MOTM

Folks,

I *finally* finished my 940/904A comparison.  I won't give you any excuses 
for the time it took.  The material isn't very exciting, in fact it is down 
right clinical. Please go to:

http://www.alt-mode.com/~motm

There are 4 files, 2 are .wav, and 2 are .mp3 (128K encoded).  One test has 
the 940 on the left and the 904A Right (if you don't have your left and 
right straight, it will be hard to tell which filter is which).  The second 
test is the same sequence but in mono alternating between the 940 and the 
904A (940 first).  The sequence is repeated with a low resonance, medium 
resonance, and high (but not oscillating) resonance.  I tried to tune the 
filters to each other as closely as possible by getting the filters to 
oscillate and using a tuner to match them.

The test setup was a single MOTM-300 SAW out into an MOTM-830 to attenuate 
the signal.  The 830 was feed into both filters and then into two Moog VCAs 
driven by Moog EGs.  The 904A was run in the middle response mode (2). An 
Encore Expressionist provided MIDI->CV conversion and CC#7 was used to 
sweep the filters after going through a MOTM 820 to smooth out the steps.

The output of the VCAs went into an Avalon AD2022 preamp, mostly to even 
out the levels, and then into an Apogee Rosetta converter into a MOTU 2408 
into Logic Audio.

Interesting observations:
- The filters sound pretty close to each other in this test
- I didn't quite get the resonance even between the two filters on the 
medium resonance test
- The resonance on the 940 is very touchy, going into full oscillation by 
about the 12 o'clock position
- The phase from the two filters is reversed - causing some phasing in the 
stereo test
- The output of the Moog filter was actually louder than the 940!
- The DC offsets are interesting between the different filters and tests...

In this test, the filters sound *very* similar.  In playing with the 940, I 
found it had a neat character but didn't quite feel the same as the 
904A.  It wasn't bad, just different.  I think a lot has to do with the 
range of the knobs.  There is a lot of range in a short span on the 940, 
particularly in the resonance!

Fire any questions you may have.  I thought about expanding this test to 
other filters but decided I didn't want to spend the time.  I could be 
persuaded if folks think there is a benefit.  I'm not sure if this simple 
sweep test really gets much of the character of a filter.  Lots of 
character comes from how it reacts to an EG or fast changing CV.  If 
someone has an idea for a good filter test, I might be interested in giving 
it a go.

	Eric

Lots of other groups are getting spammed with this email.  If it hits the
MOTM list, do not open it (or at least do not click on the link).  You get
thrashed with tons of pop-up windows that spawn like crazy.  And they are a
PAIN to close.

Cheers!
Shemp

Everyone should have one of these pop up killers:

http://www.panicware.com/popupstopper.html

or 

http://www.adsgone.com/

> -----Original Message-----
> From: Tentochi [mailto:tentochi@...] 
> Sent: Wednesday, August 21, 2002 8:39 PM
> To: motm@yahoogroups.com
> Subject: [motm] [OT] New pics here... <<BEWARE!
> 
> 
> Lots of other groups are getting spammed with this email.  If 
> it hits the MOTM list, do not open it (or at least do not 
> click on the link).  You get thrashed with tons of pop-up 
> windows that spawn like crazy.  And they are a PAIN to close.
> 
> Cheers!
> Shemp
> 
> 
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>  
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> Your use of Yahoo! Groups is subject to 
> http://docs.yahoo.com/info/terms/ 
> 
>

You mean MOTM-490<g>?

Moe
  
>>>>
Folks,

I *finally* finished my 940/904A comparison. I won't give you any 
excuses 
for the time it took. The material isn't very exciting, in fact it 
is down 
right clinical. Please go to:
<<<<

No. It's a Moog filter versus a MOTM multiple.

OK, it's really '490. I did notice the 904A is "brighter", so I looked at the spectra on WinAMP.
You can plainly see (and hear) it. This is either the CV Mod not being set exactly, or the
initial Freq not set exactly.

BUT....other than that, they sound close enough for rock. Thannk to Eric and Ben for letting me
torture their babies (the fire wasn't THAT big of a deal).

Paul S.

Dyslexia, it can strike anytime at ;)  Sorry about that.  Yes, I 
meant 490.

