Faint high pitched whine with M15 and/or AFG

Cwejman, Livewire, TipTop Audio, Doepfer etc... Get your euro on!

Moderators: Joe., lisa, luketeaford, Kent

Post Reply
User avatar
dougcl
Number 6
Posts: 4040
Joined: Sat Jul 26, 2008 3:04 am
Location: Portland OR

Faint high pitched whine with M15 and/or AFG

Post by dougcl » Sat Dec 06, 2008 3:23 am

Hi folks, I noticed that the M15 and/or AFG cause a faint whine in the rack. If either one or both is installed, the sound is noticeable, and present when they are set at a higher freq. The pitch of the whine moves with the freq of the osc's. I took out two A-111's to make room, and prior to that there was no problem. Is it normal?

Thanks,
Doug

User avatar
consumed
International Filter Conspiracy
Posts: 3698
Joined: Fri May 25, 2007 1:38 pm
Location: nor cal

Post by consumed » Sat Dec 06, 2008 3:41 am

yes, ive experienced something similar. from which output jack exactly are you hearing the high pitch? does the pitch change when you adjust either your m15 or your afg?

User avatar
Kent
Large Member
Posts: 11801
Joined: Thu Mar 06, 2008 10:17 am
Location: Vienna, Austria

Post by Kent » Sat Dec 06, 2008 4:22 am

As an experiment, it would be interesting to see if the whine disappeared if you pull the module out just far enough so that it was not longer touching the rack. Leave it plugged in and patched so that you can hear the noise at first and then 'unground' the module faceplate by lifting it away from the chassis by about 2 mm.

Whatcha get?

User avatar
3vcos
Must have slack/modules
Posts: 884
Joined: Sat Nov 15, 2008 11:40 pm
Location: I don't know.

Post by 3vcos » Sat Dec 06, 2008 5:01 am

You know you can't put VCOs near the power supply right?

alex82
Learning to Wiggle
Posts: 35
Joined: Mon Dec 01, 2008 5:29 pm

Post by alex82 » Sat Dec 06, 2008 7:59 am

I have no problems with my M15. I think thats not normal

User avatar
spbaker
Veteran Wiggler
Posts: 705
Joined: Sun Jun 15, 2008 6:15 pm
Location: melbourne australia

Post by spbaker » Sat Dec 06, 2008 9:37 am

welcome to the wonderful world of crosstalk!
i spent five or six hours the other night pulling my case apart trying different power distro set ups and spots in the case for the vco's to fix this but to no avail.
the M15 seems more vulnerable to this even powering it off a plan b protected power supply. this is how i understand crosstalk works: a VCO is a pos surge in power, (eg it sucks the power up) then it has a neg surge in power which makes the power supply on the distro boards peak and dip causing power supply issues to the other modules being powered off the same supply, this fluctuation on the rails is what is causing the whine/interference. daisy chaining distro boards can exacerbate the issue so you can try running the modules off of separate distro boards coming directly from the power supply, or ideally have them powered from sep supplies.
my AFG doesn't seem affected but it def affects the M15 as does the A110.
i'm just having to live with it for the mo, luckily most of the stuff i'm making is so noisy its kinda hidden in the mix.....
new DVD out now Fracture
things to listen to and look at:
http://abreojos.net

User avatar
BananaPlug
Super Deluxe Wiggler
Posts: 2582
Joined: Wed Dec 05, 2007 10:37 pm
Location: PHL USA

Post by BananaPlug » Sat Dec 06, 2008 10:33 am

Empty the rack, add a simple mixer module, patch that into your amp. Don't patch anything into the inputs. Try each of the M15 an AFG and and A110 one at a time (just one oscillator and the mixer) with the amp cranked up. Sweep the frequency up and down manually, play with the PWM pot. This should at least narrow down the source. If it's an interaction thing then you need to try out each possible pairing of oscillators. Next I'd try writing to the makers telling them exactly how you tested and see if they can suggest something. If they can reproduce the problem they'll want to fix it.

