SSM2164/V2164-based phasers?

[Mark Hammer]

The SSM2040 is long gone for nearly 30 years now, and any NOS units fiercely competed for by Prophet 5 owners.  The IR3109 could replace it, but you have to work at Roland/Boss or cannibalize a pedal to put your hands on one.

What we have left in the way of quad OTA chips is the SSM2164 and the Coolaudio V2164 (which Small Bear happens to carry for $3.50 a pop; less if you buy more than 25).  Though compact, unlike the LM13600/13700 or the CA3094, the 2164 does not provide a buffer for each OTA.  So it is sort of like a quad 3080.

I was curious about whether anyone had come across any phasers using the 2164.  I imagine it would be accompanied by op-amp buffer stages.

If I think about it, a pair of 13600stakes up 32 pins (2 x 16pin) worth of space for 4 stages, but provides the necessary buffers.  A single 2164 takes up 16 pins, but you could situate an 8-pin sip on each side of it for a total of 4 stages with a reasonably small footprint.  Not dramatically smaller than 13600-based, but still smaller.  In principal, an 8-stager could fit inside a 1590B.

Just wondering aloud.

[frequencycentral]

Subdecay Quasar uses them I believe.

Technically, the V2164 is not a quad OTA, but a quad VCA. You can't use it in quite the same way as an OTA to make all pass filters.

There is also a discussion here:

http://circuitworkshop.com/forum/index.php?topic=888.0

and this:

http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=0&subsubmenu=3

I've so far failed to be attracted to the V21664, probably being as the LM13700 is my all-time favourite chip. Hell, I even named my son 'LM13700'......  Also, you can buy 25 x LM13700 at a $ a shot: http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=170529005056&ssPageName=ADME:B:EOIBSA:GB:1123  I can vouch for their functionality, having used dozens.

[Mark Hammer]

Thanks!  Very helpful.

[StephenGiles]

Mark, there is an English company that uses the ssm2164 for their auto filter - Ash..... I can't remember the name but I have some info on my old PC which I haven't transfered yet.

[StephenGiles]

It's Ashdown Engineering.

[Brian Marshall]

As mentioned the 2164 is a VCA and not an OTA.  OTA's are definitely make for less complicated phasers.

The subdecay baby quasar and quasar dlx both use the 2164, although both are implemented differently.  The quasar dlx uses two opamps per stage, while the baby quasar only uses one.  Using two opamps per stage allowed us to tap different stages more easily.  The two implementations do sound different.  The single opamp per stage is imperfect.  I designed the baby quasar a couple years ago so I don't remember the specific issue, but making anything beyond a 3 or 4 stage phaser turns in to a giant mess pretty quickly.

As VCA's go the 2164 is relatively cheap.  After a bit of testing we actually switched to the V2164.  the results were basically the same.  We couldn't hear any real difference between the two.  We can also get them much more quickly rather than waiting for analog to ship them from overseas.

The 2164's preformace is highly dependent on the opamp you pair with it.  We use mostly TL07x and TLC226x opamps with it.  Results with opamps like the lm324 didn't work quite as well.  I assume this was due to input impedance.
The 2164 does have some limitations.  The voltage at the output can not vary much from mid-supply.  Maybe half a volt.  If you use it properly it's not usually an issue, but if you try to use it as a variable resistor it won't work.

The 2164 can also be used to make a pretty decent sinewave oscillator, and from that is pretty easy to extract a square and triangle as well.  a 2164, quad opamp, a few resistors, a couple caps and a pot to vary the frequency.

[Mark Hammer]

Thanks, Brian.   That`s very helpful.  Much appreciated.  Lets me put yet another project destined for incompletion to the side!