DIY Moog Ladder Filter Help?

[xombiexplox]

I goofed. You want cutoff at 3, not 9. Sorry bout that.

Roger that, Knight Rider

[Voltor07]

I goofed. You want cutoff at 3, not 9. Sorry bout that.

Roger that, Knight Rider

Also, have your modulation all the way up, source should be filter env, with Wave being destination. That way, you can change the 8-bit sound with slight adjustment to the mod wheel.

[EMwhite]

Speaking of 8-bit (music and video), you should check out the related 'nod' on Beck's Guero (http://en.wikipedia.org/wiki/Guero) and my favorite movie of all time, Scott Pilgrim vs. The World. And no coincidence that Beck's music director (at the time), Justin Mendal-Johnsen had a strong influence on the soundtrack (although it is very guitar and bass heavy).

I bought Guero as a UMD for my Sony PSP, it's awesome (the videos and visuals). There is a DVD containing bonus material also. Very cool.

[thealien666]

I've got a very technical question about the Moog ladder filter:

Why so many different implementations of the output buffers ? Sometimes a single OTA is used (CA3080 Taurus 1), sometimes two separate op amps are used (LF353 double, MG-1, Rogue), sometimes no op amps are used (Minimoog D discrete transistor pairs), sometimes a combination of discrete transistor pairs and an OTA (Prodigy).
Sometimes the VCA balance trimpot is on one of the op amps (Rogue, MG-1), sometimes the trimpot is on the OTA (Prodigy), sometimes there isn't one in the output buffers but rather elsewhere in the VCA circuit(Minimoog D, Taurus 1).

I'm only an electronics hobbyist, and not an engineer, and as much as I read the principle behind doctor Moog's ladder filter patent, I'm still a little confused about the filter output buffers and their role and why so many variations.

Any help would be appreciated. Both by myself, and xombiexplox I suspect.

Thanks...

[xombiexplox]

I've got a very technical question about the Moog ladder filter:

Why so many different implementations of the output buffers ? Sometimes a single OTA is used (CA3080 Taurus 1), sometimes two separate op amps are used (LF353 double, MG-1, Rogue), sometimes no op amps are used (Minimoog D discrete transistor pairs), sometimes a combination of discrete transistor pairs and an OTA (Prodigy).
Sometimes the VCA balance trimpot is on one of the op amps (Rogue, MG-1), sometimes the trimpot is on the OTA (Prodigy), sometimes there isn't one in the output buffers but rather elsewhere in the VCA circuit(Minimoog D, Taurus 1).

I'm only an electronics hobbyist, and not an engineer, and as much as I read the principle behind doctor Moog's ladder filter patent, I'm still a little confused about the filter output buffers and their role and why so many variations.

Any help would be appreciated. Both by myself, and xombiexplox I suspect.

Thanks...

You suspect correctly! I would like to know as well. Also, where can I find exactly what these buffers consist of?

[muksys]

I've seen those before! Those mutable ones! Gah, they're so awesome. I would seriously LOVE to have one of those Shruthi-1's in my arsenal. I see in your avatar you must know first-hand how sexy they are! (sidenote: would you happen to have any songs posted online showing that little thing off? haha) But for this, I want the learning experience and satisfaction of knowing that I put my own filter together and actually use it in music that I make.

Honestly, I absolutely love my Shruthi, but it's kinda hard getting it to fit into a song with the band I am in so I don't have much in ways of a predominant demo. I did post a youtube vid of it, but it was more showing off of a panel editor I built for it in ctrlr.

On a side note, a good little tweak on an LP/SP to get 8-bity sounds it to switch the filter to 1 or 2 pole. DIRTY!

[thealien666]

... Also, where can I find exactly what these buffers consist of?

For my previous post I've looked at the schematics of various Moog synthesizers (easily found online by typing "moog <insert your synth model here> schematics" in Google and looking at pictures results). And the output buffers are easily recognizable since they're connected right on the output of the ladder filter, just below the top two matched transistor pair.

[muna93]

I've got a very technical question about the Moog ladder filter:

Why so many different implementations of the output buffers ? Sometimes a single OTA is used (CA3080 Taurus 1), sometimes two separate op amps are used (LF353 double, MG-1, Rogue), sometimes no op amps are used (Minimoog D discrete transistor pairs), sometimes a combination of discrete transistor pairs and an OTA (Prodigy).
Sometimes the VCA balance trimpot is on one of the op amps (Rogue, MG-1), sometimes the trimpot is on the OTA (Prodigy), sometimes there isn't one in the output buffers but rather elsewhere in the VCA circuit(Minimoog D, Taurus 1).

I'm only an electronics hobbyist, and not an engineer, and as much as I read the principle behind doctor Moog's ladder filter patent, I'm still a little confused about the filter output buffers and their role and why so many variations.

Any help would be appreciated. Both by myself, and xombiexplox I suspect.

Thanks...

Hi alien. In simple words the different using of buffers are caused by the enormous differences that you can find in the amplitude of the clean signal to filter. E.g. Moog modulars, likely synth.com stuff, have an amplitude of 10V peak-peak. Serge modulars, as I can remember have 5Vpp and also doepfer's A-100. The opamp is there just to make all modules compatible with all systems.

For xombiex: go to http://www.yusynth.net/Modular/modular.html. Here you can find a lot of good DIY modules with the material list, trimming instructions, pcbs, component layouts and wirings..