Help identifying circuit block

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Help identifying circuit block

Postby sixth » 08 Jan 2015, 17:16

I'm trying to build distortion pedal, it will be something similar to Boss metal zone or Electroharmonix metal muff, however it will have a different EQ and will be two channeled. :)

However I can't understand how one circuit block works in metal zone or metal muff schematic.
http://www.hobby-hour.com/electronics/s ... l-zone.php

If you follow the link above,It's in upper left corner, connected to "3b" OP amp's inverting input, made from C034, C035, R046, R053, Q010 and R054. :oops:

Perhaps someone can explain how it works or how it is called, so i can google about it? :D
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Re: Help identifying circuit block

Postby sixth » 08 Jan 2015, 17:18

sixth wrote:I'm trying to build distortion pedal, it will be something similar to Boss metal zone or Electroharmonix metal muff, however it will have a different EQ and will be two channeled. :)

However I can't understand how one circuit block works in metal zone or metal muff schematic.
http://www.hobby-hour.com/electronics/s ... l-zone.php

If you follow the link above,It's in upper left corner, connected to "3b" OP amp's inverting input, made from C034, C035, R046, R053, Q010 and R054. :oops:

Perhaps someone can explain how it works or how it is called, so i can google about it? :D



also it has similar block at the output, I guess that it works like some kind of filter
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Re: Help identifying circuit block

Postby ggedamed » 08 Jan 2015, 20:28

Boss-MT2_opamp3b-stage_sch.png

3b is a non-inverting amplifier that has the usual feedaback resistor (R044) and the highs cutting capacitor (C032), but - instead of a resistor - has a gyrator from the inverting input to ground. The gyrator is made with Q010, C034, C035, R046, R053 and R054. You can think it as a resistor that varies its resistance according to the frequency of the signal that passes through. A simulation would look like this:
Boss-MT2_opamp3b-stage_simulated.png
So, it's a bandpass filter centered around 2kHz.

You could play with gyrator values using online calculators like http://www.griffineffects.com/tools/gyrator.html or you could simulate the whole stage with apps like LTSpice or Tina-TI (which is what I used above).
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Re: Help identifying circuit block

Postby sixth » 08 Jan 2015, 22:16

ggedamed wrote:
Boss-MT2_opamp3b-stage_sch.png

3b is a non-inverting amplifier that has the usual feedaback resistor (R044) and the highs cutting capacitor (C032), but - instead of a resistor - has a gyrator from the inverting input to ground. The gyrator is made with Q010, C034, C035, R046, R053 and R054. You can think it as a resistor that varies its resistance according to the frequency of the signal that passes through. A simulation would look like this:
Boss-MT2_opamp3b-stage_simulated.png
So, it's a bandpass filter centered around 2kHz.

You could play with gyrator values using online calculators like http://www.griffineffects.com/tools/gyrator.html or you could simulate the whole stage with apps like LTSpice or Tina-TI (which is what I used above).


thanks :) I thought gyrators were only made from op amps, but now I see that not only :D
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Re: Help identifying circuit block

Postby sixth » 08 Jan 2015, 22:39

ggedamed wrote:
Boss-MT2_opamp3b-stage_sch.png

3b is a non-inverting amplifier that has the usual feedaback resistor (R044) and the highs cutting capacitor (C032), but - instead of a resistor - has a gyrator from the inverting input to ground. The gyrator is made with Q010, C034, C035, R046, R053 and R054. You can think it as a resistor that varies its resistance according to the frequency of the signal that passes through. A simulation would look like this:
Boss-MT2_opamp3b-stage_simulated.png
So, it's a bandpass filter centered around 2kHz.

You could play with gyrator values using online calculators like http://www.griffineffects.com/tools/gyrator.html or you could simulate the whole stage with apps like LTSpice or Tina-TI (which is what I used above).


I have one more question. Does equations that apply for gyrators with op amps also applies on gyrators with transistor.
For example if we have this circuit download/file.php?id=25523&mode=view

Is it's inductance L = C3R3R4 with parasitic resistance R4 ?
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Re: Help identifying circuit block

Postby sixth » 09 Jan 2015, 21:20

I have some more questions, I'm trying to understand how metal zone works. :D

This gaining stage which is after clipping stage, has two peaks at 33Hz and 4894Hz
Double gyrator filter.png

Why is that needed? isn't there only noise at 33Hz frequency,since even at drop A tuning you have lowest possible note at 55Hz?
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