What's making this noise? Please help me figure it out!

[Thebrainless]

Hi everyone!
I've encountered a big problem that I can't solve by myself.
I need to start telling you it's not stompbox related, but it's about an "alternative" source of power for my active bass.
Long story short, my bass devours two 9V batteries in a couple of months, so I decided to go recheargable using a lithium battery from an "old" smartphone.
I've bought a charging circuit for lithium batteries (with overcharge protection, and all the other safety functions) and a step up dc-dc converter, 'cause the battery is 3.8V 3000 mah, taking it to 18V I got around 600 mah (more or less what normal batteries provide) so I should be all set.
I've made all my soldering, everything works and the readings are ok, 18V are coming out of the dc-dc converter and feeding my baby bass, that unfortunately has become a noise machine, the signal to noise ratio is like 1:1.
When I use normal 9V batteries it's almost dead silent even with all the potentiometers cranked up, nothing, now with this lithium battery it's basically unusable.
What did I do wrong? Am I missing something? Is there some kind of extra ground connection to be made? Should I simply give up the lithium battery idea and stick to disposable ones?
I've successfully put a lithium battery inside a boss odb3, making it a power supply for other pedals too, and got no issues, no extra noise added when using it.
Now why is the same circuit acting differently on a bass?
I've already tried to change the circuits, maybe there was a faulty one, but still got the same results.
I've made a video so you can hear and "see" the noise I'm talking about, here it is

I hope I'm not off topic 'cause I don't know where else to ask for help with this!
Thanks to anyone willing to help!

[FiveseveN]

Am I missing something?

Do you know how step-up converters work in general and what configuration yours uses in particular? Do you have a scope?

[DIY Bass]

How shielded is the new circuitry?  I would think that some of the oscillation in the converter would be leaking into the audio amp. It would need to be well shielded I would think, with a well grounded shield.

[GibsonGM]

Hi Brainless, welcome. there are a lot of sharp people in here with decades of combined power design experience, so I think you'll get some good advice once they see the post.

Can you post a schematic of what you have?  A pic of exactly what your setup is?  For instance - is this unit all installed in the bass yet, or is it on the desktop?  Is there any kind of shielding around the electronics?  Are you near a PC/laptop when you get this noise?  Near any transformers, ANY sort of noise-making equipment?  The more info the better.

I suspect it's the converter, too, maybe harmonics of the switching frequency down in the audio spectrum.  Proper shielding would be a way to potentially fix this; the more you amplify, the more you amplify any noise present, too! 

[aleks_tedstone]

It sounds like broadband noise (either white or pink) and your spectrum analyser doesn't seem to be showing any distinct peaks, leading me to agree with all the previous comments about shielding. If your step-up converter has an inductor in it, this will bring all the environmental electromagnetic noise into your power supply, which can then leak through to the audio path.

If this is the case (I might be wrong):
The most rigorous way to remove noise is to prevent it getting into your circuit in the first place, ie. proper grounded shielding around the converter and other active electronics in your bass.

The next best thing would be to prevent the noise getting from the power supply into the audio signal, and we would need more details about the design of your step-up converter for this. If you look at the schematic of most modern pedals (not fuzz pedals!) then you will see a variety of passive components are normally configured as filters to remove power supply noise before it powers op-amps, transistors, ICs etc.
If the converter itself is generating the noise, filtering may still be possible. The DC voltage is not as consistent as a battery, it often oscillates a little bit around the target voltage to give you 9V+/- a few mV at any given moment.

Its possible that when you did this modification to your Boss ODB3, placing it inside the metal housing of the pedal provided enough shielding to remove audible hiss.

[anotherjim]

my bass devours two 9V batteries in a couple of months

This shouldn't be unless you play 24/7. Do you remember to take the jack plug out of the bass when not playing? Usually, that automatically switches the batteries off.

[aleks_tedstone]

my bass devours two 9V batteries in a couple of months

This shouldn't be unless you play 24/7. Do you remember to take the jack plug out of the bass when not playing? Usually, that automatically switches the batteries off.

Jim taking a pencil into space while everybody else tries to design the zero-G pen...

Also you can buy rechargeable 9V batteries!

P.S. I know how incorrect the story about NASA and Soviet writing technology is, but it's a good allegory.

[Thebrainless]

Thanks everyone for answering!
So let me answer back at my best...
I'm just a noob when it comes to electronics and circuits in general, I can solder, but I don't know the basics for creating a working circuit of any kind, so I simply watched a couple of videos and read infos here and there and thought I could make this thing easily.

Do you know how step-up converters work in general and what configuration yours uses in particular? Do you have a scope?

