anyone familiar with a coron d500?

[pinkjimiphoton]

just got one of these, had to surf thru a bunch of pics to find a match on google, it's missing the battery compartment cover.

REALLY nice distortion. i mean, cleans up like a fuzzface, and sounds real warm...volume, gain, hi boost and lo boost.

just curious, anyone have a schematic? i can find nothing on the net, so assuming it's rare..

would this be a worthy candidate to clone or trace the circuit maybe?

anybody shine a little light on these? thanks!!

[pinkjimiphoton]

wow, this thing must be rare, i can't find anything about it anywhere....
i CAN say, it's not another tube screamer...

i will try and post a SPT of it so ya'll can hear it, and it may become my first candidate for trying to trace the schem i guess...
brave new world for me!!!

any tips on how best to start this process?

i think it would do my late brother good to know it's going to the community....

[Dom D]

I did some research and found pretty much nothing other than pictures at Effects Database and someone on Ultimate Guitar saying he uses one.   

Seems to be quite a mystery!

[pinkjimiphoton]

guess it's a good candidate for ressurection then i guess!

[pinkjimiphoton]

this MAY be the same, or a similar circuit, i found a thread on FSB about maxon selling stuff under the "coron" name in europe in the late 70's...this is the only box i found so far by maxon with volume, gain, bass and treble, and the sonic description is certainly close!!

[pinkjimiphoton]

this looks like it may be the same...i gotta gig, so tomorrow i'll try and see if the components are the same. it has the right knobs, anyways, lol!!

[Mark Hammer]

That's funny.     I am presently tweaking something I threw together a couple months ago that looks very similar: an op-amp gain stage with feedback-path clipping diodes followed up with a second diode pair to ground.  In my case, that's followed up by a simpler second op-amp gain stage for straight-ahead boost, with no gyrator-based tone controls or transistor output buffer.   I also use the ground leg for gain-setting, instead of the feedback resistance, and don't aim for quite so much gain in that first stage as the Coron does.

The Coron leaves all diodes in place.  In my instance, what I did was leave the feedback diodes (1N4148) in place, but make the diodes to ground (2+1 1N34) switch-selectable.  (The second set of diodes needs to have a lower clipping threshold than the first set.)  The toggle you see in the picture is 3-position.  Middle lifts the diodes-to-ground and their accompanying parallel treble-cut cap,  "Warm" also leaves those diodes out but adds more feedback capacitance in the op-amp stage to soften the clipped tone (the unit has no variable tone controls like the Coron).  "Thick" adds to that by connecting the diodes to ground plus second cap.  You lose a bit of level when "thickening" the sound, but there is still plenty left.  In the absence of tone controls, I've tried to set the fixed tone-shaping to get a useful amount of bite from a bridge pickup, but not so much to send you running for the amp controls.

In any event, all of that is the long way of saying that I can verify this approach to double clipping provides a pleasingly thick tone, and that a suitable mod might be a toggle that defeats one or the other diode pair.  Again, what D1 and D2 do to the signal should still leave enough signal amplitude that it will clip again via D3 and D4.  D1-2 and D3-4 don't have to be silicon and germanium, respectively.  As long as the first set have a higher forward voltage than the 2nd set, you're fine.  So the first set could be a 2+2 combo of 1N4148+1N34 and the 2nd set plain old 1N4148, or whatever you like or have on hand.  Heck, you could even select a pair of the same type from your bin with a forward voltage at the higher end of the tolerance, and a second pair at the lower end of the tolerance range.  And, in the spirit of many contemporary pedals, consider using a stompswitch to add some amount of preset feedback resistance to R11 and get some boost. 

(For the uninitiated, Hurry Hard is a term used in curling.  It's what you shout at your team-mates when you need them to sweep even faster to get a little more velocity on the rock.  I thought the world needed a curling-themed pedal, and the boost function was when I needed it to "hurry harder".)

[pinkjimiphoton]

neat!! any clips yet, mark?

[Mark Hammer]

I'm trying, brother, I'm trying.  Thought the video demo was 2meg.  Turned out it was 2 gig.  Got a little bit of editting to do.

[pinkjimiphoton]

oyyyyyyyyyyyyyyyyyyy!!!!!!!!!!!!!!!!



been there. except for the editing part. that, forget it...either too stupid or too lazy, or a combo of both. 

look forward to hearing it if you get it sorted out tho!

[Keppy]

The tone controls in that schem are freaking me out. I've identified the components that make a gyrator, but I can't figure out how that results in any filter that would do what I expect. I'd expect shelving or low/highpass filters, but those look like bandpass/bandstop filters as far as I can tell, with pots to move the filter from the opamp non-inverting input (cut at the filter frequency) to the inverting input (boost at the filter frequency). Am I wrong, or is that actually how it works?

[pinkjimiphoton]

i don't know if that's this actual circuit,  it looks kinda like it ...and that was a cross match. i do need to open it up, and take some pics to post.

[Ronan]

for some gut shots jimi, do a search on Gorin DS830.

Keppy, those tone controls look like a 2-band graphic eq to me, very cute.

[PRR]

> The tone controls in that schem are freaking me out.

Same-as Rod Elliott Project 30a Figure 6.



The gyrators are just "coils". C1 and C3 make Tuned Circuits. Series, so impedance is low at resonance and high otherwise.

For concept, replace the tuned circuit with a short.

Turn Bass pot to the left. The short will short-out the signal from R2.

Turn Bass pot to the right. The short against R3 will max-out U1's gain.

Go back to tuned circuit. This cut/boost will happen only at resonance, the rest of the frequency response stays flat.

Use several tuned circuits at different frequencies, get bass-mid-treble, even an 11-band EQ.

Sometimes, particularly the top band, you don't need a return to flat (because it's outside the audio band). Rod's treble control is just a cap (and a resistor so it don't go to infinite boost/cut).

[pinkjimiphoton]

for some gut shots jimi, do a search on Gorin DS830.

Keppy, those tone controls look like a 2-band graphic eq to me, very cute.

thanks ronan,
it looks like the same or similar circuit, but the layout is different...will try to post a couple pics tomorrow.

[Keppy]

> The tone controls in that schem are freaking me out.

Same-as Rod Elliott Project 30a Figure 6.



The gyrators are just "coils". C1 and C3 make Tuned Circuits. Series, so impedance is low at resonance and high otherwise.

For concept, replace the tuned circuit with a short.

Turn Bass pot to the left. The short will short-out the signal from R2.

Turn Bass pot to the right. The short against R3 will max-out U1's gain.

Go back to tuned circuit. This cut/boost will happen only at resonance, the rest of the frequency response stays flat.

Use several tuned circuits at different frequencies, get bass-mid-treble, even an 11-band EQ.

Sometimes, particularly the top band, you don't need a return to flat (because it's outside the audio band). Rod's treble control is just a cap (and a resistor so it don't go to infinite boost/cut).

If I'm understanding you right, then my original understanding of the circuit was correct. My issue was that I expected shelving or highpass/lowpass filters, but these are neither. They affect a specific band of frequencies centered on a resonance, which I would expect on a midrange control or graphic EQ band but not a treble or bass control. Live and learn, I guess.

Thanks for your help!

[PRR]

> not a treble or bass control

Shelving bass boost brings up all the supersonics in the signal. In many situations, this is not the best idea.

Rod Elliot's plan does shelf the highs. The treble is just a cap, not a cap+coil. This may in part be to avoid finding a triple opamp.

This Coron does ring-up the treble. Not only to avoid boosting supersonics, but because you can get a steeper slope and more specific action with a 2-pole than a one-pole.