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MOOG LPF clones/replicates... which is your favorite?
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Author MOOG LPF clones/replicates... which is your favorite?
MindMachine
Best of the Moog filters?
I hear some keen MOS-LAB demos and nice COTK sounds. I am thinking that the Synthesizers.com should be close to these? I recall Synthbaron saying that with a jumper move in the module, that the Q-150 can equal the MOS-LAB or COTK.
So before I go order a MOSLAB... which do you all prefer?
sandyb
not my area at all so i can't give an opinion. but, the video in this thread that john did a while ago may be interesting for you.

https://www.muffwiggler.com/forum/viewtopic.php?t=10831

sandy
Babaluma
motm 1490, prefer it to the moogerfooger mf-101. we have posted about this before, i think in a 5u thread somewhere?
mono-poly
I guess the Mos-Lab is the closest to the 904a comercial avaible.
MindMachine
Babaluma wrote:
motm 1490, prefer it to the moogerfooger mf-101. we have posted about this before, i think in a 5u thread somewhere?


I searched for a while.. maybe not effectively...
Babaluma
hey no worries, this is a LARGE place now. wink come to think of it, may have been in the DIY sub-forum, will see if i can dig it up...

i haven't owned any other moog or moog clone filters, but i do love the 1490.
SynthBaron
The MOS-LAB is the only Moog filter in 5U that is completely discrete like the original, so it's going to act the most like it (http://www.yusynth.net/MOS-LAB/904-PCB.jpg). The other clones use matched transistors on a chip, OTA's, and/or modern op-amps in the design.

The Q150 is plenty "good enough", though. With MOS-LAB, you're going to need a separate +-12 supply, so take that into account.

I'll do a MOS-LAB vs. MOTM-490 demo when I get the former in about a month or so I guess.
Ken MacBeth
...hey! The MacBeth X-Series 'backend' Filter Combo is all discrete transistors too....as are the two onboard VCAs and the two Envelope Generatators are pur discrete too! hihi


...damn, should have noticed- this is a 5U discussion.... razz

...shortly on the cards is the 5U version!
mono-poly
Synthbaron doesn't a dotcom suply +12 -12 to ?
paults
Quote:
The MOS-LAB is the only Moog filter in 5U that is completely discrete like the original, so it's going to act the most like it (http://www.yusynth.net/MOS-LAB/904-PCB.jpg).


Ummmmm.....no.

It has to do with several factors involving both the input impedance of the audio to the ladder, the matching of *certain* transistors in the ladder and the transfer function of the feedback loop with respect to the beta of *cerrtain* transistors in the ladder. I spent several months on this, ran over 100 plots on my Audio Precision analyzer and had multiple phone calls with Bob Moog about it. I looked at 6 *different* 904As, built over a 10 year span and 5 other 'clones'. I probably spent 250 hours on the analysis part.

Now, in all fairness, the MOS-LAB circuit was NOT available when I ran all of the tests.

Where most of the clones 'screw up' is getting around the reverse log taper pot needed in the original design for the resonance. Yes, I 'get around' it too but there is a "design flaw" in the original 904A that unless you replicate it (and you are only going to 'see it' if you have something like the Audio Precision) you will not get the desired audio output.

Just because you use all discrete doesn't mean it's "correct". There is a good chance he did it "correct". But even the MF-101 is not correct (it's NOT a Bob Moog design anyway) in fact it's FAR from a 904A as any other clone I looked at. The pc board layout is horrid.
sandyb
mono-poly wrote:
Synthbaron doesn't a dotcom suply +12 -12 to ?


no - dotcom supplies are +/-15V (and 5V) only
mono-poly
Ok Sandy!
paults
Here are some of the AP plots I did comparing the various clones to the MOTM-490:

www.synthtech.com/misc/ap_test_moog.zip

If you look close, there is a what Bob called 'the double dip' in the THD versus frequency response of the '490. You have to replicate the "design flaw" in the feedback loop, and do the other things, to have the 'double dip' that the 904A has.

