Ibanez MOStortion MT10

[George Giblet]

>7) Then, there is a three-band tonestack.  I haven't had the time yet to redraw the circuit in a more traditional way, but apparently it is similar but not exactly a Fender or Marshall device, since I see at least one too many capacitor and resistor in there.  Certainly a design to be further studied!

Tonestack = Same as Peavey Solid-State amplifiers

IIRC, Top Hat and Dumble use a similarly morphed fender tone stack.

[NoFi]

Here are the pics  :
http://thebin.free.fr/GC/Mostortion/

The Ceramics belong to the switching circuit except C4 at the diodes.
Flabby meant various sound wobbles and mushiness probably partly associated with intermodulation distortion. It's "passable" on single notes or powerchords but it gets really undefined, if not metallic ring modulatorish on some chords. But it works to add dirt to cean sounds. l'll do a sound clip.

As the CA3260E's are readily available at some places i'll buy one next time i need components and try it.
But the whole MOS-FET thing could really be marketing (i have mush-fets in my peadle lol).


Heavy metal ?  AC/Dc maybe.

I'm impressed by the tone stack simulation. It shows well how the mid pot can turn up the low mids.

[WGTP]

I can't see the tonestack simulation and would love to know what is going on inside my SS Peavey.   

[Mark Hammer]

NoFi,

There is the everpresent JRC4558 in the socket.  Have you used/heard the unit with the original chip?

[stm]

I can't see the tonestack simulation and would love to know what is going on inside my SS Peavey.   

You mean you can't see the image?

This is a direct link to the image: http://i4.tinypic.com/10hr95d.png

You may download it directly.

[NoFi]

Yeap Mark that was maybe two years ago. I took the chip out to see if i could improve anything, mounted the socket and tried various chips. But there was not that big of a difference really so i dumped the chip and after a few trials i went with a burr brown because it was supposed to sound "the best" lol (heck i must have read it on the internet !).
I put the 4558 in today. 
It was one of first pedals i tinkered with, so i can't really trust my ears of the time. So i'll give a chance to the designer and try the right chip.

[Mark Hammer]

At the risk of boring lots of folks, I will repeat my parable about my TS-808 clone and my change in guitars.  For years, my principal guitar was my Epi Coronet, with hotter home-made pickups, and an on-board preamp with a gain of around 3-4.  I was looking forward to my TS-808 clone being finished, and when I plugged in, I absolutely hated the pedal.  It just sounded awful, but I kept it anyways.  Later that year, I bought a Tele clone with "normal" pickups and no added boost.  Plugging into the TS, it sounded MUCH better, and conformed to everything I had heard.  The difference was the signal being fed to it.  It "wants" a modest signal, not a hot one.

Though not entirely the same, the MT10 is also one of these "can you just heat it up a bit" pedals which may, or may not, rely on a particularly type of input level to sound its best.  That's not an excuse, but a reason to be a little flexible in our collective evaluation of it.

[WGTP]

stm it must be getting blocked here at work, I'll check it out at home.  Thanks.

[NoFi]

I added a soundclip. Interest for the pedal will surely fade lol .And it's with the 4558.
http://thebin.free.fr/GC/Mostortion/

Old Ibanez guitar with hckers > Mostortion > soundcard
Eq knobs at noon.

From 0"00 to 0"35 s i boringly try to demonstrate the wobbliness of the distortion and how it changes and cleans up when lowering the gain.
Of course it doesnt do that on all chords and maybe it wouldn't do it with different equipment and the right chip.

From 0"35 to 1"13 the gain is pretty much lowered (11 - O clock) and i try to show the dynamics, how it cleans up on notes and takes off on slammed chords. But there's probably more gain than what i would usually use.

From 1"13 to 1"52 more wobbleness on another chord as i crank the gain and less i as lower it again. I'm under the impression that there is this wobbliness in the background way to often at high gain settings if i dont play "classic" chords.

And then it's just some fooling around with a tad less gain.
Sorry i'm not SRV LOL.

The pickups are pretty hot, i prefer the pedal with lower output ones but my jaguar is dismantled at the moment lol.

[stm]

May I insist that the low frequency wobbliness at high gains might have to do with excessive bass at the input.  It would be just a matter to change the 220nF cap (C5) to a lower value, like 100n, 82n or even 68n (82n produces a response similar to a TS).  Maybe an extra switch could be added to choose between the stock 220n and 100n (or whatever cap you like) for higher gain settings.

I'll have to wait until I get home to download the MP3 to listen to the samples, since MP3 files are blocked at work.

