Can we talk about the Metal Zone pre-filter?

[MF_Kitten]

I am researching what the Metal Zone is doing internally ao I can do a couple little changes to get it to where I want it.

I already know I am literally just removing the post-distortion EQ, as I just don't like what it's doing at all.

BUT

That pre-distortion EQ curve is the bigger deal to me. As it is, it's a band pass around 1KHz and it's just way too narrow with a high peak. All I really want it to do is to have a wider range, so it's focused around 500-1.5KHz or something like that instead, more open. I love the Klon curve, so it can be plenty wide without getting offensive to me!

I'm sure you've all seen this analysis:
https://electricdruid.net/boss-mt-2-metal-zone-pedal-analysis/

Looking at the "pre-distortion tone shaping" section specifically is where the change would need to be made.

This is what the Metal Zone is doing:


When you look at it, it kind of looks like a good normal OD curve that someone slapped a narrow peak filter into. That peak is what makes it so shrill and gross.

I would be very happy with something closer to the pink curve here:


Or the highest curve here:


My instinct tells me the actual 1KHz bump just needs to come down a bunch, and that would be most of the problem fixed right there... But then me not understanding electronics, I look at the schematics and I hvae no clue what everything is or what it does, and so I don't really get how to target a specific change:

[LightSoundGeometry]

wampler put out a nice video ..one of the comments won the internets 

"Sweep the mids"
"But Sensei..."
"SWEEP THE MIDS! ALL THE GAIN!"

brian links to his amazon book breaking this down in detail for you ..probably more than you ever wanted to know about the legendary MT2

http://www.muzique.com/schem/filter.htm

[strungout]

The transistor and surrounding components are called a gyrator, (it replaces an inductor, which tend to be bulky. Search it here or google it). It's a bandpass filter that creates a peak, here at 1kHz, as you said. Here's a useful link for calculating the values: http://www.muzique.com/lab/gyrator.htm What you may want to do is mess with the Q (quality factor). The higher the Q, the sharper the peak, the more extreme. Sounds like you want to go the other way around and lower it.

[PRR]

Welcome.

> way too narrow with a high peak.

You want to reduce the Q of the resonance, from strong ring to mellow hill.

Increase R046 and decrease R053 in about the same ratio.

[MF_Kitten]

You guys all really came through on this one, thank you so much!

[Steben]

Great idea. It makes the mt2 an even more versatile drive platform.

[Vivek]

It is hard to visually compare different frequency response curves when they have different X and & Y axis and aspect ratios.


It is better to measure the Q from the different graphs and compare those instead.

The Metal Zone pre dist filter has Q around 1.67 at IC output. Thats not toooo peaky as it appears on the graph.

Central Freq 970
3dB bandwidth from 716 to 1296 Hz





But maybe you wish to reduce the Q any way. AMZ and ESP have data on how to do that.

[Vivek]

I plotted effect of (47K/ ratio) and (2.2K x ratio)

for ratios from 1 to 3







At ratio 3

Central Freq 958
3 db Bandwidth 519 to 2937 = 2418 Hz
Hence Q = 0.4

[Vivek]

[Vivek]

That pre-distortion EQ curve is the bigger deal to me.

Please help me to understand how you figured out that the "problem" is the Pre-distortion EQ and not the Post-distortion EQ ?

[Vivek]

Very roughly,
The Q is around 0.32

[Vivek]

Are you modding a MT2 ?

Or building a new kit ?


Because it might be possible to modify the Post Dist EQ into a "Purple Peaker" or into a "Cabinet Sim". That could be fun !!!!

[MF_Kitten]

That pre-distortion EQ curve is the bigger deal to me.

Please help me to understand how you figured out that the "problem" is the Pre-distortion EQ and not the Post-distortion EQ ?

Yeah, that statement is assuming the post-EQ is already gone. The post EQ is what makes it mostly unusable. The pre-filter is the thing that defines how it behaves thoigh, assuming the treble and bass boosts are compensated for. That %^&*ed wah sound.

[Vivek]

That %^&*ed wah sound.

I guess you could modify the pre distortion filter with ratio 4


Also, do consider the idea of converting the post EQ filter into a purple peaker or cab sim that can optionally be switched in