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JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

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JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

Tomislav Babic
hi guys,   its been some time that im thking of how to get some spare BAS662s for my JP8
and my other Rolands like SH2 etc etc..   but these are prohibitevely expensive.  
there is shitload of these buggers used in Jup , and these dealers want $40 a pop. 


so, been reading over the countless 303/xoxbox/adafrutit/cloning sites how after sub-atomic tests
they couldnt for the love of god find any discernible difference btwn the two...  and
if there is an uber obsessive group within analog world, that far surpasses even the moog
purists (which i belong to) it has to be the 303 crowd... 

what are your thought on this... if any?


what also worries me, and im no EE, is they say the BA662 is used in 303 in such a manner
that it doesnt really influence the sound. but i cant say that for JP8 with certainty... ?


since 6110 is several times less expensive i can even allow myself to buy a bunch in order
to find a suitable one in situations where matching with others is crucial - like the colour dot BA662 versions..
similar how you buy a pile of transistors to do the matching by hand.



i thought if there is a solution it would be of use to all of us - plenty of old vintage Roland on this list.


thanks
regards
Tom

--
---
Tomislav Babic
www.babic.com - studio, mp3, info
[hidden email]

www.myspace.com/nimbusdei
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RE: JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

Lorne Hammond

Tom: 

 

My understanding is the pin outs are different.  Went through this on the chorus for the JP-4.

In the xoxbox physical pcb it has different traces/solder bridges and caps depending on which chip you use.

 

Lorne

From: Tomislav Babic [mailto:[hidden email]]
Sent: Tuesday, February 26, 2013 2:34 PM
To: analogue
Subject: [AH] JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

 

hi guys,   its been some time that im thking of how to get some spare BAS662s for my JP8
and my other Rolands like SH2 etc etc..   but these are prohibitevely expensive.  
there is shitload of these buggers used in Jup , and these dealers want $40 a pop. 


so, been reading over the countless 303/xoxbox/adafrutit/cloning sites how after sub-atomic tests
they couldnt for the love of god find any discernible difference btwn the two...  and
if there is an uber obsessive group within analog world, that far surpasses even the moog
purists (which i belong to) it has to be the 303 crowd... 

what are your thought on this... if any?


what also worries me, and im no EE, is they say the BA662 is used in 303 in such a manner
that it doesnt really influence the sound. but i cant say that for JP8 with certainty... ?


since 6110 is several times less expensive i can even allow myself to buy a bunch in order
to find a suitable one in situations where matching with others is crucial - like the colour dot BA662 versions..
similar how you buy a pile of transistors to do the matching by hand.



i thought if there is a solution it would be of use to all of us - plenty of old vintage Roland on this list.


thanks
regards
Tom

--
---
Tomislav Babic
www.babic.com - studio, mp3, info
[hidden email]

www.myspace.com/nimbusdei

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Re: JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

Tomislav Babic


On Wed, Feb 27, 2013 at 5:52 AM, Lorne Hammond <[hidden email]> wrote:

Tom: 

 

My understanding is the pin outs are different.  Went through this on the chorus for the JP-4.

In the xoxbox physical pcb it has different traces/solder bridges and caps depending on which chip you use.

 


do you think it could be used with a small adapter containing socket, then rewired to the original location?

did the sound of JP4 ensemble remain the same when you did it btw?

thanks

 

Lorne

From: Tomislav Babic [mailto:[hidden email]]
Sent: Tuesday, February 26, 2013 2:34 PM
To: analogue
Subject: [AH] JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

 

hi guys,   its been some time that im thking of how to get some spare BAS662s for my JP8
and my other Rolands like SH2 etc etc..   but these are prohibitevely expensive.  
there is shitload of these buggers used in Jup , and these dealers want $40 a pop. 


so, been reading over the countless 303/xoxbox/adafrutit/cloning sites how after sub-atomic tests
they couldnt for the love of god find any discernible difference btwn the two...  and
if there is an uber obsessive group within analog world, that far surpasses even the moog
purists (which i belong to) it has to be the 303 crowd... 

what are your thought on this... if any?


what also worries me, and im no EE, is they say the BA662 is used in 303 in such a manner
that it doesnt really influence the sound. but i cant say that for JP8 with certainty... ?


since 6110 is several times less expensive i can even allow myself to buy a bunch in order
to find a suitable one in situations where matching with others is crucial - like the colour dot BA662 versions..
similar how you buy a pile of transistors to do the matching by hand.



i thought if there is a solution it would be of use to all of us - plenty of old vintage Roland on this list.


thanks
regards
Tom

--
---
Tomislav Babic
www.babic.com - studio, mp3, info
[hidden email]

www.myspace.com/nimbusdei




--
---
Tomislav Babic
www.babic.com - studio, mp3, info
[hidden email]

www.myspace.com/nimbusdei
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Re: JP8 and other vintage Rolands VCA - BA662 - can BA6110 be used instead?

Oakley Sound-2
The quick answer is no since as already stated they have a different pin
out. But it should be noted that the BA6110 is an improved version of
the BA662. If the BA662 is R-Ohm's version of the LM3094 in a SIL pack,
then the BA6110 is a single channel version of the CA3280 albeit with a
more sensitive transconductance spec.

This means that the BA6110 has an optional linearising circuit on the
front end and different Iabc input to the BA662. The lineariser can
simply not be used so in some circuits the BA6110 can work as the BA662
producing no difference or little difference in sound.

The different Iabc circuitry is another matter. Even if you can cope
with the different pin out by using an adapter the double diode drop at
the Iabc pin is a problem in some circuits. Some VCA circuits, like the
SH-101, that use a true current drive can use an BA6110 the same as a
BA662. Those, like the TB303, that feed it with a resistance or have a
limited voltage swing cannot.

The xoxbox got around this by adding a current mirror for driving the
BA6110. This could be built into an adapter board of course but it does
up the complexity and size of such an adapter.

And speaking of adapters I built a few BA662 replacement boards that
used a single LM3080 and a discrete follower that worked very well in
the TB303. I'm not sure they'd be good enough in all applications
particularly regarding DC accuracy which could well be worse.

Tony

http://takla-makan.bandcamp.com/
http://www.oakleysound.com

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