Discrete Metal Zone

[JoMo]

If the title didn't dissuade you then welcome to my hair-brained idea.
I've had problems with op-amps in the past, mostly biasing problems, so i set out to get as similar a frequency response per-stage using mosfets and common enough values. I decided against the normal MT-2 tonestack and opted for a much simpler BMP one. You may notice there is no sign of an equivalent to the last 2 gyrators, but I never felt they did anything good, only contributed to that "angry bees" sound they're known for. I haven't built a prototype yet because i'm missing some capacitors, but i've simulated and re-simulated and i'm confident i'm at least close. But, I will be building a prototype so if you are interested just give it a day, i'll figure something out.

(not sure if i got the image to work, seems like it did, but i've been fooled and i've seen others fooled before. so just in case the link is; http://www.aronnelson.com/gallery/main.php/v/diyuser/moszone.png.html)

[nickbungus]

I loved my metal zone.  It was really versatile and I could get some fantastic tones out of it.  I sold it along with my other boss pedals to pay for my eBay habit that feeds my diy pedal habit.

I'd love to replace it with a diy pedal so this really appealing.  Is there pcb layout in the pipeline?   There is a metal zone project out there but I don't fully trust it to invest the time on such a large project.

[Bill Mountain]

I just started the planning stages for a MOSFet Distortion/Fuzz so this is really cool to see.

I was going to do almost the exact same thing you did with Q1 and 2.  Q1 at max gain and then adjust the source of Q2 as a distortion/fuzz control into, you guessed it, diodes and a modified BMP stack.  I literally bread-boarded the EQ portion last night.

[Transmogrifox]

I would be interested to find out how it goes when you BB it.  Last time I experimented with a high gain MOSFET distortion the main problem I had was too much noise/hiss.  It was really good sounding and I suppose that made up for the noise.  I never did spend the time & analysis to find out whether the noise could be reduced without changing the sound too much.

Thanks for sharing.  Yet another thing to try

[JoMo]

Well, I've breadboarded it and it does seem pretty darn close but still too far off. First I have to mention i messed up the value of the capacitor next to the diodes, I meant for it to be 10nF. Second, I'm debating whether or not to change the second mosfet to a darlington, the gain doesn't feel like it gets quite high enough. Third and lastly, the tonestack - I should say the values I chose for it - just doesn't work well at all, I'm positive it has to do with that 10k resistor before it, I'll tinker with it. I'll try and get a sample once I figure it out, prepare for the obligatory Master of Puppets riff.

[Joe]

I like this idea a lot. What do you guys think about tone control(s) for this?

[JoMo]

Okay, so I haven't had much luck with the tonestack, but I'm sure it's just because I'm stubbornly refusing to add a buffer stage. But, I've got some samples, just some Metallica based power chords at varying gains, 0%, 50% and 100%, one is tonestack bypassed raw output from the breadboard, the second is run through my DAW into the catharsis spres-high impulse, the last one is going into a VST Marshall tonestack(https://philaudio.wordpress.com/research/tonestack/) into Gclip to emulate the makeup gain stage and then into the spres impulse again. The VST tonestack sounds pretty good so I might just go for the regular 3 control stack. It's honestly been a while since I played with a Metal Zone so if it seems a little off feel free to help me out.

no tonestack, Raw: http://www.aronnelson.com/DIYFiles/up/moszoneraw.mp3
no tonestack, into impulse: http://www.aronnelson.com/DIYFiles/up/moszonespres.mp3
VST tonestack into impulse: http://www.aronnelson.com/DIYFiles/up/moszoneTSspres.mp3

[Quackzed]

+1 darlington : more gain + your tonestack might work better w/ the lower out imp...

[JoMo]

I've been messing with the breadboard, using a darlington didn't distort as well as the FETs, so I changed it around into Mosfet cathodyne driving 2 JFets in push-pull, which I consider to be an excellent substitute for mu-amps, and I was going to use negative feedback as a gain control but doing that made it impossible to get low gain so I went with a regular-old divider. I updated the schematic and I feel it's pretty much done, I suppose unless I decided to make it more like the real deal. As it is, I think what I've rigged up here sounds more like a Metal Zone with the Diezel mod.
oh, and I suppose a sample with the new tonestack would be nice, so http://www.newgrounds.com/audio/listen/656558

[FiveseveN]

Ever tried it without the diodes? Could maybe put them on a switch with some output padding for a cleaner setting.