EHX - Small Stone ( LM13600 )  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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mecmast
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Post by mecmast »

minnow wrote:Hi everyone. Some updates on this.
I have built this according to the layout (not the schematic values, refer to notes):

1. 1K8 on layout (vs 1K on schematic)
2. 100 on layout (vs 100K on schematic)
3. 33uF capacitor polarity (polarity follow schematic, not the layout)
4. 47nF cap connects LM324 pins 1 & 4 on layout (vs pins 5 & 7 on schematic)

It works! Great sounding phaser (coming from someone who dislike phaser effect).

However, there is a kind of "noise" that happens during the trebly end of the sweep (swirl). Like a flourescent lamp "eeeeeeek" noise.
When the sweep (swirl) is on the dark side of the moon, noise is not present / noticeable.
Hope my explanation is not too confusing.
This is noticeable in both switch positions. The position with deeper sweep has more noticeable "noise".

I have tried this effect without the guitar plugged in, meaning the pedal outputs directly to the amp, with a battery.
So ruled out my guitar pickups causing this problem.
I turned off my lights, turned off computer monitor (unplugged from mains) and tried the amp on two different power mains.
The amp is quiet with other pedals.

During my build, every component measured prior to soldering, and measured for contact after soldering.
STILL, probably a build error from my side.
But any help / clue on what to look out for will be great.

Could it be switch wiring error?

One more thing, when I unplug the guitar cable to the pedal, one switch position howls and squeals. Plug in again and it's gone.

I hope anyone else who has built it or anyone working on this can chime in and get this project in FSB going.
As always, thanks everyone!
Hi have you solved the "noise" issue?

I'm gonna try to build this one but i'm afraid of the same problem.

Has anyone else build this pedal? I really need comments.

Also i've a question. I couldn't find 2n5088. Shall i use BC239 instead? Or any suggestions?

Thank you.

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mecmast
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Post by mecmast »

I've obtained the 2n5088's. Ready to build. But still need comments.

Thank you.

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minnow
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Post by minnow »

Hi Mecmast,
I've not solved the issue with my build. It is still as it is.
You could try building it. Perhaps it is an error in my build, and you could make it through fine? :)
Go for it!

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Haradax
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Post by Haradax »

Hello people!
Although for a while I was sneaking around here, this is my first post, and I'm sorry for my bad English. (blame the translator, Mr.G.) :)

Thanks to everyone on this topic who helped in making this nice layout, by which I made my biggest PCB so far.
Today I soldered elements and temporary wires, and with skepticism plugged it between guitar and the little amplifier.
Vow... It started working immediately.
Maybe it's just a first impression but it sounds great, better than my proud "phase 90" made last year.
After a bit of playing I found small issues, the same, or almost the same kind described by user minnow.
It occurs when the effect is in bypass mode while the switch is in the "ON" position by the scheme ("bright side", the higher tone). The problem disappeared when I put in front some buffered pedal. As Mininow, I also suspect that the problem is around the "color" button. Or maybe a different bypass wiring (grounding input in bypass mode) can fix this little problem.
Today I will try to solve that, and write the results here, of course.

Regardless of the problem, effect is very useful. Although, if I do not fix this phasing whistling, though this effect will surely find it's place in my pedalboard. Anyway I prefer the "darker color" mode which works fine, so there is no problem at all. :wink:
image:
Image
You can see two 1M trimmers on the little black breadboard which acting 2M pot before mailman arrives from China.

As mentioned this is my biggest self etched PCB made using iron/toner-transfer method, and certainly the most beautiful one. I have changed changed layout a little, nothing significant, just to make the PCB a bit smaller. I'll try to squeeze it in 125B.
Image

P.S.
I have basic knowledge in electronics, and so far I have successfully made about 18 pedals for about two years, how long been doing this addictive hobby. Some of those you can see here.

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minnow
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Post by minnow »

Hi Haradax,
Nice layout! And thanks for updating.
I've not done anything yet to my build :(

Regarding the component values - did you use the schematic ones or the from the layout?

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Haradax
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Post by Haradax »

minnow wrote:Hi Haradax,
Nice layout! And thanks for updating.
I've not done anything yet to my build :(

- did you use the schematic ones or the from the layout?
Thank You, mininow.
Regarding the component values, I used layout one ( small exceptions: for 1uF output cap. I choose film one, and also 3x tantalum instead of electrolytic, see pic.)

Good news is that I have fixed the whistling issue (by LFO) heard in bypass mode. As I intended, different wiring of 3PDT (grounding the input) has solved a thing.
As for me, this nice phaser is verified. :horsey:

Now i have one small sweet problem. On the PCB I've etched two words for the name of pedal, but I can not choose would I name it "Smile Stoned" or "Stoned Smile"? :scratch: Please help me people!