I don't know how they work and I don't have a scope, the only info I can give you is the actual amazon link to the ones I've bought ( http://www.amazon.it/gp/product/B071H9NRTW ).

How shielded is the new circuitry?  I would think that some of the oscillation in the converter would be leaking into the audio amp. It would need to be well shielded I would think, with a well grounded shield.

The new circuit isn't shielded in anyway, 'cause I simply didn't know you're supposed to shield such circuits and I don't really know how to shield it aniway, 'cause I'm a gigantic noob that watches youtube videos of people doing things the wrong way, I guess 

Hi Brainless, welcome. there are a lot of sharp people in here with decades of combined power design experience, so I think you'll get some good advice once they see the post.

Can you post a schematic of what you have?  A pic of exactly what your setup is?  For instance - is this unit all installed in the bass yet, or is it on the desktop?  Is there any kind of shielding around the electronics?  Are you near a PC/laptop when you get this noise?  Near any transformers, ANY sort of noise-making equipment?  The more info the better.

I suspect it's the converter, too, maybe harmonics of the switching frequency down in the audio spectrum.  Proper shielding would be a way to potentially fix this; the more you amplify, the more you amplify any noise present, too! 

I don't have a schematic, I just put together 2 circuits bought on Amazon thinking they'll just work, 'cause I'm a noob, so if you wanna I can give you the link to the charging circuit (the dc-dc step up converter is the one I've already linked) http://www.amazon.it/gp/product/B0859W9LMB
I've installed everything in my bass, the circuits in the battery cavity, which has no shielding whatsoever, and the battery in the potentiometers cavity, which should be shielded since the back of its cover is covered with aluminum foil.






The noise was always there, didn't change if I move away from the pc, or the amplifier, or anything, my setup has always been dead silent, bass preamp + power amp + 4x10 cabinet, not even bad ground noise, now this costant noise came to ruin everything

It sounds like broadband noise (either white or pink) and your spectrum analyser doesn't seem to be showing any distinct peaks, leading me to agree with all the previous comments about shielding. If your step-up converter has an inductor in it, this will bring all the environmental electromagnetic noise into your power supply, which can then leak through to the audio path.

If this is the case (I might be wrong):
The most rigorous way to remove noise is to prevent it getting into your circuit in the first place, ie. proper grounded shielding around the converter and other active electronics in your bass.

The next best thing would be to prevent the noise getting from the power supply into the audio signal, and we would need more details about the design of your step-up converter for this. If you look at the schematic of most modern pedals (not fuzz pedals!) then you will see a variety of passive components are normally configured as filters to remove power supply noise before it powers op-amps, transistors, ICs etc.
If the converter itself is generating the noise, filtering may still be possible. The DC voltage is not as consistent as a battery, it often oscillates a little bit around the target voltage to give you 9V+/- a few mV at any given moment.

Its possible that when you did this modification to your Boss ODB3, placing it inside the metal housing of the pedal provided enough shielding to remove audible hiss.

Now that you mentioned it, the ODB3 was noisy at first with the battery and the circuits inside, but not like the bass, it was a more constant hiss around 5khz that kinda modulated if I touched the converter, then went away as soon as I've turned the ODB3 in a power supply for other pedals (simply shorted pin 2 and 3 on the PSU socket, so it's no longer a power input but a power output) and plugged another pedal to it, so I guess the noise issues in that case were solved by adding another pedal to the equation, maybe it acted like an extra ground? I don't know, I didn't bother to find out in this case 'cause I'll be using both pedals while playing anyway, so...

my bass devours two 9V batteries in a couple of months

This shouldn't be unless you play 24/7. Do you remember to take the jack plug out of the bass when not playing? Usually, that automatically switches the batteries off.

I always unplug the jack from the bass, even when we make like 5 minute breaks during rehearsals
I know it shouldn't devour them so fast, but still it did , 2 batteries lasted 2 months playing like 2 hours a day, 2 days a week, so let's say around 36 hours total in 2 months, I measured the current drawn by the preamp circuit, it's around 16.5 mah with the jack plugged in, and 0 with the jack unplugedd, there's no issues with its preamp circuit, by the search I've made online it appears to be a common issue with this bass, which has been in some way solved with later versions by changing the preamp circuit.
So it's 16,5 mah x 36 hours = 594 ma , which is what a common 9V battery provides more or less.
Oh, the bass' a Peavey Millennium AC BXP by the way.

my bass devours two 9V batteries in a couple of months

This shouldn't be unless you play 24/7. Do you remember to take the jack plug out of the bass when not playing? Usually, that automatically switches the batteries off.

