Subbject: [AH] REVIEW: Synthesizers.com Q150 Ladder LPF
Date: Fri, 9 Nov 2001 03:30:40 EST
From: Konkuro@aol.com
To:   analogue@hyperreal.org


I recently purchased two Q150 -24 dB transistor ladder filters from 
Synthesizers.com and I must say that they live up to the hype, for the most 
part.  These designs are based on Bob Moog's ladder filter (who is graciously 
acknowledged in the literature) with certain improvements added.

The filter sports the expected Frequency and Resonance controls, but also 
give you a straight 1V/Octive input and two inputs with level controls--one 
of which conveniently features inversion.  Signal inputs offer two variable 
inputs as well, but why Roger Arrick didn't add a a third straight input, I 
don't know.  There is certainly room for the jack and it would have added 
visual balance if nothing else.  Perhaps he figured that the Q107 State 
Variable filter (a design I like so much that I ordered a fourth Q107) had 
two signal inputs, so the Q150 should have two as well.  Whatever.

Two unique features of this filter are the circuitry that holds a constant 
amplitude when the resonance is turned up, and a switch that selects either a 
-12 or -24dB slope.  To be honest, neither of these features impressed me 
greatly.  While I realize that the Moog filters decreased in amplitude when 
the resonance was tweaked into regeneration, there are other -24dB ladder 
filters out there that don't have this problem.  As I recall, the Doepfer 
ladder filter also maintained a constant amplitude with the resonance cranked 
up.  As for the -12/-24dB switch, it might be useful if you don't own the 
Q107 State Variable Filter, but if you do, it's not much good.  The Q107 
State Variable gives you a -12 dB response, but it also allows you to tweak 
the resonance into near-Moog territory.  When the -12 dB switch is selected 
on the Q150, the response is almost reminiscent of the PAIA 2700 LPF (not 
necessarily a bad thing).  This is because the resonance control has little 
effect in -12 dB mode, which isn't the case on the Q107 State Variable Filter.

So how does this filter sound in -24 dB mode?  Effing awesome.  I can't 
compare it to a live Moog filter, as I do not own one, but I can say as 
someone who owns legions of Moog records that it sounds for all the world 
like a classic Moog LPF (and for WAY less money). You know what I mean--that 
"licking" resonance that typifies the classic Moog LPF.

As if that weren't enough, the filter is also remarkably linear.  Throw it 
into regeneration mode and you get that unmistakable sweet sine that no VCO 
in the world seems able to produce.  One of the filters I bought was dead-on 
accurate over an entire 5 octaves.  The other wasn't quite as linear and was 
good through 4 octaves (but darn near close to five). 

Compared to a previous ladder filter I owned, this filter is astonishing.  
For starters, it is quiet and doesn't hiss like Medusa on a bad hair day. It 
also has that classic Moogy sound and operates quite nicely as a sine VCO.  
Why anybody would pay top dollar for a Moog LPF nowadays when you could have 
this improved version for half the cost is beyond me.

I swear I almost sound like a shill for Roger Arrick sometimes (never even 
met the man), but the gospel truth is that the Synthesizers.com system 
delivers more bang for the buck than any modular synth I have ever seen.  
Where else can you get Moog IIIc looks with better-than-Moog-IIIc performance 
at a minimoog price?

johnm