[sdiy] OTA replacement

[Scott Gravenhorst]

jbv <jbv.silences at club-internet.fr> wrote:
>thanks for your comments on this topic.
>the replacement of the BA662 by the 3080 will actually
>take place in Roland SVC-350 vocoder in which that
>chip is used only in the compressor...
>
>BTW I was wondering if the 4558 could be replaced by
>a TL072, at least in the filter section...

Be careful here, if the TL072 was chosen for it's high input impedance (JFET input), you may have
problems since the 4558 has a bipolar input stage.

>JB
>
>> The 3080 works fine as a replacement for the BA662. I have 
>built 303 clones with both the BA662 and 3080. I have even made a 
>small pcb which converts an SMD 3080 into a 9 pin SIL and is a 
>drop in replacement for the BA662. The only issue is offset, but 
>this can be trimmed out externally. > > I have tried this in my 
>JX-3P and could tell no difference - it sounded rubbish before 
>and rubbish after - (only kidding). > > ....the 3080 doesn't have 
>the second buffer stage, but you can use a transistor or op-amp 
>to do this. > > mark > > > -----Original Message----- > > From: 
>Byron G. Jacquot [SMTP:thescum at surfree.com] > > Sent: Monday, 
>March 29, 2004 7:52 AM > > To: synth-diy at dropmix.xs4all.nl > > 
>Subject: Re: [sdiy] OTA replacement > > > > > I've just read on a 
>couple of webpages that the > > > obsolete BA662A (OTA) could be 
>replaced by > > > the CA3080. > > > Could anyone confirm this ? > 
>> > > I seem to recall people using 3080's in some TB303 clones, 
>and they > > seemed to work OK. Not that I ever sat the curcuit 
>in question > > alongside a real 303 for sonic comparison, but it 
>wasn't > > unacceptable. > > > > IIRC, The BA662 is in a SIP 
>package, and also has an onboard output > > buffer, something 
>like a 13600. The 3080 is usually in a DIP > > package, and lacks 
>the buffer. > > > > Byron Jacquot 
>

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