistor in a 550C bag!!!

both sorted now, looking and working great, next phase is boxing them up and putting some sounds through them.

I need to wait until i get the new screened cable then i'll put them in a nice 2U and transfer into the studio for testing.

stage 3 will probably be making them balanced, I have a few OEP transformers i'll try but could wind my own which i may do as ive got to wind a 5002 transformer for this other 1176 rev i've done.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 04, 2018, 05:13:42 PM
This seems the right way to go for balancing:

https://www.diyrecordingequipment.com/pages/balanced-input-output-assembly-guide
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on December 05, 2018, 05:29:36 AM
Great news!!! Let us now how the comp works.

Can you tell us on which spots did you use tantals and on which electrolytics? where to use styroflex? On 2n2F and 33pF? Where ceramics?

Thanks!!

Milan
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 05, 2018, 07:22:42 AM
Sure, I’ll report back later, bear in mind this is just the first stage, I would like to improve S/N to this unit.
I know it’s never going to be a hifi compressor but I do want to get it as good as I can.
Mainly I will be using it in parallel and blending sounds with it, rather than in series, but who knows there might be some nice dirty drum sounds with a single room mic that it can fuzzy up!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 05, 2018, 07:24:10 AM
Let’s see how it sounds first, I’ll post a video of it to let you all hear.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 05, 2018, 03:06:04 PM
Ok so here is some info on my build, this may change but might be good to emulate to see if it’s different in a wrong way!!!
Attack pot - 22k
Output pot - 10k (has 27k on one leg, other has 330R on other outside leg, middle is output.
Release pot - I found 10meg was way too much, you can get away with a 1meg or 2meg pot here and the release range is much more useable
Threshold pot - 100k

Capacitors
All 0.47uf are tantalum
33pf is ceramic but could have styrene here
2.2nf is film/wima
0.1uf is film
All others are electrolytic the 4.7uf I used a 6.8uf
And the 100uf you can use 150uf

Hope that’s helps you guys.
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on December 05, 2018, 03:12:52 PM
This seems the right way to go for balancing:

https://www.diyrecordingequipment.com/pages/balanced-input-output-assembly-guide

Personally I would probably just whack a transformer on the in & out.     If you use the That's chips then you need a  +& - 16v bipolar power supply on top of the +24v you need for the RM58.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 05, 2018, 04:10:40 PM
That was my first idea, 10k on secondary for output, do I put the same but in reverse for input txf?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 05, 2018, 04:28:49 PM
Also I put the bypass switch between the output of the preamp (Q13 emitter, 1) to C7, so just disconnects the control section.
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on December 05, 2018, 04:56:19 PM
You probably want something like a 10k:10k on input & maybe 600:600 on output but I'm no expert on this  It probably depends a bit on the output stage & what its drive capability & impedance are.


 I don't have the diagram in front of me but when you disconnect the side chain for bypass what is happening tothe control point where sidechain is connected ? Are you grounding it or is it flapping in the wind ?    You may be able to look at the 1176 bypass switch for inspiration. Or use a 4 pole 2 throw switch for a hard bypass.




Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 05, 2018, 05:13:53 PM
When I grounded it first as per 1176 it blew q13 as emitter is attached, so that’s a bad way.
Disconnecting the feed to the control circuit works fine.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 06, 2018, 03:45:35 AM
When I grounded it first as per 1176 it blew q13 as emitter is attached, so that’s a bad way.
Disconnecting the feed to the control circuit works fine.

your Q13 is a preamp output VT (regards to your V3 schem). If yes, check that you ground detector AFTER capacitor C7. if you will ground it before cap you will connect Q13 emitter directly to the ground and it will blow.
Check attached sch.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 06, 2018, 02:33:44 PM
yeah i tried connecting it to gnd after the cap and it didn't work, thats why i ended up floating it.

