Mosky Brown, a Pinnacle II clone

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elguidom
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Post by elguidom »

Hi all,

I recently bought a Brown Distortion pedal by Mosky, because I'd heard it was a clone of the Wample Pinnacle.
It does sound good, but I'm experiencing what I believe is the infamous sag issue, but that's not the point of this post.

Anyway I've opened it up and traced the components. It is indeeed a close copy of the Pinnacle, at least compared to the schematic for it that I found on this forum.
The layout is different and there are a few different values. It is well made and with quality components from what I can tell (metal resistors, film capacitors...), and therefore not noisy.

Please find attached the schematic I made that compares the Mosky Brown with the Pinnacle. I borrowed the schematic by pappasmurfsharem found here:
https://www.freestompboxes.org/viewtopi ... 40#p235716


What I need your help with, however, is understanding how the differences in component values will change the sound compared to the Pinnacle, and help me decide whether it is worth modding it to full Pinnacle specs.
I don't understand the inner workings of pedal electronics enough to do that on my own, unfortunately.

Can someone shed some light on the differences and their impact please? I'd be very grateful!

Summary of the differences:
- C4 is 47nF in the Mosky Brown instead of 22nF in the Pinnacle
- C5 is 100nF instead of 56nF
- C7 is 560pF instead of 470pF
- C10 is 47nF instead of 22nF
- R15 is 10k instead of 22k
- C14 is 5.6nF instead of 6.8nF
- R25 is 10k instead of 22k
- R26 is 10k instead of 22k


The difference for R30 is obviously a non issue, something having to do with a differently spec'ed LED or a brightness tweaking.
The rest however leaves me bit more concerned.

The message found here implies that the differences in R15 and R25 would be aimed at tweaking the response of Q5 and Q6, so I guess I should not change those.
https://www.freestompboxes.org/viewtopi ... 00#p216600

But what about the rest? How do they change the sound compared to the Pinnacle II?

Thanks a lot to anyone who can help!
Attachments
Mosky Brown schematic
Mosky Brown schematic
Mosky Brown gutshot
Mosky Brown gutshot

elguidom
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Post by elguidom »

No answer yet? :cry:

Anyway, I took the time to do a layout picture. The component names match the names in the schematic from my previous post.
Hope this helps at least someone out there.

(Sorry for the thin red lines in the picture, I used them to do perspective correction from the picture I had taken. I believe they're not much of a distraction.)
Attachments
Mosky Brown layout
Mosky Brown layout

alexradium
Resistor Ronker
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Post by alexradium »

i'll tell you this,all those differences are just minor and those which count are basically in the biasing of the jfets,which was really specific in Wampler's case,he had them tested for the specific circuit and nobody knows the exact specs,plus he went through different layouts too,that makes a high gain pedal work good or bad big time.
If you don't have enough electronics skills and you don't have an original to compare,don't do shit,that's my 2 cents.

elguidom
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Post by elguidom »

Thank you for your input.

I would however very much like to understand what the changes actually do (if they do anything).

I believe the change in R26 just means that the Mosky can have a higher output than the Pinnacle, because with the volume pot it looks like a simple voltage divider which cannot go to 100% of its voltage input. Not much point in tweaking that, unless I find myself needing my volume knob to be less touch sensitive and there is plenty enough volume as it is.

I do wonder though if other changes might have an impact on the sag issue I have. Maybe that issue is not as present on the Pinnacle. Basically right now the pedal is generally usable but I have an issue when doing a pinched hamonic on the G string, at fret 4: the attack is swallowed by the sag and I hear nothing for an uncomfortable length of time and then the note comes in. My pickups are medium high output, not very high, I think (a Bare Knuckle Cold Sweat in the bridge, in the present case, which is basically slightly lower output than a Duncan JB). Pickup height is not unreasonable so the Wampler suggestion for lowering the pickup does no fly for me, especially since I never experienced any similar issue with my other pedals and amps.
I'm willing to try the tweaks suggested in the Pinnacle/Sovereign - to much sag topic (especially the C6 tweak), but I believe it would be silly to do that without first checking if the issue isn't coming from the deviation from the original Pinnacle design.

