freestompboxes.org

Intripped wrote:What about making the input impedance of the buffer the same as the amplifier's input impedance?
Would this arrangement make the buffer more "transparent"?

As long as you also include the capacitance of the cable, yes, it should sound just like the buffer isn't there. You'd keep some advantages, like some noise immunity (or a lot, with balanced signal) and indifference to cable length (within reason).

what about the output impedance of the buffer?
I mean, if we make it the same as the guitar's output impedance, does our buffer still work as a buffer [...] ?

Nope. The whole point is to have low output impedance. The input impedance is I guess a matter of taste.

Hey, I made a very layout for the buffer - still unverified. Will let you guys know if it works upon building it. Also, I'm sure there's a way of making the layout more compact and elegant, but this is one of my first - apologies for that.

Verified. You weren't kidding, this buffer is stupidly awesome! The much simpler Tl071 buffer I was previously using was quite obviously coloring my tone. With your circuit there is barely any audible difference between plugging straight into my amp and running the signal through the buffer, my entire bypassed effect chain, and a passive 25k volume pedal. Entirely worthy of the stupidly awesome name.

I raised input cap to 1uF and it sounds great for bass. If I put a variable resistor between pins 2 and 6 would this act as a gain control?

Iforgot wrote:Hey, I made a very layout for the buffer - still unverified.

You need a track cut between pins 1 and 8 of the IC.

Pin 1 is the output offset pin, which is not used, and pin 8 is NC - No Connection.

I was under the impression that a pin marked as NC could be connected to what ever you wan't. That there would be no connection to anything internally inside the IC itself.

Looking on the Texas Instruments datasheet for a TL071 pin 8 - NC - is labelled as "Do not connect" but then at the bottom of the table it also says "No internal connection" so it might be ok with this chip.

When I was an apprentice I was always told to leave NC pins unconnected as sometimes they are connected internally, old habits die hard!

It seems old habits are better than bad habits. I googled around a bit after writing my last reply.´There are indeed situations where the NC pins are connected internally to do calibration or other things.

In this specific case it would be better to not connect pin 8 since there is nothing connected to the strip at right hand side of the IC anyway. Just to play it safe...

Some observations of a slightly more pedantic nature (which will require absolutely no PCB rework):

- swap the placement of R7 and D1 (which will increase RF/noise immunity towards power supply lines)
- solder a smal mini-melf SMT 15-18V 0.5W zener across the opamp pin 3 and 4 on the PCB trace-side to add input protection

deltafred wrote:

Iforgot wrote:Hey, I made a very layout for the buffer - still unverified.

You need a track cut between pins 1 and 8 of the IC.

Pin 1 is the output offset pin, which is not used, and pin 8 is NC - No Connection.

Wo I hadn't checked this thread until now. Will try adding a track cut and see what happens. That said the buffer has been working well despite the mistake. (Maybe that will improve it though! )

bool wrote:Some observations of a slightly more pedantic nature (which will require absolutely no PCB rework):

- swap the placement of R7 and D1 (which will increase RF/noise immunity towards power supply lines)
- solder a smal mini-melf SMT 15-18V 0.5W zener across the opamp pin 3 and 4 on the PCB trace-side to add input protection

It's never pedantic to suggest ways of improving a circuit! I for one will try this out.

Just curious, what buffer circuit do you favor? This one has been working well, but after digging into DI box projects - settled on the amazing Bo Hansen di - I wonder whether this circuit is all that transparent.

Someone made a tighter layout for this on the tagboardeffects forum. Just noticed it, I figured it should be posted here too: http://guitar-fx-layouts.42897.x6.nabbl ... .html#none

hi,

although I'm only an amateur, I love Jack Orman's thinking -- especially his approach to "building blocks" -- and I feel tempted to use this stupidly awesome buffer like he uses that JFET buffer for splitting the signal -- see here -- and as he does that with that op-amp... see here, after "dual buffer" down the page ...

practically, I wonder how to connect two instances together of the SAB

if the purpose is to

A: split the signal - make it appear on two outputs...