need to make lorlin 2.2meg Lin stepped pot with 11 steps, anyone have a calculator or able to let me know values please?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 06, 2018, 02:46:48 PM
could i go with:
1 - 0
2 - 100k
3 - 220k
4 - 520k
5 -750k
6 - 1M
7 - 1.2M
8 - 1.5M
9 - 1.8M
10 - 2M
11 - 2.2M
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 06, 2018, 02:53:28 PM
could i go with:
1 - 0
2 - 100k
3 - 220k
4 - 520k
5 -750k
6 - 1M
7 - 1.2M
8 - 1.5M
9 - 1.8M
10 - 2M
11 - 2.2M
its necessary linear pot for release so your steps are Ok.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 06, 2018, 04:42:59 PM
I got the weekend off so I’ll try and finish this, also I’ll move that cap and put the switch after down to gnd.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 07, 2018, 07:28:46 AM
Also just to remember I used 50k trim pot for R27 and adjusted waveform for symmetry.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 07, 2018, 01:17:03 PM
Just for fun, I experimented today with a 2018 version of the circuit.
I replaced all transistor amplifier circuits with OpAmps. (A single quad-OpAmp can be used.)
Also I modified the circuit around the FET a little, in order to reduce the distortion.
Another modification reduced the noise significantly.
The redesign sounds pretty good...
If there is any interest in this, I will publish the circuit here in the near future.

Title: Re: Roger Mayer RM57 build?
Post by: ilfungo on December 07, 2018, 01:44:29 PM
Interested!!!
THANKS!!!
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 07, 2018, 02:39:51 PM
OK, here is the first version of the prototype. Some component values may change.

The modifications: the value of the series resistor from the input to the FET is now 18 K.
This reduces the noise significantly.

Also C3/R4/R12 reduce distortion, by modulating the gate of the FET with the audio signal.

P7 should be adjusted with the wiper of P3 to ground, in such a way that the audio signal is just not attenuated.
The correct value of the voltage over C9 depends on the FET used.  It may be necessary to change the value of R18 and/or P7.

P3 sets the level at which the signal is limited.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 07, 2018, 04:58:42 PM
Great work!!! I would be interested in hearing this, might knock up a version, if that’s ok ruud?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 08, 2018, 04:59:08 AM
Feel free to build one!
It may be necessary to optimize some component values, but the result is pretty good already.
Keep in mind that the TL074 needs symmetrical power, so +15V and - 15V on pins 4 and 11.
I have calibrated the prototype in such a way that I get 1 V AC on the 'top' of P2. This means 30 mV AC over the FET.
Signal to noise ratio ('A' weighted) is in the order of 80 dB re. 1 V AC, so very acceptable.
Next thing I would like to optimize is distortion at low frequencies with fast release times. (Always a problem.)
I have already changed a couple of component values, and added a 'composite release' switch (optional).
With this switch closed, you get a fast release on isolated peaks but a longer release on more constant limiting.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 08, 2018, 09:25:42 AM
Ok my problems so far are mains hum on one channel and one channel is missing a release pot.
I must say though it’s a very musical  compression, I will try and connect up transformers to get it balanced and get both channels working the same then look at why I’m getting main hum.
Maybe I don’t have Psu connected correctly?
Or maybe I need better filtered psu?
My earth is connected to chassis but no where else, pretty sure this is correct.
Title: Re: Roger Mayer RM57 build?
Post by: ilfungo on December 08, 2018, 09:35:33 AM
Where could be the meter connected?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 08, 2018, 10:02:55 AM
In case you are referring to the '2018' version: you can use the same part of the original schematic to connect a gain reduction meter.
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on December 08, 2018, 10:12:34 AM
Ok my problems so far are mains hum on one channel and one channel is missing a release pot.
I must say though it’s a very musical  compression, I will try and connect up transformers to get it balanced and get both channels working the same then look at why I’m getting main hum.
Maybe I don’t have Psu connected correctly?
Or maybe I need better filtered psu?
My earth is connected to chassis but no where else, pretty sure this is correct.

You may be getting an issue because the unit is unbalanced.  I would try just touching a wire between 0v & Chassis ground and see if it goes, 10 sec work & you know the answer.......
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 08, 2018, 11:34:38 AM
Ok rob, good shout, will try in a bit.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 09, 2018, 04:21:24 AM
Here is a picture of an original RM57 PCB. Just in case someone wants an example of the layout.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 09, 2018, 07:11:26 AM
Question, i am getting quite a lot of compression, is there a way to reduce the amount of compression?
with attack CCW and release at fastest, bringing up the threshold does kick the compressor in quite hard, i wondered if there is a way of reducing this.

