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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Moog 907A / 914 - topology Fixed Filter Bank PCB
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Interested?
No - no need for a FFB
7%
 7%  [ 3 ]
No - not without real inductors
5%
 5%  [ 2 ]
Yes - as long as you get "the sound" with your technology
86%
 86%  [ 33 ]
Total Votes : 38

Author Message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Feb 20, 2009 3:21 am    Post subject: Moog 907A / 914 - topology Fixed Filter Bank PCB
Subject description: can use real inductors or electronic inductors. Runs on +/-15V or +/-12V
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some of you may still remember my efforts to make a modern version of the Moog Fixed Filter bank (the smaller model, 907) for Synthesis Technology / MOTM.

This is a faithful reproduction of the original passive circuit topology, but with the inductors replaced with low noise General Impedance Converter technology. (Not the "usual" noisy single-opamp Gyrator circuits!)

Now that Paul has announced not to release this as a MOTM module, I have decided to offer PCBs for this. (I have a working prototype in my studio for many years, so all I have to do is make a PCB layout.)

In order to decide if it makes sense to do this, from an economical point of view, I'd like to get some feedback from all who are seriously interested in such PCBs. Please send an email (no PM) if interested. (These are *not* binding pre-orders yet - just to see how much demand there is.)

As for pricing: It will probably be two 160 x 100 mm PCBs, so I expect a price of 54 Euros for the two PCBs.

I know there have been samples published for this (probably by myself, or by Paul). If anybody has a link to these samples, please post it.

Looking forward to hear from you,

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Last edited by jhaible on Sun Apr 25, 2010 12:07 am; edited 2 times in total
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krisp14u



Joined: Nov 11, 2006
Posts: 206
Location: uk

PostPosted: Fri Feb 20, 2009 4:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi JH
I have 2 of the Yusynth FFB that I am very happy with how would your FFB be different to this?

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jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Feb 20, 2009 4:55 am    Post subject: Reply with quote  Mark this post and the followings unread

krisp14u wrote:
Hi JH
I have 2 of the Yusynth FFB that I am very happy with how would your FFB be different to this?


I just saw that there is a Yusynth FFB.
Apparently it's the big one (914), while I've cloned the small one (907).
From what I can tell, the Yusynth one doesn't preseve the Moog passive topology, but uses active BPFs instead.
I'm keeping the Moog structure, and only replace the *inductors* with active circuits.

I won't say one is better than the other (though I've chosen my approach on purpose, of course) - but you asked about what's different.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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kkissinger



Joined: Mar 28, 2006
Posts: 1214
Location: Kansas City, Mo USA
Audio files: 29

PostPosted: Fri Feb 20, 2009 7:22 am    Post subject: An FFB for my Aries synth
Subject description: the missing link
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I always wished that Aries had come out with an FFB -- definately interested to add an FFB to my modular synth.

I'm not picky about the technology Smile

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fluxmonkey



Joined: Jun 24, 2005
Posts: 696
Location: cleve

PostPosted: Fri Feb 20, 2009 7:31 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
I just saw that there is a Yusynth FFB.
Apparently it's the big one (914), while I've cloned the small one (907).
From what I can tell, the Yusynth one doesn't preseve the Moog passive topology, but uses active BPFs instead.
I'm keeping the Moog structure, and only replace the *inductors* with active circuits.

I won't say one is better than the other (though I've chosen my approach on purpose, of course) - but you asked about what's different.

JH.


Similar question to krisp, but less about the design and more about the function: how might this sound different than the active BPF design? and/or how might you use it differently? i've never touched an actual moog modular, so i don't have that to reference to. And i'm sure i'll purchase, just trying to learn more... thanks as always for sharing your sonderful designs.

bbob

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jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Feb 20, 2009 8:02 am    Post subject: Reply with quote  Mark this post and the followings unread

bbob wrote:
jhaible wrote:
I just saw that there is a Yusynth FFB.
Apparently it's the big one (914), while I've cloned the small one (907).
From what I can tell, the Yusynth one doesn't preseve the Moog passive topology, but uses active BPFs instead.
I'm keeping the Moog structure, and only replace the *inductors* with active circuits.

