Roger Mayer RM57 build?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
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?
 
Spencerleehorton said:
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.
 
Spencerleehorton said:
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.
 
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.
 
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...
 
Vac11 said:
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.
 

Attachments

  • RM emul1.3 print.pdf
    44.2 KB · Views: 37
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!?
 
Spencerleehorton said:
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.
 
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.
 

Attachments

  • Roger Mayer RM58 schematic.pdf
    33.1 KB · Views: 53
Back
Top