  Eric

--- In motm@y..., "mate_stubb" <mate_stubb@y...> wrote:

> You mean MOTM-490<g>?
> 
> Moe
>   
> >>>>
> Folks,
> 
> I *finally* finished my 940/904A comparison. I won't give you any 
> excuses 
> for the time it took. The material isn't very exciting, in fact it 
> is down 
> right clinical. Please go to:
> <<<<

--- In motm@y..., "Paul Schreiber" <synth1@a...> wrote:
> OK, it's really '490. I did notice the 904A is "brighter", so I 
looked at the spectra on WinAMP.
> You can plainly see (and hear) it. This is either the CV Mod not 
being set exactly, or the
> initial Freq not set exactly.
> 

Yes, it is really hard to get two filters, especially an old 904A 
that barely oscillates, to tune and track together.  I tried to get 
the initial frequency correct with a tuner but it was hard to 
maintain that over the entire sweep.


Eric

Though it could just be the tuning difference noted below, I like the sound
of the 490 better.  To me it sounds more "vintage" and "warm".  :)  I assume
most people will be going for that kind of sound with that filter (I know I
will).  I hear Wakeman and Emerson, rather than Carlos - which was perhaps
intended based on Paul's comment about it being close enough for rock, etc.
(So maybe it does sound a little like a Mini, and not strictly like the 904a
- though I've never owned/played either so I couldn't say.)

Either way, it's on my WTB list.  Unfortunately, I haven't x'd anything off
that list for a long time as my live gig (worship leading at church) has
eaten most of my gear funds this year.  Gotta get the VCOs first - oh and
that pesky MIDI/CV thing... :)  Life is good when your biggest $ concern is
when you'll be able to buy your next module (even if the time is measured in
Quarters!)

Larry David
(motmclergy/"some other Stooge")

> From: "alt_mode" <yahoo@...>
> Date: Thu, 22 Aug 2002 12:55:32 -0000
> To: motm@yahoogroups.com
> Subject: [motm] Re: MOTM 940/Moog 904A comparison
> 
> --- In motm@y..., "Paul Schreiber" <synth1@a...> wrote:
>> OK, it's really '490. I did notice the 904A is "brighter", so I
> looked at the spectra on WinAMP.
>> You can plainly see (and hear) it. This is either the CV Mod not
> being set exactly, or the
>> initial Freq not set exactly.
>> 
> 
> Yes, it is really hard to get two filters, especially an old 904A
> that barely oscillates, to tune and track together.  I tried to get
> the initial frequency correct with a tuner but it was hard to
> maintain that over the entire sweep.
> 
> 
> Eric

I just finished my 490.  This filter ROCKS!
 
I did find the resonance setting a bit too sudden, so I changed R29 to a
68K to have more range for low resonance, as suggested in the assembly
doc.  Fortunately I was able to do this from the top of the PCB without
disassembling the module.
John Loffink
jloffink@... 

-----Original Message-----
From: Larry David [mailto:ldavid@...] 
Sent: Thursday, August 22, 2002 2:44 PM
To: alt_mode; motm@yahoogroups.com
Subject: Re: [motm] Re: MOTM 940/Moog 904A comparison
 
Though it could just be the tuning difference noted below, I like the
sound
of the 490 better.  To me it sounds more "vintage" and "warm".  :)  I
assume
most people will be going for that kind of sound with that filter (I
know I
will).  I hear Wakeman and Emerson, rather than Carlos - which was
perhaps
intended based on Paul's comment about it being close enough for rock,
etc.
(So maybe it does sound a little like a Mini, and not strictly like the
904a
- though I've never owned/played either so I couldn't say.)

In a message dated Sat, 24 Aug 2002 3:52:16 PM Eastern Standard Time, jloffink@... writes:

> I just finished my 490.  This filter ROCKS!
>  
> I did find the resonance setting a bit too sudden, so I changed R29 to a 68K to have more range for low resonance, as suggested in the assembly doc.  Fortunately I was able to do this from the top of the PCB without disassembling the module.
> John Loffink


 I agree... This filter sounds AMAZING. :)  I think I might do the resonance range mod too. For my use, I don't think there's enough of a sonic change past the halfway point in the res pot to warrant keeping it this way.

 I can see myself ordering one or two more of these filters in the near future. 

