CA3098, is there an available replacement?

[Scruffie]

I'm looking at the 4 knob EHX deluxe octave multiplexer, the schematic calls for a CA3098 which seems obsolete and the ebay prices are high, is there a suitable work around for it?

[armdnrdy]

Hey Scruffie,

Don't you mean CA3094?

If so, check out this thread for a possible work around:

http://www.diystompboxes.com/smfforum/index.php?topic=105341.20

[Scruffie]

Hey Scruffie,

Don't you mean CA3094?

If so, check out this thread for a possible work around:

http://www.diystompboxes.com/smfforum/index.php?topic=105341.20

Sadly I do not, there are 2 CA3094 which I know how to replace but I know nothing of the CA3098, it's a Programmable Schmitt Trigger.

[armdnrdy]

Hey Scruffie,

I downloaded your drawing from the other site and I see two 3094s. Is the drawing wrong?

I just found this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=88374.0

[Scruffie]

Hey Scruffie,

I downloaded your drawing from the other site and I see two 3094s. Is the drawing wrong?

I just found this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=88374.20

No my schematic is right but it's for the 5 knob deluxe model, there was an earlier 4 knob version which used a different fundamental extractor and circuit in general, I think the same one from the EH Guitar Synth.

[armdnrdy]

Gotcha!

I haven't come across that drawing.

[Scruffie]

Gotcha!

I haven't come across that drawing.

I knew there was one and that it used a CA3098 as i'd seen guts of it but i'd only seen the schematic for sale and I didn't fancy paying $5 just to look at it so i've had my eye out for a copy.

But looking for something else today, I ended up on Dirk's site and noticed he'd traced one - http://www.dirk-hendrik.com/temp/EH_1325D.pdf

[R.G.]

The circuit as shown doesn't use all the CA3098's talents. I believe it can be replaced by some careful design to get the same function out of a dual opamp. This is a design-to-function, not a pin-for-pin replacement.

The 3098 implements a window comparator and an internal flipflop with some current-controlled output sinking and other stuff that's not needed in this application. It is possible through careful design to make an opamp schmitt trigger that will trip at the desired points from the circuit, and then to trigger the following flipflop directly.  A more detailed copy of the function would use two opamps to copy the "window comparator" function and then another opamp or two to do the output signal to the following flipflop. This second way is more parts but less work to get right as it's a less critical design.

[Scruffie]

Thanks for the info R.G, sounds a bit above my pay grade and a hair too much work though, i'll stick to the 5 knob version I think the design is an improvement any way.

[StephenGiles]

Barely readable !

https://www.dropbox.com/s/soxtm6cgyhb4r4i/EHdeluxeoctave_a.gif
https://www.dropbox.com/s/nbn7t89bovqkuy7/EHdeluxeoctave_b.gif

[Scruffie]

Barely readable !

https://www.dropbox.com/s/soxtm6cgyhb4r4i/EHdeluxeoctave_a.gif
https://www.dropbox.com/s/nbn7t89bovqkuy7/EHdeluxeoctave_b.gif

I should know to just ask you in future!  Thanks Stephen as always... and barely readable hasn't stopped me redrawing them in the past 

I don't suppose you have the schematic for the solid state reverb do you?

[StephenGiles]

Barely readable !

https://www.dropbox.com/s/soxtm6cgyhb4r4i/EHdeluxeoctave_a.gif
https://www.dropbox.com/s/nbn7t89bovqkuy7/EHdeluxeoctave_b.gif

I should know to just ask you in future!  Thanks Stephen as always... and barely readable hasn't stopped me redrawing them in the past 

I don't suppose you have the schematic for the solid state reverb do you?

What was it called?

[Scruffie]

Barely readable !

https://www.dropbox.com/s/soxtm6cgyhb4r4i/EHdeluxeoctave_a.gif
https://www.dropbox.com/s/nbn7t89bovqkuy7/EHdeluxeoctave_b.gif

I should know to just ask you in future!  Thanks Stephen as always... and barely readable hasn't stopped me redrawing them in the past 

I don't suppose you have the schematic for the solid state reverb do you?

What was it called?

That is the name, EH-5500 Solid State Reverb. It uses an MN3011.

[StephenGiles]

No I don't have that one.

[Scruffie]

No I don't have that one.

It was a bit of an obscure one/long shot, thanks for checking anyway 

[StephenGiles]

No I don't have that one.

It was a bit of an obscure one/long shot, thanks for checking anyway 

I've looked through my EH stuff and cannot see my original printed version if the CA3098 deluxe OM. That scan is dated 2000 on my hard drive! If I find it I'll do a hi-res scan and straighten the image.

[Scruffie]

No I don't have that one.

It was a bit of an obscure one/long shot, thanks for checking anyway 

I've looked through my EH stuff and cannot see my original printed version if the CA3098 deluxe OM. That scan is dated 2000 on my hard drive! If I find it I'll do a hi-res scan and straighten the image.

With Dirks redraw and the copy you provided I should be able to do one of my patented 'redraws' so don't worry about it too much.

Did you come across a copy of the MN3007 clone theory though? I've traced gut shots against the schematic redraws and there's some differences and weird stuff (412pF caps!?) checking a factory copy might help clear things up.

I think i've nearly covered all the vintage EHX stuff now though! Think the last on my list are the Echo 600 and the solid state reverb.

[Scruffie]

Oh, it seems the Solid State Reverb may have been called the 'Reverbatron' on schematics if that helps.

[StephenGiles]

No I don't have that one.

It was a bit of an obscure one/long shot, thanks for checking anyway 

I've looked through my EH stuff and cannot see my original printed version if the CA3098 deluxe OM. That scan is dated 2000 on my hard drive! If I find it I'll do a hi-res scan and straighten the image.

With Dirks redraw and the copy you provided I should be able to do one of my patented 'redraws' so don't worry about it too much.

Did you come across a copy of the MN3007 clone theory though? I've traced gut shots against the schematic redraws and there's some differences and weird stuff (412pF caps!?) checking a factory copy might help clear things up.

I think i've nearly covered all the vintage EHX stuff now though! Think the last on my list are the Echo 600 and the solid state reverb.

Found them!
https://www.dropbox.com/s/8ay7oq5fn0hnrk0/EH%20delux%20Octave%20Mult%201a.jpg
https://www.dropbox.com/s/4bn3xc1iigo31ne/EH%20delux%20Octave%20Mult%201b.jpg

There is a lot of photocopying dirt in the background but I've managed to minimise it!