# EHX Small Clone pops when first turned on...



## kw_guitarguy (Apr 29, 2008)

Hi everyone,

I have an EHX Small Clone - EHX.com | Small Clone - Analog Chorus | Electro-Harmonix

It sits after my Crybaby wah on my board and it pops the first time I turn it on. I know there was a recent thread about something similar, but I thought I would start a new one.

Is this something I need to fix on the inside?

Thanks!

~Andrew


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## Moosehead (Jan 6, 2011)

I had started the thread on it. 

Love this chorus BUT still pops.... not as much as when i first got but i might just be getting used to it

Mine is a 90's model. I set in second last in my chain after wah and drive(s) but before delay.

Anytime you have something driving the signal (boost, drive ect.) it pops. 

IF there is a fix out there I havn't found it yet.
not a very mod friendly circuit board...


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## kw_guitarguy (Apr 29, 2008)

Thanks Moosehead...that's not the news I was hoping for! 

Hopefully one of the effects gurus might have an opinion as well...if not, I will try moving it in the chain as you have done.

~Andrew


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## mhammer (Nov 30, 2007)

Switch-popping tends to occur when switching an effect "on", though usually not when switching it "off". There are two primary sources of switch-pop.

One is sudden discharge of the current stored in an input or output capacitor. Any time you have an unterminated cap, it has the potential to accumulate charge. If it has a way to drain that charge off to ground, then when you switch the effect "off", that cap will be draining through a resistor. Switch the effect back on, providing a path to ground via either a pedal or amp after the offending pedal, or a gutar or pedal before it, and there will be no "urge" for the cap to drain off because it has already done so. If there is no path for the cap to drain off in the background, then when you suddenly provide a path, all that stored current drains off at once, producing the pop.

Pedals that use mechanical true-bypass switches generally provide such paths to ground. Those pedals that use _electronic_ switching, with a buffered input (like Boss, DOD, Yamaha, Behringer, etc.) do not disconnect the input or output to do bypass switching. Their switching is done internal to the circuit. They generally assume that their pedal will be preceded or followed by a similar one. The result is that they tend to have a "hanging" capacitor on the input, without any terminating resistor to drain it off in bypass, because it is not normally disconnected in bypass mode.

HOWEVER...if you precede such a pedal with one that uses a true-bypass switch, whether DPDT opr 3PDT, every time you stomp on that switch, it will temporarily disconnect then reconnect the hanging input cap on the next pedal. And THAT is why you hear a pop. Plug your guitar directly into the pedal that uses E-switching, and you will not hear any pop. Plug your guitar into a TB pedal, then the amp, and you will also not likely hear a pop because the pedal will have suitable terminating resistors. But stick a TB and E-switching pedal in series, THEN you start to hear pops.

You will also likely notice that the pop will be most likely to occur if you have used the ffect a little while agao, but not switched it since. Step on the stompswitch of the preceding effect a couple of times, and you will hear less and less pop, and very likely none after the first stomp, because you have allowed the stored charge to drain off and not accumulated new charge.

Is there a fix? Yes. Since the e-switched pedal has its input cap permanently connected to the input jack, run a 1M-2M2 resistor between the hot lead (tip connection) on the input jack to ground. That will allow the charge to drain off. It will have a modest loading effect, but not enough to notice.

To sum. The popping comes from the e-switched pedal, and is "cured" by a small modification to the e-switched pedal, but is _*caused*_ by a TB pedal on its input.

In the case of the Small Clone, I can confirm that while it may look like it uses a stmpswitch for TGB, in fact it uses a stompswitch to accomplish E-switching internally, simply lifting and engaging the wet/delay signal, rather than bypassing the entire circuit. It has a "hanging" capacitor on its input. In this regard, it is exactly like a Boss pedal. Precede it with a Boss pedal and you'll have no pop. But stick a TB pedal in front and it will pop.

Cause #2. More rare, but it happens. Status LEDs on pedals draw current. Connecting them to power suddenly (as happens with TB pedals) results in a sudden draw in power, which produces a spike on the power line. The pop is not *from *the audio path, but has an impact *on* the audio path. The cure here is to make the current draw more gradual. Check this webpage for a cure for that source of pop: AMZ - LED Popping


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## kw_guitarguy (Apr 29, 2008)

Another great response Mark.

If I understand it all correctly, I can modify the Small Clone to hopefully remove the pop?

~Andrew


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## keeperofthegood (Apr 30, 2008)

Q: Can I unscrew the bell of my cable and put the 2M2 across the center and shield wires there? (assuming non-moulded ends)


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## mhammer (Nov 30, 2007)

> If I understand it all correctly, I can modify the Small Clone to hopefully remove the pop?


Yes. A simple 1M resistor across the input jack ought to do the trick.


> Q: Can I unscrew the bell of my cable and put the 2M2 across the center and shield wires there? (assuming non-moulded ends)


Yes. While larger/higher value resistors result in less loading, the intent is to bleed off current to ground. The higher the value of the "hanging" input cap, the more charge gets stored in the cap. Which means you want to make it as easy for all that charge to bleed off as possible. The schematics I have for the Small Clone show that input cap as .033uf, for which a value as high as 2M2 wouldn't be too bad. If it was something like 2.2uf (as found on a Fuzz Face, I would lean more towards 470k to 1M to let the greater charge drain off more efficiently. The idea is to balance off quick draining of current with loading.


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## kw_guitarguy (Apr 29, 2008)

Alright, since I am not too sure where the resistor has to go, I found a link to some high res interior shots of the small clone:

Tech - Brown Sound (bottom of the page)

His only mod is he's changed the adapter plug. Can someone point out where the resistor needs to go?

~Andrew


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## mhammer (Nov 30, 2007)

As near as I can tell from the pictures, the added resistor would go bet6ween the lug where the blue wire goes, and ground.


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## kw_guitarguy (Apr 29, 2008)

Thanks Mark...

I have a goodie bag with some resistors that I got from you years ago. I tried Googling the colour bands but am really confused. Any hints as to what a 1M resistor will look like?

Also, some of the resistors are fatter than others...

~Andrew


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## mhammer (Nov 30, 2007)

It will be brown-black-green-gold. Any size will do.


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## greco (Jul 15, 2007)

Andrew... on a 4 band scheme the colours will be ........Brown Black Green

The last (4th) band should be silver or gold

The fatter resistors are just capable of handling more power...nothing to be concerned about for your application.

Cheers

Dave

P.S. mhammer and I were posting at the same time...he won...LOL

P.P.S. Let me know if you need one of these...I'm almost sure I have a few.


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## kw_guitarguy (Apr 29, 2008)

Thanks Mark and Dave...no such luck in my goodie bag.

Dave - I will be in touch soon 

~Andrew


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