Neovibe oscillation noise

Swoon · August 25, 2009, 04:29:01 AM

Hey hey,

I just finished my first Neovibe and I quite like the sound.
There's 1 probleem though, I can hear a constant LFO like noise/whine in my signal path. Even without anything plugged in to the input.

I'm using a filtered 18V power supply which delivers about 1.9A.

Where can I start to debug this issue? At the moment it seems like there's a little UFO in my Vibe.

I did use 25V elco's for the 1000uF caps due to lack of 35V caps. But I wouldn't suspect that being a problem?

De Vibe is built according to the schematics of the GeoFX neovibe. (http://www.geofex.com/FX_images/vibeschm.pdf)

I've read on these forums that it could be the lamp that is just using too much power? (12V 40mA) However, considering the PSU power I wouldn't think so.
I've just hooked up the 18V after the diode, but no change. 10uF and .1uF over the power rails doesn't seem to make a difference either.

It doesn't seem to be power hum to me, as it is a quite high pitched noise, oscillating at a constant speed.
Could it be that my wiring is bad? I did use leftover resistor legs to wire the speed pot.

Any clues?

Thx!

Stefan

R.G. · August 25, 2009, 09:37:49 AM

The most likely issue is either
(1) Component placement or pinout error
(2) soldering problem, either a short or an open
(3) if you built your own PCB, a PCB open/short error
(4) a wiring error
(5) possibly your power adapter is oscillating all on its own.

Swoon · August 25, 2009, 11:35:26 AM

Hi,

Is there a way I can check (5) withour buying a new 18V adapter. It's the only one I have...

Thanks!

powdered hearts · January 14, 2010, 08:10:56 AM

Starting to get old, this thread is...
Just wanted to say that I have experienced the exact same problem with my neovibe, I get the lfo swooshing noise through the amp all by itself. The noise follows the speed setting on the neovibe, so it would not likely be the PSU oscillating then. Did threadstarter resolve this issue? The pedal itself works just fine when played through, could it still be a wiring error?

blueserik · March 08, 2011, 03:53:55 PM

hi.
I have the same problem as "powdered hearts"
Anyone have any idea what it could be?
It works fine but there is this noise all the time that goes higher when I turn the volume up and faster with the speed pot.

blueserik · March 08, 2011, 04:10:44 PM

And here is a video of it.
http://img716.imageshack.us/i/33q.mp4/

R.G. · March 08, 2011, 04:45:05 PM

I wish I could offer more help remotely. That's not something where the DC voltages will lead to "AHAH! Replace C15!" I don't think.

From the sound, it resembles very much that the LFO is acting like a tremolo for a hum getting in from somewhere, but it doesn't sound like power line hum or ripple to me.

My first step would be to use a couple of 9V batteries in series to power it temporarily to see if the hum goes away. If it does, it's a power supply problem. If not, the unit itself is oscillating. My second step would be to use an oscilloscope.

Can you try the batteries and let us know?

blueserik · March 09, 2011, 02:20:18 PM

Hi.
I haven't tested with two 9V yet but I just wanted to say that I tested with a voodoo lab pedal power 2+.
Since I haven't received my voltage doubler cable I only tested it with the 12V output.
I guess thats not the problem just thought I should mention that.

I will test with two 9V batteries tomorrow.

blueserik · March 10, 2011, 02:15:59 PM

Hi I just wanted to say that it works now.
I tried it with the right cable and now it works fine.
I tried it with 12V before and now I tried with 24V and it sounds amazing.
Now I'm going to put it in my enclosure and it will be ready for the stage.
Thank you R.G for sharing this with us.

yeeshkul · March 10, 2011, 02:59:46 PM

1. The same thing happened to me when i placed 7815 wrong way (i was using 18VDC/1.9A switching supply)
2. 18V is not enough, use 24V for top notch performance

blueserik · March 12, 2011, 02:02:24 PM

Hi.
I must post again.
I am not sure if it is working like it should because I have never heard one live.
I really love the sound but there is a small oscillating sound going on when I turn it all the way up. Volume, Speed and depth.
Here is a sound clip. Its not loud and goes away when neovibe in bypass and you don't hear it when you play.

http://www.2shared.com/audio/xUW76-CU/Memo.html

Is it normal that it's not dead quiet?
Thanks Erik.

blueserik · March 13, 2011, 08:47:22 AM

Hope I'm not to annoying.
Just wanted to share my different readings when measuring the voltage.

