New development on old project: Roger Mayer RM58

[thomasdf]

I've placed an order for PCBs Thanks again Soapfoot. Can't wait to start building this drum squasher.
For those interested (in EU preferably) I'll have PCBs leftover as the min order was 5 units.

Cheers

 

[soapfoot]

Good luck! I'm considering building a second unit for home. It's not for everything but I really do like it quite a bit when it's the right thing

 

[groselicain]

I've placed an order for PCBs Thanks again Soapfoot. Can't wait to start building this drum squasher.
For those interested (in EU preferably) I'll have PCBs leftover as the min order was 5 units.

Cheers

Good luck! I'm considering building a second unit for home. It's not for everything but I really do like it quite a bit when it's the right thing

If either of you establish a good way to go about the calibration, please include it here!

 

[richiyobs]

Good luck! I'm considering building a second unit for home. It's not for everything but I really do like it quite a bit when it's the right thing

Have you ever tried it on the master with gentle settings?
It s great... Read somewhere it was used on psycho killer, talking Heads...
For better calibration check with the Scope the mirror bjt at rectifier going to Att and REL controls
My units are still unbalanced... Also used +4dBu signal and got good calibration
There s a trimmer at sidechian input... 100k iirc... It defines your thr
Another one at the end of timing net it s the bias
Get the right meter... Or it will get strange ballistic, specially at fast attack
Hope it helps

 

[richiyobs]

these are from old simulation based on opa version.... a way for me to easy understand the circuit and both meter and detector behavior
really don t know if picked the right file, but the symmetry looks quite fine
also attached a solution i m running for a reversed meter
jfet is J175
best

 

[pucho812]

I’m behind. Possible to send me files and info?

 

[thomasdf]

@richiyobs what's the right meter ? I’ve read 300mA somewhere...

 

[soapfoot]

I’m behind. Possible to send me files and info?

Now that the forum allows larger uploads, I'll just post them here

 

[richiyobs]

@richiyobs what's the right meter ? I’ve read 300mA somewhere...

I m using 500uA... But little mods to meter driver... The best tracking is not reversing the meter and use 200uA... I posted it in other answers long this thread, just change any resistor values
If I find my last running updates I ll post again
But according to the meter you own you can adjust the amp to get the proper range

 

[richiyobs]

@richiyobs what's the right meter ? I’ve read 300mA somewhere...

https://groupdiy.com/threads/new-development-on-old-project-roger-mayer-rm58.76961/post-1027775Check the picture.... Look at the values on the left of the range.. Sorry I said 200uA... Instead is 100uA!
Pm2 100uA it s the model I m using
At Reichelt their are cheap... You can put them also in 1U rack... Also monacor make the same one
I believe is also good to fit into Gssl
Best

 

[1wildthing]

Hi guys, I have a noob question for you and I apoligize for that in advance.
As I'm not expert in Mosfet but I have to match 2n3820s, can I do that using the hFE function of my multimeter or I need to do it in an another way?

 

[soapfoot]

I did it using a cheap $20 transistor tester from Amazon. Either that did as well as needed, or I got lucky

 

[scott2000]

I have to match 2n3820

iirc fripholm's OP76 build guide had a simple test setup for matching fets. Not sure if it's relevant for this...

 

[1wildthing]

Thanks I’ll try it out!

 

[thomasdf]

This is a test of my RM58 build, still uncalibrated, but sounding very interesting on some drum tracks.

I had missed this also, I love the production, very lofi 70s (in a great way !!), kudos

 

[ashdot]

I had missed this also, I love the production, very lofi 70s (in a great way !!), kudos

Thank you!

 

[richiyobs]

Hi folks,
had time to simulate a new embarrassing version
some might think why?
cause i want to learn and undestand
really don t know if doable or a totally ********...
the idea is a mix of the opa version and the standard design for sidechain and meter

the input buffer it s from W.Jung opaBook pag 454 ( diff. line driver ) , used it also for balancing output... don t know if it s an appropriate configuration
symmetry is fine, also the meter driver seems to track better ( 500uA )
i m using 100k for Att and 10M for Rel, i know it s longer but performance seems better, more control, and if you want go back to RM57 values, you have range

the amp out should be a classB, i hope! i wanted to test...

attached also calibration at bjt mirror both fast and slow Att
of course can contain errors, still learning the long way of electronic
simulated each single part before putting together my Frankenstein
believe i will build it if someone can confirm it s doable...
best

 

[richiyobs]

Working just for fun to a 500 version of my proto
also after different attempts i finally got a simple led vu meter for reduction... it offers a better tracking respect to a standard Gr-VU, specially at fast settings when the old needle overshoot for peaks
hope it will be easy to self-etching
best

 

[MidnightArrakis]

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

I realize that you are just a "DIY PCB Designer", but I thought you might like to know that your little PCB layout contains a few instances of a "PCB-design NO-NO" and that is the use of -- acute -- angles within your routing. These -- acute -- angle routes are known as "acid-traps" and over a period of time, they can cause the copper routes to -- delaminate -- or "come off" of the PCB FR-4 material. And, of course.....this is something that you really don't want to have happen to your circuit boards, right???




In general, even though your PCB-design is "single-sided", there are lots of areas within your layout that could stand significant improvement. Would you like to receive some information on "PCB Design Guidelines, Standards & Techniques"? I have about 500MB of PDF files just on this area of design engineering alone!!! Interested???

Now.....you don't have to pay any attention to anything I make comment on here because.....what do I know??? I have only designed Printed Circuit Boards for NASA that contained thousands upon thousands of nets and required 16-layers, including multiple split "Power & Ground Planes" and U.S. defense contractors designing all manner of PCB's for "covert intelligence-gathering, surveillance and/or tracking operations" projects requiring 4-mil (0.004" or 0.1016mm) track and space routing using Surface-Mount 0201-size components.

In addition, your schematic diagram drawings could also use a fair amount of "work" in order to "bring them up-to-speed", too.

/

 

[richiyobs]

I realize that you are just a "DIY PCB Designer", but I thought you might like to know that your little PCB layout contains a few instances of a "PCB-design NO-NO" and that is the use of -- acute -- angles within your routing. These -- acute -- angle routes are known as "acid-traps" and over a period of time, they can cause the copper routes to -- delaminate -- or "come off" of the PCB FR-4 material. And, of course.....this is something that you really don't want to have happen to your circuit boards, right???

View attachment 106382
View attachment 106383

In general, even though your PCB-design is "single-sided", there are lots of areas within your layout that could stand significant improvement. Would you like to receive some information on "PCB Design Guidelines, Standards & Techniques"? I have about 500MB of PDF files just on this area of design engineering alone!!! Interested???

Now.....you don't have to pay any attention to anything I make comment on here because.....what do I know??? I have only designed Printed Circuit Boards for NASA that contained thousands upon thousands of nets and required 16-layers, including multiple split "Power & Ground Planes" and U.S. defense contractors designing all manner of PCB's for "covert intelligence-gathering, surveillance and/or tracking operations" projects requiring 4-mil (0.004" or 0.1016mm) track and space routing using Surface-Mount 0201-size components.

In addition, your schematic diagram drawings could also use a fair amount of "work" in order to "bring them up-to-speed", too.

/

Hi
As you noted I have no basic knowledge... Learning slowly from my errors
It s just a miracle I can simulate and put together components for my diy projects
Thanks a lot for making me notice what s wrong!
Of course I d like to read something more about pcb design...
Can you upload your files in tech Doc... I believe should be useful also for other people who want to learn and investigate....
Thanks for your attention
Best