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Re: Electro Harmonix SmallStone


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6/16/1999 4:20 PM
MKB
Re: Electro Harmonix SmallStone
Hi, CJ. I currently have a Small Stone ('70s model) on my pedalboard. The pedal has been pretty much rewired, with a new footswitch and toggle switch. I am using the pedal on 9V regulated supply based on a LM317. I do notice a slight volume drop when the effect is on. I kind of like it however, because I mostly use it when I am playing clean stuff, and I mostly roll down my volume for that on the overdrive channel anyway.  
 
 
 
BTW, the Small Stone was the cause of a horrible noise problem in my pedalboard. The noise would change frequency when the rate pot was turned. This was with the 9V regulated supply! I eventually cured the problem by placing a RC on the power supply input of my Boss CS-2, which seems to be highly sensitive to supply noise. I guess the clock was bleeding through the supply into the chorus.
 
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6/16/1999 6:16 PM
CJ Landry

MKB,  
 
What issue of Small Stone are you using? I would like to see if the volume drop follows a particular issue of the Small Stone.  
 
 
 
There are like 3 or more different versions of the Small stone and each one is not like the other. One version generated a -V supply and it was done in a very bastard type of simple circuit.  
 
 
 
CJ
 
6/17/1999 2:17 AM
MKB

Hello again, CJ. How might I determine which issue of Small Stone that I have? I'm not that great a follower of EH effects, but this Small Stone sure sounds great!  
 
 
 
I played it awhile ago and definately confirmed the slight volume drop. To me, it sounded more like the drop was caused by the phasing, i.e. the phase cancellation was causing the drop, which would make sense. Is it necessary to boost the gain in a phaser to compensate for the cancellation, or are phasers generally "unity gain" designs? I haven't played with phasers much, only fuzzes and tube amps.  
 
 
 
Well, if you could maybe pass a clue on dating my Small Stone, I'll check it over the weekend, as that is when I will see it next. Thanks.
 
6/17/1999 3:32 PM
CJ Landry

Some EH small stone's have the issue right etched into the PCB. Also, Issue J used EH4800 IC's and the earlier ones used EH1048. I think these numbers are correct. I just had a brain fart and couldn'e remember. I have the info on some schematics I have at home.  
 
 
 
As far as the gain issue, I do not think so because in theory the peak of the phased wave should be at the same gain level as the input, however, through tolerances in parts and each stage may add a slight attenuation in the output signal. So maybe the last stage op amp needs to be tweeked for a little more gain than what is presently there.  
 
 
 
CJ
 
6/17/1999 4:59 PM
jason

Issue J (the one with orange writting)used EH1048 chips(8 pin) and the red and black one(EH4800 phase shifter) used 16 pin chips (the chips in the unit I have here are marked LM13600-I got the pedal used so these may not be the original chip #'s).  
 
jason
 
6/17/1999 2:20 AM
MKB

Oh, I forgot to mention; I have installed a DPDT footswitch for a true bypass in my Small Stone. It came originally with a SPDT.
 
6/16/1999 7:06 PM
Mark Hammer
I don't have a small stone, but I DO have a Y-triggered filter. When I replaced the stock SPDT footswitch with a DPDT switch, I noticed a clear drop in volume with the effect engaged.  
 
 
 
My sense is that some aspects of the design of some of these boxes is intended to match levels when SPDT switching is used, with all of its attendant problems.  
 
 
 
I may be wrong in my guessing, but quite frankly, if it was me designing these things, and I *had* to use a SPDT switch to save money, I'd probably build in level matching.
 

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