I'm modding a Mosky Plexi-m closer to a 2204. I changed the gain pot to 100k (where I like it),
and removed the single SMT LED replacing it with wires for a new diode stack.
I prefer symmetrical clipping so I utilized 2 small red leds in place of the SMT single.
I believe the circuit is the same in the Tonecity Model M which was modded in a similar fashion and
I do like it alot. They will each have homes in different rigs.

 My question is regarding the asymmetrical clipping of the 3 diode setup which has some tones I like. Once converted to 4 LEDS, If I replace the original double pair with matching small leds, would a small resistor in series add  slight bit of the asymmetry back in?. I think I'd like a touch of it but no where as much as you get with the 3 diode setup. What value would one use for 1/2 to 1/3 of an additional diode and does it matter which end of the diode pair it goes?
In other words reintroducing a touch of asymmetry that does not screw up higher gain.
I should point out I play rhythm and don't mind "Not cutting through" as much. The 3 diode asymmetric config does seem to "cut" better in an attention grabbing way. Not usually my job....

   I forgot to ask:  Is there a big difference between the smt red leds and the small standard ones?
I ask in case I decided to not add asymmetry as the led pairs might be different enough.

I once used a red LED as a voltage regulator for an AFC circuit in an FM receiver and it turned out to run at 1.88 volts.  I doubt there would be much difference between small packaged diodes and SMT diodes although you may be on a different part of the conduction curve.  BTW I also used a green LED as a voltage dropper in one circuit and it had 2.05 volts across it.

A warning: some people put the LED's in holders where they can see them during a performance.  Bad idea.  The stage lighting will induce leakage currents so if you are under fluorescent lighting, there will be hum modulation.

So it appears there is a difference between some SMD and discrete leds. The SMD's in the mosky clip faster (lower threshold) than regular 3mm leds.
With the gain pot changed to 100k and 3mm leds the pedal's breakup is more to my liking.
According to some web sources some SMD are 10ma and 3mm are 20ma.

I also did have to change the LF347 as it was defective in the brand new pedal, fizz is gone.

Finally found an answer this thread:

What happens if you put a resistor in serie with the clipping diode on a TS?

If the resistor is in series with only one diode, the clipping will become slightly asymmetrical.

Quote from: screamersusa on May 07, 2025, 12:54:02 PMAccording to some web sources some SMD are 10ma and 3mm are 20ma.

web source = datasheet

You can dial in the asymmetry with a choice of resistor on one end of the clipping, or by chaining a different number of diodes on the two polarities of the clipping. Your choice really. You can also employ a ladder of diodes (different kinds even) if you want the clipping to become harder as the level increases. You can also feed the diode clipping into an amp with some inherent nonlinearity (like a FET, or a Darlington transistor, or a CMOS element) in order to make the clipping more dynamic.

If you drive a symmetrical clipper with a sine wave of increasing levels, you will approach a square wave which has the fundamental plus all the odd harmonics in inverse level to the order of the harmonic i.e. fundamental plus 1/3 of the 3rd plus 1/5 of the 5th plus 1/7 of the seventh etc.  This output would sound like a clarinet.  But the guitar input is not a sine wave or even symmetrical, so you do get some even harmonics with symmetrical clipping.

There are some diode clipping circuits where the diodes are AC coupled in the circuit and they tend to adjust their own bias to the point where even asymmetrical clippers or an asymmetrical input can cause the bias to adjust itself towards symmetrical clipping.

Symmetrical clipping of a guitar input should not bring you even close to a square wave but changing the symmetry will change the sound.