So basically it looks like the resistor value changes are of no import, but that leaves me with the capacitor changes. Specifically, could C4 and C10, being twice the original value, be limiting the signal somehow and causing the issue?
The differences for C7 and C14 are lesser so I'm guessing they are less meaningful, but I could be wrong.
Finally C5 is almost twice the original value and I find that intriguiing.

howmuch
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Post by howmuch »

Hi,
Out of interest, what JFETs are they using in the Mosky?
I very much doubt they are J201s since they are only manufactured in SMD now (MMBFJ201).
And it seems that carefully selected J201s with the right pinch-off voltage and biased correctly are hard to substitute in a pedal like this.

Probably best to check the biasing of the Fetzer valve JFETs (Q5, Q6).
See this http://runoffgroove.com/fetzervalve.html

As for the caps:
C10 forms a HPF and its frequency drops from 88Hz to 41Hz, so it's letting in a bit more low end. Tightening up the bass end by reducing the value of C10 might help.
C4 forms a HPF and its frequency drops from 7Hz to 3Hz, so nothing to worry about there regarding Mosky vs Wampler, but again tightening up the bass end by reducing the value of C4 might help. I wonder if a 10n or even 2n2 would be better here?
As you say, C7 and C14 are close enough to be unimportant.
Not entirely sure about C5, I'd have to brush up on the workings of the "JFET mu-amp". Try the suggestions you already linked to (Pinnacle/Sovereign - too much sag)

elguidom
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Post by elguidom »

Thank you for your help.

You are right, I checked the value of all components except the transistors. They seem to be Fairchild made J201 (they are marked with the F logo, then D52S then J201 on the second line). The Mosky Brown is marketed as being 'hand wired'. Maybe they do sort through their stock of J201s to find satisfying individuals?

Thanks again for pointing out the Fetzer valve thing and explaining what the capacitors do. I should have seen the RC filters right away, dunno why I didn't. I'll try bringing C4 and C10 down and see if that helps.
It might take me a while to source for the components in these trouble times (I'll see what I have in my parts drawer), but I'll be sure to keep you updated on my findings, as it will surely help others.

elguidom
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Post by elguidom »

After all this time, I finally found the time to try some tweaks.

I changed the following parts for the listed value:
- C4 10nF
- C5 56nF
- C6 10nF
- C7 470pF
- C10 22nF
- C14 6.8nF

As you can see, C5, C7, C10, C14 were swapped for values matching the Pinnacle schematic. I did that because I can, and because I wanted to get close to the Pinnacle. We already established that C7 and C14 were probably unnecessary changes, but I was modding the pedal anyway, so I figured why not?

C4 and C6 were changed for lower values than the Pinnacle, in the hope of fixing the perceived sag issue.

I am not sure that changing C5 was wise, as in the thread about the sag someone mentions that lowering the value might bring issues with transients.

I had to use some Xicon greenies caps that are taller than the other components but the board still fits in the case.
I noticed while doing the changes that the PCB uses value names matching that of the schematics, at least for the parts I swapped.

Results: my issue with the pinched harmonics is gone, so that's good. I still experience some sagging in the low end, but only for notes played on the first few frets of the low E string (and possible some on the A string, but to a lesser extent). Also it seems to me that this would not work well with low or drop tuning.
So I think I'll try some more tweaks to get rid of that.

What about lowering the values for C6 and C10 again, to 4.7nF or 5.6nF? (values as they are currently available to me)

elguidom
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Post by elguidom »

OK so I've just swapped C6 to 5.6nF and C10 to 10nF.
This did reduce the sag, it's almost gone. I guess I could live with it now but there is still a tiny bit of it present so at some point I think I'll try to drop C6 to a lower value.
Definitely usable in standard tuning, and also in drop D.

elguidom
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Post by elguidom »

OK so in this next episode, I tried to drop C6 to 2.2nF but it did not reduce the sag.
So instead I tried to drop C10 to 5.6nF and that seems to have done it for the sag.
As a side note I had only tried the pedal with my BKP Cold Sweat pickups until now, and when I tried with a bridge Duncan Custom, the sag was much worse. The Duncan Custom (in the guitar where it is installed) is both higher output and has more bass than the Cold Sweat, so that is probably why. In any case, now the sag is under control.

However I wonder if dropping C6 that low did not produce some harshness in the tone. Late at night is not the best moment to figure this out, so in the next episode I will try to see if I can dial out that harshness with the tone and contour pots, and if not I'll try getting C6 back to 5.6nF or even 10nF, now that it appears that my sag issue might have come from C10 more than C6.

Stay tuned!

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