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stnky1
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Post by stnky1 »

Hey all:

I'm gonna try building this one eventually...has anybody been able to source the proper 2Meg rev. audio (2MC) pot or are you just using linear taper?

I tried all my usual suspects (Smallbear, Tayda, Sayal, Digikey, Mouser etc...) and can't seem to find one.

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Haradax
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Post by Haradax »

stnky1 wrote:Hey all:

I'm gonna try building this one eventually...has anybody been able to source the proper 2Meg rev. audio (2MC) pot or are you just using linear taper?

I tried all my usual suspects (Smallbear, Tayda, Sayal, Digikey, Mouser etc...) and can't seem to find one.
Hi.
Neither I haven't found the right pot.
I put one of 2.2M lin. found on ebay. Responding to the speed change is not linear as it should be, but it can be used.
When you do not have right 2M rev.log. here it is better to be a some larger resistance.
We can also try to find 2M log. pot and wired it opposite.

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Haradax
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Post by Haradax »

One month ago I finally squeezed this one into 125b box.

Image Image
That big pot in the photo is the wirewound 2.2M Lin from e-bay. (rheostat :D)
Meanwhile I found more suitable potentiometer, a CTS 3M Rev-log at musikding.de.
It can be used as it is, or with a 6.8M resistor in parallel to get exactly 2M. The taper stays almost the same.

Image

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Post by DiscoVlad »

If you double the size of the 22uF Cap in the LFO to 44uF (or use 47uF because it's the nearest preferred value) you can use a much easier to find 1Meg pot.
Attachments
Modified LFO
Modified LFO

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syamilaliff
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Post by syamilaliff »

Hi,

Sorry for reviving an old thread.

Does anyone still have the pcb transfer file for the project?

Appreciate it if you guys can share it again.

syamilaliff@gmail.com

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dj_shen
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Post by dj_shen »

How to add depth mode in small stone circuit made with lm13700? 🗣🙏

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The G
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Post by The G »

dj_shen wrote: 04 Oct 2020, 19:21 How to add depth mode in small stone circuit made with lm13700? 🗣🙏
Here we go again: EHX Small Stone Modding by Remörk Inc..
Look at section #2, but you'd better read all the article. Apparently, the author was not happy with the depth mod.

LM13700 contains two OTAs (operational transconductance amplifiers) in one integrated circuit, so the mods should be the same as for CA3094 or CA3080 circuits - only the pinout is different.

Other information sources (you should study their PDFs):
LATER: If you need further help, create a new topic in the Pedal Debugging & Troubleshooting Support forum (just click on this link), name it "Electro-Harmonix Small Stone depth mod", and post:
  1. The schematic and layout you used.
  2. Clear photos of your build and wiring.
  3. The description of your issue, as accurate as possible.

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Post by slammer88 »

Is the recent drawn layout confirmed somehow?

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Post by slammer88 »

DiscoVlad wrote: 10 Jan 2018, 04:20 If you double the size of the 22uF Cap in the LFO to 44uF (or use 47uF because it's the nearest preferred value) you can use a much easier to find 1Meg pot.
In this scenario, what can I do to make my B1M or B2M pots to act like a C1M pot as I can't find any C taper in Turkey? Also I'm using 22uf with B1M and range is pretty acceptable, only thing is that the taper of the pot itself, it doesn't respond well and tends to accumulate on the last quarter.

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Post by duckfeeling »

Hello!

I'm new there, so I hope I'm posting in the right place. I just bought an used Small Stone on Reverb (my first purchase there). It's great, but as I cleaned it up a bit, I noticed a strange resistor soldered on the back of the PCB. I contacted the seller, but he wasn't the first owner and did not mod the pedal. So I was wondering if you recognize something that could be factory done or a mod?

I'm not sure from which era is this Small Stone. I think it's a reissue from the 2000's, it has the "Made in USA" on the front and the power supply is the old EHX one, before they switched to standard Boss types.

Here is a picture, it's on the left of the back:
Image

Thanks!

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slammer88
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Post by slammer88 »

Haradax wrote: 30 Oct 2015, 08:06
minnow wrote:Hi Haradax,
Nice layout! And thanks for updating.
I've not done anything yet to my build :(

- did you use the schematic ones or the from the layout?
Thank You, mininow.
Regarding the component values, I used layout one ( small exceptions: for 1uF output cap. I choose film one, and also 3x tantalum instead of electrolytic, see pic.)

Good news is that I have fixed the whistling issue (by LFO) heard in bypass mode. As I intended, different wiring of 3PDT (grounding the input) has solved a thing.
As for me, this nice phaser is verified. :horsey:

Now i have one small sweet problem. On the PCB I've etched two words for the name of pedal, but I can not choose would I name it "Smile Stoned" or "Stoned Smile"? :scratch: Please help me people!
How did you make the connections for 3DPT to solve the whistling sound when bypassed?

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