Buffered splitter spill-over

[lars-musik]

Here's another one I caught lately. This is a fuzz circuit that is supposed to provide an unfuzzed (=split) signal with a gain of around 4.5 to trigger some sidechain tools. I integrated my usual buffered splitter at the input but get some audible spill-over from the fuzz circuit into the "Trhough" output when engaged. Not really a problem because the triggering works good, but I wonder why that is anyway.

[antonis]

Try to eliminate any "unnecessary" VB connection, like clipping diodes, Clean & Dirt pots, etc, by replacing them with GND..

[lars-musik]

Thanks for helping out, Antonis.

Would it help as much if I'd just put a second "VB" via voltage divider on the secondary out's opamp?

[antonis]

Yes, lazy boy...

Just remeber to add a capacitor on new VB..

[lars-musik]

Yes, lazy boy...

Well, there you got me!

Just remeber to add a capacitor on new VB..

Will do. Thanks!

[duck_arse]

can I ask questions? why two voltage followers instead of one follower with two spltting/isolating resistors at its output? and also why a 10uF followed by a 100nF?

[lars-musik]

Hi Stephen,

a late answer – somehow your comment eluded me, sorry.

The splitter is a tiny pcb I had populated and handy, and I thought the 10uF wouldn't spoil anything, so I just slapped in in front of the circuit.
No, not correct. I didn't think, I just did it.

But surely you are right and one saved opamp would be good.

Would this be correct?



Thanks!

Lars

[antonis]

10μF cap & 220k resistor form a HPF of subsonic frequency..

You could delete that cap and leave 100nF in place - even a 47nF cap should be fine..
(same stands for lower op-amp stage..)

P.S.
Is there any particular reason for using such a high value resistors (1M/220k) for such a low gain (X4.5) other than high input impedance purpose..??

[lars-musik]

10μF cap & 220k resistor form a HPF of subsonic frequency..

I guess that's one of the drawbacks of ready-made building blocks. Combined with the lack of training in spotting those things, subsonic filters happen. Thanks for pointing that out, I'll go with the 100n.

Is there any particular reason for using such a high value resistors (1M/220k) for such a low gain (X4.5) other than high input impedance purpose..??

No special reason since adding the buffer in front. What are the drawbacks?

[antonis]

No drawback other than "noise", input bias offsets & impact of parasitics (bad high freq behaviour)..

None of the above is actually utilized on your specific circuit..
(although, I'd object a little bit to 10M on op-amp C NFB loop..)

[duck_arse]

lars - yes to all. what? now I'm more confused. first, you have a 1k followed by a cap followed by a 220k [I'm having trubble reading those values .....] - why two series resistors [and I know, because I said splitters, and because building blocks]? but then I look closer, and see you have two identical stages following the first follower stage. now howcome?

[lars-musik]

Well.....  the schematic I posted here is not the whole truth. The circuit on the right (starting with "IN") is a "Brown Dog" Fuzz. The original has a secondary output that allows the 4.5x amplified clean signal to trigger the envelope filter of a "partner pedal" called the "Agent 00 Funk". Now the first schematic I was following just branched off this output after the first opamp. That of course doesn't make sense in true bypass pedal because in the bypassed state of the fuzz the envelope filter didn't work anymore  (I haven't had an original unit, so I have no idea how they did it). Now I know that in some scenarios a true bypass pedal is wished for by true bypass disciples and so I was looking for a way to make the whole mess switchable.
This is what I came up with now, trying to isolate the whole true bypass/buffer/seconday-out shebang from the main cirucit, so I can build it without, too. There surely are easier ways but at least this one I understand.... Kind of.... 



By the way, you can click on this image and enlarge the schematic:

[duck_arse]

it is true, and I did know, I can click on and see. only, the image on the new page displays [here] at the same size, or close to, as in this page. if I then click the new page image to enlarge that, it just stays the same size, as there is no empty space on my screen around the image. I would have to click on download original, save that somewhere, go off to find where it was and open it in an image browser, which would display it 'fit to screen' [ie, the same size again] or '1:1', which would mean scroll scroll scroll across up and down the image, just to drink in all the circuity beauty.

computers, huh. picnic.

