>
> Doesn't this go against the MOTM "CD quality" philosophy? There is
> no way a filter based on 741's etc. is going to be quiet.
Not necessarily true.
a) it depends ∗where and how∗ the '741 is used in the circuit. In the SEM filter, it's used in
the resonance feedback portion. So, not in the audio 'path' per se.
b) Noise is annoying only if you can hear it. Now, in today's uber-quiet CD world, it's certainly
∗easier∗ to hear noise. The Audio Precision test set I use to look at stuff can show this. But,
just because it measures "bad", doesn't make it ∗objectionable∗. The MOTM-480 CS-80 filter
measures the noise floor 12dB HIGHER than the MOTM-440. Yet, no beta testers have even mentioned
it, even though I specifically asked them to "listen for noise".
c) The MOTM-440 is the only "clean" VCF in the line. The MOTM-420 uses 4558 op amps, because they
have a distinctive sound associated with synths of the '80s. Side-by-side with the '440, and on a
GOOD playback system (like my Event 20/20bas monitors, no Mackie mixer in the chain), the '440
has much better 'slam' (transient response in lower frequencies) and clearer overall sound..
The Moog 904A clone MOTM-490 is very quiet (as is the original Moog).
I am pondering an ARP 4072-type, 4-pole lowpass clone (with added VC resonance). This was used in
the later "orange-faced" 2600s, and uses LM3900 Norton amplifiers. A ghastly part designed to be
the world's cheapest quad op amp for use in Delco automotive electronics (and used extensively in
Serge modules). However, it's that part that creates the 'bubbly, gurply, reed' sound.
Paul S.