Small Clone Mods

[phillip]

I was thinking about building a Small Clone and I was wondering if anyone has posted any modifications for the circuit.  It sounds great as it is, but it would also be good to add some mods, too.

Phillip

[Ed G.]

Check out moosapotamus.com. He's got some good ideas there.
Also, read this: http://groups.google.com/groups?q=small+clone+capacitor&hl=en&lr=&ie=UTF-8&oe=UTF-8&selm=9iCs4.94%24nH.1548%40bgtnsc04-news.ops.worldnet.att.net&rnum=1

From that article, this is the important part. This may be the part that Analog Mike is referring to when he said he found a part difference b/w the schem of the small clone and some original small clones that he thought made a big difference. Natch, because he's selling his own clones of the 'clone' he neglected to say what part that is, but read here and judge for yourself:
"I can also tell you that there is a "buzz" around the
net about a "secret cap." value. Could it live here? I would suspect it does
and it may be the one that connects between the two 39Ks and the emitter/10K
junction of the buffer. The last clone that I serviced had this cap. value
at .0037, yet the schem. shows a .0029. I guess the issue becomes the
amplitude of the delayed signal and it's ability to be perceived with the
"raw" signal. If the filter attenuates incorrectly, or too much, some of the
"audio" signal could be dumped to ground as well. Of course, this is all
just a SWAG on my part."

This may be why I've heard one reissue pedal sound 'weak' compared to bypass, there was a small volume drop.

[Fp-www.Tonepad.com]

I've just uploaded an updated small clone pdf.

http://www.tonepad.com/project.asp?id=8


It includes the depth mod and the stereo mod (based on the MXR stereo chorus)

Fp

[george]

The last clone that I serviced had this cap. value
at .0037, yet the schem. shows a .0029.

Ed pardon my impertinence but the standard values are .0039 and .0027 (also my SC schemo shows .0027 in the location you mention)?

Regards
George

[ExpAnonColin]

I've just uploaded an updated small clone pdf.

http://www.tonepad.com/project.asp?id=8


It includes the depth mod and the stereo mod (based on the MXR stereo chorus).

Fp

Very nice!  I find it's easier to do the depth mod by replacing the switch with a 100k pot.  Thanks to Tim Kaiser for this tip.

I have a factory made one, any tips on doing the stereo mod?  The parts layouts are much different, it's not quite so easy to do.

-Colin

[Fp-www.Tonepad.com]

I have a factory made one, any tips on doing the stereo mod?  The parts layouts are much different, it's not quite so easy to do.

You'll have to find the nodes and solder wires probably on the copper side of the board. It shouldn't be too hard. Look at the main schematic in the PDF, it shows where each pad is connected to.

If you send me a picture of both sides of the board, I can find them for you.

Fp

[Ed G.]

The last clone that I serviced had this cap. value
at .0037, yet the schem. shows a .0029.

Ed pardon my impertinence but the standard values are .0039 and .0027 (also my SC schemo shows .0027 in the location you mention)?

Regards
George

George,
I hope I didn't confuse anyone with that post. I quoted an article that I found on usenet. Those are not my findings but I found that article interesting in light of what Mike Piera says about his copy of the Small Clone chorus. This is from the analogman.com site:

"As a tribute to this great Electro-Harmonix pedal, and due to the need for an excellent analog chorus, aNaLoG.MaN decided someone must make this pedal available. We came up with an exact duplicate, in a smaller, more rugged box. AnalogMike organized everything, and with the help of Alfonso Hermida (electrical engineer and pedal designer) we found all the original parts and decided on all the components and layout of the pedal. We also realized after building our first batch that the factory schematic is not quite correct and effects built to that spec will sound a bit weak. So we dissected my original Small Clones and found one tricky part that's value was slightly changed and made all the difference in the sound. "

As far as the differences b/w the schem values, it could be different circuit revisions. Or maybe the guy who wrote the usenet article got mixed up.
I think it's a well-known fact that Electro-Harmonix rarely stuck to certain values, esp. on the Big Muff Pi, and would use whatever they had on hand.

[Fp-www.Tonepad.com]

"We also realized after building our first batch that the factory schematic is not quite correct and effects built to that spec will sound a bit weak. So we dissected my original Small Clones and found one tricky part that's value was slightly changed and made all the difference in the sound. "

The tricky part is quite possibly the capacitor connected to CD4047 pin1, in some schems it's 100pF and in some it's 150pF.

Fp

[george]

As far as the differences b/w the schem values, it could be different circuit revisions. Or maybe the guy who wrote the usenet article got mixed up.

That's OK - it sounds like it would be worth trying a .0039 uf cap in the location you mentioned.