Also are we able to figure out where all the trimmers should be set or at least have some sort of guess?

Mains hum still present so far, will try another PSU and see if it cleans it up, so far having chassis connected to pin 1 gives mains hum. Haven't checked with this disconnected yet.



Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 09, 2018, 07:36:20 AM
The input of the limiter is pretty sensitive, -30 dB or so.
This is done intentionally, to reduce distortion, because the (AC) voltage over the FET should be low.
There are two ways to reduce the 'threshold':

1- Reduce the level before the input and add extra gain after the limiter to restore the level.
Signal to noise ratio will suffer.

2- Reduce the level going to the detector. (The signal going to the base of Q9. Increase the value of VR5)
Disadvantage is that the distortion will be higher.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 09, 2018, 12:50:34 PM
any idea what sort of signal to noise the original is compared to your version?

Your version sounds very promising, its a very musical compressor, i've tried it on drums and bass and so far its very fun to use, just a shame (the old version) has its limitations.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 09, 2018, 02:48:45 PM
I would like to improve the metering.
A meter range of 40 dB is ridiculous. (If someone wants to limit 40 dB, he is crazy anyway!)
Personally I think a meter range of 20 dB is more than adequate.
Another problem is that 5 dB gain reduction is about half the scale...
What I would like to see, is the use of a standard VU meter, that can be used to measure the output level OR the gain reduction.
In such a way that the meter indicates 0 dB without any gain reduction going on, and the needle moving backwards when gain reduction occurs.
It seems this is the way how it is done in the newer issues of the RM58. (The mono box.)

And about the signal to noise ratio: in my "2018" version this is close to 80 dB re. 1 Volt. ("A" weighted.)
This value is also mentioned in the specifications of the original, but I doubt very much if this is true...

By the way: interesting to see what the going price of this compressor is nowadays: €7,714.85 for a handful components...
https://reverb.com/item/11866606-crazy-rare-roger-mayer-rm-57-stereo-compressor-from-the-record-plant-in-nyc-modded-bra  ;D
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on December 09, 2018, 03:35:48 PM
Thank you Ruud, for your work and great info. Pleas could you recommend us input and output transformer for balancing  input and output of original circuit? Which ratio? Resistance of primary and secondary?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 09, 2018, 03:51:07 PM
If you would like to add an input transformer, I suppose a 1:1 input transformer with a specified impedance of 10 K would be suitable.
Because the input is pretty sensitive, it might be a good idea to put an attenuator in front of the transformer.
This way the signal level for the transformer will be lower.
(For example 3.3K in series with each input wire, and a third 3.3K resistor in parallel with the primary.
This will produce about 10 dB of attenuation and lowers the LF distortion in the transformer.)

For the output you should think about a 1:1 transformer with a specified impedance of 600 ohms.
Because signal levels are pretty high here, the transformer should have a core that is not too small.
A small modem transformer will work, but you will lose the lowest frequencies.
Also the core will saturate at low frequencies.
Most standard audio line level output transformers will work fine.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 09, 2018, 06:57:30 PM
Would you be able to put up a drawing of how the input and output should be with transformers please.
I always find it much less confusing.

Could I use OEP 2;1 txf set to 1:1 and use resistors?
Or should I wind my own?
I have made several 10468 txf in mumetal cases with 80% nickel core which may help?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 10, 2018, 01:58:32 AM
I tried wiring up the oep txf and the output level was very low and much more distortion, so I’ve either wired it up wrong or they are not the best type for this application?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 10, 2018, 04:14:49 AM
Connection of an input/output transformer can be as simple as this.
Small transformers won't work properly as output transformer.
For input you will need a (relative) high-Z transformer, for the output a low-Z one.
Usually you will connect the balanced input- and output wires to pins 2 and 3 of and XLR connector. Pin 1 connects to ground.
The R/C at the output is optional and depends on the transformer used. (To optimize frequency/square wave response.)
Keep in mind that the output capability of a TL074 is limited, don't expect +26 dBm!
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on December 10, 2018, 08:57:31 AM
Would a 5534 be better on the output ?  At least it has some drive capability and in conjunction with a complementary pair of power transistors is quite good
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 10, 2018, 09:40:38 AM
i'm a sucker for a drawing!!! thanks ruud

would a 10468 type transformer be ok to use?
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 10, 2018, 09:56:00 AM
i'm a sucker for a drawing!!! thanks ruud

would a 10468 type transformer be ok to use?