[TELEFUNKON]

terrible intermodulation tremolation hickup

[NoFi]

Just to be sure, i reversed my input cap mod (C1 was 0.1uF) , changed the 4558 for the BB, took my P90 equipped guitar... and it's the same.
If i understand correctly modding C5 changes what frequencies are clipped, for instance with the 220nF cap, result is no or less clipping below 267hz. But those frequencies are not totally cut, and they are still outputted (since they go out from the first opamp at pin 7 and head for the tonestack) ?
I guess i'll have to try that.
Constantin is your pedal doing that ?

[NoFi]

0.1uF at C5, instantly more TS like, less bass perceived, more clarity. The intermodulation is more reasonnable but still there. I have to push the gain knob further to get the same amount of clipping as before. It's bit like castrating the pedal but a switch would probably be a nice addition if anyone ever builds it.   
Before with the knobs at noon it "equaled" the bypassed sound. Now i have to set the bass knob right up, the mid knob to 9 O'clock and the treble knob slightly back not to have too much of a difference.

[stm]

I listened to the audio sample and I liked it. Looks this pedal cleans up much better than an SD-1, well, at least compared to the SD-1 clone I have.

I agree changing the 220n cap for 100n might appear as "castrating" the pedal in terms of gain.  You can also try replacing the 2k7 resistor with a 1k5 resistor. This will have an equivalent frequency response but with increased gain, effectively acting like "squeezing the pedal's balls" or, put in another way, like a mid boost.

( instead of replacing the 2k7 resistor with 1k5 you can place a 2k2 resistor in parallel )

If the bottom end seems reduced when this is done, you can look for a way to add more capacitance somewhere ahead in the circuit to compensate for this side effect. This would require then a DPDT switch.

[stm]

Just a clarification to the suggestion above:  you either change the 220n for 100n OR change the 2k7 for 1k or 1k5.  The former reduces overall gain (in the bass area), while the latter will make gain a bit hotter (in the mid and high area).

[NoFi]

It's nice you liked it, indeed it's the clean/dirty zone that's interesting.
Thanks for all the suggestions, but i'm afraid i will not try them right now because i have already too many projects going. I reversed the mods to recover the bass frequencies. I was thinking of building a clone of this pedal anyway, with a boost and maybe a boss type overdrive in the same enclosure to cover all my overdrive needs, and also get rid of those everpresent buffers that seem to brighten the tone compared to true bypass.

By adding more capacitance ahead fo the circuit, do you mean for instance, changing C12/C13/C15 or the output cap ?

[toneman]

So why is this thingie called a "MOS" distortion??
No MOSFETs anywhere.
No CMOS anywhere.
Just bipolar & opamps.
Strange Days
Must be "marketing"..... 

[NoFi]

CA3260A and CA3260 are integrated circuit operational
amplifiers that combine the advantage of both CMOS and
bipolar transistors on a monolithic chip. The CA3260 series
circuits are dual versions of the popular CA3160 series.
Gate protected P-Channel MOSFET (PMOS) transistors are
used in the input circuit to provide very high input
impedance, very low input current, and exceptional speed
performance. The use of PMOS field effect transistors in the
input stage results in common mode input voltage capability
down to 0.5V below the negative supply terminal, an
important attribute in single supply applications.
A complementary symmetry MOS (CMOS) transistor pair,
capable of swinging the output voltage to within 10mV of
either supply voltage terminal (at very high values of load
impedance), is employed as the output circuit.
The CA3260 Series circuits operate at supply voltages
ranging from 4V to 16V, or ±2V to ±8V when using split
supplies. The CA3260A offers superior input characteristics
over those of the CA3260.

[toneman]

Oh Kay, NoFi
MOSFETs inside...

[stm]

It's nice you liked it, indeed it's the clean/dirty zone that's interesting.
Thanks for all the suggestions, but i'm afraid i will not try them right now because i have already too many projects going. I reversed the mods to recover the bass frequencies. I was thinking of building a clone of this pedal anyway, with a boost and maybe a boss type overdrive in the same enclosure to cover all my overdrive needs, and also get rid of those everpresent buffers that seem to brighten the tone compared to true bypass.

By adding more capacitance ahead fo the circuit, do you mean for instance, changing C12/C13/C15 or the output cap ?

I don't know which cap yet, but my idea was among the lines of either changing something in the tonestack for extra bass, or doing something around the second opamp.

To finish beating the MS10 mod and tweak subject, the two diodes in series in the feedback loop (which are of the 1N4148 kind) might be replaced with two 1N4001 + 1 Ge, in a similar way as discussed in the latest SD-1 mod posts.  Of course red LEDs are another possibility.