Do you need a schem of the actual eq, or just how to hook up
in the FB loop of an op amp? I have the later around
somewhere, or you could probably get it from Spectra Sonics
Aviation in Ogden Utah. Last I checked though, they will not
give up actual schematics, which seems kinda silly to me.

John Noll wrote:
I'm looking for a schematic for a SpectraSonics 500 passive EQ.
It's the 4-knob, two band version with selectable frequencies.
Thanks.

Bryson wrote:
Do you need a schem of the actual eq, or just how to hook up in the FB
loop of an op amp? I have the later around somewhere, or you could
probably get it from Spectra Sonics Aviation in Ogden Utah. Last I
checked though, they will not give up actual schematics, which seems
kinda silly to me.

John Noll wrote:

I'm looking for a schematic for a SpectraSonics 500 passive EQ.
It's the 4-knob, two band version with selectable frequencies.
Thanks.



I'm looking for a schematic of the actual EQ if there's one available,
but what I'm trying to do is exactly what you said: hook it up into the
feedback loop of an opamp. In a google search I've found pinout
connections to a Spectrasonics 101 but I'm hoping I can use a 990 opamp
instead.

--
--
John Noll
Retromedia Sound Studios
Red Bank, NJ 07701

Phone: 732-842-3853 Fax: 732-842-5631

http://www.retromedia.net

John Noll wrote:
Bryson wrote:

Do you need a schem of the actual eq, or just how to hook up in the FB
loop of an op amp? I have the later around somewhere, or you could
probably get it from Spectra Sonics Aviation in Ogden Utah. Last I
checked though, they will not give up actual schematics, which seems
kinda silly to me.

John Noll wrote:

I'm looking for a schematic for a SpectraSonics 500 passive EQ.
It's the 4-knob, two band version with selectable frequencies.
Thanks.




I'm looking for a schematic of the actual EQ if there's one available,
but what I'm trying to do is exactly what you said: hook it up into the
feedback loop of an opamp. In a google search I've found pinout
connections to a Spectrasonics 101 but I'm hoping I can use a 990 opamp
instead.


I Spoke to Greg Dilly at Spectrasonics. Correct. They will not release
the schematics. They are sending me "Operating Instructions" for $25.
Hopefully there'll be something usable in there.

--
--
John Noll
Retromedia Sound Studios
Red Bank, NJ 07701

Phone: 732-842-3853 Fax: 732-842-5631

http://www.retromedia.net

Bryson wrote:
Here's a post on the subject, by Fred Forssell:

Date: 2000-08-22 23:00:44 PST

The EQ's are designed to run as follows...

1) Connected a 10.7k resistor from the output of an opamp to its
inverting input.
2) Connect the EQ's in and out terminals in parallel with the 10.7k
resistor. Connect the ground terminal of the EQ to audio ground.
3) Connect a 100 ohm resistor from the opamp's inverting input to
ground.

Be sure to check to make sure the opamp is not oscillating. If it is
you may need to add a comp cap across the 10.7k resistor.

Any good opamp will work, but I'd use the JFET990-2 modules that I sell
if I were you! grin

I hope that helps.

Fred Forssell
Forssell Technologies
www.forsselltech.com



Thanks. I missed that one.


--
John