Neovibe whining

[axg20202]

..that's the neovibe, not me, although I guess this is a whine of sorts 

I've just completed the build and I'm loving the sound, but I've noticed a faint siren-like whine in the background which is in time with the LFO. Does anyone know how I can cure this?

[R.G.]

That's a new one. Congratulations - you have a disease we don't yet have a name for. 

I wonder if it's the voltage regulator oscillating. Is your build completely stock? Modified? On a pre-etched board? Perf?

[axg20202]

Hi RG,

My build isn't completely stock. It's built on a board I etched myself. The following differ from stock:

1) 200k mix trimmer in place of the two 100k resistors - here's a possible clue. If I turn this fully ACW i.e. offset the mix completely to this side, the whining goes away, but turning this CW increases the whining, with the fully CW position having the highest level of whine. This suggests that one half of the mix is providing the lovely whine.
2) TIP-120 bulb driver
3) R49 = 10k (instead of stock 4.7k) depth mod
4) True bypass unity gain mod
5) LFO pulsing LED coming off the base of Q12
6) True bypass switching with status LED powered directly from the 15v regulator

Other details:

Power by 18v DC (isolated power jack - the rectifier etc are on the board as per layout) - no other devices are sharing the power source.
The 15v regulator is a 7815
Aluminium enclosure

[axg20202]

Oh, while I'm here....I guess I may as well share a pic of the completed build. Pretty poor photo but you get the gist.

http://picasaweb.google.com/ipitythecrazyfool/UntitledAlbum/photo#5047090078423473778

[R.G.]

here's a possible clue. If I turn this fully ACW i.e. offset the mix completely to this side, the whining goes away, but turning this CW increases the whining, with the fully CW position having the highest level of whine. This suggests that one half of the mix is providing the lovely whine.

It is a clue.

The "mix" mixes straight, dry signal from the input preamp (Q1-Q3) with effected signal which comes through the phase line. So one of these has no whine, the other does.

Audio probe time. Which side produces the whine? Phase line or dry side? If phase line, where in the phase line does the whining start. If dry, where does it STOP?

[axg20202]

Hi RG,
I have managed to get a good mix setting where the whine is barely audible, even with gainy pedals following the vibe unit, but it is still there and with a cranked amp it is noticeable in more delicate passages. Not majorly annoying, but there. If it can be eliminated - great - but I can live with it if not. I'll have a poke around with a probe when I get a chance.

[3/4 North]

Try this, ground the output jack with a wire connection instead of using the box.
Hook it from the output jack shield to one of the un-used ground pads on the board either "O" or "I"

I think this would probably solve many of the "my neovibe hums" threads too.

[axg20202]

Thanks, I'll give it a try. I'm not convinced this will work but its easy enough to try. I'll probably just connect the ground directly between the in and out jacks instead of via the board.

[axg20202]

OK RG, I've had a probe around and I think I might be getting somewhere - but I'm still totally confused! The whining noise (an up-and-down-in-pitch sine-wave-shaped whine, constant amplitude) is present in many places on the board. I eventually came to probe the power pads onto the board. It seems that the oscillating whine is significantly louder at the point of power onto the board. In fact, if I probe the (18v DC positive) sleeve of the power input jack from my power supply while it is connected to the isolated power socket of the pedal (there is a small section of the jack sleeve protruding when the jack is connected) I get a very loud whine.

So, I'm thinking, loudest whine = source of whine. So, it's my power supply?....but hang on, maybe not......the rate of the siren-like whine is controllable with the speed knob! Basically, I haven't got a scooby doo what's going on here! Here's hoping you do!

Thanks,
Andy.

[Serge]

Sorry for hacking this thread for a second, but talking about the power supply for the Neovibe, is it possible to simply use a charge pump in the Neovibe?

[axg20202]

er...not wishing to be rude but your question has nothing to do with debugging the neovibe and is completely unrelated to this thread. Come on man, don't be lazy. Do a search then start a new thread...

[Serge]

ok - sorry  .  It thought it was a related yes/no question .  I did a search by the way, but I only found the same questions - unanswered.  But hey, it's your thread, you're the boss 

[axg20202]

No worries. Didn't mean to come across all stroppy. FWIW, in reading pretty much every post on the neovibe before I built it, I vaguely remember seeing a post by someone that was using a charge pump. Have a look for it.

[axg20202]

OK, i've been trying a few things out like swapping out the 7815 (for a 78L15) but still no joy. Any ideas? I guess I could try a different power supply, but does anyone have any other suggestions before I fork out for one?

[albatross]

Did you try an audio probe? they are very easy to make and use.

Try to find out where it begins and ends, i know the circuit is quite complex but it can be done if you think of it as different areas, as gainstages / lfo etc..
Start from the input. Thats what I would try anyway, you should then be able to find out whether its a cap etc.

[axg20202]

Yep, see above.

[R.G.]

So, I'm thinking, loudest whine = source of whine. So, it's my power supply?....but hang on, maybe not......the rate of the siren-like whine is controllable with the speed knob! Basically, I haven't got a scooby doo what's going on here! Here's hoping you do!

I think you're right on target. You have a strong suspect - the power supply. So let's try some things there.

What are you using for a power supply? Is it possible for you to replace it with two or three fresh 9V battteries in series temporarily for a test? If the whine goes away, it was the power supply. If not, it's on the board. Divide and conquer is powerful.

hmmm.... I wonder if I should translate Sun Tzu's "Art of War" into electronics debugging?   

[axg20202]

Yeah, I hope that's the problem because it's an easy thing to replace. The power supply is one of those laptop supplies. I guess I could try setting it to 9v and seeing if it causes other pedals to produce a whine. Also, I hadn't considered the battery approach - I'll give it a try.

Thanks!

[R.G.]

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

It's highly likely that this is your whining problem.

[3/4 North]

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?