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Hi guys.  This surely must be a known point to you pedal guys here.

I have an older Boss CH-1 Super Chorus pedal which has lost a nut from one of its jack sockets.  These are Boss' "far eastern" types so don't have our standard Imperial thread sizes.  The socket has a slightly thinner nose which a standard sized socket or potentiometer nut just drops over.

It appears to have a fine thread 8mm nose on it so I would guess it would be a M8 x 0.75mm fine thread.  The usual coarse thread for M8 is a 1.25mm pitch and this is far too fine to be that.  Then there is fine at 1.0mm pitch which again does not look right.  Finally there is the 0.75mm pitch I mentioned earlier.  You can buy the "official Boss pedal replacement nuts" which would seem from the price to be hand carved out of billet platinum but the alternatives are available as simple stainless steel standard items if you just know the correct thread.

Can anyone confirm this thread or, if this is wrong, suggest what it is?

Hi guys.

I'm simulating the following SRPP stage in LTSpice with the schematic below.  The idea is to use it as a clean boost stage so driving it into clipping is not the aim. It must accept a range of input signals up to about 1V which explains the additional R9. I added this to lift the DC levels of J1 and, I would think, offer greater headroom at the input. Yes it cuts down on headroom at its drain but that I can spare. For bigger signals I can switch the rail voltage to a generated 16.5V and more than regain it. Thankfully all that seems to be what I'm seeing.



Originally I set it up without R7 and R10 in place with the input from V1 connected directly to R11. The frequency response top end was flat to way beyond the audio range. I didn't think there was anything odd in adding a divider (simulated drive control) to the input which may have allowed me to remove R9 but when I did I got the response plot below.



The top end rolloff now displays a 3dB point of 6.6kHz. Investigating a little further shows that any series resistance in that input line, adding a series parasitic resistance to V1 for example, affects the upper rolloff.

Now I can't really see any mechanism which would account for this but then I'm much more a BJT than a JFET man. Maybe the additional R9 in the source line is having an effect I did not anticipate. Can anyone explain what I am seeing here?


And if anyone can suggest why I'm having to post the thread before I can get to the link location for the images which then have to be "modified" into place I would appreciate it.  Using Firefox, is it an "eccentricity"?

Hi guys.  I've been working with what is usually considered to be the Okko Diablo schematic to come up with my own take on it.  I have found this same version in a number of places on the web.  The circuit is pretty standard stuff that has been tweaked fairly well.  2 x Mu-amp stages and a source follower.  It should offer good performance for classic overdrive rather than metal stuff, at least that's what I'm hoping.

Understanding the action of the SRPP stages is not too hard but the schematic doesn't seem to have things as I expected.  I've attached a pic of one stage of what normally passes as the circuit for reference.

Usually the bottom end of C4 would be expected to be connected to the lower end of R6 not the upper end as it is here.  Surely R6 is having no influence in this circuit?  The intention is for C4 and the upper JFET follower to bootstrap R6, (put the same AC signal at both ends so there is only a constant DC current through it with no changing AC current).  This makes it appear to the lower JFET as an extremely high impedance load.

Can anyone else who knows a bit about this circuit shed any light?  I do wonder if the original schematic has been drawn out incorrectly.  This same oddity occurs in both gain stages of the Diablo and in the Boost portion too.  If there is anyone out there who has one of these pedals and can check this out I would appreciate it.

Hi guys.  I'm building a Diablo Clone and putting in the 18V rail option.  The MAX1044 circuitry is simple enough but it has a confusing aspect.  I've tried to attach it below, I hope it comes through ok.

I have looked into the suggested applications in the Maxim datasheet which is very clear and helpful with a voltage doubler mode straight out of the Diablo schematic.  The 1044 works by alternatively applying the rail voltage and the ground to pin 2 the base of C18 and top of C20.  This allows C18 to charge to almost V++ (-Vdiode) before lifting it onto the rail voltage to dump its charge into C19 bringing that to around 2xV++.  C20 is irrelevant to all of this and while it is all going on, it's bottom end is alternatively linked to the ground and pin 5 which is not used.  Why are the two systems being used in the Diablo circuit?  For voltage doubler mode surely C20 is redundant.

Is there anyone who has experience with the MAX1044 or the Diablo who can point me at something I've missed?