[sdiy] Problems with linearized SSI2164 ?

Mattias Rickardsson mr at analogue.org
Thu Feb 7 00:01:01 CET 2019


Strange deluxe!
Sounds a bit like the SSI2164 is broken, perhaps in a way so that it
doesn't tolerate the louder signal input (-5V via 30k to feedback VCA
input)?

/mr


Den ons 6 feb. 2019 23:47 skrev Danjel van Tijn <danjel at intellijel.com>:

> Yes and I had coincidentally just tried switching those to 100k and it
> fixes the issue (-5V via 100k to feedback VCA input) and then the +5V
> connected via 100k to CV summing op amp.
>
> Why does this not work with 30k but it is ok with the coolaudio ones?
>
> On Wed, Feb 6, 2019 at 2:42 PM Mattias Rickardsson <mr at analogue.org>
> wrote:
>
>> Hi Danjel,
>>
>> with 30k for Rin, do you mean one of the 100k in the linear control
>> circuit?
>> If so, that's probably the reason it misbehaves.
>>
>> Best,
>>
>> /mr
>>
>>
>> Den ons 6 feb. 2019 23:19 skrev Danjel van Tijn <danjel at intellijel.com>:
>>
>>> Hi there,
>>>
>>> Has anyone else experienced issues with the SSI2164 used in place of a
>>> Coolaudio 2164 in a linearized VCA configuration?
>>>
>>> With no CV applied to the circuit control pin of the VCA should be close
>>> to 0 (and it is when I swap back in a coolaudio chip)  but with a SSI2164
>>> the voltage at the control pin is around 0.85V.
>>>
>>> I am using accurate voltage sources for the negative and positive
>>> voltage references (-5 and +5). and as aforementioned swapping in a
>>> coolaudio chip returns the circuit to working as expected.
>>> Opamp is a  TI TL072CPWR.
>>>
>>> The only two differences from the datasheet version are that we are
>>> using 30K for Rin and 510R+560p for stability;  both are within range of
>>> acceptable values according to datasheet.
>>>
>>> Any thoughts?  possibly bad batch of ICs?
>>>
>>>
>>> --
>>> cheers,
>>>
>>> Danjel van Tijn
>>> Intellijel Designs Inc.
>>> m. +001 604-773-2426 <(604)%20773-2426>
>>>
>>> www.intellijel.com
>>> https://www.instagram.com/intellijel/
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>>> www.youtube.com/intellijel
>>> www.twitter.com/intellijel
>>>
>>>
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>> --
> cheers,
>
> Danjel van Tijn
> Intellijel Designs Inc.
> m. +001 604-773-2426 <(604)%20773-2426>
>
> www.intellijel.com
> https://www.instagram.com/intellijel/
> www.facebook.com/intellijel
> www.youtube.com/intellijel
> www.twitter.com/intellijel
>
>
>
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