[sdiy] BA662 (Was Re: SPV-355 -15V rail issue)

brianw brianw at audiobanshee.com
Wed Jun 21 23:34:44 CEST 2023


Questions:

Is there a difference between a diode-connect transistor and a diode? ... other than specifics like Von?

Can you replace a diode-connected transistor with a diode that has the same characteristics? (admittedly, it may be difficult to find a diode with the same characteristics...)

Brian


On Jun 19, 2023, at 3:13 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
> Interestingly, thre are a few minor differences between the reverse-engineered Open Music Labs schematic (which the Re-303 uses) and the Alfa clone. Some of the differences are obvious stuff, like diode-connected transistors being shown as diodes, for example, but not everything.
> 
> Here's the Open Music Labs version:
> 
> http://wiki.openmusiclabs.com/wiki/x0xb0x
> 
> And here's Alfa's:
> 
> https://www.alfarzpp.lv/eng/sc/AS662D.pdf
> 
> 
> On 19 Jun 2023, at 13:10, Todd Sines <sines_list at scale.la> wrote:
>> Din Sync make them for their RE-X0X series
>> 
>> Todd
>> 
>> On Jun 19, 2023, at 4:39 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
>>> Yes, Alfa make a clone - or at least a chip with that number:
>>> 
>>> https://www.alfarzpp.lv/eng/sc/AS662D.pdf
>>> 
>>> On 19 Jun 2023, at 04:41, Adam (synthDIY) <synthdiy at adambaby.com> wrote:
>>>> Actually, yes you're right, the Roland BA662 OTA that they used a lot around this time, both for VCAs and VCFs. I've sent you the schematic.
>>>> 
>>>> I think they've been cloned successfully in recent years




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