13700 Noisegate/Expander

[Kipper4]

I did a bit of searching and bought those trannys.
really reasonably priced thanks.
So this is on my xmas build list.
What you have done has not gone unnoticed Larry we all appreciate your work.
Its about time some decent diy noise gates came up.
I have most of the bits to build the maxon too.
Something tells me im gonna have a noise gate run on soon.
Thanks again Larry your one in a million.
and to DIMstompboxs too and Rob

[deadastronaut]

nice one larry..

still got my head in my 4pt delay cooking at the mo, but this will be on my 'just build it '' list after xmas.

anyone done a demo of it yet?...

[pinkjimiphoton]

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.

i think i did some of that acid too   

[DIMstompboxes]

Guys,
Yes it's verified with TL061 and CA3080 and using NPN 2n5088 PNP 2n3906 with Zener 1n5228.
BTW you can also use 100K log for better threshold just experiment.
Sorry for the delay i'm so busy  I benchmarked all with the same set up with my TScreamer and AMP. First on the FRONT using single coil guitar-noisegate-TS-AMP. TS set to full drive and AMP loud enough to hear the noise. Result.: Expander- just minimum threshold good fade at the end no trailing noise, guitar sound one is to one when on and off
Boss- full threshold with minimum or considerable stuttering or trailing noise, guitar sound one is to one when on or off
Mxr clone- 95% threshold with no stuttering but lost in volume, guitar sound not one is to one when on and off.
Now I put the noisegates at the BACK chain Guitar-TS-noisegate-AMP.
Result: Expander - max or full in threshold with minimum stuttering when fading but very considerable.
Boss - full threshold loud hum can not tame the noise defintely failed in test it is only good at the FRONT of the chain.
Mxr clone - full threshold hum still audible but not louder than Boss, guitar sound fairly low. THAT IS WHY I DITCH OUT my MXR and use the casing for other project

My Rating
Mxr 80% due to volume lost
Boss 85% good on FRONT
Expander 95% but not 100% or perfect.

Cheers,

[Kipper4]

you mean to say you didnt make the lm13700 one DIMstompboxes?
That was kinda the point of this thread and the reason larry did all the graft.
I'm waiting on supplies when i get some chips i'll do it over christmas.

However i'm pleased you like it and rate it better than the others.

[armdnrdy]

I think this review is from a previous build of the noise gate/expander from the Japanese stomp box PDF.

Not from the version that I posted.

[Kipper4]

Gottya I beg your pardon

[knutolai]

Something I thought of when looking at the circuit (nice work btw!):
Could this be build as a wrap-around for a noisy effect pedal, say something with a constant oscillator bleed like a Ring Modulator, to fade away unwanted noise when nothing is being played? I'm mean I know that's what a noise gate do, but would it optimize the noise suppression if one placed the noisy pedal at the C3 point instead of in front of the whole expander circuit?
This way the noise generated from the pedal won't affect the amount of attenuation. Hope I'm making sense 

[armdnrdy]

Could this be build as a wrap-around for a noisy effect pedal, say something with a constant oscillator bleed like a Ring Modulator, to fade away unwanted noise when nothing is being played?

If you have a breadboard, you can experiment with a simpler circuit. You can "tweek" components until it's working correctly for your circuit.

Here's a circuit you can try:

[bean]

Really interested in building this. I decided to have a go at a layout using the unused buffers in place of Q1 and Q2. Here is the re-draw.

edit: check pdf project file below for schematic re-draw

And the layout:



If anyone wants to have a look at the my schem and confirm it I'm happy to post the PCB artwork, so long it is okay with armdnrdy.

[armdnrdy]

Post away Brian!

I'm just curious if the first darlington buffer will "blast" too much current into the non inverting input of IC2 (061) and the inverting input of IC1. (13700)

Might have to adjust R4 for the increased HFE.

The other buffer is after T2 which can be adjusted for level, but if anyone wants to replace T2 with a pot for a level control....might cause issues.

or.....am I completely wrong?

[bean]

Here is the project file. I named it "Fencepost" since Gate_Expander is...well, descriptive but not fun.

Eagle files/pdf/BOM all in the zip.

http://www.madbeanpedals.com/projects/Fencepost/Fencepost.zip

[Kipper4]

Did you build it yet Bean.
I'm anxious to hear how it works.

[armdnrdy]

I'm a bit curious as to the effect of darlington pairs in place of single NPN transistors in this circuit.

Darlingtons have twice the base emitter voltage drop when saturated.

Can someone pop in and give some input?

