Looking for reviews for a guitar buffer schematic and layout

Thread Starter

Ramon Marco Navarro

Joined Apr 30, 2017
4
Hello,

I am easing my way in to DIY guitar pedal building. To start with I am planning to build a guitar buffer based on AMZ Super Buff. It is just basically the AMZ Super Buffer but with only one dual op amp chip; which is just a simple voltage follower circuit.

I need reviews, critiques and sanity checking for the schematic and stripboard layout. I want to know if I may have committed a layout mistake that might make the circuit not perform at its best.

Thank you for reading!
 

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MrChips

Joined Oct 2, 2009
19,911
Your schematic drawing shows an 8-pin DIP layout. Any designer has to reverse engineer your circuit in order to understand how the two stage op-amps are connected. Show functional op-amp diagrams instead of pin diagrams.

Stripboard assembly is for development and testing purposes only. Do a proper PCB layout for optimum circuit performance.
 

#12

Joined Nov 30, 2010
18,167
It's hard to wreck an audio amp (with a gain of one) with a layout problem. The frequencies are just too low have much of a problem with how the traces are arranged. It seems to me you have gone a bit extreme in filtering the battery voltage. Most stomp box designs don't even try to filter the battery voltage. I'm talking about cost/benefit ratio.

Your RC calculations seem correct but I don't know what your goal is with C6 and C7.
 

Thread Starter

Ramon Marco Navarro

Joined Apr 30, 2017
4
Your schematic drawing shows an 8-pin DIP layout. Any designer has to reverse engineer your circuit in order to understand how the two stage op-amps are connected. Show functional op-amp diagrams instead of pin diagrams.

Stripboard assembly is for development and testing purposes only. Do a proper PCB layout for optimum circuit performance.
Thank you. I'll upload another schematic later after work. I'll look in to using a PCB for my project.

It's hard to wreck an audio amp (with a gain of one) with a layout problem. The frequencies are just too low have much of a problem with how the traces are arranged. It seems to me you have gone a bit extreme in filtering the battery voltage. Most stomp box designs don't even try to filter the battery voltage. I'm talking about cost/benefit ratio.
Re: power filtering: I was planning to power this using a wall wart. I have a guitar pedal here that could be battery powered or using a wall wart. When I'm using the wall wart the pedal is very noisy. I am hoping that the filter with this project would avoid the problem I have with my previous pedal.


Your RC calculations seem correct but I don't know what your goal is with C6 and C7.
Embarrassingly, I didn't do any calculation for this circuit. All was done by Jack Orman at this page. According to the original circuit's designer, it is used to ensure that we have a "full response"; whatever the connected load is.
 

#12

Joined Nov 30, 2010
18,167
it is used to ensure that we have a "full response"; whatever the connected load is.
I call B.S.
Look at figure 1-8 showing the impedance of a typical aluminum electrolytic capacitor is lowest at about 40 KHz.
There is no purpose in adding a film capacitor to get a frequency response in the range of 1 MHz and higher.

Here's another idea: A low dropout voltage regulator which loses 1/8th of the voltage R5 uses up and provides a more stable voltage than a resistor. This exact chip isn't in stock right now, but it isn't the only chip that can out perform the filter you have right now.

Yeah, that's right. I'm throwing rocks at Jack Orman. You can do better for cheaper in at least two places.
 

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Thread Starter

Ramon Marco Navarro

Joined Apr 30, 2017
4
I call B.S.
Look at figure 1-8 showing the impedance of a typical aluminum electrolytic capacitor is lowest at about 40 KHz.
There is no purpose in adding a film capacitor to get a frequency response in the range of 1 MHz and higher.

Here's another idea: A low dropout voltage regulator which loses 1/8th of the voltage R5 uses up and provides a more stable voltage than a resistor. This exact chip isn't in stock right now, but it isn't the only chip that can out perform the filter you have right now.

Yeah, that's right. I'm throwing rocks at Jack Orman. You can do better for cheaper in at least two places.
Thank you for your helpful replies. I will read up more on some materials before I continue with my project.
 

#12

Joined Nov 30, 2010
18,167
The key word is, "LDO" for, "Low Dropout".
That's what you're looking for in a voltage regulator.;)
 

Thread Starter

Ramon Marco Navarro

Joined Apr 30, 2017
4
I have a question with the biasing for the non inverted inputs. I don't know if I should have posted this in a new thread. Anyway.

If I have set the bias voltage to Vs/2, does that mean that Vout will be Vs/2 when the guitar pickups are silent? If yes, then shouldn't the output jack's ground should also be connected to this bias and not to Gnd so that the next pedal in line has a correct "0v" reference?
 
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