freestompboxes.org

Hi all

Almost a year ago I built myself a Mudhoney clone following the stripboard layout from TagboardEffects, which follows the two schematics to be found online. But as it turned out to work quite a bit different than the original I have tried to modify my build in numerous different ways to make it work as intented. But still, it didn't sound as would like it to. But now I have bought myself an old used unit and have tried to trace it!

This is my first trace and I have yet to try building it, but I thought there might be other people interested in this pedal. To me it is a really great sounding pedal that deserves to be traced.



If anything looks odd or wrong please let me know, I am eager to learn

Here are some photos of the circuit: https://ibb.co/album/yWRyfB

Happy new year
/Kasper

Nice work on the schem!

However. Are you sure about the way the boost switch is wired? In that position, when activated it takes the 2k2 in parallel with gain pot + the 150R. And that would mean the ohm value on feedback loop would be set at something like 2K1 even with 47K pot maxed.

Otherwise this looks good. Well drawn, easy to read etc.
+m

Ah I see! I was unsure about what the correct way of writing the switch. It is the opposite that was my intention! When the switch is off the 2k2 is in parallel - when activated it is floating. Just so I understand you; Pin 1 and Pin 3 should just switch around?

Thank you man!

Nice

Are you sure C10 and C11 are both 4.7uf ?

The feedback circuit looks like the RAT mod circuit, C10 should then have a value of 2.2 uF, but perhaps a different frequency response was desired by the developer.

Kasper, thank you for taking the time to do this ! I've seen the two earlier traces as well and always wondered about the differences.

C10 has been 4.7µF in the other two Mudhoney schematics on the net as well, so I assume it's correct. It lowers the corner frequency of that RC filter from the 1539 Hz of a stock Rat to a very Tube Screamer ish 720 Hz.

So the boost switch changes the range of the gain pot and R11 from between 150r and 48.5k to 140r and 2.1k. Very clever, as it keeps the frequencies of the RC networks intact, unlike the usual Ruetz switch.

In one of the other traces, there is a third parallel RC network that's always in the circuit. It consists of a 2.2k resistor and 0.1µF cap for, again, a very TS-ish 723 Hz. The switch takes out the 47r + 4.7µF and 560r + 4.7µF networks.

Which version of the boost switch is the older / newer / current version ?

Kasperrosenlund wrote: ↑02 Jan 2023, 19:36Just so I understand you; Pin 1 and Pin 3 should just switch around?

Pin numbering doesn't matter. I just wasn't sure which way the boost was on. :) The 140R+1.5K just seemed to me like a way too little resistance in the feedback.

Cub wrote: ↑03 Jan 2023, 07:40 Which version of the boost switch is the older / newer / current version ?

If i recall correctly, the clones made with those earlier schems didn't sound quite right. Could it be that those both were just wrong?

It really is just a tweaked Rat!

mictester wrote: ↑03 Jan 2023, 12:22 It really is just a tweaked Rat!

I don't think anyone disputed that... :)

But i think it's cool to get the mods correct after years of erroneous clone builds that didn't sound right.

So.. Will someone try this out? Unverified atm. // aaand this is verified on the blog (4.1.2023)
+m

mirosol wrote: ↑03 Jan 2023, 12:10

Kasperrosenlund wrote: ↑02 Jan 2023, 19:36Just so I understand you; Pin 1 and Pin 3 should just switch around?

Pin numbering doesn't matter. I just wasn't sure which way the boost was on. The 140R+1.5K just seemed to me like a way too little resistance in the feedback.

I heard of people replacing the stock 100k gain pot in their Rat for 50k or even 25k because they don't like their Rat to be fuzzy (boo!) but 2.1k is extremely low.
It might make a fun gain range switch with a 100k pot for the stock sound and parallel resistors to taste - 100k for a combined max of 50k, 33k for 25 and the Mud's 2.2k for 2.1k

mirosol wrote: ↑03 Jan 2023, 12:10

Cub wrote: ↑03 Jan 2023, 07:40 Which version of the boost switch is the older / newer / current version ?

If i recall correctly, the clones made with those earlier schems didn't sound quite right. Could it be that those both were just wrong?

Good point, that could very well be the case.

CheapPedalCollector wrote: ↑03 Jan 2023, 00:07 Are you sure C10 and C11 are both 4.7uf ?

Yea, I'm positive

mirosol wrote: ↑03 Jan 2023, 12:10 Pin numbering doesn't matter. I just wasn't sure which way the boost was on. The 140R+1.5K just seemed to me like a way too little resistance in the feedback.

Got you!

Cub wrote: ↑04 Jan 2023, 08:54

mirosol wrote: ↑03 Jan 2023, 12:10

Cub wrote: ↑03 Jan 2023, 07:40 Which version of the boost switch is the older / newer / current version ?

If i recall correctly, the clones made with those earlier schems didn't sound quite right. Could it be that those both were just wrong?

Good point, that could very well be the case.