It would be helpful in implementing LM13700s in other circuits.

Here's Brians redraw with the two darlingtons replacing single NPNs. The darlington collectors are connected to VC internally inside of the 13700.

[bean]

Would increasing R3 to 1M or 1M5 mitigate that somewhat?

[DIMstompboxes]

you mean to say you didnt make the lm13700 one DIMstompboxes?
That was kinda the point of this thread and the reason larry did all the graft.
I'm waiting on supplies when i get some chips i'll do it over christmas.

However i'm pleased you like it and rate it better than the others.

Not to confused or any malicious intent, my previous username here was rogeryu_ph which I also using it on FSB so I elected to change it here with a new DIMstompboxes which mean Do-It-Myself stompboxes not DIYstompboxes and thats the only reason.
I posted my breadboard report here way back 2008 on Downward Expander Noisegate
here http://www.diystompboxes.com/smfforum/index.php?topic=66277.0

Presently on my analog set up I only just using the Downward Expander noisegate and the NS2 is redundant so I keep it only for future back up. I'm also using Digital set up with my Boss GT10 in some venue when direct to mixing desk.
Also the reason why I delete my Youtube video report that time was to prevent and NOT to compete with Tonepad MXR noisegate and I highly regard Francisco for his works.
Lately I chime in on this armdnrdy's thread and share somehow he might use and design LM13700 OTA as replacement for CA3080.
That's the whole story just to payback and share what I learned to this great forum.

[DIMstompboxes]

Here is the project file. I named it "Fencepost" since Gate_Expander is...well, descriptive but not fun.

Eagle files/pdf/BOM all in the zip.

http://www.madbeanpedals.com/projects/Fencepost/Fencepost.zip

Hat off to you Brian, nice to see you here. I'm a member in your forum aka angelo 
Cheers,

[PRR]

> Darlingtons have twice the base emitter voltage drop when saturated

Saturated? Pretty much all through the Active range.

Do math.

Assume Q1 base sits at 4.5V, then check if that is true.

Single transistor:

If base is at 4.5V then emitter is at 3.9V. It feeds 22K so must flow 3.9V/22= 0.177mA. Any decent jellybean has hFE over 100. So base current is 0.177mA/100= 0.00177mA. This much flow in 510K is 0.00177mA*510K= 0.9V drop.

So first-crack, base actually sits at 4.5V-0.9V= 3.6V, and emitter is near 3.0V. That reduces the flow in the 22K and all throughout. I suspect the drop in the 510K comes to less than 0.8V but more than 0.2V, emitter sits at 3.1V to 3.7V.

Darlington:

Assume base is near 4.5V. Emitter near 4.5V-1.2V= 3.3V. Current in 22K is 0.15mA. Darlington hFE is over 10,000. Base current less than 0.000,015mA. In 510K this is 0.000,015mA*510K= 0.0077V drop, "zero".

So first (and final) crack, base at 4.5V, emitter at 3.3V.

What is the difference between "3.1V to 3.7V" and 3.3V? Hardly-any.

Either way you can get 2V peak for-sure. Since it is hi-Z loaded you can approach 3V.

But (on 'Brians redraw') isn't there a 15K missing near the OTA input? Guitar can run near 500mV. The OTA can only take 20mV-50mV before it goes gross. Usually we take something like 15K:1K voltage divider. There is a 15V on the other side of the OTA input, but not on the signal side input.

The "idle" OTA-- in theory, if you nail Iabc to the negative rail it goes dead. Leaving it open "seems to" do the same, except it tends to pick-up crap. I think if you run 1K from Iabc to V-, you can forget all the other pins on that OTA. Saves 12 cents.

[DIMstompboxes]

Here's the original breadboard pictures report on my photobucket using CA3080. Fortunately I saved it on my photobucket but unfortunately that time my camera can only save up to 512mb and video can't be saved on photobucket that year(2008) only on Youtube and I erased and never did saved it. Don't let me do the video demo again i'm kind of shy type of guy hahhhhahhha.
Cheers,

[DIMstompboxes]

Oh btw, this is becoming interested to me 
Brian is here lately, PRR is here and still waiting for Mark to chime in once more and also R.G.
I'm eager to pull that CA3080 and use it for Dyna compressor which I already have Ross and planning to build expander noisegate into smaller box with LM13700 which I have 3pcs of it and use
the existing box for bigger project.
I'm not much into math and theory like PRR only I know that pin5 of the CA3080 is the current control plus there is a 2k trimer on the input of the OTA.
Cheers,
Roger