13700 Noisegate/Expander

[armdnrdy]

So when it's all said and done...and you do the math...the circuit should work about the same with the darlingtons in place of the single transistors.

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.

I believe that Brian used my redraw for his drawing. Both are as the original circuit, no missing 15K.

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.

Are you referring to the unused OTA pins?
I followed the advise from a T.I. applications engineer to put the unused device in a known valid operating state.
It was suggested to set the part as a unity gain follower with input at half of supply.

[Kipper4]

I think the schematic was this one right?

http://hammer.ampage.org/files/Expander.gif

[Kipper4]

Is this it PPR

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[DIMstompboxes]

I think the schematic was this one right?

http://hammer.ampage.org/files/Expander.gif

YES that's the schematic and PCB I built from a Japanese genius  
First I breadboard it and file a report here with Youtube demo with couple of mod I made after that I boxed it. Then followed by (kmr) member here also who just used half of the 4558 not TL061.
Then came (DimebuGG) also a memeber here and FSB with his own PCB design. After that no other one who dare to built it and that thread when away so I posted a thread "Tired of MXR fet noisegate use this Downward Expander"
I felt I might get wrong competing with MXR user of Tonepad so I delete that Youtube demo.
I just want to share that there is an alternative noisegate beside NS2 and MXR that I have and this is it. I haven't tried the ISP decimator but I shared this one with Evan at FSB and replied me just thanks. I was hoping only I could compare it with ISP because I can't get THAT2181C chip here.

Here's the couple of mod I just made:
Add a series 1.5v zener after the (470ohms and 4.7k resistor with signal diode) junction and before signal diode with circle T and circle C. The zener should be anode pointing to TR3. This help to smooth threshold gated sound and decay more natural. Depend on your ear just experiment from 1v-4.5v zener.
 
I used A100k Log instead of 1MA for sensitivity. These were just my own radical changes and thinking while it was still on breadboard, just try the stock first and do improvement later then share it buddy.


  

[Kipper4]

Heres my perfboard layout
If you see anything wrong feel free to correct me thanks
Rich

sorry its drop box. I tried to post a link but it was so small you couldnt see it. and I figure not everyone has the same version of DIYLC.
At least this way you can import to photoshop (read other image viewers) and enlarge easily.


https://www.dropbox.com/sh/7ma9n53c5jqdgsr/nTW79Toq_J/NOISE%20GATE%20EXPANDER%20LM13700%201.png

[bean]

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

It will be a while before I can, unfortunately. Although I do very much want to build one.

[Kipper4]

I realise your a busy man SD. I wasnt pressuring you mate. Just wondering:)
I will probably build it myself in the next week hopefully.



I just want to make sure my layout is ok first. Anyone?

[deadastronaut]

hi rich, its a bit on the large side..

no chance of a 1590b with it.

[Kipper4]

Good point. Thanks Rob.
I'll condense it when i know its a goer. Meh

I'll rework it
thanks mate

[DIMstompboxes]

Oh I browse with my messages on FSB it was FrankWhite not Evan that I shared. If you know the guy.
BTW,  I don't have 1MA log before that year that is why I used 100KA log. Just try the stock first.

Cheers,

[DIMstompboxes]

I done a simple demo it's a holiday, using SINGLE COIL (center) with TS( drive) just to increase hum with OPEN STRING fair to just give you an idea. We all generally know that the strat single coil reputable for its annoying hum
Again, I will delete this sometime next year January for I don't want anybody to get me wrong especially the Boss community. Also this is not a comparison just sharing you it works. Strangely the youtube decreases the hum (for better quality playback I think) or I don't know why just use your headphone for better monitoring.

 

Cheers,

[Mark Hammer]

That's a very favorable comparison, I have to say, and a strong recommendation for making the expander.

I still tend to recommend building an SSM2166-based compressor, since it includes downward expansion onboard (and does a great job of it), but I suppose there can be circumstances where one wants the expansion without the compression, or vice versa.  Mind you, given the manner in which the downward expansion is adjusted, it is probably feasible to use a SPST (or DPDT, since one likely wants LED indication) to enable/disable the expansion function.  You can also switch back and forth from a minimum to preset maximum-compression with a similar footswitch, but the complication is that more compression comes with higher output level, so it is tricky to easily alternate between negligible compression (largely equivalent to bypass) and noticeable compression while maintaining the same average volume level.

[deadastronaut]

+1 works really well..

[Kipper4]

Thanks for the comparaison video.
That works a treat doesnt it.

[DIMstompboxes]

That's a very favorable comparison, I have to say, and a strong recommendation for making the expander.

I still tend to recommend building an SSM2166-based compressor, since it includes downward expansion onboard (and does a great job of it), but I suppose there can be circumstances where one wants the expansion without the compression, or vice versa.  Mind you, given the manner in which the downward expansion is adjusted, it is probably feasible to use a SPST (or DPDT, since one likely wants LED indication) to enable/disable the expansion function.  You can also switch back and forth from a minimum to preset maximum-compression with a similar footswitch, but the complication is that more compression comes with higher output level, so it is tricky to easily alternate between negligible compression (largely equivalent to bypass) and noticeable compression while maintaining the same average volume level.

It's a NO HOLDS BARRED and I let it just ring out to let you hear how it clamp and decay.
Yes, there is a exp/norm so I opted to normal and lazy to drill for another hold.
BTW, for smaller version box this is okey but what i'm trying to achieved before for bigger box is to have a send/return. Some may use this LOOP SEND unto their drive/highgain pedals then RETURN it to expander to isolate those dirt box then connect OUTPUT unto their modulation pedals (delay/reverb) so the modulation can't be affected.
Wish merlinb of ET would chime in also to do some wizardry and help this project to get this smarter as smartgate 
Community lets all in.
Cheerio,
Thanks Rob and Kipper4

[knutolai]

what i'm trying to achieved before for bigger box is to have a send/return. Some may use this LOOP SEND unto their drive/highgain pedals then RETURN it to expander to isolate those dirt box then connect OUTPUT unto their modulation pedals (delay/reverb) so the modulation can't be affected.

I could see that being a very useful feature! Was really what I was trying to suggest in my other post. 

[DIMstompboxes]

Yes mate,
This is an added feature plus if somebody or merlinb could make this a basic compressor/noisegate with two footswitch. One for clean guitar compressor and the other footswitch to disengaged the compressor and engage the noisegate for the dirt box would be GREAT. Meantime, let us focus on noisegate with the LM13700 first then later with the LOOP feature.
BTW the Downward Expander noisegate perform much better in the front of the chain so its feasible for compressor/noisegate project.
I'm still waiting for both armdnrdy and brian's progress on this, maybe too much busy....
Also I forgot to thank you Mark 

[DIMstompboxes]

Just to demo how it gate the hum background with DRIVE on a single coil and still no coloring of the sound. Again use headphone for better monitoring.



Happy New Year

[Mark Hammer]

Silence is golden, innit? 

[Kipper4]

Innit.