Hi Greg,
should be in the archives:
http://launch.groups.yahoo.com/group/motm/messagesearch?query=485I'll try to list everything that has been mentioned.
If it's not complete PLS someone set some additional pointers ;-)
HTH, :-) Michael.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Tue, 19 Jul 2005 09:00:11 -0500
The resonance of the '485/GX-1 is done in a very odd way, and is a function of
the harmonic content of the output. There is a trim pot that allows you to
"tame" this down to a degree. The original VCF was done as cheaply as possible
using diodes as the control elements. And Sallen-Key filters sound a little odd
as well.
The GX-1 has limited waveform selection and really not that wide of a tonal
palette (I call it 'squonky'). Also, the cutoff frequency range of this topology
is not nearly as wide as OTA-type filters (it's about 100Hz to 8Khz).
But it does sound ∗completely different∗ than any other MOTM filter, and that's
a good thing :)
Paul S.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Thu, 4 Aug 2005 01:04:21 -0500
Subject: [motm] MOTM-485 typo
OK this slipped past 4 people :)
The second instruction for inserting the resistors, the resistors are 22K1 1%
(parts list and schematic correct.
Will fix it on future CDROMs.
Dave Wright has his built and squeaking like Minnie Mouse on helium :)
Paul S.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Sat, 6 Aug 2005 09:19:35 -0500
Subject: [motm] ∗∗Attention all you MOTM-485 builders∗∗
I suspect today/tomorrow is a lot of '485 activity.
I've already got several reports about "this filter acts odd" and "res pot
doesn't seem to do much", etc
It's all there in the manual :) I wrote a ∗whole section∗ about it. PLEASE read
it.
This filter ∗does not behave∗ like any other MOTM filter. Yes, it sounds very
'ring-mod-ish'. Yes, the HP mode is VERY ODD.
Yes, the Q PEAK pot is critical to getting a good resonance range.
Paul S.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Sat, 6 Aug 2005 10:31:49 -0500
Subject: [motm] Possible MOTM-485 resistor tweak
For those of you looking at building kits this weekend :)
I am going to look at a ∗possible∗ resistor change to see if I can increase the
resonance a bit, mainly for the LP mode.
So, if you want to hold off until I finish (no later than tomorrow afternoon,
will try to get it later tonight but today is pretty busy), then do so.
I don't think the change will be that dramatic, and you will have to provide
your own resistors (I'll try to give several possible values).
Grumble....diode filters....mutter......
Paul S.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Sat, 6 Aug 2005 21:48:55 -0500
Subject: [motm] No penguins = MOTM-485 mods
OK, I was supposed to see the 'March of the Penguins' movie but instead I sat at
the bench for 2 hours and tweaked.
1) the resistors in the current kit are what are used in the Yamaha modules.
2) Yamaha was never a fan of high resonance
3) So, the following mods WILL increase the resonance (especially in LP mode)
R23 was 2K2, change to 1K2
4) the following mod will allow a +5V signal into RES IN to generate much more
resonance
R15 was 120K, change to 47K (51K will also work if you have one handy)
I am going to make this s 'running change' for kits not shipped (Paul H. will
swap them out).
If you bought a kit and want to make the change and do not have access to these
resistors, send me a SASE (self-addressed stamped envelope) and I will send you
these 2 parts taped to the back of a rare, collectible business card :)
Also: please note that toggling the HP/LP switch is just like switching the MODE
in the WaveWarper: you are disconnecting multiple 'pins' from the circuit. You
will get clicks, thumps and such. There is no way around it, and it's not
'broken'. Rather, think of it as "circuit bending" :)
Lastly: the HP mode in this filter is VERY ODD, which according to Dave Wright
and Robert Rich is a good thing.
OK, everyone back to soldering.
Paul S.
--------------8<-----------------------8<-------------------
From: "djbrow54" <
davebr@...>
Date: Sun, 07 Aug 2005 05:23:58 -0000
Subject: [motm] Re: No penguins = MOTM-485 mods
Nice mods. Certainly opens up the range of the Q Peak trimmer so
you can adjust how 'gritty' you want the HP filter. I'm running
mine at about 30%.