as input? not sure. May be in backward, like this (attached). In a such connection it works as stepdown, so you will get less level and less threshold of compression.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 10, 2018, 10:45:01 AM
Would a 5534 be better on the output ?  At least it has some drive capability and in conjunction with a complementary pair of power transistors is quite good

Yes, a 5534 would give you more output 'power'.
But I used a TL074, because I liked the idea to have only one chip in the design.
Personally I would prefer the THAT receivers/drivers for balanced inputs and outputs.
Less iron = less distortion. (But maybe transformer distortion is what some people like...)
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 10, 2018, 10:48:07 AM
A 10K->600 ohm transformer will have a ratio of  ~16:1.
That means the level at the 600 ohm side is ~24 dB lower than at the 10 K side.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 10, 2018, 11:02:21 AM
A 10K->600 ohm transformer will have a ratio of  ~16:1.
That means the level at the 600 ohm side is ~24 dB lower than at the 10 K side.

I think you forgot square root.
10K:600 = 4:1 turn ratio. So 1V in = 0.25V output. 12dB gain loss.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 10, 2018, 11:20:00 AM
So are you now saying ideally a 1:1 or a 2:1 for input and for output it would be a 4:1 ratio?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 10, 2018, 03:26:49 PM
I think you forgot square root.
10K:600 = 4:1 turn ratio. So 1V in = 0.25V output. 12dB gain loss.

Yes, you are right!
(Is was probably too early here!  ;) )
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 11, 2018, 07:25:59 AM
Mains hum coming from shoddy PSU i've built as i have an adjustable DC PSU which i've put on and with both channels it pulls 0.18A current at 18v.
Both channels noise wise sound more than acceptable, and this thing compresses like a beast!!!

Like you said Ruud the bottom end distorts quite badly so if there are any mods which could improve this?

I'm running unbalanced as I haven't built any TXF yet!! I think the 2018 version will be a real winner if the S/N comes down and the bottom end distortion is addressed.

Great fun compressor

could someone suggest a good PSU to build please, so i don't get any ripple, i'm using a 7818.

Ive splashed out £1.28 on a proper PSU!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 11, 2018, 08:05:51 PM
Typical it isn’t being delivered until Feb!!  So I’ll have to build one!!!
Pretty easy to copy from the pictures!!
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on December 12, 2018, 04:29:11 AM
link to that £1.28 PSU ? :)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 12, 2018, 06:12:57 AM
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F263346981532
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on December 12, 2018, 12:12:07 PM
Oh ok the PSU is single rail ?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 12, 2018, 01:17:54 PM
Yeah, ive made 3 pcbs now, will populate and test in the morning as i gotta 12 hour shift to do tonight!!!
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on December 12, 2018, 01:24:36 PM
Good luck with that !
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 13, 2018, 04:58:45 AM
This is my 'more serious' prototype.  Stereo limiter on 7 x 10 cm.
Signal to noise ratio is 81 dB ("A" weighted) re. 1 Volt.
Stereo tracking is within 0.5 dB (I found 2 'matched pairs' out of 20 FETs)
Distortion is 0.3% @ 10 dB limiting (400 Hz, fast attack, fast release).
Metering circuit is 'under construction'.
It will directly take the voltage from the gate of the FET, so no extra FET for the meter circuit.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 13, 2018, 05:28:24 AM
Great work, can’t wait to hear this version.
Title: Re: Roger Mayer RM57 build?
Post by: ilfungo on December 13, 2018, 06:55:45 AM
Great work, can’t wait to hear this version.
Me too!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 13, 2018, 02:25:29 PM
My stereo version is fully operational and sounds fantastic, top tip if you can, cut at 49hz and the distortion goes away.
If there was a way of doing this within the circuit perhaps? HPF?
Title: Re: Roger Mayer RM57 build?
Post by: mjrippe on December 13, 2018, 02:32:14 PM
My stereo version is fully operational and sounds fantastic, top tip if you can, cut at 49hz and the distortion goes away.
If there was a way of doing this within the circuit perhaps? HPF?

