Harmonic Energizer, Zapper, Parsec, ...

[Matopotato]

Hi,
I was planning on building a copy of the Systech Hamronic Energizer and came across several implementations of it but using various different component values.
First the schematic from here at pedalpcb (https://docs.pedalpcb.com/project/Zapper.pdf)


Then schematic from Aion FX, Parsec (https://aionfx.com/app/files/docs/parsec_documentation.pdf)


I also look at Dirtbox layouts (https://dirtboxlayouts.blogspot.com/2019/06/systech-harmonic-energizer.html)


My confusion is about a few differing values and choices, while some differences are probably more of protection, pull down resistor etc.

1. Zapper use 1M for pull down, while Parsec use 10M a bit further in?
2. Zapper use one TL072 op-amp as buffer (?) while Dirtbox and Parsec use a 2N5458 (which then has impact of surrounding Resistors, but that I assume is how each choice would dictate). What is the reason for using the TL072 here instead of what I guess is the original design?
Even if both methods "do the same thing", there was still a reason for the TL072 choice I suppose?
3. Zapper C2 (10uF electro) vs Parsec 1uF film box vs Dirtbox using 10uF electro but swapping the polarity as compared with Zapper?
4. Zapper using 10uF C102 in the voltage divider for Vref, vs Parsec using 47uF (C11)?
5. Zapper using IC 1.2 in the power section before Vref (Some buffer as well?)
6. Zapper output use C6 100nF and Volume pot A100k (as does Dirtbox) but Parsec has C9 1uF and A50k pot instead?

Perhaps no choice has any great impact on the final build, but I am always keen on learning and understanding why some choices ended up they way they did. Not asking to pick the designer's brain, but an overall understanding why one would make either choice in the end.

 

[jwin615]

I'll try my best but none of the below is warrantied

1) meh. Whatever works
2)see above. Maybe for more repeatable results. Maybe it was extra after the vref buffer?
3)little audible difference between them except maybe a little on bass. Use a 100-220n film. Done.
4)rule of 10x to prevent oscillation/ringing?
5)yes..vref buffer
6) see #3. It's decoupling only (blocks DC) and not part of a filter. They're all big enough to not attenuate any low end on a guitar signal. So, doesn't really matter.

I'll throw in the Madbean Karate Shop as well. Let's really change the voltage divider up.

 

[drew.spriggs]

Hi,
I was planning on building a copy of the Systech Hamronic Energizer and came across several implementations of it but using various different component values.
First the schematic from here at pedalpcb (https://docs.pedalpcb.com/project/Zapper.pdf)
View attachment 103632

Then schematic from Aion FX, Parsec (https://aionfx.com/app/files/docs/parsec_documentation.pdf)
View attachment 103633

I also look at Dirtbox layouts (https://dirtboxlayouts.blogspot.com/2019/06/systech-harmonic-energizer.html)
View attachment 103634

My confusion is about a few differing values and choices, while some differences are probably more of protection, pull down resistor etc.

1. Zapper use 1M for pull down, while Parsec use 10M a bit further in?
2. Zapper use one TL072 op-amp as buffer (?) while Dirtbox and Parsec use a 2N5458 (which then has impact of surrounding Resistors, but that I assume is how each choice would dictate). What is the reason for using the TL072 here instead of what I guess is the original design?
Even if both methods "do the same thing", there was still a reason for the TL072 choice I suppose?
3. Zapper C2 (10uF electro) vs Parsec 1uF film box vs Dirtbox using 10uF electro but swapping the polarity as compared with Zapper?
4. Zapper using 10uF C102 in the voltage divider for Vref, vs Parsec using 47uF (C11)?
5. Zapper using IC 1.2 in the power section before Vref (Some buffer as well?)
6. Zapper output use C6 100nF and Volume pot A100k (as does Dirtbox) but Parsec has C9 1uF and A50k pot instead?

Perhaps no choice has any great impact on the final build, but I am always keen on learning and understanding why some choices ended up they way they did. Not asking to pick the designer's brain, but an overall understanding why one would make either choice in the end.

1. No practical difference. Use whatever is on hand. I've got stacks of 1M so use them everywhere.
2. One lets you get away with a single quad op-amp, one requires three duals (as you drop the vref buffer). No real practical difference - layouts are often easier with multiple op-amps though.
3. Polarity would be because of the differing voltages on either side due to the buffer. Will make no real difference to frequency response. 1u film would be easy enough.
4. You could argue it's due to buffered vs unbuffered vref, but practically no difference. Either will suffice.
5. Buffered vref. Easy role to throw a spare op-amp into if you're doing nothing else with it.
6. Inaudible filter difference, but most people are used to a 100k volume pot and have stacks floating around. In practicality you could go down to 10k or so, but to maintain the filter point would need to use a 1u coupling cap (which is usually more of a cost).