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Arp Odyssey, moog filter?
Old 27th February 2011
  #1
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John_Seward's Avatar
 

Arp Odyssey, moog filter?

Hello!

Does anyone know which of the Mk2 models that have the moog filter?

Thanks
Old 28th February 2011
  #2
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There's no known record of serial numbers of those 4035 moog filter equipped units. The only surefire way is to pop the hood, they're labeled on the encapsulated module.
Old 28th February 2011
  #3
none of the oddys have exact copy of a moog filter. in a sense that altough its a ladder, its not built with manually paired discrete transistors as minimoogs or 900 modulars, but with a replacement in form of CA3086 transistor array chips i.e. pre-made pairs. these do lend a specific type of ladder sound. its very liquid, more open in the highs than minimoog, but not as humongous in the low range. at least that's how it seemed to me. phenomenal self oscillator sound, maybe most beautiful ive heard.

i had one arround 'for a while, in form of a friends mkI Axxe. we did some comparison with the mkII axxe, which used 4075 a.k.a. "post-lawsuit filter".. which is darker, thicker, and more agressive, abrassive. both beautiful on their own right.



iirc early black n gold Oddys were still 12dB OTA filter i.e. mkI guts in mkII body. and some late blk and gold moved on to mkIII guts i.e. 4075 filter.. so somewhere in the middle i suppose youll find black n golds with 4035. edit: damn, or was it other way arround... as poster below implies that some white ones already had 4035... cannot recall anymore, but there was a detailed text about this,, i think on vintagesynth forums..
Old 28th February 2011
  #4
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Only a select number of the white faced odysseys had the "Moog type" ladder filter.
Old 28th February 2011
  #5
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Only the Black and Gold 2810 had the 4035 Moog filter.
2800 models had the 2 pole 4023 filter.
2813 and 2823 models had the 4 pole 4075 filter

I personally like the 4075 filter it has better low end and is a bit more aggressive. I have the White face 2800, Black & orange 2823 and the black & gold 2813


.

Old 28th February 2011
  #6
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Quote:
Originally Posted by JEBEQ View Post
Only the Black and Gold 2810 had the 4035 Moog filter.
2800 models had the 2 pole 4023 filter.
2813 and 2823 models had the 4 pole 4075 filter

I personally like the 4075 filter it has better low end and is a bit more aggressive. I have the White face 2800, Black & orange 2823 and the black & gold 2813


.

Hehe, looks kinda familiar heh



I like the 2800 whitefaces's 2-pole filter the best where you don't loose volume as you crank the resonance. The 2810 and there were also some model 2811 and 2812 black/gold ones which are the only ones to have the transistor ladder filter NOT any whitefaces.
Old 28th February 2011
  #7
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Dought is right; the models 2810-2811-2812 (late '74/early 1975 to circa fall 1976) originally came with the so-called "moog" 4035 filter**. Note that some early mk 2's had the same type of oscillator/S&H/LFO board as found in the mk I 2800. Most of them however feature the newer and more stable B-II oscillator/S&H/LFO board.

** 4035 + 4034 filter = refined versions of the original 4012 Moog ladder filter.
Old 28th February 2011
  #8
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Note that even though certain ranges were supposed to have certain filters, ARP offered upgrades/changes over the years and the only real way to know what you're buying is for the seller to pop the hood and take a look. Same with the 2600's - you'll find a range of filters in them regardless of model/panel color.

I remember buying a 2600 sight unseen. The seller said VCO 2 wasn't working. When I got it and popped it open to fix a transistor or jack problem, I found that the VCO 2 module was actually missing...
Old 28th February 2011
  #9
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Quote:
Originally Posted by mikael488 View Post
Dought is right; the models 2810-2811-2812 (late '74/early 1975 to circa mid 1976) originally came with the so-called "moog" 4035 filter**. Note that some early mk 2's had the same type of oscillator/S&H/LFO board as found in the mk I 2800. Most of them however feature the newer and more stable B-II oscillator/S&H/LFO board.