That's awfully close to the 50Hz mains.  Possibly power supply ripple?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 13, 2018, 02:45:11 PM
No I’m meaning when you input a signal into it, the distortion is reduced.
There is no mains hum now, clean as a whistle.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on December 13, 2018, 03:11:10 PM
There is always a problem with low frequencies and fast release times.
In this case you get the situation that the release already sets in  during the waveform.
As a result, a sinewave will be converted in something that looks like a sawtooth.
The only solutions are: a longer release time, or less LF feeding the compressor.
(Or maybe: a high-pass filter in the side chain, but this means the lower frequencies will be less limited...)
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 13, 2018, 04:39:42 PM
This is my 'more serious' prototype.  Stereo limiter on 7 x 10 cm.
Signal to noise ratio is 81 dB ("A" weighted) re. 1 Volt.
Stereo tracking is within 0.5 dB (I found 2 'matched pairs' out of 20 FETs)
Distortion is 0.3% @ 10 dB limiting (400 Hz, fast attack, fast release).
Metering circuit is 'under construction'.
It will directly take the voltage from the gate of the FET, so no extra FET for the meter circuit.
Wow wow, not so fast!))
smart and beauty build, congrats!
Title: Re: Roger Mayer RM57 build?
Post by: desol on December 15, 2018, 09:40:11 AM
You guys are starting to make this sound interesting!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 15, 2018, 10:32:37 AM
Build one, or two they are really fun sounding, my version which I’m assuming is the RM57 is a bit noisy but still very useable.
I’m happy to post the pcb print for everyone to make their own, just print out with a laser printer on cheap photo paper then iron on copper clad board, then dip in some ferric chloride for about an hour, wash off then drill holes and populate!!
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 15, 2018, 01:35:03 PM
Build one, or two they are really fun sounding, my version which I’m assuming is the RM57 is a bit noisy but still very useable.
I’m happy to post the pcb print for everyone to make their own, just print out with a laser printer on cheap photo paper then iron on copper clad board, then dip in some ferric chloride for about an hour, wash off then drill holes and populate!!

Making of a sound/video samples of your final build would be great!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 16, 2018, 05:17:29 PM
Don’t worry I’ve got some time off over Xmas, some videos will be done!!
Title: Re: Roger Mayer RM57 build?
Post by: desol on December 17, 2018, 05:37:07 PM
I'm interested to hear it.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 17, 2018, 10:45:52 PM
Rather than recording it through my iPhone I’ll use camtasia and my webcam, just need to sort my internet as an Ethernet cable has stopped working!!
That way you can see protools and the compressor in action and I’ll babble along!!!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 18, 2018, 11:01:23 AM
Sorted my Ethernet problems, last 12 hour shift then 9 days off!! so I’ll start doing some stuff tomorrow morning.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 29, 2018, 10:32:22 AM
Finally got round to doing a video:

https://youtu.be/ophORxkruoo

will do a few more once i get the RM68 noise gates done.
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on December 29, 2018, 02:32:00 PM
That sounds really nice ! love it
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 29, 2018, 05:51:19 PM
Yes I think it really works parallel , need to try it out more in a session though
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on December 29, 2018, 06:44:41 PM
Did you thinked about trying to implement a mix knob ?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 29, 2018, 11:38:16 PM
I’m happy with it to be honest, only thing that would improve it would be sidechain eq.
Title: Re: Roger Mayer RM57 build?
Post by: dirty1_1garry on December 30, 2018, 02:34:39 AM
Finally got round to doing a video:

https://youtu.be/ophORxkruoo

will do a few more once i get the RM68 noise gates done.

Sounds cool!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on December 30, 2018, 03:31:41 AM
If anyone wants me to post my dodgy pcb print I’m happy too.
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on December 30, 2018, 04:20:06 AM
Of course, please do :)
Title: Re: Roger Mayer RM57 build?
Post by: desol on December 31, 2018, 07:15:46 PM
Not bad...
Title: Re: Roger Mayer RM57 build?
Post by: abbey road d enfer on January 01, 2019, 07:00:30 AM
Hey, don't you think it appropriate to rename this whole thread to Roger Mayer RM58 compressor build?
RM57 (noise-gate) is discussed elsewhere.
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on January 01, 2019, 08:27:06 AM
I'm pretty sure the noise gate is RM68, this compressor had two version RM57 and RM58, i think the difference was front panel design, dual concentric pot to separate pots.
Ive already started a RM68 post and i'm printing out pcbs at the moment.

