High Gain Metal Pedal?

[PenPen]

PenPen,
Note that, somewhat like the TS-9, placing the gain control in the feedback loop means that as gain is increased, treble is cut back.  I'm using a 100k pot, rather than the 150k unit which is supposedly stock.  I notice the slight reduction in treble, although it's not huge.  I suspect the bandwidth restriction that comes with gain may be more a product of the compensation cap than the 100pf feedback cap, but the basic point is that one actually gets more treble (though less growl and obvious fuzz) at lower gain settings.  Running two in series (you are a sick, sick man, my friend) may work out better if one is set for only modest gain, but high output.

Note as well Jack Orman's suggestion to use a 3300pf tone cap instead of the stock 200pf if the tfilter control is not muting enough for your tastes.

Haha, I don't use them like that for serious work. Actually, I use my Rat as more of an overdrive, distortion is never over 11 oclock and the volume is maxed, to hit the tubes more than anything. I have a Rat clone on breadboard right now, and I hooked my stock Rat to the chain to flip back and forth to check the tone of my clone. When I had them both on it was just chaotic.

Actually, I've been playing with the caps in the feedback loop to change the sonic properties of the pedal. I found that going with a single RC network to ground, 220Ohm for the R, and 1uF for the cap results in a fantasticly smooth distortion, along with replacing one of the clipping diodes with LED. My goal, however, was to get a wider freq range including better low end, so I then tested 10uF in that postition. The OA doesn't seem to like that much gain across such a wide range, it clipped horribly, so to smooth it out I then changed the 100pf bypass cap to 220pf to chop off a bit of the higher end, and that helped it quite a bit. I also went with the alternate compensation from the datasheet, 100pf cap from pin 8 to ground. That's supposed to provide better bandwidth. Still sounds like a Rat to me. I'm finding that no matter what changes are made, it ALWAYS sounds like a Rat. I'm still in the experimenting stage, so I'll try out some of your suggestions. Thanks.

[5150]

At the moment I'm having quite a bit of luck with the Ibanez SM-7 for the Cacophony tone - I originally just had to find a suitable sound for a slightly less '80s' demonstration of some Ozzy stuff (couple of Jake Lee songs and a bit of Wylde... which I'm surprised to have pulled off with passive pickups) so I tried replacing a couple of the diodes (not even sure which ones were the clipping diodes, but I had plenty to spare so I threw several in here and there) and putting a fairly small cap on what appeared to be the PCB connections to the outer lugs of the volume pot (as suggested in the Simple Mods page), and it had the right punch and enough compression for the leads, so that may be a good commercial pedal to try.

As far as DIY, I've heard some nice things about a BSIABII after a fairly substantial boost, but I doubt that would work too well.  The Rat could very easily do the trick (unless you cut the mids out completely, in which case the meatiest of pedals will sound wimpy).  I'm working on the Dual Rec emulator and will post a clip if I can finish it.

Jeff

[Marcos - Munky]

I suggest you the Obsidian, I used one when I was playing Slayer songs with a few friends. The BSIAB2 will give you a Marshall-like sound, you can try it with an overdive to boost it, like Zakk Wylde do. I tried my BSIAB2 with the Zakk Wylde overdrive, and it gives a good gain boost. Also, it's not DIY, but the Digitech Metal Master have great tones too.

[Melanhead]

here's my shredding pedal, started out with the rat schematic .... 

From the original post ...

"Just for fun, I wanted to make a Rat type circuit using a 4558 and no transistors ... I also wanted to make it a bit smoother with less mushy bottom end ... this is the result ... I love it! "

http://aronnelson.com/gallery/melanhead/HeadCaset

http://aronnelson.com/gallery/melanhead/HeadCase_layout

enjoy ...

The layout was verified by me this weekend but I tweaked it since to make it a bit smaller ... should be fine though.

Soundclip added April 12/06:

man my Strings are dead! ... Marshall sorta clean, then Marshall and Headcase ... Enjoy!

http://users.eastlink.ca/~melanhead/MP3/HeadcaseMarshall.mp3

It's slightly less gain than a rat though ... but works for me;)

[mydementia]

I assume you've probably made a choice already, but I have to put in a vote for the Rat and Dr. Boogey.  I just built a Rat yesterday and it's great...running it into the Dr. Boogey is just silly (in a good way!).  Here's the thread with a nice vero layout and schemo:
http://www.diystompboxes.com/smfforum/index.php?topic=39819.0

Have fun.
Mike

[SECONDandBOWERY]

I assume you've probably made a choice already, but I have to put in a vote for the Rat and Dr. Boogey.  I just built a Rat yesterday and it's great...running it into the Dr. Boogey is just silly (in a good way!).  Here's the thread with a nice vero layout and schemo:
http://www.diystompboxes.com/smfforum/index.php?topic=39819.0

Have fun.
Mike

Yup - I'm gunna build a Rat but with a Big Muff Pi tone control.  As for the layout, I''ll probably just use the layout on http://www.tonepad.com.  The tone controll could probably contructed entirely on the pot, right?

Rock'n'Roll,
--Andy

[col]

When I built my rat the schematic I had showed a bp transistor instead of a FET and I didn't look at the component number until it was too late!    I stuck in a BS170 as it was the only one I had with the correct pin out and the pedal sounded OK but had only unity gain at full volume. Last week I stuck in a 2N7000 and what a difference! It is now a high gain pedal in every sense of the word. The sustain is also incredible. It might be worth trying but be aware that the pin out for a 2N7000 is different to the one specified for the rat,

Col

[SECONDandBOWERY]

So this is what I'm thinking so far...