** 4035 + 4034 filter = refined versions of the original 4012 Moog ladder filter.
Does that include all 2811-2812 units or just some of them?

Oh and thanks everyone!
Old 28th February 2011
  #10
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Xero's Avatar
the best option imo is the 40235 filter, which is a combination of the 4012 and 4035 and is switchable between the two. Apparently if you start with an ody that had a 4075 as well, you can make it switchable between all 3...i've been curious to see if i could build one of these and install it in my whiteface, but i might be pushing my luck
Old 28th February 2011
  #11
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Yes I believe all 2811's and 2812's originally were like that. However, like oldgeargyy said above ARP offered upgrades and changes over the years, which means you may find either model with the 4075 filter and PPC.
Old 28th February 2011
  #12
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Come to think of it, when I got my Black and orange serviced at Kurt's keyboards& amps he did a few mods on my 2823. He turned the 4075 filter to sound like a 4023 2 pole style and he also improved the signal path which greatly improved the wave shape and also added a great deal more of low end. So I guess thats why I like my 2823 Oddy better. These mods made a huge difference and I am actually thinking of getting them done on my other Odysseys at CMS.
Old 16th October 2013
  #13
Gear Maniac
 

Just tested a black and gold 2810 and the low end cuts a bit when raising the Resonance... it doesn't have the CMS 'Filter' logo on the back. Is that a non-moog filter ARP ? Can you tell by the serial numbers ?
Old 16th October 2013
  #14
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Quote:
Originally Posted by gilwe View Post
Just tested a black and gold 2810 and the low end cuts a bit when raising the Resonance... it doesn't have the CMS 'Filter' logo on the back. Is that a non-moog filter ARP ? Can you tell by the serial numbers ?
There is no known list of serial numbers to correlate ARP filter modules.

Observe the filter behavior with the cutoff set high: If the low end drops when raising the resonance, that's how the ladder filter works.

If the low end does not drop when raising the resonance, that's more likely the 4023 filter which is not a ladder filter. But the 4023 is still a nice sounding filter, it is the predecessor to the Oberheim SEM filter and has a similar sound. I don't think it is a SVF like the SEM.

I don't know how the later 4075 filter behaves under these conditions.

ARP filter modules usually have a label on them, but those labels could fall off with age.
Old 16th October 2013
  #15
Gear Maniac
 

Well, it does cut when trying what you suggested. Is that the 4035 moog one ? I was under the impression that it's the other way around (meaning - moog is the one who doesn't cut).
Old 16th October 2013
  #16
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Wow !! A lot of urban myth floating around on this one. It also illustrates the power of a patent and an invention.

Beyond that ( and Bob Moog should be very proud)... the Oddy had many other virtues that transcended the filter. And the ARP filter was nothing to sneeze at. I once bought a Roland SH3A thinking I had aquired the holy grail....well.....
Old 16th October 2013
  #17
Gear Maniac
 

Well I just checked VSE and there it says the Black and Gold 2810 MKII which doesn't have all the externals is the 4035 while the one which has them uses 4075. The one I was testing is the second one (with the externals) but definitely aggressively cuts the low when setting the cutoff to high and raising resonance.
Old 16th October 2013
  #18
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Quote:
Originally Posted by Teknobeam View Post
Wow !! A lot of urban myth floating around on this one. It also illustrates the power of a patent and an invention.

Beyond that ( and Bob Moog should be very proud)... the Oddy had many other virtues that transcended the filter. And the ARP filter was nothing to sneeze at. I once bought a Roland SH3A thinking I had aquired the holy grail....well.....
Back in those days, a lot of synth makers envied that ladder filter. They couldn't infringe on the patent, like that ever stopped ARP

Quote:
Originally Posted by gilwe View Post
Well, it does cut when trying what you suggested. Is that the 4035 moog one ? I was under the impression that it's the other way around (meaning - moog is the one who doesn't cut).
"Cut" is a vague term... cut as in attenuate, or cut through in a mix?