I won't say one is better than the other (though I've chosen my approach on purpose, of course) - but you asked about what's different.

JH.


Similar question to krisp, but less about the design and more about the function: how might this sound different than the active BPF design? and/or how might you use it differently? i've never touched an actual moog modular, so i don't have that to reference to. And i'm sure i'll purchase, just trying to learn more... thanks as always for sharing your sonderful designs.

bbob


I can't, and won't, compare my circuit to that of a fellow designer's, *especially* when I haven't done any analysis of his circuit.

I can only say what my design goals were:

* Lowest Noise
* Graceful overload behaviour
* Exact behaviour of interaction between channels, like the original.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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dingebre



Joined: Aug 10, 2008
Posts: 257
Location: Salt Lake City, UT USA

PostPosted: Fri Feb 20, 2009 1:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd be very interested in two sets of boards.

Thanks

David

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iceowl



Joined: Dec 12, 2008
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Location: Silicon Valley, California

PostPosted: Fri Feb 20, 2009 1:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am interested and I'd be much obliged to be considered for 1 set of boards if you go through with this project.
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The Alison Project



Joined: Jul 21, 2006
Posts: 187
Location: Canada
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PostPosted: Sat Feb 21, 2009 1:40 am    Post subject: Reply with quote  Mark this post and the followings unread

I am interested in one or two.
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yusynth



Joined: Nov 24, 2005
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Location: France

PostPosted: Sat Feb 21, 2009 4:26 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
I just saw that there is a Yusynth FFB.
Apparently it's the big one (914), while I've cloned the small one (907).
From what I can tell, the Yusynth one doesn't preseve the Moog passive topology, but uses active BPFs instead.
I'm keeping the Moog structure, and only replace the *inductors* with active circuits.


As I say on my site I chose the Delyannis BPF structure instead of the simulated inductor approach because I wanted to keep the number of parts as low as possible considering that it is the big version (Moog 914). I managed to obtain the same response as the original Moog 914 (I worked on the basis of measurements made with a spectrum analyzer on a genuine Moog 914). I noted no issue of noise so far.

jhaible wrote:
I won't say one is better than the other (though I've chosen my approach on purpose, of course) - but you asked about what's different.


I had the opportunity to test side by side (same input signal) a genuine Moog 914 (thanks to Olivier Grall) a Q128 dotcom FFB and the yusynth FFB and I can say without self-praise Embarassed that my FFB sounds very close to the Moog 914, the Dotcom sounds a bit metallic in comparison (probably because of a slightly higher Q, I presume).

I fully agree with Jürgen that the main difference between the BPF and the true inductor version is the way they behave for high signal levels (how they saturate so to speak). I don't know if simulated inductors also behave like true inductors with respect to saturation ? May be Jürgen, can you tell us a bit more about that, did you run tests in saturation mode ?

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jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Sat Feb 21, 2009 5:28 am    Post subject: Reply with quote  Mark this post and the followings unread

yusynth wrote:
I noted no issue of noise so far.


I think every active circuit is inferior to a true LC circuit in terms of noise. (But the real inductors might pick up more hum.)
I don't know who it was who used simple single-opamp gyrators for a fixed filter bank (certainly not you!) - this stuff *must* be noisy.

But let me stress this again: I'm not comparing "my noise" with "your noise", and I won't even try to make any measurements and publish data. All I wanted to say is: real inductors always have an advantage in terms of noise, and I try to preserve the topology while using active circuits and do my best to keep noise low. With the level potentiometers at the filter inputs, I always get more noise than at the outputs, for instance. But I keep this, and take it as a design constraint.

Quote:

I don't know if simulated inductors also behave like true inductors with respect to saturation ?