Pcb print attached, happy new year yall!!!
Title: Re: Roger Mayer RM57 build?
Post by: abbey road d enfer on January 01, 2019, 11:58:13 AM
I'm pretty sure the noise gate is RM68, this compressor had two version RM57 and RM58
You're correct, my bad  :-[
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 27, 2019, 10:41:13 AM
My version of the Roger Mayer limiter.
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on January 27, 2019, 10:57:33 AM
looking neaaaaaaat ! Wish i knew how to make such good looking panels...
Title: Re: Roger Mayer RM57 build?
Post by: thomasdf on January 27, 2019, 12:06:06 PM
Beautiful RuudNL! Very classy & efficient design !

Would you mind sharing more info (transformers, build info) and maybe your PCB design?
I have quite a lot of unfinished project but this one has been on my wishlist for quite a while now !
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on January 27, 2019, 02:12:26 PM
Beautiful build Ruud! Congrats! Could you share schematic?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on January 28, 2019, 12:48:23 AM
That looks so nice!!! Congrats

Could we see it in action?

My version seems fine just runs better if frequency is cut at 50hz to stop it distorting a little.

Is there a way of cutting at this frequency? Say with a capacitor on a switch?
And where in the circuit would I go?
I would think it would need to go before q10?

I suppose this would be classed as a sidechain right?

I am aware that to find this capacitance the equation would need resistance and voltage but don’t know where I could implement it?

Any ideas?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 28, 2019, 04:48:18 AM
Here is the schematic of the 'modernized' version I am using.
If you would like to use side chain filtering, this can be done at the point C8/P3.
(Even inserting a lower value capacitor would work here.)
I don't have problems with serious LF distortion, as long as I don't use extreme fast release times.
The standard release can give 'agressive' limiting (when using a fast release time), but sounds very pleasant at medium or longer release times. The 'composite' release acts more as a leveller, without audible pumping.

I have added an extra resistor in series with the input, because otherwise the circuit was too sensitive with +4dB signals.
I used a quad OpAmp for the circuit. (TL074)
Signal to noise ratio is 81 dB ('A' weigthed, re. +4dBv), good enough for me.
Maximum distortion is 0.4% THD @ 400 Hz (10 dB limiting)

For stereo, it is important to match the FETs. (I found two pairs from 20 pcs.)
I used a multiturn trimpot for the FET bias, because this setting is pretty sensitive.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 28, 2019, 04:58:34 AM
And the PCB layout, as seen from the copper side.
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 28, 2019, 05:02:12 AM
And for those who can use Sprint6 files, here is the project file:

http://www.vansteenisaudio.nl/RM58.lay6

You can download a free Sprint viewer here: http://www.abacom-online.de/updates/Sprint-Layout60_Viewer.exe

Note: on the PCB design I have omitted C8, because there is no significant DC offset at the output of the OpAmp.
(And if there is an offset, this can be compensated with the 'Detector balance' trimpot.)
Title: Re: Roger Mayer RM57 build?
Post by: Vac11 on January 28, 2019, 05:21:01 AM
Oh thank you very much! Can you pleas also post how did you solve the VU meter, bypassing and input output balancig/debalancing? Do you designed your own circuit for VU meter? Which VU meter did you use?

Thank you

Milan
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 28, 2019, 06:01:19 AM
The VU meter I used is a pretty standard one (I think it was a Monacor), for the measurement of the output level it is simply connected through a 3.6K resistor to the output. (Driving impedance is low here, so no extra distortion from the rectifier in the VU meter.)
For the gain reduction measurement I am using an experimental circuit.
Without signal, the VU meter indicates 0 VU and moves back when gain reduction occurs.
At the moment I am still optimizing this circuit, because there are a few (small) problems:
- The '0 VU' drifts a little with temperature (You can see the small holes between the meters for '0 VU' calibration.)
- Indication isn't really exact. (At 5 dB a bit too much, at 10 dB a bitt too little.) Not a real problem, error is in the 1 dB range, but I would like to see the exact amount of gain reduction.