I don't think the 4075 filter was in ANY black/gold Odysseys, only the later orange/black ones. That may be the 4035.
Old 16th October 2013
  #19
Gear Maniac
 

"Cut" for "Attenuate".


VSE:

Mark II series
2810 mk II 75 - 76 Black+Gold 4035 A-II, B-I or B-II, C-II Rotary knob No interface jacks Wrap around vinyl bottom

2810 mk II 76 - 78 Black+Gold 4075 A-II, B-II, C-II Rotary Knob or PPC CV/Gate+Trig Wrap around vinyl bottom
Old 16th October 2013
  #20
ValhallaDSP
 
seancostello's Avatar
 

Quote:
Originally Posted by The Real MC View Post
There is no known list of serial numbers to correlate ARP filter modules.

Observe the filter behavior with the cutoff set high: If the low end drops when raising the resonance, that's how the ladder filter works.

If the low end does not drop when raising the resonance, that's more likely the 4023 filter which is not a ladder filter. But the 4023 is still a nice sounding filter, it is the predecessor to the Oberheim SEM filter and has a similar sound. I don't think it is a SVF like the SEM.

I don't know how the later 4075 filter behaves under these conditions.
I think that any filter that has 4 one pole lowpass filters in series, with negative feedback, will have the low frequency cut when the resonance is increased. This holds true for Moog ladder filters, ARP 4075, and the various 4-pole OTA filters out there.

My theory is that a highpass filter in the resonance feedback loop will reduce this behavior for bass frequencies, but I have yet to read about this in the published literature, just various forum posts and synth-DIY threads (not to say that those don't count).
Old 16th October 2013
  #21
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Quote:
Originally Posted by The Real MC View Post

I don't think the 4075 filter was in ANY black/gold Odysseys, only the later orange/black ones. That may be the 4035.
Actually the majority of mkII black/gold Odysseys had the 4075...
Old 17th October 2013
  #22
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-groovatious-'s Avatar
 

That's an amazing collection JEBEQ!

I have a black/gold Odyssey in need of a service - might have to ask you a few questions
Old 21st October 2013
  #23
Gear Maniac
 

I disassembled my CV/Gate equipped 2810 and found it actually has a 4035 filter (while VSE says these should have the 4075). Interesting.
Old 2nd December 2014
  #24
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Anyone own a post Moog filter Arp? On VSE it mentioned a problem. (see quoted below) Any of you guys notice this issue?



"Arp and Moog came to an amicable agreement and a small licensing fee was paid by ARP for units previously manufactured. ARP soon after designed a new 4-pole, low pass filter - the model 4075 filter - which was used in all subsequent Odyssey models. Unfortunately, while the new model 4075 version of the filter was still beefy at low frequencies and very stable, it also had a well known bandwidth limit error around 12 to 14 kHz, resulting in a weak sound at high resonance or when driven into self-oscillation. This has made the rarer black and gold 2810 Odysseys with the model 4035 Moog-like ladder filter the more sought after and pricier models."

Quote from:

ARP Odyssey | Vintage Synth Explorer
Old 3rd December 2014
  #25
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Yes, you need to change 4 resistors in the 4075... Details are here -

http://machines.hyperreal.org/manufa...filter.mod.txt
Old 5th December 2014
  #26
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Syntronics's Avatar
 

I have don the 4075 mod with the 4 resistors and I could get it to spec out at about 14.5khe at best.
Old 29th January 2015
  #27
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Could any odyssey experts chime in on the best midi to cv options for an odyssey. Mine is a 2810 with the "moog" filter. I thought the Kenton USB solo seemed promising, but I've heard recommendations for Doepfer as well. Isn't there a consideration for controlling the filter via cv? Any input most welcome.
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