13700 Noisegate/Expander

[armdnrdy]

There were a couple requests to retrofit a LM13700 into a noise gate/ expander board that originally called for a CA3080.

This is one of the projects that appeared in a Japanese effects book from the 80s. These files have been available on Mark Hammer's site (Ampage) as well as a few other places on the net.

I kept the board layout close to the original, but added a few things. Among the things that were added were input/output pull down resistors, a resistor tied to V+ and pad for effect engaged LED, and a few extra ground pads. Also, the original 2SC1222 and 2SA640 transistors were changed to BC550 and BC560.

There were a few discrepancies between the original schematic and original board routing/layout. These were mainly component positions switched. (C10<>R14, C8<>R12, C6<>R8) The redrawn schematic reflects the original board layout.

As noted above, there is a pad for an effect engaged LED. This would be the pad in the upper right corner marked "LED".
There is an additional LED marked "D5". This should be a gating indicator, and should turn on and off with the gating.

It is my thought that some experimenting can be done with this circuit. The Expand/Normal switch (SW1) can possibly be changed to a 50K pot. (with an additional resistor to ground?)

TR2 can be changed to a 5 or 10K pot? Level control?

Just some things I'm throwing out for the mod minded.

Here's the project file PDF:

https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/Noisegate-Expander%20file.pdf

[Kipper4]

Excellant Larry thanks so much.
Another one for the list.

[Mark Hammer]

Now THAT's citizenship!

Many thanks.

[armdnrdy]

Now THAT's citizenship!

Many thanks.

I wanted to take a break from all of the flanger madness and work on something easy!

I don't even want/need a noise gate! 

[Fender3D]

I wanted to take a break from all of the flanger madness and work on something easy!

You traitor...
 

Why don't use IC's buffers instead of Q1 and Q2?

[armdnrdy]

I thought about it but I would have to mess with some of the other components (darlington versus single tranny) and my bread board is full with the Tyco flanger pedal circuit.

If someone wants to play with it....I'll redo the board.

I'm not a traitor...I just needed a break! I started hearing flanging in my sleep! 

[deadastronaut]

I started hearing flanging in my sleep! 

that's mad, i remember when i first got a phaser when i was 14, i used it so much that i swear i could hear phasing in everyday life...cars..people talking...etc...very weird feeling.


hows the gate on this..abrupt?..smooth fade?..

[armdnrdy]

I haven't built this.
The first request to retro the board came from the forum member DIMstompboxes who built one with the original 3080.
Maybe he'll pop in and describe the gating.

I'm just a bystander in this one...not really of the innocent type though. 

[DIMstompboxes]

Great new layout armdnry, Any PNP or NPN can be use and you'll not regret after you built this one. Three of us has verified DimebuGG, Kmr and included me you can PM them and they are members here.
But Note, we all used both TL061 and CA3080. This will surely kick out the MXR fet noisgate with lot of lots of  issues.   

[armdnrdy]

I forgot to include in the BOM......the footprint for the trimmers is a Bourns 3362P.

A copy of the Bourns trimmer can be found at Tayda.

http://www.taydaelectronics.com/potentiometer-variable-resistors/cermet-potentiometers/3362p.html

[DIMstompboxes]

TR2 is just for level control I used 5k outside knob for it and the other knob is for sensitivity A 1M knob. That TR1 is 2k trimpot for balancing. 
Cheers,

[armdnrdy]

Thanks for the info.

What did you do for the Expand/Normal switch? I don't see a switch on your build.

It looks like gate LED, Effect LED, bypass switch, and the two controls you outlined.

[slacker775]

Anyone have Eagle files for this or have it shared on Oshpark?  I've had an odd interest in building a Noise gate for bit.

[armdnrdy]

Eagle schematic file:
https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/Noise%20Gate-Expander.sch

Board file:
https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/Noise%20Gate-Expander.brd

[DIMstompboxes]

Thanks for the info.

What did you do for the Expand/Normal switch? I don't see a switch on your build.

It looks like gate LED, Effect LED, bypass switch, and the two controls you outlined.

Just connected it to the ground for NORM and use the sensitivity control knob, EXP seems too fast for gating and release and little bit compress but you can add that mod just lazy to drill another hole. You'll not regret it, there is no stuttering note alike the MXR I built and sustain as a good decay.   

[deadastronaut]

Cool...be nice in a 1590b..

[Kipper4]

How. Critical are the transistors?
And are they replaceable with something that I have in stock like a 2n5088, 2n5089, bc109 although the gain might be a little low on the bc109.
Are the bc550 , 560s a common reasonably priced model.
Just asking
Thanks
Rich

[armdnrdy]

How. Critical are the transistors?
And are they replaceable with something that I have in stock like a 2n5088, 2n5089, bc109 although the gain might be a little low on the bc109.
Are the bc550 , 560s a common reasonably priced model.
Just asking
Thanks
Rich

I switched the Japanese transistors to what I thought would be more easily sourced transistors for you in the U.K.
The BC trannys that I chose are very common. They are even sold at Tayda.

The original NPN (2SC1222) is a low noise amplifier.
I believe that this tranny was used in this design because.....if you were going to use a noise gate....you were probably concerned with noise and didn't want to add to it. Logic 101 

The PNP transistors are not in the signal path so.......I don't think that they are critical.

By the way...hold the phone on the original board. Due to Rob's (deadastronaut) little nudge, I reworked the board to fit in a smaller enclosure. Thanks Rob! It's not like I don't have enough to do! 

[deadastronaut]

Ahhhh...good man. Nice one..

 

i know you like to keep busy...

[armdnrdy]

For your small box pleasure.




PDF file:

https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/Noise%20Gate%20-%20Expander%20build%20PDF.pdf