Inputs and outputs are unbalanced at the moment, because the inserts on my mixer are unbalanced.
Will be continued...
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 28, 2019, 06:54:39 AM
This is the circuit I use at the moment for the gain reduction meter:

The negative voltage on the inverting input of the OpAmp is amplified and inverted.
P1 and P2 are adjusted in such a way that the VU meter indicates 0 VU without any gain reduction.
If gain reduction occurs, the FET will conduct more and the voltage on the non-inverting input of the OpAmp will get lower.
This will result in a lower voltage for the VU meter.
The trick is to adjust P1 and P2 in such a way (they interact!) that the indication of the gainreduction is about right, and the meter is still on 0 VU without any gain reduction.

If someone gets crazy and uses more than 20 dB gain reduction, the polarity at the output of the OpAmp would change, making the needle rise again! To prevent this, a diode is placed between the output of the OpAmp and the meter.
Values are still experimental.
Title: Re: Roger Mayer RM57 build?
Post by: thomasdf on January 28, 2019, 12:06:58 PM
Thanks for giving us the key to the gold mine :)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on January 29, 2019, 02:23:26 AM
Yes I second that thomasdf, I will build your version and compare to my original design.
I’ll also try and implement the side chain on both.
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on January 30, 2019, 06:07:39 AM
RuudNL, how did you sorted the balancing/unbalancing of the unit ?
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on January 30, 2019, 12:35:15 PM
RuudNL, how did you sorted the balancing/unbalancing of the unit ?

My version is unbalanced (as was the original RM58), because I use it on the inserts of my mixer and those inserts are unbalanced.
But I suppose the best way to add balanced inputs and outputs, is to use the well knows THAT line receiver/transmitter chips.
Or real transformers, if you like...
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on January 30, 2019, 02:12:43 PM
OK just wanted to check.. I'm going unbalanced as well ;) Or might try some laying around transformers just to see what happens !
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on February 01, 2019, 06:41:54 AM
A quick demo video with my "RM58". Different release settings and pretty heavy limiting!

https://www.youtube.com/watch?v=ltjhpPj-_yE
Title: Re: Roger Mayer RM57 build?
Post by: dasnevestheo on February 01, 2019, 07:05:51 AM
Sounds neat ! Well done  :)
Title: Re: Roger Mayer RM57 build?
Post by: Rob Flinn on February 01, 2019, 10:44:24 AM
That sounds really good !
Title: Re: Roger Mayer RM57 build?
Post by: kosi on February 01, 2019, 11:14:25 AM
I second that, sounds impressive !  In your video, I was hoping you move the Attack  too ;)
Title: Re: Roger Mayer RM57 build?
Post by: mikeyB on February 02, 2019, 11:20:26 AM
Do the FETs have to be matched? That is the audio FET and the meter FET.
Great sounding unit by the way
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on February 03, 2019, 04:12:42 AM
Yes, to obtain good stereo tracking, you should match the Fets. (Since there is no way to adjust the tracking.)
In my case, tracking is better than 0.5 dB over 20 dB gain reduction.
I found two pairs out of 20 Fets.
The meter tracking circuit should use Fets that have the same characterictic as the attenuator Fets.
So in an ideal case a 'matched quad'.  (Although a small difference isn't that critical in the meter circuit, but try to match them as good as you can.)
Title: Re: Roger Mayer RM57 build?
Post by: mikeyB on February 03, 2019, 04:27:10 PM
Thanks RuudNL
Title: Re: Roger Mayer RM57 build?
Post by: RuudNL on February 04, 2019, 03:24:10 PM
If there is a small tracking error, you can cheat a little and vary the value of R1 (18K) a little.
This way you can optimize small tracking errors!
Title: Re: Roger Mayer RM57 build?
Post by: mikeyB on February 09, 2019, 10:44:35 AM
Thankyou,
Probably my next project - I've got an albums worth of drums to squash!
Title: Re: Roger Mayer RM57 build?
Post by: dmp on March 08, 2019, 11:12:53 AM
Pcb print attached, happy new year yall!!!

Hi Spencer
Can you post the final schematic you used that corresponds to this layout?
I'd like a build an RM57... heard about it in a song exploder this morning with Butch Vig.