I'm sure this is in fact the case. The old schematics did'nt work at all like the original. I don't know if there are many different versions of this pedal (mine is a v.1.1 according to the pcb), but none I've played has functioned like the old schematics. So to me the trace I've made reflect how the boost in fact is - not a new/old/current version, if you get me

mirosol wrote: ↑03 Jan 2023, 15:52 So.. Will someone try this out? Unverified atm.
+m

Wow, nice work! As I am occupied with other projects atm, I can't for now build it myself and compare it to my original, but I am thrilled to see that someone already did verify your layout on Tagboard

Kasperrosenlund wrote: ↑04 Jan 2023, 15:18

Cub wrote: ↑04 Jan 2023, 08:54

mirosol wrote: ↑03 Jan 2023, 12:10

Cub wrote: ↑03 Jan 2023, 07:40 Which version of the boost switch is the older / newer / current version ?

If i recall correctly, the clones made with those earlier schems didn't sound quite right. Could it be that those both were just wrong?

Good point, that could very well be the case.

I'm sure this is in fact the case. The old schematics did'nt work at all like the original. I don't know if there are many different versions of this pedal (mine is a v.1.1 according to the pcb), but none I've played has functioned like the old schematics. So to me the trace I've made reflect how the boost in fact is - not a new/old/current version, if you get me

Crystal clear ! It seems such an unlikely mistake, though.
To see an added resistor on a switch in the feedback loop and then write it down as a third parallel RC network with a switch that takes out the other two.

Now this is rather intersting.. Doing an image search for T Rex Mudhoney schematic on duckduckgo, we get result like below. That points to False electronics blog, that links to a russian site: http://valentinych.ru/wp-content/upload ... /Pic_8.gif - which isn't loading right now (could be gone for good). Blog post is from 2017 and the url on the actual schematic image says it's uploaded in july 2013. And if we look at the schem, the boost switch is wired the same as in Kasper's trace. And that is not the same as the two other schematics that can now deemed as wrong.

So i guess there was also a correct drawing floating around since 2013. None of us spotted it though. Well. Better late than never.
+m

Cub wrote: ↑05 Jan 2023, 07:11 Crystal clear ! It seems such an unlikely mistake, though.
To see an added resistor on a switch in the feedback loop and then write it down as a third parallel RC network with a switch that takes out the other two.

Yea, it is a bit strange..

mirosol wrote: ↑05 Jan 2023, 12:48 Now this is rather intersting.. Doing an image search for T Rex Mudhoney schematic on duckduckgo, we get result like below. That points to False electronics blog, that links to a russian site: http://valentinych.ru/wp-content/upload ... /Pic_8.gif - which isn't loading right now (could be gone for good). Blog post is from 2017 and the url on the actual schematic image says it's uploaded in july 2013. And if we look at the schem, the boost switch is wired the same as in Kasper's trace. And that is not the same as the two other schematics that can now deemed as wrong.

So i guess there was also a correct drawing floating around since 2013. None of us spotted it though. Well. Better late than never.
+m

Interesting! Here it is loading
...I could've saved myself some time doing a search on DuckDuck Go

Needless to say, but i think Kasper's work finalized the issue of correct Mudhoney (rat mod) topology. So, Kudos!

Now. Anyone have a schem for Alberta?
+m

Found the "Valentinych" site: http://valentinych.ru/o-zvuke/gitarnye- ... rmy-t-rex/
I noticed a few differences between Kasper's and Val's schematics,
but I can't see a version number on the boards on Val's site.

Cub wrote: ↑05 Jan 2023, 20:06 I can't see a version number on the boards on Val's site.

It's hard to make out but the board on Val's site is labeled MP V11 the same as the one in Kasper's pics.
The pot date code on Val's appears to be earlier however as it is dated 7C4 where Kasper's is dated 8H2.

Axldeziak wrote: ↑06 Jan 2023, 15:12

Cub wrote: ↑05 Jan 2023, 20:06 I can't see a version number on the boards on Val's site.

It's hard to make out but the board on Val's site is labeled MP V11 the same as the one in Kasper's pics.
The pot date code on Val's appears to be earlier however as it is dated 7C4 where Kasper's is dated 8H2.

Doh, I completely missed the link to Kasper's shots !

I flattened both Kasper's and Val's pics of the boards so it would be easier to compare them, but I don't think there are any differences in the components of which the values are visible ?
Though I have to admit, I'm starting to reach that age where it's getting harder to tell colours apart. Therefore, I attached them so younger eyes can have a look as well.

Cub wrote: ↑05 Jan 2023, 20:06 Found the "Valentinych" site: http://valentinych.ru/o-zvuke/gitarnye- ... rmy-t-rex/
I noticed a few differences between Kasper's and Val's schematics,
but I can't see a version number on the boards on Val's site.

Code: Select all

 Kasper   │ Val
──────────┼──────────
 R1  470r │ Rb1  100r
 R2   10k │ Rb2  6.8k
 R3   10k │ Rb3  6.8k
 R10 100k │ missing  
 R11 150r │ Ra9   15k
 R20 510k │ Ra17 100k
 R22 100r │ Ra19 1.5k
 missing  │ Ra20  10k
C16 100nF │ Ca14 10nF
D5 1N4007 │ missing  

Thanks!
I will recheck mine and see if I missed something.
One thing I now know that is missing in my trace is the 10k at the output - that is in mine as well, apparently just forgot it in the schematic.

I will look into it one of the next couple of days.

so, we can make a rat sound like a mudhoney with just two mods, 4.7uF in place of the2.2uF cap on the feedback loop and a 1uF cap in place of the 22nF on the input, interesting