Any comments?

col:  Did you have to change any other components when you put the 2N7000 in, or did you just move them so that the pinout was OK?  I'll probably end up with a 2N7000 based on your description of the sound.

Rock'n'Roll,
--Andy

[PenPen]

You may want to breadboard that first. If you go with the BMP tone stack you make wish to also use the output stage of the BMP. From what I read that tonestack takes away quite a bit of volume, and the output stage provides a bit of gain to compensate. Personally I had planned to use that tone stack so I used that output stage also, but ended up omitting the tone stack entirely so it has even more volume than my stock Rat.

Also, may I recommend you do that to also test different caps for the feedback network, and try out the alternate compensation method.
I recommend testing using two 4.7uF caps in the feedback network, with a 1nF for the bypass cap. Or, 1uF total for the feedback (two 470nF) and stock (100pF) bypass. The alternate compensation method is instead of 30pF from pins 8 to 1, try 100pF from pin 8 to ground.

Just a few suggestions to try out based on my experimentations with the Rat.

[WGTP]

The BS170 and 2N7000 are Mosfets.  I guess they work the same as the Jfet most Rats have?  I used a MPF102.

Be sure when you messing with Rat's to try LED's and multiple SI's for the clipping.  Lots of variations to be had.  For some serious asymmetry try an LED/GE combo.  Also, check out the AMZ Warp Control.  In addition, nothing makes distortion sound sick and heavy like a big old notch in the EQ around 1000Hz.   

[SECONDandBOWERY]

You may want to breadboard that first. If you go with the BMP tone stack you make wish to also use the output stage of the BMP.

I might try that.  Does the output stage of the BMP "muff" the sound at all, or is the sound still biting (if that's a good word.)

Also, may I recommend you do that to also test different caps for the feedback network, and try out the alternate compensation method.
I recommend testing using two 4.7uF caps in the feedback network, with a 1nF for the bypass cap. Or, 1uF total for the feedback (two 470nF) and stock (100pF) bypass. The alternate compensation method is instead of 30pF from pins 8 to 1, try 100pF from pin 8 to ground.

What is the alternate compensation method?  I will try those alternate cap values.

Be sure when you messing with Rat's to try LED's and multiple SI's for the clipping.  Lots of variations to be had.  For some serious asymmetry try an LED/GE combo.  Also, check out the AMZ Warp Control.

I definitly plan on trying different clipping diodes (symmetrical and not), but since I want to try and house this in an old Boss SD-1 case, I want to limit the circuit to having 3 knobs so I'm gunna leave out the warp control (for now).

Rock'n'Roll,
--Andy

[PenPen]

Output stage doesn't affect the sound at all. Its only a slight gain stage so it doesn't introduce extra clipping. Yes, it is still biting. I tested my build next to my stock Rat, my build still has the characteristic bite of the Rat, pretty much no matter what I did to the diodes and feedback caps it still sounded like a Rat. I only changed the freq response of it to complement my stock Rat. Stock it favors the high end, I tailored mine to favor the low end more to add some bottom end to the signal when I run them together.

The stock compensation method is to use 30pF cap between pins 1 and 8 of the chip. The datasheet also specifies using 100pF from pin 8 to ground as an alternative. This restricts the bandwitdth a bit, which I found provides a more focused sound. I tested both ways and liked the alternate method better.

I also replaced one of the diodes with an LED and liked it. I second this recommendation.

[col]

When I thought it was a bipolar transistor I did my stripboard layout to accept a CBE layout transistor so that I could try a few and I needed a FET type transistor that would fit this pinout so I didn't need to change anything and the 2N7000 fit with no modification.

Col

[SECONDandBOWERY]

So, if I'm understanding this correctly, as long as the collector, base, and emitter are in the right places, no other values in the output stage need to be changed?

Rock'n'Roll,
--Andy

[SECONDandBOWERY]

Oh, and here's a revision of the schematic with some mod options and the 2N7000 output stage.  Does this look about right?

Rock'n'Roll,
--Andy

[PenPen]

Erm, better. However, I'm not sure you want to use (possibly) a 1uF cap for bypass. The good value I tried and ended up using is 1nF. Thats 1000pF, or 0.01uF.

Also, the compensation is either 30pF from pins 1 and 8, OR 100pF from pin 8 to ground and leave pin 1 unconnected.

[SECONDandBOWERY]

Tah-dah?

Rock'n'Roll,
--Andy

[PenPen]

Looks good, as far as the mods I suggested. I can't comment on the mosfet output stage, but as far as I can see it LOOKS ok. Are you going to breadboard this before doing it on pcb/perf?

[SECONDandBOWERY]

I'll probably just build it right onto the http://www.tonepad.com PCB for the Rat and make all the mods that won't fit on the board in a point-to-point fasion.  That is, unless, you highly reccomend breadboarding it first.

Rock'n'Roll,
--Andy

[PenPen]

Eh, your way will work. I'm just one of those people that likes to test and retest everything they possibly can before commiting to soldering. I'd probably get a lot more builds done if I just DID them off the bat, instead of spending weeks adjusting values and opamps and whatnot. My first build ever, before I had a breadboard, didn't work, and I wasted the caps and perfboard and such since its a pain to desolder everything. Since then I've just taken to breadboarding EVERYTHING before building.