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Vintage threads from the first ten years

Re: Electro Harmonix SmallStone

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6/17/1999 9:46 AM
JD Sleep	Re: Electro Harmonix SmallStone I have 2 small stone issue J's from the seventies, one black/red face and one organge lettered. Both are completely stock, including the STDP bypass footswitch and both have a slight drop in (at least percieved) output when switched on. I'd like to know more about the transistor bias...anyone else think that could be the cure for the problem? JD

6/17/1999 2:19 PM

I have an issue j (the one with orange writting) and my buddies black and red one right here(says small stone eh4800 phase shifter) both are totally stock and both have no volume drop what so ever. The only thing I have ever done to these two pedals is (on both pedals) resolder all joints (I think eh came from the old "bigger the blob the better the job" solder school) and on the issue "J" I had one of the OTAs go bad so I replaced them all with CA3094's.

But both these units are confirmed as of 5 minutes ago to give no signal drop what so ever.

jason

6/21/1999 2:35 PM

I put my 'Stone in a wah pedal so I could have foot control over the LFO rate. It was a pretty easy task -- the PCB fits right in there. I put a 220K resistor in series with the wah's 150K pot to get the LFO in the right speed range. I really just wanted slo/fast like a leslie. But then I noticed the volume drop. It's not really so much of a volume drop as it is a treble roll-off (which your ear perceives as a vloume loss...) So what I did is this: the 1st transistor (2N5088, marked on the PCB as "N") has a 10K collector resistor and a 470K biasing resistor (from the base) going to V+. Try tweaking these values (8.2K? 6.8K?) I only changed the collector resistor. YMMV Also, there's two pads on the PCB with a jumper across them, but the silkscreen reads "1uf." I went ahead and threw a 1uf cap in there. Seems to help the sound of the pedal. Also note that most of the noise from the box seemed to be caused by these two transistors. Changing them both the high-gain, low noise types may improve performance.

BTW my 'Stone is the model with 6 EH1048s (CA3094) instead of the issue "J" which uses two PNP tansistors and an EH1048 as the LFO (only has 5 ICs.)

Farrow

6/22/1999 3:31 PM
Alex	Thanks for all the responses, it has been educational

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