BA6110 (was: Re: The science of reverb springs and TB's VCA)

[Fraser, Colin J]

> -----Original Message-----
> From: Tony Allgood [mailto:oakley at techrepairs.freeserve.co.uk]
> Sent: 25 February 1999 19:07
> To: synth diy
> Subject: Re: BA6110 (was: Re: The science of reverb springs and TB's
> VCA)
> 
> >I remember some early Roland synth had a 4-pole filter built from
> these.
> Would it be worth building that, would it sound different from 3080
> based filters?
> 

The System 100m and Sh09 filters are both BA662 based at least - there may
be more.
I can't comment on the 100m filter, but I always thought the Sh09 filter
sucked - especially at high resonance. More of a breathy whistle than a sine
wave.

I replaced the filter in my Sh09 with a SSM2045, and this was a great
improvement, especially with DC coupling thru the filter/vca.

I had 5 BA662 left over too ;-) (4 poles + vca)

> I think filter sound has more to do with
> topology rather than devices.

Well the Sh09 filter was 4 x OTA, and so is the SSM2045, but they sound
completely different...
Having said that, they are more similar to each other than either would be
to say a diode ladder, so I would guess there's maybe a 70/30 split between
topology and implementation for filter characteristics.

Colin f