The 904A is a 'bad design', just like the Harley intake manifold is (which is why it "sounds like a Harley", and which is why the 904A sounds like a 904A). Bob stated this was not intentional, it has to do with the parts he had available at the time. Bob was located near many defense contractors in upstate NY (also near Corning Glass and Kodak) and there was a large electronics surplus market. He loved to buy large lots of parts for cheap: this is why he used LOTS of transistors, he bought 250,000 at once for 7 cents each when they were about 22 cents each new at that quantity. He chuckled at that, also telling me "..and I threw half of the damn things away!" The same was true for caps (every look at those odd-ball 904A caps?). He would look to see what the local market used (since mostly military or high-end industrial, the 'good stuff' for 1970 at least) and thats what went into the modular. If you compare schematics over the years, Bob used about 7 *different* transistors in the ladder stuff, based on what he could dig up at the time. Remember, no Mouser, Farnell or DigiKey Dead Banana
SynthBaron
paults wrote:
Quote:
The MOS-LAB is the only Moog filter in 5U that is completely discrete like the original, so it's going to act the most like it (http://www.yusynth.net/MOS-LAB/904-PCB.jpg).


Ummmmm.....no.

It has to do with several factors involving both the input impedance of the audio to the ladder, the matching of *certain* transistors in the ladder and the transfer function of the feedback loop with respect to the beta of *cerrtain* transistors in the ladder. I spent several months on this, ran over 100 plots on my Audio Precision analyzer and had multiple phone calls with Bob Moog about it. I looked at 6 *different* 904As, built over a 10 year span and 5 other 'clones'. I probably spent 250 hours on the analysis part.

Now, in all fairness, the MOS-LAB circuit was NOT available when I ran all of the tests.

Where most of the clones 'screw up' is getting around the reverse log taper pot needed in the original design for the resonance. Yes, I 'get around' it too but there is a "design flaw" in the original 904A that unless you replicate it (and you are only going to 'see it' if you have something like the Audio Precision) you will not get the desired audio output.

Just because you use all discrete doesn't mean it's "correct". There is a good chance he did it "correct". But even the MF-101 is not correct (it's NOT a Bob Moog design anyway) in fact it's FAR from a 904A as any other clone I looked at. The pc board layout is horrid.


I still stand by my original statement.
paults
Based on *what* criteria, exactly? Guinness ftw!
SynthBaron
paults wrote:
Based on *what* criteria, exactly? Guinness ftw!


That it's the closest thing to an exact clone of a Moog 904a available in 5U, especially since it runs off the original +12/-6 power, no matter what pile of rejected components they used to build them that day.
Peake
Babaluma wrote:
we have posted about this before, i think in a 5u thread somewhere?


Yes, more than one, on more than one forum, same cast of characters too.

meh
paults
Oh well, then. That sure makes more sense than all my knowledge, analysis and Bob Moog conversations. very frustrating Please, never let reality get in your way.
Peake
.com.
JohnLRice
Here are some inside shots of a Moog CE clone. (I nabbed these pics off of MatrixSynth's site . . that he nabbed off of someone's auction 8_) )

Not that making it neater would necessarily make it sound better but, I'm surprized that for the prices he charges a little more effort wasn't put into the construction. meh



paults
1 wire is the WRONG COLOR. Therefore it cannot *possibly* sound the same.
SynthBaron
paults wrote:
Oh well, then. That sure makes more sense than all my knowledge, analysis and Bob Moog conversations. very frustrating Please, never let reality get in your way.


You're trying to pick apart my statement, when there was nothing more meant by it. Don't do that. I at no time said it was better or worse than any other 904a topology filter. I was just saying it uses the same discrete circuitry.

The OP seemed to be implying he wants a Moog format module, which your 490 isn't. I have one and plan to buy a couple more, I don't have a problem with your designs. I think you're getting bent out of shape for no reason. This is not TGS, I'm not being an asshole...lol.
paults
OK, I see the point you were making, it was like JLR's about the physical-ness of it versus the actual circuit design.

Yes, I get bent out of shape. It's my nature screaming goo yo

Look at the AP plots, you can plainly see what I am referring to. Certain people tend to "dismiss" these sort of things are getting in the way of opinion. I do not. Rather, they *remove opinion* and point back to reality.

I like reality. It's why I was first interested in chemistry, then physics (my Dad was a nuclear physicist), then electronics. You can measure, calculate and it's all *repeatable*. As Carl Sagen liked to say, the only reason science exists is because it's repeatable.
mono-poly


Above a cloned one by a friend.
Underneath a RA clone by Moog CE.
Synthbuilder
Last week I had an interesting conversation with a chap who owns a very large Moog modular. He told me this - playing his 901s through a Doepfer ladder filter sounded more Moogy than playing Doepfer VCOs through any of his various 904s. This effect could be replicated with his 921 VCOs too.

At some point I may have a chance to test this for myself.

Tony
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