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>the DC converter puts out around 12v with no load and around 9v under load...

This is quite common. If you connect an LED (and associated resistor) to the output, you will have both a handy indicator that it is working, and likely enough load to keep the output close to 9V.

>For filtering try 22 Ohm and 470uF instead.

I would not expect a 1/4W resistor to last very long here with the current draw of a few pedals + some inefficiency in the DC-DC converter.

>typical switching frequencies of these 5v chargers ... 50kHz or more, 33kHz

Heterodyning between the charger and DC-DC converter might be the culprit. If your charger is whining at 50 kHz, this will beat agaist the 62 kHz DC-DC converter to give you noise at 12 kHz and 112 kHz (which will only bother the neighbourhood bats).

If you can get a low dropout 5(ish)V regulator between the charger and DC-DC converter, you may be able to filter out the 50 kHz and thus prevent the heterodyning. Alternatively, try another changer. At the price we (don't) pay for them, I would expect the quality to vary from crap to marginally ok. Also, a 33 kHz switching charger will have advantages in this application...

Is the crack down the centreline between the bolts?
A photo might help...

>You can find knobs specifically for rotary pots

That I didn't know - thanks.
For the plastic shaft swtiches (or other non-splined versions) , a set screw is a must.

Many of my knobs come from pedal parts uk. The only ones from there that fit (although I haven't tried every last one) are the chicken heads. Having looked closer, they have pretty decent descriptions for each knob, and it would appear that many won't fit on the 6mm solid-shaft pots either.

Haven't seen thonk before - thanks for the pointer.

I never had any intention of drilling out the knobs - I would expect those with metal inserts would just spin the insert.
I will shave the odd shaft if needs be, but I was/am looking for a less annoying option for future builds - which seems to be to make sure I order knobs designed for a 1/4" shaft. It seems most of those in the UK are 6 mm, which is why I have few options in my stash.

>Any 1/4" knob with a set screw.

I guess that must be it, and having had a look with fresh eyes I see that at least Stew Mac advertise tele knobs for both 6mm and 1/4" shaft.

http://www.stewmac.com/Hardware_and_Parts/Knobs/Dome_Knob.html

That's my last resort.
I have a number of projects that do/will use these, so I don't really want to have to do that on a regular basis.

The length isn't the problem - they get cut down like most other pots.
The problem is that the shaft has a diameter of 6.3 mm as opposed to 6.0 mm for 16 mm (and many other) pots. That extra 0.3mm is too much for almost all of the various pots in my collection, which must have an inner diameter of <6.3 mm.

I guess this is why you only see chicken head knobs on varitone switches in guitars - none of the usual suspects fit.

I considered that, and it's a reluctant option. The chicken head knobs fit beautifully, so there must be other options out there with similar sleeve dimensions.

I'm looking for recomendations for knobs.
But wait.
Specifically, those that will fit on rotary switches with an (allegedly) 6.3 mm (1/4") plastic spindle like this:


Chicken heads will fit, as will some of the Davies (maybe cloned) knobs with plastic inserts. What else have you good people found to work?
I have one of these in a bass, which looks a bit fugly with chicken heads, so anybody found a tele(ish)-style knob that will fit these?

Thanks

Magnavibe.

Fair enough, and something to try for version 3.

I wonder if the degree of ticking might depend on the LED(s) used. Some have much higher capacitance than others, which will help to smooth out the spikes in current draw.

A better solution is to keep the 47R (or whatever value) resistor, but tap off before this to feed the voltage regulator - you get better filtering of the analogue circuit. Something like the power section of this:

https://dl.dropboxusercontent.com/u/11996927/ACE_Tremolo_2_Schem.jpg

I have also found that if you round the corners of the square wave just a little bit, then it can make a big difference too, without sounding any different. This is done in software, but if you flash you own chips, this is a relatively easy 'fix'.

Congratulations on getting the monkey off your back.
Are you thinking of postdoc'ing once you get the viva out of the way?

What's the minimum delay you can get with this setup - my guess is that the 'shaky ground' will add substantially to this?

I have a physical switch to switch off modulation completely. I don't know how short the delay is with a minimal setting (there is some), but it is not audible (so, way below a slapback). It adds just a bit of "space" to the tone. I will post a video to give you a better idea.

excellent - looks like a cool design