[sdiy] Something better than CD4066 to switch CVs?

Ullrich Peter Peter.Ullrich at kapsch.net
Tue Feb 19 21:30:49 CET 2019


Hi!

If the ON resistance is a problem you could spend some money and use better analog switches that have a resistance downto 0.35 ohms!
I used Maxim types in the 1 ohm range in one of my projects. Some of them even have a +/- 25V signal range...

See www.maximintegrated.com for analog switches and multiplexers if you are interested.

Ciao
Peter
________________________________________
Von: Synth-diy <synth-diy-bounces at synth-diy.org> im Auftrag von Tim Ressel <timr at circuitabbey.com>
Gesendet: Dienstag, 19. Februar 2019 20:16
An: synth-diy at synth-diy.org
Betreff: Re: [sdiy] Something better than CD4066 to switch CVs?

This is a good point. In general any resistance in series with a v/oct
vco input will introduce a tracking error. This is why things that drive
vco inputs have to be designed carefully. Assuming 100K input resistance
on the vco input (seems to be the standard) and 3 cent max error allowed
(@ 10 volts), 25 ohms is the max added resistance allowed. This can
loosen up if tracking to 10 volts isn't important.

--TimR

On 2/19/2019 10:09 AM, chris wrote:
> On Tue, 19 Feb 2019 18:35:44 +0100 Florian Anwander <fanwander at mnet-online.de> wrote:
>
>> Am 19.02.19 um 11:06 schrieb Tom Wiltshire:
>>> The Prophet 5 managed to switch Oscillator B into low frequency mode about thirty years ago, so it must be possible.
>>>
>>> I had a look at the schematic and it doesn’t look like they switch an extra cap in though. Instead they switch an extra -15V into the CV. The Pro-1 uses the same trick.
>>>
>> Someone more knowledged may correct me, but I think this may work with a
>> coarse parameter change, but with tracking sensitive controls, the inner
>> resistance of the 4066 might become an influence.
>>
>> Florian
>
>
> But once you're entering LFO range, IMHO tracking becomes less important.
> And I don't think an *open* switch will affect audio tracking.
>
> I agree that using a CMOS switch in tracking relevant areas requires at
> least some consideration. Switch resistance may be specified as foggy as
> "yes, it's there, and it's something around ^&@&%* ohms at room
> temperature".
>
> Christian
>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
>
--
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com

_______________________________________________
Synth-diy mailing list
Synth-diy at synth-diy.org
http://synth-diy.org/mailman/listinfo/synth-diy



The information contained in this e-mail message is privileged and confidential and is for the exclusive use of the addressee. The person who receives this message and who is not the addressee, one of his employees or an agent entitled to hand it over to the addressee, is informed that he may not use, disclose or reproduce the contents thereof, and is kindly asked to notify the sender and delete the e-mail immediately.




More information about the Synth-diy mailing list