Jim taking a pencil into space while everybody else tries to design the zero-G pen...

Also you can buy rechargeable 9V batteries!

P.S. I know how incorrect the story about NASA and Soviet writing technology is, but it's a good allegory.

I really don't get this comment...
Rechargeable 9V batteries aren't the best solution IMHO, they don't deliver the full 9V, it's always 8.75 or something like that, plus I wanted to make something with the lithium batteries laying around here, I like tinkering with stuff and learn something new in the process, so had this idea...

I hope I've provided enough infos to understand what's causing the noise and how to solve this, most of you wrote about shielding, so what should I exactly do now?
Thanks a lot!!!!

[GibsonGM]

Yes, 9V rechargeables can be a pain, not the full 9V (most of my regular 9V don't read that, LOL)....but you avoid the boost circuit, which uses switching to jack up your voltage.   That switching represents "ON OFF ON OFF", meaning a current is drawn, then stopped, then drawn etc...very very rapidly.  This switching current causes an EMF around the wires it's associated with...this can couple into nearby wires and circuits, causing a whine, hum, noise...the switching frequency is generally much higher than 20kHz, the limits of human hearing, but harmonics from it can be heard.  That may be your problem, without the shielding (and sometimes with it).   There is a whole field of study in making this stuff quiet!

Get the wiring perfect, then dig into the shielding...I do all of my guitars with foil, and my single coil strats/tele's are quiet as can be (weren't before).  I think the switch box could benefit from it, but HOW to do it so it's not terrible...?   But the rest of your bass could use it as well, appears the control compartment isn't shielded.   Has to be foil-lined, the WHOLE thing, incl. the cover, and all parts must make contact.  Do a net search before we all talk about it

[R.G.]

You also need to be prepared for some intense learning. It is tough to get any switching power supply to power low signal audio equipment without introducing noise, so you've accidentally picked a tough first project.

Switching power supplies switch the entire power on and off at ultrasonic or RF freuqencies, so they're perfectly suited to make and broadcast RF noise by conduction and by radiation. The comments you got about shielding and filtering are a reflection of this concept. Switching power noise is bad enough that the exact placement of every PCB trace and the location (physical and electrical) of every wire going to and from the power supply can make a difference in noise.

I say this to prepare you - it may not be only one thing, and it may not be easy. So look at it as a challenge, and go learn, learn, learn. It won't kill you, and it will definitely make you more knowledgeable and therefore stronger. 

[Thebrainless]

Get the wiring perfect, then dig into the shielding...I do all of my guitars with foil, and my single coil strats/tele's are quiet as can be (weren't before).  I think the switch box could benefit from it, but HOW to do it so it's not terrible...?   But the rest of your bass could use it as well, appears the control compartment isn't shielded.   Has to be foil-lined, the WHOLE thing, incl. the cover, and all parts must make contact.  Do a net search before we all talk about it

So I did my homework, serched the web, saw videos and stuff, here's the results:
I've shielded the battery cavity, nothing changed, the noise was still there as before.



Ok, it wasn't beautiful to watch, but I can assure you there was continuity all over the cavity shielding and in the cover too, so...
Oh, another thing, the control compartment seems to be shielded with shielding paint and the cover with aluminum foil, so the problem should be elsewhere...but where? 

You also need to be prepared for some intense learning. It is tough to get any switching power supply to power low signal audio equipment without introducing noise, so you've accidentally picked a tough first project.

Switching power supplies switch the entire power on and off at ultrasonic or RF freuqencies, so they're perfectly suited to make and broadcast RF noise by conduction and by radiation. The comments you got about shielding and filtering are a reflection of this concept. Switching power noise is bad enough that the exact placement of every PCB trace and the location (physical and electrical) of every wire going to and from the power supply can make a difference in noise.

I say this to prepare you - it may not be only one thing, and it may not be easy. So look at it as a challenge, and go learn, learn, learn. It won't kill you, and it will definitely make you more knowledgeable and therefore stronger. 

Oh I'm ready to learn and dig deep, I thought this project would be an easy one, once again a noob thought!
Since shielding didn't work, what about filtering? I know nothing about it, so...