Any thought of making this into a 500 series version?
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on March 08, 2019, 12:41:05 PM
Hi DMP,

yeah this could easily be worked into a 500 series, I think RuulNL's version would be better as its a smaller footprint on the PCB.
I haven't printed out Ruul's version yet but will do it next week, just need to design the meter for it.
The schematic is per the original and I think I shared all info?
Let me know any help you need.
Title: Re: Roger Mayer RM57 build?
Post by: dmp on March 08, 2019, 01:38:23 PM
Yeah, but you posted several schematics so I wasn't sure which one was the final. the layout says V5 but I never saw a schematic with that in the name. If the last one was the final? "Schematic_RM58-Clone.sch_Sheet-1_20181123115959.pdf"

Not sure I followed everything but RuulNL's was a different "inspired from" design using opamps instead of discrete transistors
Title: Re: Roger Mayer RM57 build?
Post by: iampoor1 on March 08, 2019, 05:48:14 PM
Yeah, but you posted several schematics so I wasn't sure which one was the final. the layout says V5 but I never saw a schematic with that in the name. If the last one was the final? "Schematic_RM58-Clone.sch_Sheet-1_20181123115959.pdf"

Not sure I followed everything but RuulNL's was a different "inspired from" design using opamps instead of discrete transistors

+1

Im having a hrd time finding the verified working schematic. Can someone repost it, or link to the post its in? My brain is just not cooperating today.  ;D
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on March 09, 2019, 12:46:30 PM
I’ll sort this Monday for you.
Title: Re: Roger Mayer RM57 build?
Post by: iampoor1 on March 09, 2019, 12:47:24 PM
I’ll sort this Monday for you.

Thanks! Super excited to buy one of these for 20$.....sure beats 8500$  ;D 8)
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on March 09, 2019, 04:35:31 PM
That’s exactly why I built it!!!
Easy enough to make the pcb, the design I’ve done could easily be made better, I was just in a rush so drew it out quickly, and at the time we weren’t sure it was correct.
I’ll put up all details of Psu as well.
Title: Re: Roger Mayer RM57 build?
Post by: iampoor1 on March 11, 2019, 07:40:49 AM
That’s exactly why I built it!!!
Easy enough to make the pcb, the design I’ve done could easily be made better, I was just in a rush so drew it out quickly, and at the time we weren’t sure it was correct.
I’ll put up all details of Psu as well.

Great!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on March 12, 2019, 05:24:27 AM
This is the schematic I did and used, transistor wise it didn't matter what i used i got the same result, BC550C, BC550B, 2N3391 or 2N5088.

For Q1 use PNP BC560c and for the FET's use the 2N3820, match them if you can.

The 4.7uf I used 6.8uf didn't seem to matter, everything else was as per original schematic.

Hope this helps and clears up any confusion, happy building.
Title: Re: Roger Mayer RM57 build?
Post by: dmp on March 12, 2019, 10:11:45 AM
Cool - thanks Spencer
Title: Re: Roger Mayer RM57 build?
Post by: Hummingwire on June 05, 2019, 06:15:53 AM
I would be very interested in building a 500 version (either RM57 or RM58) as well!
Title: Re: Roger Mayer RM57 build?
Post by: Spencerleehorton on June 09, 2019, 04:32:02 AM
Go for it and show us your build!!
Title: Re: Roger Mayer RM57 build?
Post by: diggy fresh on June 20, 2019, 08:20:58 AM
Hi Spencer,  thanks alot for the redrawn schematic. I want to try a layout but i'm a bit confused about how it goes together because nothing is labeled on your schematic.

Can you update it or tell us what the connection points are? That would be very appreciated. thanks
Title: Re: Roger Mayer RM57 build?
Post by: Fuzz Face on June 20, 2019, 08:47:18 AM
Hi Spencer,  thanks alot for the redrawn schematic. I want to try a layout but i'm a bit confused about how it goes together because nothing is labeled on your schematic.

Can you update it or tell us what the connection points are? That would be very appreciated. thanks

I was trying to use that schem as well and all of the pots are shown wired as (fixed) resistors. I guess the wipers are supposed to tie to one of the outer lugs?