Snap crackle pop .....THAT's not what it's supposed to do!

[Mark Hammer]

I was boxing up a Roger Mayer Octavia,  Works great, and sounds great***, exactly like it should, except there is a very objectionable crackling noise that sounds a lot like a vinyl album in bad need of replacement.  Crackling is about as accurate a description as I can find, and it is ruining this otherwise pleasing pedal.

Any ideas what I should look for?  Is this likely a cap issue, a transistor?

***The gain control on both the Mayer version and the Tychobrahe suffers if it falls below, or at the perimeter of, spec.  The Mayer Octavia uses a 10k Drive pot, but you'll find that your average Alpha pot will be below that.  I found it useful to select a 10k pot that is as close to 10k (or over) as possible (Many of those in my binwere <9k) and supplement the drive pot with a fixed resistor to add up to something a little over 10k (e.g., a 9k1 pot and a 1k fixed resistor)  Alternatively, use a 20-25k pot and add a suitable parallel resistor to get a useful tape and suitable resistance range.  Note that gain in the circuit is highest when the resistance of the pot is at minimum, and lower as the resistance increases.  This is not a sweet circuit, and to my ears sounds awful if the gain is too high.  If you want those shy octave tones like Hendrix' "One Rainy Wish", you need to be able to dial in a suitable range of high resistances in the 9k-11k range, so that the octave just begins to kick in without the severe distortion.

[timd]

Works great, and sounds great***, exactly like it should, except there is a very objectionable crackling noise that sounds a lot like a vinyl album in bad need of replacement.  Crackling is about as accurate a description as I can find, and it is ruining this otherwise pleasing pedal.

Sounds like something I would purposely make.

[Mark Hammer]

Bah!  Twas a false alarm, cured by a fresh battery.  Weird.

[Electron Tornado]

Yeah, but now you need a pot so you can decrease the battery voltage and get that real authentic vintagey sound of the union of a needle and pure vinyl. 

[Jdansti]

Works great, and sounds great***, exactly like it should, except there is a very objectionable crackling noise that sounds a lot like a vinyl album in bad need of replacement.  Crackling is about as accurate a description as I can find, and it is ruining this otherwise pleasing pedal.

Sounds like something I would purposely make.

Another eureka accidental discovery, Tim!  Now you'll need to test all of your pedals under development with a dying battery feature. Who knows what you'll find! 

[timd]

I'm welcoming the dying battery simulator with open arms!

[Paul Marossy]

Yeah, but now you need a pot so you can decrease the battery voltage and get that real authentic vintagey sound of the union of a needle and pure vinyl. 

And then it could be called the "Rice Krispies Drive". 

[Jazznoise]

The high gain problem is one I've been trying to solve, I'm thinking of paralleling a cap with the diodes so the high frequencies don't undergo the rectification as it messes with the transients too much and adds alot of high frequency IMD.

I forget which pot I used, but on the lowest gain setting I get less than Unity but a very pleasing octave effect for chords and single note lines.