LM13700 - CA3080 adapter board

[Mustachio]

Haha what 2 3080 adapter board! crazyness!

I actually need one of those ...

Blasphemy! Your in luck I believe thats called an LM13700    

Madbean's Sharkfin (FSH-1) uses two 3080s instead of an LM13700. Brian said it was because it fit better on the layout, but the two 3080s are right in line with each other, so I'm a little confused by that reasoning. I bought the 3080s, but every time I look at them, I think "eewwwww."

Oh nice Jon! I built the FSH from tonepad a few years ago. I hadn't seen madbeans version but I gotta say everything that comes from madbean is top notch! Its a very cool pedal but I did have a time getting the sample hold part how I liked it. Had to play with a bunch of different j201s . In the long run it was great but I had almost wished I built it with less controls like the original. Switching modes had me changing most the controls to get it how I liked the sound , so having 2 foot switches was pointless on mine . I would have been better off wiring the S/H mode on a toggle like the filter direction mode.

Are you gonna do a video when you build yours ? Id like to hear it because I wasn't fully happy with mine and started cannibalizing it for parts. The filter section on it was really nice though!


That expander/gate from Mark looks really neat! Instead of redesigning for the lm13700 should just make the adapter board armdnrdy made for this thread. I've been needing a noise gate maybe ill give it a try soon.

Thanks again for the Adapter board armdnrdy I think it will help a lot of people out !

[armdnrdy]

I just finished up the files for a LM13700 - CA3094 adapter board. This first version is for use in a circuit that leaves pin one unconnected (frequency compensation) and ties pin 8 (source /drive output) to V+.
I've seen a lot of circuits that use this configuration.

The second version is a bit more difficult. It includes the use of both pin 1 and 8.

It will include a discrete split darlington pair with a 2K resistor on the first transistor's collector and a 47K base resistor on the second transistor.

I still have to work out some of the details for the second version. Every step I take....I'm forced to learn something! 

[armdnrdy]

Looking through available data on darlington pair calculations, it looks like to properly calculate the specs of any given pair...you would need the information from the individual application.

The 3094 spec sheet lists the hFE at min. 16,000 / max. 100,000 for the given test conditions. That's quite a swing!

So..if you were to use four 3094s in the issue "J" small stone, you would have to "match" the buffers hFE to guarantee similar performance in each phase stage. (In theory of course)

Since I don't think that would have been a wise production decision, EHX would have installed available 3094s to achieve the desired effect without "matching".

With that being said, I'm looking to devise the easiest way possible for users to construct a "work alike" 3094 adapter board using a 13700 OTA, and a split darlington pair.

My thought is to use a known low hFE transistor for the first Q of the cascade, and a known high hFE transistor for the second.
Something like a PN2222 and a MPSA18.

I don't have any 3094s for testing purposes...and at $5.00+ for questionable authenticity.....I think it's going to stay that way!

Am I on the right track or way off the trail?

[armdnrdy]

I whipped up this schematic showing the common pins of the 3094 and the potential work around.

[Kipper4]

If your tired of using FET for MXR noisegate I recommend this http://hammer.ampage.org/files/Expander.gif
I got this way back years on Mark's website and I built this using separate TL061 and 3080 and its verified. I just copied the PCB design and scale to fit my case.
Although the PCB is not for LM3700 but I think it can be done. If only someone can redesign the PCB into LM3700 

I wonder If anyone is intrested in making this gate to suit the lm13700 please
It looks intresting to a bunch of us who are striving to rework the mxr noise gate. Please pm me if you think you can help.
thanks
Sorry for threadjacking.

[armdnrdy]

Rich,

I'm not sure I understand your request.

If this project is reworked for a 13700, how is that going to help "rework" the MXR noise gate which is JFET based?

[Kipper4]

True It might not help with reworking the mxr gate.
We are trying all differant ideas to get a Gate that works without defunkt parts (2n5952)
and is reasonable to build. theres lots of other considerations but for now an lm13700 is one of the considerations so it just might help Larry .

[armdnrdy]

Gotcha!

On your build, I see two controls...one for the sensitivity. What is the other one? In the schematic I see a switch for expander/normal. Did you put that on a rotary type switch or use a pot to make it adjustable?

[Kipper4]

It was DIMstompboxs post i qouted. sorry cant help

[armdnrdy]

Here's your noise gate with a LM13700.

I'll post the project tomorrow. (it's 1:00am right now....time to sleep!)

[Kipper4]

Omg
Thanks dude
Thats excellant I'll give it a try
Rich

[GodSaveMetal]

Here's your noise gate with a LM13700.

I'll post the project tomorrow. (it's 1:00am right now....time to sleep!)

And? what happend with this? yeahhhhhhh please don´t let it DIE!!!!!!!!!!!!!!

[armdnrdy]

And? what happend with this? yeahhhhhhh please don´t let it DIE!!!!!!!!!!!!!!

Search function..."noise gate"

http://www.diystompboxes.com/smfforum/index.php?topic=105397.0

[chicago_mike]

What about using the CA3280 ?

[armdnrdy]

What about using the CA3280 ?

A 3280 would work just fine in this circuit. Due to the different pinout..you would have to make a daughter board or rework the routing. The 3280 has been discontinued for years. That's why I used the easily obtained 13700 for a replacement for the 3080. If you have a drawer of 3280s and some time on your hands...go for it!

[StephenGiles]

Hi Larry from our temporary environment of hot sun, palm trees, fresh air & fun (!!) somebody once posted a rework of the EH Smallstone using 3280s, possibly back on the old forum days in the 90s. Mark may remember.

[armdnrdy]

Hi Larry from our temporary environment of hot sun, palm trees, fresh air & fun (!!)

Hey Stephen,
From your decription...it sounds like you are visiting my neck of the woods....Southern California.