Ok.
Q4= 4,74v
R18=11,29v
Q5=3,71v
R32=5,96v
Q10=5,46v
R40=13,55v
Q12 jumped from 11.2 to 13,5.
C25=23v

A little bit different from the schematic shared here.

Thanks.
Erik

blueserik · March 15, 2011, 05:24:12 PM

Guess this will be my last post regarding this problem.
Think I have solved it now.
What I did was

1. Replaced Q1 and Q13 with 2N3904.
2. Removed diode bridge.

Now it's quiet. Well almost...
If I turn the knobs all the way up and the amp on 10 then I hear a very low UFO sound that goes with the same speed as the lamp.
Well, this I can live with.
Thanks once again.

Brossman · March 15, 2011, 09:24:31 PM

Hmm... a good friend of mine has a Pigtronix Envelope Phaser... when the LFO is engaged, there is a similar effect - a kind of warbling hum - in/out phase with multiple pickup combos doesn't make it go away, so it's not being induced by the 60-cycle hum of single coils...

If it's not PS, and it's not Pups, is it possible that there is some voltage coming from the LFO?

Maybe it's bleeding to somewhere where it shouldnt...?

Perhaps a ground/shorting issue?

Of course, these are all shots into the dark...

blueserik · March 16, 2011, 03:04:01 AM

Hi.
Ok. So there shouldn't be anything at all when i turn down the guitar? Its not loud at all but I guess that if this pedal should be dead quiet thats what I'm aiming for. Well check all my grounds because when I touch the chassis there's actually a small spark noice.

Brossman · March 16, 2011, 10:38:51 AM

EDIT::: oops, wrong topic...

R.G. · March 16, 2011, 10:39:33 AM

Quote from: blueserik on March 15, 2011, 05:24:12 PM
2. Removed diode bridge.

This makes me think that the problem was with a grounding issue on the external adapter versus signal ground. The diode bridge makes one side of the external adapter be one diode above ground or below ground, depending on the current direction. If there is any other connections to the external adapter, this can cause intractable noise.

SnakeSK · August 13, 2012, 02:26:56 PM

Quote from: blueserik on March 15, 2011, 05:24:12 PM
Guess this will be my last post regarding this problem.
Think I have solved it now.
What I did was

1. Replaced Q1 and Q13 with 2N3904.
2. Removed diode bridge.

Now it's quiet. Well almost...
If I turn the knobs all the way up and the amp on 10 then I hear a very low UFO sound that goes with the same speed as the lamp.
Well, this I can live with.
Thanks once again.

(NEOVIBE PCB from GEOFEX)

You saved my day

I was desperate! I knew it was around there. At first I thought it was C1 and C2 issue by touching them but then only C1 and after 2 days searching and thinking it is the PS (EH 18V DC EU, 500mA not regulated gives 24.4V) trying to filter LFO it with no success and then I hit the jackpot with your post on Q1 and Q13. Well my Q13 was already the 2N3904 but the Q1 wasn't. When I checked the scheme then the "light bulb" came up ohh yes it must be it since it is connected to C1 and R3 R4 circuit. Good I bought more of those 2N3904 so switched it and viola the sound of noise is gone all thou not completely but much much less. Now I assume that that 2N5088 are much worse than 2N3904 and probably would be best altogether not using them. Maybe I try to change the Q2 as well and see if the noise goes completely away.

Many thanks to Blueserik. Cheers to you.

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Neovibe oscillation noise