Osamu Hoshuyama Totem Pole VC LPF

Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

An elegant and streamlined filter (but maybe a bit tricky). I don't understand how differential pairs work in Moog filters but i'd like to know this and the difference.

http://electro-music.com/forum/phpbb-files/vcftp0211_180.gif

Has anyone here made or heard this fascinating filter?

I cannot find information on the TD62507A Toshiba transistor array Hoshuyama used in the design. Anyone point me to a data sheet or what transistors a substitute for the transistor array would be?

Lastly any likely changes to run on 12V?

mph · Joined: Aug 25, 2007 Posts: 88 Location: France

Hi
the TD62507A seems to be a simple NPN low gain transistor array, nothing fancy:
https://pdf1.alldatasheet.com/datasheet-pdf/view/32291/TOSHIBA/TD62507F.html

Maybe a CA3086 would do the job, it has already a differential pair + 3 spare transistors.

Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Hi mph

Thanks for finding the data sheet - really helps Smile

But I don't think the 3086 can be used - Totem's configuration is unlike the differential pair (

Suppose I could try to shove in a bunch of standard npn's (matched sort of!) - the chances of me not bungling are high as it is quite a complicated schematic for me to breadboard. Also I am on 12V.

Toshiba's transistors have a 'parasitic diode' am not sure what that is although am guessing it is to stop stuff going the wrong way in the array.

Be really good to know if anyone has heard this filter or some more info

gabbagabi · Posted: Thu Jul 04, 2019 6:43 am Post subject:

may iam allowed to post an inspiration.

attached my attempt so takkle the ms20-vcf from Jürgen Haible.
This was always to much for my brain drunken

to put on stripboard.

As u can see, even that is not finished, the opamp is missing.
The plan was to mount the opamp on a piece of stripboard, and glue it there where it would belong.

If i would do the totem pole i would probably use two tl072 in a similar manner.
And i will do it (both) in the future, i promise Shocked