No, they don't. They can't.
But the topology of the original Moog filterbank is such that *any* distortion that's caused by the first LC resonator is strongly filtered out by the second LC resonator in the signal chain, which in turn operates at a lower signal level than the first, and is thus unlikely to produce a lot of distortion by itself.
I have no idea how important that is in the original LC version - but that topology is really friendly for an active solution, where overload performance is more of an issue.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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Electronicant



Joined: Feb 23, 2006
Posts: 81
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PostPosted: Sun Feb 22, 2009 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you´re going to make the vocoder and if the vocoders filter bank could be used as a ffb, I think I´ll prefer that one. But I´m not shure. What will the difference be between them? more bands?
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jhaible



Joined: May 25, 2007
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PostPosted: Sun Feb 22, 2009 1:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Electronicant wrote:
If you´re going to make the vocoder and if the vocoders filter bank could be used as a ffb, I think I´ll prefer that one. But I´m not shure. What will the difference be between them? more bands?


Entirely different.

The vocoder will have a filter bank designed by me (with inspiration from EMS and maybe Sennheiser, but certainly not Moog).

The Fixed Filter Bank will emulate the Moog design, with all these notches in the frequency response that are typical for that specific design.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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leitner6



Joined: Sep 25, 2008
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PostPosted: Fri Feb 27, 2009 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Dumb question.

Why do people go out of their way to design around inductors? I know there isn't such a thing as a perfect inductor, but would it be any harder than matching the RxC value like in your frequency shifter? (except RxLxC i'd imagine) It just seems to me that the inductor characteristics is what gives it part of its charm.

-Larry
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jhaible



Joined: May 25, 2007
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PostPosted: Fri Feb 27, 2009 11:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

leitner6 wrote:
Dumb question.

Why do people go out of their way to design around inductors? I know there isn't such a thing as a perfect inductor, but would it be any harder than matching the RxC value like in your frequency shifter? (except RxLxC i'd imagine) It just seems to me that the inductor characteristics is what gives it part of its charm.

-Larry


It's much harder to get the "right" inductors than to select capacitors.

Inductors have a certain character, under certain circumstances - but each type of inductor hat its own character. If you don't use the same core material - probably if you don't use the same geometry! - this character will be different from the original even if you're using inductors.

Having said that, I doubt that the influence of the inductor's own character is *that* important in *this* circuit. As I said above, the Moog Filterbanks were designed in a way that any harmonics that are generated in the first stage of each channel, are filtered out in the second stage.

Of course in the end your ears decide.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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vtl5c3



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PostPosted: Tue Mar 09, 2010 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Juergen,

Is this project dead, or just on the back burner?

R.
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loydb



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PostPosted: Tue Mar 09, 2010 11:53 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm pretty much down for a couple of anything you produce Smile
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jhaible



Joined: May 25, 2007
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PostPosted: Tue Mar 09, 2010 12:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

vtl5c3 wrote:
Hi Juergen,

Is this project dead, or just on the back burner?

R.


It's one of these things that are readily designed, a veroboard prototype exists, an I just need some time and motivation to make a PCB. Can't say when, though.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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TekniK



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PostPosted: Tue Mar 09, 2010 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Motivation



Very Happy
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tomcat



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PostPosted: Tue Mar 09, 2010 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ill take 1 Smile

Its just a small number but maybe it helps with the motivation Wink
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TekniK



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PostPosted: Tue Mar 09, 2010 3:03 pm    Post subject: Re: Moog 907A-based Fixed Filter Bank, MOTM version Reply with quote  Mark this post and the followings unread

jhaible wrote:

In order to decide if it makes sense to do this, from an economical point of view, I'd like to get some feedback from all who are seriously interested in such PCBs. Please send an email (no PM) if interested. (These are *not* binding pre-orders yet - just to see how much demand there is.)

As for pricing: It will probably be two 160 x 100 mm PCBs, so I expect a price of 54 Euros for the two PCBs.

JH.


I buy 2 pcb sets for sure.


who is the next one that gonna motivate him? Very Happy
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numbertalk



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PostPosted: Tue Mar 09, 2010 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'll take 1!
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Luka



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PostPosted: Tue Mar 09, 2010 6:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

count me in
1 maybe 2

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intercorni



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PostPosted: Wed Mar 10, 2010 6:15 am    Post subject: Reply with quote  Mark this post and the followings unread

I'll take 1!
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fluxmonkey



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PostPosted: Wed Mar 10, 2010 5:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

i would like 1 for sure.
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