Revv G4 Pedal - Verified

[anders]

The schematic is finally up on pedalPCB's site.

*edit*
Now verified by Hozy

[Travis]

Great looking layout

[music6000]

Treble should be 50kA
Personally, I would use the PedalPCB board, This is a lot of hard work!

[Hozy31]

Call it verified! Sounds really good. I used a b50k for treble and the sweep is good. Will try a50k just to see if its better. Cheers for the layout anders!

[anders]

Woohoo! Thanks for verifying Hozy!

[Strassercaster1]

Great looking layout ! I did the board and compenents yesterday. I Wanted to verify it . I took a break after I saw it was verified and got couch paralysis ha ha . I  can’t wait wire it up tonight .looking forward to the G3 . I watched a lot of videos comparing the G3 and G4 I think I like the G3 better it sounds less scooped .

Thanks for the layout !

[Strassercaster1]

If there is a project you want verified  let me know I’m always wanting to try something new and if it helps you out I’d be happy to do it !

[daveycroc]

Finished this build tonight and it worked first time. Sounds great.

Couple of small points. D1 could be moved from column 4 to 3. I had to as my LED had a rim around the outside which stopped them sitting straight on the board.
The parts detail says that D1-3 are LED's whereas it should be D1-2.

One question there is a 100nF cap in the power section missed out based upon the Schematic. Why is this?

Anyways the above a very minor points, congrats on a great layout hope to see it on the front page soon!

[anders]

Thanks for the headsup. Updated the layout above. Regarding 100nf power filter cap, I left it out because there is simply no room for it. And it doesn't affect the the sound at all unless you have a really bad power supply adapter.

[daveycroc]

Not a problem.

That's what I thought was the case about the cap.

[Frank_NH]

The 100nF capacitor is there to filter out high frequency ripple in the power supplied to the pedal.  Theoretically, it shouldn't be needed, but if you make pedals for someone else, they may have a so-so power supply and thus this kind of extra filtering may be needed.  For your own pedal, you can decide it it's needed or not based on your own power supply (battery, wall wart, isolated effects power supply).

If you do add the 100nF cap, make sure it is a ceramic cap (much better for filtering than film types).

There is an extensive thread on DIYstompboxes on this topic:

https://www.diystompboxes.com/smfforum/index.php?topic=116491.20

[HamishR]

Same as the "unnecessary" series polarity protection diode.  Yup, it IS unnecessary if you have a good power supply.  But as I found out when showing a friend one of my pedals if you leave that diode out and try to use the pedal with a cheap'n'nasty power supply you can get howling noises.  Put a diode in line between the power and the board and all quiet.  That diode can act as a rectifier as much as a polarity protector.

The 100nF cap on the power filtering reminds me of old tube amps where they would put a 100nF cap in parallel with the 100µF filter caps - Matchless still do this.  Probably a reflection on how dirty power used to be?

[Frank_NH]

Regarding the 100nF cap, I've read that it is good op amp circuit design practice to put a 100nF cap to ground as close to the op amp power pin as possible (i.e. pin 8 on a dual op amp like the TL072).  Now, many will say this isn't necessary for audio applications, but I wonder if for high gain circuits this can cure some of the noise issues.  I've not done any conclusive testing in this regard, but passive components like capacitors are cheap and as long as you have the space, why not?

This thread has caused me to go back and review the various approaches that different circuits (and even different makers) use for power conditioning.  For example, for bias voltages (4.5V) some use a voltage divider, other use a JFET, and some even use an op amp.  Which is best?  They all seem to work, and perhaps most of the time it doesn't matter, but still you wonder...  I suppose that's why we have electrical engineers!

[HamishR]

I'm slowly learning more but learning too fast makes my head hurt.  So I still don't really know how any of this stuff really works!  I don't understand electricity.  Buy thanks to places like this my home-brew amps and pedals sound better and better all the time.  :-)

[Teddeeh]

The latest tone mob podcast with mr black, he says its all necessary. Part quality and placement all make a difference. Ive noticed recently in a build. Most of the time i cant notice but i used wima caps in a high gain, high treble/presence build and the difference was very noticable with regards to noise and feedback.

[Strassercaster1]

THANK YOU SO MUCH OR THE LAYOUT ITS AWESOME. !I finished it a couple weeks ago but had a nice session with it today . Its pretty cool .Now for the face melter and Revv G 3 . Both are giving me a headache ha ha

[Surgeon]

Hey Anders,

I've been away from building for a long while and I want to confirm something with you about the layout.

Can you please confirm that this is the correct pole-identification for the on/off/on DPDT please? Just to make sure, my memory's a bit fuzzy... thanks!