 Andrew

I'm sure the 940 resonance was designed to be similar to the 904a, but I
don't mind changing the response to something more useful.  I tested
this with a 100K pot and thought a 75K value gave the best range, but I
don't have that value in my resistor stock and didn't want to muck up
the board with parallel resistors.  There is some difference at maximum
resonance when you change R29.  The sine wave is not as "pure" at
rez=10, instead it seems to be more "modulated" by the input waves.  But
I tend to stay at low to medium resonance, so it didn't matter to me.
John Loffink
jloffink@... 

I agree... This filter sounds AMAZING. :)  I think I might do the
resonance range mod too. For my use, I don't think there's enough of a
sonic change past the halfway point in the res pot to warrant keeping it
this way.

I can see myself ordering one or two more of these filters in the near
future. 

Andrew

Dang it, now I'm doing it!  490, not 940.
John Loffink
jloffink@... 

-----Original Message-----
From: John Loffink [mailto:jloffink@...] 
Sent: Saturday, August 24, 2002 9:01 PM
To: ixqy@...; motm@yahoogroups.com
Subject: RE: [motm] Re:MOTM 940/Moog 904A comparison
 
I'm sure the 940 resonance .

Actually, the 490 resonance response is quite different from the 904A.  On 
the 904A, the oscillation is very weak and doesn't really start until you 
hit 2 o'clock or so.  It is also true that many 904A's don't even 
oscillate.  One of mine didn't until Paul "fixed" it.  I'm not quite sure 
why the response on the 490 is so touchy.  I'm going to look into the mod 
for the range too.

         Eric


At 09:01 PM 8/24/02 -0500, John Loffink wrote:

>I m sure the 940 resonance was designed to be similar to the 904a, but I 
>don t mind changing the response to something more useful.  I tested this 
>with a 100K pot and thought a 75K value gave the best range, but I don t 
>have that value in my resistor stock and didn t want to muck up the board 
>with parallel resistors.  There is some difference at maximum resonance 
>when you change R29.  The sine wave is not as pure at rez=10, instead it 
>seems to be more modulated by the input waves.  But I tend to stay at low 
>to medium resonance, so it didn t matter to me.
>
>John Loffink
>jloffink@...
>
>
>I agree... This filter sounds AMAZING. :)  I think I might do the 
>resonance range mod too. For my use, I don't think there's enough of a 
>sonic change past the halfway point in the res pot to warrant keeping it 
>this way.
>
>I can see myself ordering one or two more of these filters in the near 
>future.
>
>Andrew
>
>
>Yahoo! Groups Sponsor
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I loved the demos.  I am looking forward to building mine (which looks as if
it will be a while)  :(
LH

----- Original Message -----
From: <ixqy@...>
To: <motm@yahoogroups.com>
Sent: Saturday, August 24, 2002 7:21 PM
Subject: [motm] Re:MOTM 940/Moog 904A comparison


In a message dated Sat, 24 Aug 2002 3:52:16 PM Eastern Standard Time,
jloffink@... writes:

> I just finished my 490.  This filter ROCKS!
>
> I did find the resonance setting a bit too sudden, so I changed R29 to a
68K to have more range for low resonance, as suggested in the assembly doc.
Fortunately I was able to do this from the top of the PCB without
disassembling the module.
> John Loffink


 I agree... This filter sounds AMAZING. :)  I think I might do the resonance
range mod too. For my use, I don't think there's enough of a sonic change
past the halfway point in the res pot to warrant keeping it this way.

 I can see myself ordering one or two more of these filters in the near
future.

 Andrew







Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

on 8/24/2002 8:21 PM, ixqy@... at ixqy@... wrote:

> In a message dated Sat, 24 Aug 2002 3:52:16 PM Eastern Standard Time,
> jloffink@... writes:
> 
>> I just finished my 490.  This filter ROCKS!
>> 
>> I did find the resonance setting a bit too sudden, so I changed R29 to a 68K
>> to have more range for low resonance, as suggested in the assembly doc.
>> Fortunately I was able to do this from the top of the PCB without
>> disassembling the module.
>> John Loffink

    So the 490 kits are shipping? I didnt know.

                -John
-- 
ELECTRO:DISCO:RETRO:FUTURE
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