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Best DIY buffer pedal
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Old 17th July 2017, 04:29 AM   #31
PRR is offline PRR  United States
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> I don't know how to edit my previous post.

You get only a few minutes to go back and edit. Enough to fix fumble-fingers. Not enough to change the past. Apparently back-editing has been a problem here, the current policy is considered appropriate for this mob.

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Old 17th July 2017, 12:10 PM   #32
jdiego is offline jdiego  Chile
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Originally Posted by PRR View Post
> I don't know how to edit my previous post.

You get only a few minutes to go back and edit. Enough to fix fumble-fingers. Not enough to change the past. Apparently back-editing has been a problem here, the current policy is considered appropriate for this mob.

Within the time-out, you will see a Click the image to open in full size. icon below your post.
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Old 17th July 2017, 02:52 PM   #33
Mark Johnson is offline Mark Johnson  United States
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Best DIY buffer pedal
For those who prefer discrete components instead of ICs, here's a voltage follower with very wide output swing, Figure 1 below.

Don't be frightened by my squirrely use of scientific notation; R1 is simply 22 megohms and R4=1.2 megohms.

Input impedance is plotted in Figure 2; it remains above 1 megohm out to 20 kHz.

Frequency response is plotted in Figure 3. The green curve is the circuit's response when the optional components are omitted (Roptional = 0 ; Coptional = 0). The blue curve is the circuit's response when the optional components are included; the -3dB rolloff is about 30 kHz. You can finagle this by jacking around with the values of the optional components.

_
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File Type: png Zin_2EF.png (28.3 KB, 51 views)
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Old 17th July 2017, 07:21 PM   #34
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by jdiego View Post
I opened this thread and now I'm not sure what pedal to make.
Honestly, it really doesn't matter. Your musical talent, your ability to play the guitar, and your ability to connect with your audience, all are far more important than any buffer you use (or don't use).

Adding some sort of buffer can make a (slight) change in your sound; changing between two or three good buffer designs will make hardly any difference at all. I bet your audience will neither know nor care what buffer you're using.

My own experience is that it is very easy to get so many different opinions and choices on the Internet that I become paralyzed, and end up building nothing at all. That is the worst possible outcome - so please don't let it happen to you!

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Originally Posted by jdiego View Post
I think Cornish LD-1 (BC549) and Lehle Sunday Driver (ICL7660S/OPA2132PA) performs a lot better than JHS (TL072).
If you like the Cornish booster, by all means, build it! These are simple circuits, using only a few dollars worth of components, and they only take a little of your time to build. So if you build the Cornish design and then don't like it, just set the board aside, and build another circuit to see if you like that one better!

If you do build the Cornish booster, I would recommend that you use a 0.047 uF (same thing as 47 nF) capacitor instead of the 4.7 uF capacitor shown on the veroboard layout. This will fix the problem of the subsonic "hump" in the frequency response, and it won't change the sound of the booster at all.

You can also leave out the 50k resistor (top right corner of the veroboard). It does nothing whatsoever.

Incidentally, I find that the most expensive parts when you build a pedal are usually the metal case, and the switches, pots, input and output jacks, and power supply jack. You can do your initial tests without a metal case. That way, if you don't like the pedal, you can re-use the switches, jacks, and case in your next attempt, with a different circuit of your choice. The case won't have holes in it in all the wrong places from your previous pedal experiments!

As an aside, if you think you might want to experiment with more than one circuit, another possibility is to make yourself a little test and experiment fixture. Mount a solderless breadboard on a piece of wood plank. Add a piece of L-shaped aluminum extrusion to carry a power supply jack and two 1/4" jacks on it. Drill a couple more holes in the aluminum to mount pots and switches.

Now you can experiment very easily with different circuits, and when you find one you like, you can build that one properly on Veroboard or whatever. You can see an example here: DIY Breadboard

(Personally, I would solder solid-core wires to the pots rather than use clip-leads, but that is a trivial detail.)

Quote:
Originally Posted by jdiego View Post
The Cornish vero board will have a negative impact on low frequencies?
It has a poor low-frequency response, sure. But lots have been built and sold, so chances are the problem hasn't really been a show-stopper for anyone.

Best of all, you can fix the problem very easily - just replace that 4.7 uF capacitor with 47nF (same as 0.047 uF). Problem solved!

-Gnobuddy
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Old 2nd September 2017, 04:38 AM   #35
jdiego is offline jdiego  Chile
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My first attemp was a painful failure, I wasted some nice Wima caps for a buffer that didn't work. This is the last time I make a stripboard with a knife.

The second time I build it using cheap generic caps. I made the PCB following this layout:

Perf and PCB Effects Layouts: Cornish Buffer

It works great, I'm very pleased with the result.


Next time I will make a buffer with a switch for toggling between this cornish buffer and the IC buffer from general guitar gadgets. I could yet use another switch for toggling between 4.7uf and 47nf caps.Click the image to open in full size.Click the image to open in full size.
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