Stupidly Awesome Buffer

jeepe · Post by **jeepe** » 17 Jan 2020, 16:31

[quote="Manfred"]Hi Jeepe, you meant in that way?

exactly !!! thank you so very much !!!

= = =
you know what?
I was, after some 5-10 times of going at it and getting stuck, right now coming back to Supidly Awesome Buffer, cause
our fellow-forumer, Iforgot posted at tagboardeffects, under IvIark's buffer post http://tagboardeffects.blogspot.com/201 ... ffers.html that he had been using that vero for some time and he was
never really satisfied with it, and so he was about to try Stupidly Awesome Buffer, and mentioned that he even made a vero of it, and posted this link... as of Aug 2015...
AND here I was, again, after so many times

I was always tempted by this circuit, but since I have NOT made any buffer yet, I was also tempted by simplicity... (of Jack Orman's)
but then, thanks to Iforgot, I would, again and again, get back here, to the sophisticated, and beautifully performing Stupidly Awesome Buffer

but since I need two (to mix a bass guitar with a stereo "AUX" in, in a practice headphone amp, CMoy, you know), I'd have to draw the vero, and it's not only becoming complex, but also annoying, cause I know that 1 or 2 sections needn't to be duplicated... (around the +IN and the VCC+ legs)...
but how will I know that it works well?
or how will I know why it doesn't if it doesn't?

so, as I came here, again, I just saw this schematic, and right away I knew what that was

and then I realize that it's posted there only lately, oh, and even because I asked

THANKS so much!!!

also for the explanatory indication of modification

(!!

)

and I hope that anybody will find it who's into building a buffer....

AND THEN

a strip layout? (???)
with PDFs??

and PCB style photo illustrations???

you're simply generous

and extremely elegant

BUT, I'm trying to view this NOT from my personal aspect only, but from that of the community of DIY-musicians, who can not design circuits, but only build them...

and from Soulsonic's aspect, too... (hi! it is a privilege to have you in this part of the conversation !

)
his work is not extended, both as a DUAL BUFFER, and in time, as a Buffer which is an active project even in the 2020s

anyhow, thanks to the both of you,
as well as thanks to Iforgot, who gave it a try seeking a better one than that simple Jack Orman "building block"

jeepe · Post by **jeepe** » 17 Jan 2020, 16:54

soulsonic wrote:
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.

thank you for sharing the sophisticated splitting concept!
sounds absolutely logical even to me!
and I'm happy that anyone wanting to build a very high quality DUAL BUFFER / splitter (I'm repeating these terms for google's bots) can find it right here, from the OP

thank you!

soulsonic wrote: I think I posted a schematic for this somewhere here already?

I couldn't find it... but this could be my fault (I couldn't find a "search _this_user_'s posts" link)

and of course, if you posted it again, it would be great, just for completeness' sake

(I am always taken aback by the fragile ephemerality of BASS and guitar culture in DIY circles... I mean, many of the websites don't even have SSL, picture links are broken, not to mention that parts have died out in the mean time, so it looks like it is not gonna make it to the 2030s, for example,
but luckily, freestompboxes.org is updated to today's standards, and to have those "drawings" of yours here, could be great)

AndrewGallios · Post by **AndrewGallios** » 05 Mar 2021, 10:56

hi

i want to ask about the R6-1k output resistor

does it have to be 100 ohm for low output impedance or the 1k its fine?

bmxguitarsbmx · Post by **bmxguitarsbmx** » 05 Mar 2021, 19:03

AndrewGallios wrote: ↑05 Mar 2021, 10:56 hi

i want to ask about the R6-1k output resistor

does it have to be 100 ohm for low output impedance or the 1k its fine?

Either is probably fine.

You could totally overthink this and calculate the output resistor for the power supply and the maximum output current of the op-amp. But, since this buffer doesn't have input or output protection, I wouldn't be bothered. (Input protection from being driven while buffer is not powered. Output protection from the discharge of C3 when powered off)

george giblet · Post by **george giblet** » 09 Mar 2021, 01:01

does it have to be 100 ohm for low output impedance or the 1k its fine?

The resistor is there to stop oscillation with a capacitive load, 1k will work 100% of the time.

AndrewGallios · Post by **AndrewGallios** » 13 Oct 2022, 20:40

Hi I have a question if someone knows

What values in the parts should be changed to get a little bit of gain in this buffer? Just a touch more from unity gain

Cybercow · Post by **Cybercow** » 13 Oct 2022, 23:58

Should be as simple as adding some resistance between the output of the opamp and the negative input of that same opamp. Try a 20K or 25K trimpot there and see what you get sound wise as the trimpot is turned with a signal going thru it.

mauman · Post by **mauman** » 14 Oct 2022, 00:37

With a non-inverting op amp, you'll also need a resistor R10 to the reference voltage (junction of R3/R4). And a cap in line (C6) will roll off the gain to ~~zero~~ <edit: unity> at DC, which is good practice. For a gain of 2 (+6 dB), make R9 = R10, and as you increase R9, the gain goes up. For a gain of 1.5 (+3.5 dB), make R9 half the value of R10, and as you decrease R9, the gain goes down. I'd suggest R10 = 10k, and C6 = 4.7 uF or 10 uF. Make R9 = 4.7k for a little over +3 dB, or 10k for +6 dB.

: Buffer with gain

Cybercow · Post by **Cybercow** » 16 Oct 2022, 18:44

What mauman states is a better proposition for increasing the gain on this buffer circuit. Providing a reference to pin #2 helps stabilize the circuit by keeping the audio signal at or near a zero reference. Without it, as I postulated in a previous comment, the opamp can end up with a DC offset and the audio signal will be off-balance from a zero reference point.

m4268588 · Post by **m4268588** » 17 Oct 2022, 03:13

I don't understand necessity of C6.
Connecting C6 to Vref instead of GND results in low noise. And you are using the FET input device OP-Amp.
Is C6 inevitable?

mauman · Post by **mauman** » 17 Oct 2022, 04:00

m4268588 wrote: ↑17 Oct 2022, 03:13 I don't understand necessity of C6.
Connecting C6 to Vref instead of GND results in low noise. And you are using the FET input device OP-Amp.
Is C6 inevitable?

It will work without C6, but this blocking capacitor rolls off the gain to unity at DC. The value is large enough so it doesn't affect audio frequencies. The goal is to reduce the effect of any input offset voltage in the op amp, which can be more than 10 mV in a TL071.

m4268588 · Post by **m4268588** » 17 Oct 2022, 10:57

I got it

Stupidly Awesome Buffer [documentation]