From: Carl Virtanen <virtanen@uoguelph.ca>
Subject: Modding the Realistic Moog (mg-1)

Hey there!
    Well, thanks to Mark Glinsky for passing along the schematics, i was 
able to finally take the plunge and do a mod on the Moog mg-1.  I'm not 
sure about the rest of you, but doing that first mod, ie-sticking your 
soldering iron in there and hanging on for dear life, can be a very nerve 
racking experience. Especially when it's that precious little analogue 
jewel you can't afford to screw up on.  Anyways, it was a simple mod 
so relatively painless. Hence, i'm passing along the info for other mg-1 
owners:

External source filter input mod for the moog-mg1 (realistic)

What you need:
soldering iron
phillips screw driver
knife
solder
0.1 uf capacitor
short length of wire

Carefully remove the case to the mg-1 by unscrewing the screws on the 
bottom and the one in the bottom, middle, back side. This should allow 
you to tilt up the case to expose the bottom of the main circuit board. 
You'll have to take this board out as well by removing the 5 screws that 
secure it in place. Make sure you remember to take the knobs off on the 
front of the synth and be careful with the foam dust covers inside as 
they fall apart easily.
 
LocATE the level sliders for tone source1 and 2.  In between these, you 
should see a polarized capacitor (c14). Locate the (-) negative pole and 
turn the board upside down to expose the solder joint. You'll want to 
connect one end of your wire to this point on the circuit board using 
some solder.

The next step is to connect that wire to the external input. Now, instead 
of drilling a new hole, i used the right aux in from tape. To be quite 
frank, these inputs are kind of ridiculous in the first place, as they are 
only useful if you want to put your stereo through and play accompanying  
music to James Last or perhaps Santa Claus plays the Moog (one of my 
faves!). Most people will probably not miss this... ;)

So the next step is to locate the circuit board where these inputs and 
outputs are inside the mg-1. Don't bother removing the board as it's 
riveted in.  Locate the right aux input on the back of the board (should 
be the one on the far left). You should see where the centre of the plug 
connects and traces up and to the left and the outside of the plug 
connecting to the common ground:

 \   <--Using the knife, gently scrape away the trace here to sever the 
  \     connections from the positive centre of the plug to the outputs.
   |
   |\
   | |
    0   <--Next, solder one end of the capacitor to the positive (centre)
           part of the plug. 

Connect the other end of the capacitor to the wire you soldered on the 
main board. The nice part is that the connector is already grounded so 
you don't have to do any more work! Reassemble the beast and connect a 
line level input to the aux in. You should now hear it going through the 
filter! Great for shortwave, didgeridu's, or 808 toms!

Hope this makes sense to everyone. Might be a bit much but i tried to 
write it with the novice in mind.

Good luck, and all the usual disclaimers apply... Ie-proceed at your own 
risk!

Oh, and make sure you unplug it before doing all of this ;)

carl



From majortom@muc.de Thu Apr 25 12:11:08 1996
    25 Apr 96 15:10:59 +0500
    25 Apr 96 08:08:42 +0500
From: majortom@muc.de (Michael Wesemann)
Subject: Re: Joining the growing hoard of MG-1 users
Date: Thu, 25 Apr 1996 13:20:23 +0200
Organization: mw
References: <199512172004.MAA24759@taz.hyperreal.com>

From: David Johnson <djohnson@unix.ieway.com>

>It's not very flexible...unless I route it through my Quadraverb...

Don't be deceived by it's appearence. The MG-1 has a surprising
bandwith of sounds.

>Is the MG-1 truly related to the Moog Rogue...

In my opinion it is superior to the Rogue because of it's crossmod/
ringmod function (I don't know which it uses) labeled "Belltone".

The MG-1 suffers a bit from it's cheap manufacturing. I've found it's
output signal quality is higher when using the headphone jack on the
front.

For those who performed the filter input mod the following might be of
interest: after modding a friend's MG-1 this way I found that the
signal I put through lacked a lot of bass and had too much high's
instead. In my case the cause was the capacitor used in the mod.
Together with resistance from elsewhere in the circuit it acted as a
highpass filter which filtered out large portions of the bass. After
removing the cap the signal was just as I'd expect from a Moog
filter... Also it behaves in a very musical way when overdriven which
imo is another very typical aspect of Moog filters. Though it's very
different to an overdriven Minimoog filter, for me the family
resemblance is still obvious and I could imagine some instances where
I'd prefer the MG-1's overdrive which in my ears is a bit less
"brutal".

________  michael  __________________________________________________
          http://www.muc.de/~majortom/analogue/amusic.htm





Date: Thu, 7 May 1998 13:38:17 +0200 (MET DST)
From: Lothar Bittner <lothar@bintec.de>
To: analogue@hyperreal.org, ddwagner@chatcarleton.ca
Subject: Re: Mg-1 Input mod -what da smeg?

Hi,
>  
>               I was reading the posts in the AH archives, I'm about to
>  do the inpute mod myself, and am very curious about the extra 0.1
>  capacitator's function? Did anyone ever find out what it was for?
>  Someone in the archives was mentioning that they did the mod without it,
>  but there was no reply to his message saying if that was ok or a big
>  no-no!

Well, since you spotted the archives already, I had the same problem last
August, and started a small discussion on AH regarding this subject (the
mails were about "Concertmate MG-1"), and Paul Schreiber advised me to 
use a 0.47mf capacitor instead of the 0.1 one mentioned elsewhere.

The reason for it was, that the 0.1 cap takes away some bass (it forms 
a passive filter with some other components of the MG-1), and the 0.47 cap
does not, but still protects the input from DC coupling.

Or something to that effect. For technical details refer to the archives,
for installation instructions - feel free to ask me.

Oh, and yes, I did the mod, first without any cap, then with the 0.47 cap.
No directly audible differences to me... both seem to work, but the mod with
the cap is safer perhaps?


Lothar
 