B: make two independent buffer, like Left and Right channels..

question mark

before seeing these variations, my plan was to just duplicate the SAB as it is...
but now I can imagine more elegant methods, too...

in case B, for example, it seems logical to make jumpers at R2 and pin-7 of the IC...
but I could only guess if R2 is to be repeated /per instance, of not... I mean, if this is the way to do it at all...

so, any help would be great...
and hopefully, not for me only

thanks in advance

Peter

Assuming you are talking about the *TWO INDEPENDENT BUFFERS (STEREO)* circuit,,
Then I'd make R2 1k and repeat on IC1B after Cx. R3&R6 are jumpered.
For extra shorted output protection I would add a 100R~470R series resistor on both outputs.
Phil.

hi Phil, thanks.. but looks like I hadn't manage to make clear what I meant

I meant connecting 2 Stupidly Awesome Buffer circuits..
similarly to how Jack Orman did it with those circuits -- without repeating the entire circuit...
(as in "DUAL BUFFER 2", for example)...

A:
I'd like to make a dual buffer, 1 input, 2 (or more) identical outputs...

B:
and I'd also like to make (another thing)
a stereo buffer, two independent inputs and outputs...

in both cases using the stupidly awesome buffer...

(I'd like to put together a practicing headphone amp with an instrument (bass/guitar) and a stereo line as inputs, and
a buffered output of the guitar, and an buffered output of the stereo line, too... -- all this is theoretical only, I think of it as if playing with building blocks )

thank you, and sorry for the misunderstanding...


Peter

jeepe wrote:hi Phil, thanks.. but looks like I hadn't manage to make clear what I meant

I meant connecting 2 Stupidly Awesome Buffer circuits..
similarly to how Jack Orman did it with those circuits -- without repeating the entire circuit...
(as in "DUAL BUFFER 2", for example)...

A:
I'd like to make a dual buffer, 1 input, 2 (or more) identical outputs...

Then; http://www.muzique.com/lab/splitter.htm
Bottom Schematic.

jeepe wrote: B:
and I'd also like to make (another thing)
a stereo buffer, two independent inputs and outputs...

Then; http://www.muzique.com/lab/splitter.htm
Top Schematic x2

jeepe wrote: in both cases using the stupidly awesome buffer...

(I'd like to put together a practicing headphone amp with an instrument (bass/guitar) and a stereo line as inputs, and
a buffered output of the guitar, and an buffered output of the stereo line, too... -- all this is theoretical only, I think of it as if playing with building blocks )

thank you, and sorry for the misunderstanding...
Peter

No problems ,, yes it's hard to convey complex stuff in words.
As for the headphone and preamp build ,,,well that is a whole other subject.
If you want it all in one box then you would need to work out a signal path??
Phil.

hi, Phil, and everyone,

I'm in the making of one, finally, and I was just googling, and I was surprised when landing here (again) that this guy had the same problem / plan / question as I

In any case, Phil,
I don't want to make a preamp in one box with a headphone amp (no way)...

the thing that I'd like to make is a splitter...
2 buffers together, 1 input, 2 outputs
based on this "stupidly awesome buffer"...

NOTE:
I know I could as well use Jack Orman's JFET transistor splitter ("buffer set"), BUT I'd prefer trying this stupidly awesome buffer, multiplied by 3

my only concern is whether there are some elements of the circuit that need not be multiplied
I mean, how to go about it in an electronically elegant way, which I no nothing about

Hi Jeepe, you meant in that way?

Here the strip layout for the split buffer. Lochmaster 4.0 file:

Really happy to see people have built this and gotten good results!

I've built several different splitters over the years, and I would usually use 3 buffers: One like this circuit at the input and then splitting into two or more, one for each output. Having the buffer at the input lets you split to many buffered outputs without any additional loading on the input. I also did a few that had isolation transformers on one output to break hum loops that would frequently happen when using multiple amps. I think I posted a schematic for this somewhere here already?