BTW, I've found something that could help, but I wasn't able to find an exact schematic:
There are Warwick basses that come with lithium battery and mini-usb charging socket right off the factory, those are the Masterbuilt Custom Shop ones, here's the explaination

I've managed to find the spare PCB from Warwick shop, but I'm not spending the 125 euros of course
https://shop.warwick.de/en/pickups/accessories-parts/bass-electronics/22064/warwick-parts-charger-pcb-for-rechargeable-lithium-battery

So, as I wrote before, I couldnt find the schematics for that PCB anywhere, Warwick gives just the preamp and the wiring ones, nothing else.
It'd be great to see what they put in it and how they managed to solve the noise problem (if they ever got one building this).
I'll keep searching, but unless there's some owner willing to share photos, I don't think I can find any specific infos

[Thebrainless]

Further research led me to understand that charging board isn't from Warwick but it's Fishman's, apparently they got the license to use it or something, still no schematics anyway, but buying one now costs around 98 euros, still not doing it though.
I got 1 and a half more days to figure this out (rehearsal day), otherwise I'll be back to disposable 9V batteries, but I'm not giving up anyway!

[iainpunk]

have you tried a filtering cap and a low value resistor between the power supply and the active circuitry? a bit of power supply filtering cant do harm iirc

cheers

[Thebrainless]

have you tried a filtering cap and a low value resistor between the power supply and the active circuitry? a bit of power supply filtering cant do harm iirc

cheers

Yep, been there done that, didn't work
I've also switched the battery, but the other one (a standard 18650 lipo) once connected made the bass "scream", there was a constant feedback like high pitched scream plus the usual noise, I really don't know why, I'm starting thinking the charging circuit might be responsible somehow...

[iainpunk]

are the batteries you use the ones th charger was designed for?
13650 cells are rated at a different nominal voltage (lower) than phone batteries. is it maybe that you use a too-low voltage battery here?

cheers

[Thebrainless]

are the batteries you use the ones th charger was designed for?
13650 cells are rated at a different nominal voltage (lower) than phone batteries. is it maybe that you use a too-low voltage battery here?

cheers

I'm using a phone battery and this circuit is made for any lithium battery from 3.7V to 6V, everything works fine, the battery fully charges and the step up booster gives an output of 18V, it's all working, except this damn noise coming from who knows where 

[Thebrainless]

So, somebody suggested to add a zener diode to eliminate output ripple....
Any idea how and where should I do this? 

[DIY Bass]

It doesn't look to me as if you have really done shielding - at least not what I had in mind.  The charging PCB and the dc-dc converter need to be individually shielded from everything else.  They need to be in metal conductive containers that don't short out anything on the boards, and which are themselves connected to ground.  It is not enough just to have the cavities shielded.

[Thebrainless]

It doesn't look to me as if you have really done shielding - at least not what I had in mind.  The charging PCB and the dc-dc converter need to be individually shielded from everything else.  They need to be in metal conductive containers that don't short out anything on the boards, and which are themselves connected to ground.  It is not enough just to have the cavities shielded.

You really think the noise comes from not shielding the circuits?
On the Warwick bass doesn't seem there's that much shielding, I can try anyway of course...
Do you think using a can (like a coke one) to create each individual shielding would work? Otherwise what should I use?
I don't really think this shielding thing might solve this problem, cause on the odb-3 the shielding might be the pedal itself ok, but when I took the circuits out of it there's still no noise... Or maybe it's the battery that needs shielding? Cause in the odb-3 again the battery stays inside all the time, underneath the pedal circuitry, but from what I can remember even with everything exposed there was no noise.
I don't know, I guess I'll try this individual shielding of both circuits, any suggestion on how to do it?

[GibsonGM]

"...That switching represents "ON OFF ON OFF", meaning a current is drawn, then stopped, then drawn etc...very very rapidly.  This switching current causes an EMF around the wires it's associated with...this can couple into nearby wires and circuits, causing a whine, hum, noise...the switching frequency is generally much higher than 20kHz, the limits of human hearing, but harmonics from it can be heard.   That may be your problem, without the shielding (and sometimes with it).   There is a whole field of study in making this stuff quiet!"


ANY part of that bass that's involved in the electronics that isn't shielded can have noise coupled into it, leading to the hiss...one way to shield the battery is a metal battery box that is grounded.  The power wires would need to be shielded too if they pass thru a 'blank' spot inside the bass.  The controls, the pickups...all shielded.    Foil will work, and work well, if done properly.  All parts must be continuous, and the foil is grounded - but as said, whatever circuit you're putting inside doesn't short to it.    There are probably many videos on this on Youtube.     I've used spray adhesive to line cavities successfully.

Then you want to look at some form of 'star grounding' (another topic) to ensure how everything grounds...to 1 point only.  So you don't get noise coming back on the ground line.    This isn't a trivial or easy project, as I'm sure you're finding out!   Nor one that someone can easily just 'tell you how to do it'...which is why the 9V battery is so popular...