As for the 100pF - 150pF cap that FP mentions, one of Charlie Barth's mods is to replace this with a 4-position switch that switches between 4 caps ranging from about 33pF to 330pF (IIRC?).  The effect of this is to go from "very mild chorusing" to "extreme pitch bending".  From my own experiments, if you use a BIGGER cap (say 220pF) you'll get a lusher chorus effect that doesn't go out of tune too much as the LFO sweeps up and down.

[Muldoer]

From the page Ed posted:

The frequency of pins 10
and 11 is half of the osc. freq. or 60Khz each. Without anything else, the
small clone could simply operate as a delay pedal.

How would I go about making this mod?  A small clone delay would be nice to hear.  

[Kyle Agee]

Can anyone tell me HOW to wire the depth pot, I have the Schematic. . . well I'm a film major, not an engineer and I can follow schematics, sort of, can anyone just tell me where to solder the leads?  I get what to take out and what to replace it with, just where do the wires get soldered at?  I am using the PCB from tonepad.com.

Thanks

Kyle

[Chico]

You cannot make a small clone "delay" without also performing an overhaul to the lpf section after the delay chip.

In my build report over at Tonepad, I provided the details of a mod that serves as a nice alternative to Charlie's multiple switch/cap mod.  The discrete cap mod is pretty cool, but a simpler and cheaper approach is to replace the fixed 39k between the lfo and the CD4047 with a 4.7k resistor in series with a 100k linear pot.

In the original circuit, the 39k resistor, along with the 150pf cap between pins 1 and 3 of the CD4047 control the clock speed of the MN3007 delay chip. In Charlie's mod, the timing of the clock is changed by changing the value of the capacitance between pins 1 and 3.  

The above potentiometer mod uses a single capacitor (so no click when making adjustments) and it lets you continuously vary the delay time over a remarkably useful range. With the 100k pot, I was able to replace the cap with a larger value (I used a 250pf).

With the potentiometer and cap value above, my small clone "can" dial  very short, Flange approved delay times  into slap back delay territory.  That said, my small clone does not sound like a flanger.  Moreover, clock whine begins to bleed through with longer delay times.

That said, think of it as multiple "colors" of chorus and enjoy.

Best regards

Tom

[Bent Penguin]

In the original circuit, the 39k resistor, along with the 150pf cap between pins 1 and 3 of the CD4047 control the clock speed of the MN3007 delay chip. In Charlie's mod, the timing of the clock is changed by changing the value of the capacitance between pins 1 and 3.  

Hi Tom, I'm 95% done with a small clone from a Tonepad PCB and wanted to do your mod. However I'm a bit confused, is the 39k to change the one in the very top right corner of the layout? One side of the 39k joins with the 150pf and then onto pin 3 of the 4047.

This was the most intriguing mod of the build reports and I'm hoping to get it to work on the first try

Thanks

[Chico]

Bent Penguin:

You are correct.

Looking at the currently posted Tonepad schematic, there is a 39k resistor that connects at one end, to the 10uf cap and the voltage divider feeding out from the LFO (4.7k and 2.7k).

The other end of the 39k resistor connects to pin 3 of the CD4047, and to cathode end of the diode (to pin 2 of the CD4047) and to the 150pf capacitor (to pin 1 of the CD4047).

The nice thing about this mod is, as you point out, the 39k is seen in the upper right hand corner of the layout.  There is a long horizontal trace (seen in blue) just to the left of the 39k resistor.

When I performed my implementation of the mod, I simply soldered a 4.7k resistor in place of the 39k.  (You may want to experiment with this minimum value).  I took an exacto knife and cut the blue trace to the left of the 39k, and drilled two new holes to either side of the cut, and I wired the 100k pot in that spot.  The wires thus sit behind the depth pot.

Good luck
Tom


I would also socket that 150pf cap and experiment.

I simply replaced

[Bent Penguin]

Thanks for the help Tom. I split the trace and driled the two holes, that came out real pretty. Unfortunately it doesn't work yet. I get sound in the bypass and on modes but it's just slightly different sound in the on mode. Time to double check what I did...

[Chico]

Bent Penguin:

This sounds like the LFO signal is not making it to the CD4047.

First, check the obvious.  Did you do the depth pot mod?  Is the depth turned up?  The new 100k pot lets you change the "center" of the delayed signal.  The lfo will modulate the delay about that center.  Did you try sweeping the 100k pot?  On mine, fully ccw the effect is almost imperceivable.  It then transitions through chorus and into slap back range fully clockwise, albeit with clock wine at the maximum delay.  Here, the clock whine is reduced by setting the depth to zero.

Now that the obvious is out of the way, one thing to check is to make sure that no strands of wire from your potentiometer are shorting to the ground lines just behind or beside where the pot was wired in.  These are pretty tight layouts, so I'd grab a multimeter and check this out.  If that looks ok, then check to make sure that the trace was cut clean enough so as to not short out.

If all that looks ok,  check the capacitor.  Is it socketed?  Is is sitting firmly in the socket?

Let us know how it turns out.

Best regards

Tom