Plan B
banned 4 repeated baseless legal threats
Posts: 284
Joined: Tue Dec 02, 2008 11:44 am

Post by Plan B » Sat Dec 06, 2008 10:38 am

Why is this happening?

It's not the M15, it's not AFG. It's the Doepfer, Analogue Solutions and Analog Systems power rails. All of them daisy chain the ground. This is a potentially problematic system as some of you have witnessed.

This means that any noise which backs into the buss - noise from LEDs, from PWM circuits - things of this nature which are known for these types of problems will transmit these artifacts down the ground line of the busboard. ANnything that's connected downthe line will pick it up. This is why Dieter recommends you put VCOs and things which are sensitive to this (actually, it's things which have audio outputs) towards feed end of the busboards, because it limits this transmission (the further down the line, the more accumulative daisychaining, the higher the potential for this issue)

A second problem is some of the manufacturers who make Euro gear do not incorporate the types of safeguards which can prevent these sorts of things. I've seen very hot signals floating around modules. Op amps which are dealing with signals which are very close if not to the power rail amplitude in TLO series op amps. This is not dangerous (you willnot shock yourself or anything like that) Not electrically, but sonically dangerous. As a rule, one should not push a TLO series Op Amp greater than about two volts under its power rail. This means signals no louder than 10 volts in a 12 powered system.

As a note, there's a bit of distortion out there for the recommended corrective action. It matters not where you place the module in the rack, it matters where it's getting it's power feed - which position on the buss. the closer to the large wires which come off the buss to the PSU, the better as far as noise isolation.

If we ever make cases (cough cough), each and every buss conection is gong to have it's own path to ground. While i's perfectly OK to daisy chain the power, the grounds a problematic.

I hope this helps.

- P

User avatar
consumed
International Filter Conspiracy
Posts: 3698
Joined: Fri May 25, 2007 1:38 pm
Location: nor cal

Post by consumed » Sat Dec 06, 2008 1:12 pm

in my particular case, the source of the high frequency was my AFG and it was present at a filter output that nothing was plugged into (it was sitting next to my AFG). and it only happened when the AFG was running at very high frequency. i couldnt find the crosstalk surface anywhere else.

User avatar
dougcl
Number 6
Posts: 4040
Joined: Sat Jul 26, 2008 3:04 am
Location: Portland OR

Post by dougcl » Sat Dec 06, 2008 2:16 pm

Hi guys, this is all very helpful. If it is a grounding related issue due to the bus architecture, I'm wondering if it wouldn't help to run ground wires to each ground terminal on the busboard back to the power supply. Currently I just have the one on each busboard.

I may spend the afternoon isolating modules, trying different combinations and re-reading the posts here.

Doug

User avatar
revmutt
Knutty For Knobs
Posts: 1040
Joined: Sat Dec 06, 2008 4:24 pm
Location: NYC

Post by revmutt » Sat Dec 06, 2008 5:07 pm

This is just what I need to hear right now..

I'm about to "man up" and try a non Doepfer case, adding my own bus boards and stuff. I already have had some nervousness about it despite having some common sense and experience.

TD

User avatar
dkcg
I pity the fool w/o enough VCAs
Posts: 9142
Joined: Mon Jul 14, 2008 12:35 pm
Location: LA

Post by dkcg » Sat Dec 06, 2008 6:02 pm

revmutt wrote:This is just what I need to hear right now..

I'm about to "man up" and try a non Doepfer case, adding my own bus boards and stuff. I already have had some nervousness about it despite having some common sense and experience.

TD
You're making your own busboards? :eek:

User avatar
consumed
International Filter Conspiracy
Posts: 3698
Joined: Fri May 25, 2007 1:38 pm
Location: nor cal

Post by consumed » Sat Dec 06, 2008 6:05 pm

dkcg wrote:
revmutt wrote:This is just what I need to hear right now..