[lars-musik]

I neither want to miss your help, nor do I want to stick to three part fuzzes...

Agreed, too many clicks but it could work!

If you first click the thumbnail


another tab opens and displays (again the same size).




if you hover over that one with your mouse (arrow becomes a magnifying glass) but click right and hit "open in new tab"



the next tab displays the full resolution (at first - again - scaled but when you click on it AGAIN it gets large and scrollable)

Now I counted 5 clicks. Not really good.

[antonis]

Shouldn't be more convenient to post image with its original size, Lars, rather to shanghai Stephen into eternal clicking..??
(possibly resulting into defective mouse..)

P.S.
For your info:
Stephen also prefers reversed colour (white lines on black backround) schematics..
(like most of down-under cranky guys..) :cider: :cider: :cider:

[lars-musik]

Shouldn't be more convenient to post image with its original size

I would! But thought this "Add image to post" button in the "Post reply" box was consensus here. How do you go about posting images?
And I seem to remeber that some people complained about too large pictures that weren't comfortably displayed on their monitors?

[PRR]

> thought this "Add image to post" button in the "Post reply" box was consensus here

Not "consensus". There was a panic when the popular image host changed their rules and half the innernet vanished. I happened to see the PostImg forum-tool and mentioned it. Next day Aron had implemented it. I think it is good, a lot better than nothing, or random choices of bad image hosts.

It has faults. I prepare a NEAT 2-color GIF of reasonable size, and when I get it back from the forum it is fuzzy and a different size. If you give it a "line drawing" of 32k colors, already somewhat fuzzy, it makes it fuzzier. PostImg apparently JPEGs everything and not low-loss settings. Kittens and porno may come through OK, line-drawings suffer.

[Rob Strand]

PostImg apparently JPEGs everything and not low-loss settings. Kittens and porno may come through OK, line-drawings suffer.

PNG works.

What people don't know is you *can* save JPEGs without blurring single lines so much.   You need to turn off "Chroma Sub-sampling".    I only know of Irfanview offering the setting.

https://www.impulseadventure.com/photo/chroma-subsampling.html
https://matthews.sites.wfu.edu/misc/jpg_vs_gif/JpgCompTest/JpgChromaSub.html

The default is Chroma sub-sampling is on; IIRC defaulting to 2x2.  The causes a kind of colour averaging across two pixel spans and blurs thin lines, especially single lines.

You of course need to set the compression to a high-quality setting.

I tend to use PNG these days but I suggest people try turning off Chroma Sub-sampling to see the enormous improvement it makes on diagrams with thin lines.

[PRR]

I know how to save loss-less images: GIF!

I'm saying that when PostImg stashes my image it messes with it.

As that first link shows, if you feel you must save as JPG, PhotoShop (and apparently PaintShop Pro) set CSS according to the 1-100 number on the Quality slider. I've always used about 14 for general girlie-pix and that's OK, when I need to transmit an image with NO loss I've used 1 (but the result may be large).

PNG has aspects of both. It can do wonderful lossless, and if you pick a proper process it can be economical. Smaller than GIF due to 2-D action and better compression. Apparently implementations vary a lot.

[bluebunny]

And I seem to remeber that some people complained about too large pictures that weren't comfortably displayed on their monitors?

Yes, for two reasons: 1. back in the days of dial-up or not-so-broadband, it would take an age to display your multi-megapixel masterpiece; and 2. your multi-megapixel masterpiece is bigger than the browser or even the screen, so is unviewable in its entirety.  (#1 is probably irrelevant these days...)

So insert into the [IMG] tag either HEIGHT= or WIDTH= to control how it appears (the whole thing is still downloaded by the browser).  If you want it full-size you click on it.  Or right-click and "open image in new tab" (or similar incantation).