Ace 250 faint high pitch sound

[Ren]

I have a Ace 250 that I have barely used. I am getting a faint high pitched sound coming from the detector. I unplugged the coil and it goes away. It happens with coiled connected. It is really faint. Is this normal? Thanks.

[SouthFLdigger]

Sounds like a capacitor in the circuit. My Ace 150 does the same.

[Ren]

Is this something that I should be worried about or affect the detector you think?

[flgliderpilot]

I would not be worried about it ... sometimes components can make a high pitched whine.. is it coming from the unit or the coil itself?

[Ren]

From the Unit

[Anduril]

How young are you? (no need to answer..)
My guess is you are hearing the MD oscillator. If you're still young enough to have excellent hearing, you might be able to hear frequencies as high as 15 to 20 kilohertz.
As you get older (30+), it becomes much more difficult to hear high-pitched sounds. Even under 30 if you don't protect your hearing (guns, concerts, headphone volume too high, etc..)
Old analog TV sets used to have a horizontal line rate of about 15,750 Hz that you could hear "whine" on some models. Without even looking, you could tell if someone turned on the TV.
This would have been the 1970's / 80's and earlier.

Check your coil connections (wiggle them at both ends) to see if the amplitude changes (i.e., louder or softer).
If so, then verify you're making good contact. Otherwise, you could have a loose ground or shield somewhere in the electronics section.
It may also just be a design issue, and you just never noticed it before.
Either way, if it is the oscillator, I doubt it would really affect the Ace 250's operation.

One other "possible" explanation is that something EXTERNAL is interfering with your detector.
By this, I mean strong external radio-frequency fields (like from a nearby AM/FM Station, etc..).
This is particularly likely if you're hearing music or some other program audio, but less likely if it's just a steady, high-pitched whine.

Another possibility is the Ace 250's audio amplifier is oscillating.
You might be able to rule this in/out by seeing if the noise goes away at lower volume settings.
It's not conclusive, but many audio amps tend to oscillate 'only' when they are at or near maximum volume.
Though some designs never oscillate, and some are so bad they may as well be oscillators (not amplifiers).
BTW: An audio amp can both oscillate and amplify sound at the same time.
It's not quite analogous to "runaway" oscillation (squeal) like you might hear if you placed a microphone in front of a working speaker (amplifying the mic).

[Phantasman]

How young are you? (no need to answer..)
My guess is you are hearing the MD oscillator. If you're still young enough to have excellent hearing, you might be able to hear frequencies as high as 15 to 20 kilohertz.
As you get older (30+), it becomes much more difficult to hear high-pitched sounds. Even under 30 if you don't protect your hearing (guns, concerts, headphone volume too high, etc..)
Old analog TV sets used to have a horizontal line rate of about 15,750 Hz that you could hear "whine" on some models. Without even looking, you could tell if someone turned on the TV.
This would have been the 1970's / 80's and earlier.

Check your coil connections (wiggle them at both ends) to see if the amplitude changes (i.e., louder or softer).
If so, then verify you're making good contact. Otherwise, you could have a loose ground or shield somewhere in the electronics section.
It may also just be a design issue, and you just never noticed it before.
Either way, if it is the oscillator, I doubt it would really affect the Ace 250's operation.

One other "possible" explanation is that something EXTERNAL is interfering with your detector.
By this, I mean strong external radio-frequency fields (like from a nearby AM/FM Station, etc..).
This is particularly likely if you're hearing music or some other program audio, but less likely if it's just a steady, high-pitched whine.

Another possibility is the Ace 250's audio amplifier is oscillating.
You might be able to rule this in/out by seeing if the noise goes away at lower volume settings.
It's not conclusive, but many audio amps tend to oscillate 'only' when they are at or near maximum volume.
Though some designs never oscillate, and some are so bad they may as well be oscillators (not amplifiers).
BTW: An audio amp can both oscillate and amplify sound at the same time.
It's not quite analogous to "runaway" oscillation (squeal) like you might hear if you placed a microphone in front of a working speaker (amplifying the mic).

Good call. He could unplug the coil during the event to make sure it's not a sloppy output signal to the coil causing the ultrasonic's. Dogs can hear as high as 45 khz. Humans about 25khz. Detectors are usually transmitting mhz. But sloppy is usually all over the sound spectrum. And frequencies are at play with a MD.

[Ren]

Thanks for the answers guys. I'm 29. Yeah I couldn't remember if I heard this sound when I first got the detector. I'm pretty sure it didn't make this sound when I first got it. But as long as I know it doesn't affect the detector while detecting. Love the support, thanks again!

[Anduril]

Just to correct something earlier in the thread, so as not to confuse future readers:

Metal Detector oscillators are usually in the 5 to 20 kHz range. (That's kilohertz, not megahertz).
This is in the range of normal human hearing.

I think the Ace 250 is a single-frequency design at 6.25 kHz, adjustable in very small steps.
I don't own a 250, so just going by what I read online.
So, the third harmonic (i.e., a fairly reliable indication of an amplifier in oscillation) would be 18.75 kHz, which would indeed be a high-pitched whine.

[mick56]

My 250 has made the same whine for the 10 years I have used it. I'm twice as old as you, and I can hear it. I doubt if it's anything to worry about.

[flgliderpilot]

Actually thinking back, my 350 did it also.