I'm about to "man up" and try a non Doepfer case, adding my own bus boards and stuff. I already have had some nervousness about it despite having some common sense and experience.

TD
You're making your own busboards? :eek:
im about to do the same thing for my expansion cabinet, using stripboard.

User avatar
wetterberg
Super Deluxe Wiggler
Posts: 7673
Joined: Thu Jul 24, 2008 5:31 pm
Location: Copenhagen, Denmark.

Post by wetterberg » Sat Dec 06, 2008 9:17 pm

busboards are hella easy!

User avatar
dougcl
Number 6
Posts: 4040
Joined: Sat Jul 26, 2008 3:04 am
Location: Portland OR

Post by dougcl » Sat Dec 06, 2008 9:24 pm

wetterberg wrote:busboards are hella easy!
Seriously, of all the DIY projects this has to be the simplest. Why haven't I done it? I guess $90 at AH for a pair of busboards is cheap enough.

I found the source of the M15 whine... pretty sure it's due to it being near a reverb tank. Not sure what the deal is with the AFG though. I installed additional ground wires between the busboard an the power supply, so now there are three: one at each end and one in the middle. Didn't seem to make much difference. Removing all the other modules from the buses didn't make any difference either. The only thing that made a difference was unplugging the reverb tank, and that was only for the M15.

User avatar
dougcl
Number 6
Posts: 4040
Joined: Sat Jul 26, 2008 3:04 am
Location: Portland OR

Post by dougcl » Sat Dec 06, 2008 9:33 pm

Kent wrote:As an experiment, it would be interesting to see if the whine disappeared if you pull the module out just far enough so that it was not longer touching the rack. Leave it plugged in and patched so that you can hear the noise at first and then 'unground' the module faceplate by lifting it away from the chassis by about 2 mm.

Whatcha get?
No difference at all.

User avatar
revmutt
Knutty For Knobs
Posts: 1040
Joined: Sat Dec 06, 2008 4:24 pm
Location: NYC

Post by revmutt » Sat Dec 06, 2008 9:49 pm

dkcg wrote:
revmutt wrote:This is just what I need to hear right now..

I'm about to "man up" and try a non Doepfer case, adding my own bus boards and stuff. I already have had some nervousness about it despite having some common sense and experience.

TD
You're making your own busboards? :eek:
I bought the Doepfer busboards. I'm just going with a generic rack and a power supply and hoping I don't fry anything.

User avatar
dougcl
Number 6
Posts: 4040
Joined: Sat Jul 26, 2008 3:04 am
Location: Portland OR

Post by dougcl » Sat Dec 06, 2008 10:30 pm

I think the main thing to remember is that even though your switch might be off, there might still be power to the rack upstream of the switch. Just always unplug the power before you stick your hand in there. At least that will keep you safe. You can also use a voltmeter on the case or anything else you might be thinking about touching before you touch it, just to make sure you haven't got 110AC where you shouldn't.

User avatar
revmutt
Knutty For Knobs
Posts: 1040
Joined: Sat Dec 06, 2008 4:24 pm
Location: NYC

Post by revmutt » Sat Dec 06, 2008 11:06 pm

Based on my experience with Moog power supplies I am assuming that once the bus boards are mounted (insulated of course) and connected to the power supply I can simply measure with my meter that I am getting a +12/-12 and know whether I am good to go.

Whether or no I will have to do some sort of additional grounding to the case, I don't know but will open up a G6 and see what it looks like and use that as my model.

User avatar
dougcl
Number 6
Posts: 4040
Joined: Sat Jul 26, 2008 3:04 am
Location: Portland OR

Post by dougcl » Sat Dec 06, 2008 11:10 pm

Yeah just measure a lot as you go, and you should be fine. Having a G6 to look at should make it a no brainer.

Post Reply

Return to “Eurorack Modules”