..that's the neovibe, not me, although I guess this is a whine of sorts :icon_biggrin:
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?
That's a new one. Congratulations - you have a disease we don't yet have a name for. :icon_eek:
I wonder if it's the voltage regulator oscillating. Is your build completely stock? Modified? On a pre-etched board? Perf?
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
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 (http://picasaweb.google.com/ipitythecrazyfool/UntitledAlbum/photo#5047090078423473778)
Quotehere'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?
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.
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.
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.
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.
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?
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...
ok - sorry :icon_redface:. 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 ;)
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.
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?
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.
Yep, see above.
QuoteSo, 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? :icon_biggrin:
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!
Laptop power supplies are NOT designed to supply clean power to audio pedals.
It's highly likely that this is your whining problem.
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?
Quote from: R.G. on April 02, 2007, 09:16:37 AM
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. :icon_smile:
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).
Quote from: 3/4 North on April 02, 2007, 09:44:54 AM
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.
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.
Quote from: Torchy on April 02, 2007, 10:43:18 AM
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....
QuoteI 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
Quote from: R.G.Laptop power supplies are NOT designed to supply clean power to audio pedals.
Quote from: axg20202It 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.
Quote from: R.G. on April 02, 2007, 11:01:35 AM
QuoteI 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.
Quote from: R.G. on April 02, 2007, 11:01:35 AM
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.
Quote from: R.G. on April 02, 2007, 11:01:35 AMThere 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.
...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.
QuoteI'm not completely thick and I appreciate your help. I was merely trying to inject a bit of humour.
No offense intended or taken.
QuoteI 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.
QuoteIf 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.
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?