Distortus Maximus

[Crawf]

http://www.aronnelson.com/gallery/v/mydementias-Gallery/KrunkDM/DistostortusMaxiusProject.JPG.html


Hi, I've built this from this layout and was wondering how to tame the highs,i have only tried it through a tiny practice amp but can tell it will probably too bright for my tastes, i used a 100kA pot for the highs as that was all i had but i can change it know as i have the right pot and i used a LM386-1 as thats all i could get.


The 22nf non polarised caps are marked  223 so they seem right but i used small box caps marked .1 with a 63 below which i presume are the 100nf caps and one cap with 4n7k 100 which i assume is the 4.7nf cap, can someone verify these are right. If they are, are there cap value changes that would tame the highs, other than that the pedal sounds ok as the purpose was to build a highish gain pedal so i'm nearly there, thanks, Crawf. 

[John Lyons]

Those caps are correct.
The 250K pot for the highs should make a big difference although with 100K you should be getting less highs...
If you change the 470P for q 250P you will get less midrange and closer to a fender type EQ.
The tone stack in the schematic is more like a marshall.

Make sure you have wired it correctly.
You should be able to get a darker sound with the treble turned down, especially with a 100K-A pot.

John

[dschwartz]

just put a 10nF (try different values) cap between output and ground...that will tame the highs, i use that sort of like an ultra simple cab sim...

[jakenold]

Try to lower the input impedance of the buffer. That might work!

Jake

[Crawf]

Hi, Sorry can you eleaborate on how to "lower the input impedance of the buffer" i'm afraid i'm a paint by numbers DIYer

[Crawf]

Hi again, I have just connected the proper value High pot 250kA and it seems ok, rolls off the highs no problem but if anyone has more input to offer on this pedal i'm all ears, thanks Crawf.

[bluefarm]

I think u should try LM386-N3 as you can read in data sheed it has bigger output gain
see http://cache.national.com/ds/LM/LM386.pdf
I hope this will help you.

[dschwartz]

Hi again, I have just connected the proper value High pot 250kA and it seems ok, rolls off the highs no problem but if anyone has more input to offer on this pedal i'm all ears, thanks Crawf.

did you even consider my sugestion??

[Crawf]

Daniel,of course i considered your suggestion but when i connected the proper value pot for the highs 250kA and fixed the gain pot which i wired wrongly and then put it in a temporary box, i then tried it through my boogie and voila! it sounds great and not too bright for my taste,thanks to all for your help, Crawf.

[Gus]

The circuit looks like it could use some help.

One the input R is kind of low under 43k  (real input is 43K || 470K || hfe x 390 ohms) (||, in parallel)

Two the tone stack looks like a cut and paste of a tube circuit tone control.

  I would decrease the tone stack resistor values and increase the cap values because the 386 is a power amp chip AND you will have less interaction with what ever you place behind the tone stack.  If you decrease the resistors/pots by 10 increase the caps by 10 OR find the marshall 3005 solid state preamp circuit for hints.  Go to duncans page and model the tone stack using the tone control software put the correct source resistance and change the load.  I would make the source R 8 ohms and then try 1 meg down to 47K as the load after the volume control and watch what happens.

[johngreene]

Those caps are correct.
The 250K pot for the highs should make a big difference although with 100K you should be getting less highs...

Really? I entered the values into the Tone Stack Calculator and the 100K doesn't cut the highs as much as a 250k. 

--john

[johngreene]

just put a 10nF (try different values) cap between output and ground...that will tame the highs, i use that sort of like an ultra simple cab sim...

Output of what? The pedal or the 386?  If you put it on the output of the volume control the corner frequency is going to change depending on the volume control setting. If you put it on the output of the 386, it might not have that much of an effect because the 386 has a lot of drive capability and the tone stack doesn't present much of a load. Dumping all that energy to ground, although possibly giving the desired frequency response, is just wasteful of precious battery life. I wouldn't do it without some series resistance.

--john

[dschwartz]

i meant..before the volume control.. on the outer lugs of the pot...

kind of what ROG did in the thunderchieff..i use it on my dr boogie when i want to plug it in a preamp..

[John Lyons]

Those caps are correct.
The 250K pot for the highs should make a big difference although with 100K you should be getting less highs...

Really? I entered the values into the Tone Stack Calculator and the 100K doesn't cut the highs as much as a 250k. 

--john

I was thinking about it backwards I guess.

[Crawf]

Hi again,Well i boxed it up properly and used a 3PDT to allow me to add an LED so when i had it all wired i noticed right away it popped when switched on(didn't do it when wired to a DPDT which is how i wired it just to make sure it worked)and the Vol control was scratchy plus the pedal seemed to lack output, as soon as i diconnected the led everything was back to normal, i tried two methods of wiring the 3PDT but both gave the same result so i went back to a DPDT and it sounds fine so thats the way it's boxed up and i'm sure i'll know when it's on but i wondered if anybody knows why this would happen  ???thanks again Crawf.

[johngreene]

Hi again,Well i boxed it up properly and used a 3PDT to allow me to add an LED so when i had it all wired i noticed right away it popped when switched on(didn't do it when wired to a DPDT which is how i wired it just to make sure it worked)and the Vol control was scratchy plus the pedal seemed to lack output, as soon as i diconnected the led everything was back to normal, i tried two methods of wiring the 3PDT but both gave the same result so i went back to a DPDT and it sounds fine so thats the way it's boxed up and i'm sure i'll know when it's on but i wondered if anybody knows why this would happen  ???thanks again Crawf.

Where are you getting power and ground for the LED? Try taking it from as close to the battery as you can. There are several LED 'smoothing' circuits on the web you can try too.

--john

[Crawf]

Hi John, power from the PSU input and used the EZ 3PDT wiring from Dragonfly's Gallery and the wiring from Tonepad and both had the same effect, don't get me wrong although all my builds have had an LED fitted, for this one not to is no big deal,as i said i'm sure i'll know when its on! thanks Crawf.

[John Lyons]

If the Volume pot is scratchy then there is probably DC on it. Measure the hot pin and see if you get any DC.
This will cause the switch to pop. The DC builds up and when you hit the switch it transfers DC to the signal.
But without the LED you don't get any scratch or popping?

John

[johngreene]

The low output comment makes me suspicious. The only reason for this that I can think of is that the LED is drawing enough current to pull down the supply voltage. This would definitely cause it to pop....

The scratchy volume pot also is suspicious of DC as John Lyons points out.

--john

[Crawf]

Hi Again,As it stands using a DPDT switch is fine,plenty of volume or when i disconnected the LED from the 3PDT everything was back to normal, could it have been the way i have connected the 3PDT? i've used the Tonepad way loads of times with none of the issues. 


(i'm afraid i'm a bit electronically challanged when it comes to problem solving, a bit out my depth i'm afraid, my initial question was my own doing as i had wired the gain pot incorrectly and had the wrong value high pot but those issues are resolved)