My module seemed to be sensitive to long power leads and being
outside of the cabinet without the bracket. Seems a bit more
behaved in the cabinet with the normal power cable so I'm thinking
of opening up the Q Peak trimmer a bit more.
Photo of the finished module at
http://modularsynthesis.com/modules/motm/MOTM-485.jpgDave
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Sun, 7 Aug 2005 00:50:28 -0500
Subject: [motm] MOTM-485 with longer power cables
3 people have noted that using longer (over 20") power cords makes the '485
twitchy.
This is due to the very high impedance FET buffer picking up AM radio signals
(really!)
Use only 20" power cords, and mount the module ∗away∗ from any VCOs or Power
supplies.
I haven't tested this, but you ∗may∗ see improvement if you ∗replace∗ the 2
ferrite beads (L1/L2)
with 33 ohm 1/4W resistors AND increase C1 and C2 to 100uf (Mouser
647-UVZ1V101MED at 35 cents each).
Old Crow noted that on the BP version of this filter such a newtork was needed.
Might be worth a try (this I'm not doing as
an official change).
Paul S.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Sun, 7 Aug 2005 09:47:35 -0500
Subject: [motm] Another typo for '485 manual
OK, the OUT jack is J4 on the pc board. The instructions state 'J2' on Page 11
but obviously that isn't correct.
Paul S.
--------------8<-----------------------8<-------------------
From: "Paul Schreiber" <
synth1@...>
Date: Sun, 28 Aug 2005 22:21:04 -0500
Subject: Re: [motm] '485 resonance demo?
You have to have some sort of CV ∗input∗ first, like a LFO.
Paul S.
----- Original Message -----=20
From: Pete=20
To: motm@yahoogroups.com=20
Sent: Sunday, August 28, 2005 10:08 PM
Subject: Re: [motm] '485 resonance demo?
I only notice the resonance slightly when tweaking the freq knob down fro=
m its highest setting with the res knob all the way up in LP mode. Now with=
the filter in HP mode it really squeals! Also I set the Q peak trimmer all=
the way to the right to maximise Q. My prob is that I don't hear any diffe=
rence at all adjusting the CV Mod pot? Is there something wrong with mine?
pete
On 8/28/05, Robert van der Kamp <robnet@...> wrote:
Hi all,
I've just completed one of my '485 modules. Love the HP mode=20
(probably overdosed on King Crimson ;).
I'm not sure about the amount of resonance I get in LP mode.=20
I _do_ get some, but it's very subtle, I didn't even hear=20
it initially and had to use headphones to detect it. (May=20
also have been caused by a low freq setting, or the source=20
signal).
Anyway, could someone point me to a '485 demo mp3 in LP mode=20
where the resonance is dialed in and out?
Cheers,
Robert
--------------8<-----------------------8<-------------------
From: Pete <23isgood@...>
Date: Fri, 2 Sep 2005 23:54:17 -0700
Subject: [motm] 485 demo
Hi everybody. Check out this silly tune I made using the GX1 filter.=20
Everything is MOTM except for one sound that I used a Ken Stone Synthacon=20
filter in.You can hear the Synthacon filter, Its in the bassy grungy sound=
=20
in the middle of the song. I'm sweeping the freq of the Synthacon filter as=
=20
its output goes into the GX1 filter. The GX1 sounds very grungy when its in=
=20
overdrive. Multytracked using Ableton Live and some reverb and delay.
http://s33.yousendit.com/d.aspx?id=3D1RWZ6F6NI568Y0ORIDNIZSO9UI
pete
--------------8<-----------------------8<-------------------
Greg Amann wrote:
>Time to build my 485. I remember that when this baby was released,
>there were a few blurbs on this list aboot substitutions and tweaks.
>So my question is this: do I follow Paul's manual verbatim or are
>there any universally approved mods, tweaks etc. that can be summarized?
>
>Thanks in advance, Greg
>
>