Neovibe whining

[axg20202]

Laptop power supplies are NOT designed to supply clean power to audio pedals.

Well, you can't argue with that point. They're designed for laptops I believe. 

Seriously, though, it's not an actual laptop supply. It's a laptop-style enclosure, yes, but it is a selectable voltage multi-adapter affair that doesn't appear to be designed for any specific use. It's not junk either. Sure, it's not designed specifically for stomp box use. I've used PSUs 'designed' for a particular commercial pedal that have been worse than quality unbranded jobber supplies like this. It seems buying any regulated power supply is a gamble, no matter what its quoted intended use.* I might not have been lucky with this one, that's all.

*notable exception being the Diago PSU I recently acquired, which is superb. There is an 18v adapter accessory that can be added to this, but I think the Neovibe would require more juice than it is spec'd for (30ma).

[axg20202]

What happens if you run the signal through another pedal first - like a Big Muff?
Is the whine still there or does it go away?

Makes no difference at all. From my audio probing I'm pretty sure it's the power supply rather than anything to do with the effects chain. I just haven't had an opportunity to test an alternative power source yet.

[Torchy]

I think you'll find laptop power supplies are switch mode, and fairly basic at that. Sounds like its the switching thats inducing the whine. 

[axg20202]

Sounds like its the switching thats inducing the whine. 

Quite possibly. My main supply for all my other stompers is a small switch-mode device, but it was designed specifically for the purpose so its not a fair comparison. However, I do have another switch-mode supply that is a no-brand cheap multi-adapter (sadly not able to supply 18v) and it is whisper quiet. Like I said, it's a gamble....

[R.G.]

I think you'll find laptop power supplies are switch mode, and fairly basic at that. Sounds like its the switching thats inducing the whine.

Thanks for explaining torchy. I seem to have shot over ax's head with

Laptop power supplies are NOT designed to supply clean power to audio pedals.

It seems buying any regulated power supply is a gamble, no matter what its quoted intended use.*

No, you just have to know that its intended use was, and take that into account. Switching style power supplies are intended to provide a lot of power, usually to digital circuits which don't care if there's 5-10% ripple on the power supply. Audio circuits with no power supply rejection will sing at the power supply ripple frequency, and may heterodyne the ripple back down into the audio band if the ripple is above audio.

There is at least one switching power supply - the 1Spot - which is specifically designed for, tested for, and proven to work with guitar effects. I think the recommended retail price is about $25, but as we all know, recommended retail is a fiction, and it can be had for significantly less if you find the right dealer in the right mood.

[axg20202]

I think you'll find laptop power supplies are switch mode, and fairly basic at that. Sounds like its the switching thats inducing the whine.

Thanks for explaining torchy. I seem to have shot over ax's head

With respect, not at all - I'm not completely thick and I appreciate your help. I was merely trying to inject a bit of humour. I have had good results with switchmode supplies in the past so I see no harm in trying them out. This particular supply I had already and, subject to some tests, is probably not suitable. However, I know from experience that switchmode power supplies can be fine for this application. My Diago supply is a switchmode supply, for example. The key is quality I guess, but I've also had success with S/M supplies that were general purpose.

No, you just have to know that its intended use was, and take that into account.

Assuming it has one. I already have a dedicated 'designed for purpose' supply for the rest of my pedal chain (Diago). If I have to buy a dedicated 'for pedals' supply for this one effect then so be it, but first I'm exploring a couple of easily obtained regulated power supplies that are for no specific purpose.

There is at least one switching power supply - the 1Spot - which is specifically designed for, tested for, and proven to work with guitar effects. I think the recommended retail price is about $25, but as we all know, recommended retail is a fiction, and it can be had for significantly less if you find the right dealer in the right mood.

I will explore other options once I have established that the PSU is the problem and that an alternative cheap supply is unsuitable.

[axg20202]

...on the subject of suitable supplies....R.G.: do you have a rough idea of how much current the Neovibe draws? I have an option to add an 18v 'add-on' to my existing 'designed for purpose' power supply, but I have a feeling the add-on is rated too low (30ma).

Thanks.

[R.G.]

I'm not completely thick and I appreciate your help. I was merely trying to inject a bit of humour.

No offense intended or taken.

I have had good results with switchmode supplies in the past so I see no harm in trying them out.

Great. The only loss is that this one has run you around in circles for a while. Engineering is a pragmatic science. Whatever works, works.

If I have to buy a dedicated 'for pedals' supply for this one effect then so be it, but first I'm exploring a couple of easily obtained regulated power supplies that are for no specific purpose.

That's fine. However, the Univibe, if built to the normal schemo, has a regulator on it, so you just have to give it clean(ish) DC for the LFO and bulb and keep the whine out of the audio path. It may be that a 100R resistor and a 0.1uF ceramic cap in series with the incoming +V line will tame the whine, as long as it's not coming in on the ground. It's possible that you could put 51R in both sides + and - from the incoming power supply and suppress whine with the 1000uF caps on board supplemented with some ceramics to specifically attack the whine.

[axg20202]

Usefuly info. Thanks RG. I'll maybe explore these tweaks if the new power supply I've ordered (a fixed-voltage, transformer-based one) doesn't work out. The ideal scenario would be to have it running from my Diago supply though - can you comment on the approx. current draw of the neovibe?