Markbass CMD121P high pitched noise when operating

[Bright Midnight]

Hey guys,

What could be causing the Markbass CMD121P to start having a high pitched 'whine' when operating? Could this be a faulty fan?


Thanks!

 

[Bright Midnight]

*BUMP*

 

[Sparky Mark]

The piezo tweeter in this combo is always on and has been known to annoy some owners at lowish practice volumes as it does hiss a fair bit. Never bothered me at gigs though.

 

[Jeff Scott]

Does the noise go away when you put earplugs in?

 

[Phaidrus]

Hey guys,

What could be causing the Markbass CMD121P to start having a high pitched 'whine' when operating? Could this be a faulty fan?


Thanks!

Could be, if the bearings of the fan are done. You could try determine the source of this noise; just stick your ear next to the fan at the back of the head. You may have to remove the head from the cab (4 screws) to gain better access to it. If you do so, be careful!! It has no lid, so don't touch anything inside the head and get electrocuted! If it is indeed the fan making this noise, you have to remove the entire pcb to be able to replace it.

 

[Bright Midnight]

Guys, here's a clip of the sound the head makes when operating - without the fan coupled.

Could be, if the bearings of the fan are done. You could try determine the source of this noise; just stick your ear next to the fan at the back of the head. You may have to remove the head from the cab (4 screws) to gain better access to it. If you do so, be careful!! It has no lid, so don't touch anything inside the head and get electrocuted! If it is indeed the fan making this noise, you have to remove the entire pcb to be able to replace it.

Well, we got the head out, uncoupled the fan, yet the noise remained. We also discovered that the noise stops when unplugging the speaker. We then plugged in a Mesa 115 cab and the noise returned, yet slightly less loud....then we plugged the 112 speaker back in, and the noise was there again...strange strange strange...

 

[Phaidrus]

Guys, here's a clip of the sound the head makes when operating - without the fan coupled.


Well, we got the head out, uncoupled the fan, yet the noise remained. We also discovered that the noise stops when unplugging the speaker. We then plugged in a Mesa 115 cab and the noise returned, yet slightly less loud....then we plugged the 112 speaker back in, and the noise was there again...strange strange strange...

I suppose it's time to send it to the Markbass service. Is it still under warranty?

Had a look on the MB website and this is what I found for Belgium:

 

[Sparky Mark]

Guys, here's a clip of the sound the head makes when operating - without the fan coupled.


Well, we got the head out, uncoupled the fan, yet the noise remained. We also discovered that the noise stops when unplugging the speaker. We then plugged in a Mesa 115 cab and the noise returned, yet slightly less loud....then we plugged the 112 speaker back in, and the noise was there again...strange strange strange...

It's that pesky piezo tweeter I'll bet. It is loud enough for a few owners to disconnect permanently or replace with a Monacor HT-30 miniature horn.

 

[Bright Midnight]

It's that pesky piezo tweeter I'll bet. It is loud enough for a few owners to disconnect permanently or replace with a Monacor HT-30 miniature horn.

Is there a way to permanently disconnect the tweeter on a CMD 121P?

 

[MarkA]

Guys, here's a clip of the sound the head makes when operating - without the fan coupled.


Well, we got the head out, uncoupled the fan, yet the noise remained. We also discovered that the noise stops when unplugging the speaker. We then plugged in a Mesa 115 cab and the noise returned, yet slightly less loud....then we plugged the 112 speaker back in, and the noise was there again...strange strange strange...

Browsing on my phone just now, I don't see a clip of the sound to play.

If the sound you're talking about is the usual high-frequency static/hiss emitted to varying degrees by most amps, it makes sense that it would show up more in some cabs than others, as some are more and some less sensitive in that range.

If it is something else, as "whine" seems to imply, I'd investigate further - if there's an issue with the amp, you might cover it up by disconnecting the tweeter but you won't address the root cause.

I'm curious as to whether the level of the noise varies with gain and volume or whether it's fairly constant, even with those dialed down. Does it come through the DI as well? If you have another amp, it might be instructive to hook it up to the combo cab in place of the Combo Head.

Is there a way to permanently disconnect the tweeter on a CMD 121P?

As for disconnecting the internal tweeter, it can be done pretty easily - on my older, Italian-made CMD 121P combo, there isn't a "true" crossover - the woofer runs full range and the piezo is high-passed (and perhaps padded back).

There are some threads that discuss this as well as a mod some folks have performed, replacing the stock tweeter with a Monacor HT-30 horn - I had the mod done to mine, along with adding an on/off switch for the tweeter. Haven't yet played the amp that way at gig volume and am not yet ready to say it's a good idea, but I can confirm that, at home-practice volumes, output from the Monacor is lower than that of the stock tweet and that the impact of the tweet is more apparent off-axis than directly on.

Ditto for the stock tweeter - when I thought that there might be an issue with it (ended up being the amp, recently repaired) and tried running with it disconnected, the difference in high-frequency response between tweet/no tweet was more apparent off to the sides (where the woofer would start to beam higher frequencies more narrowly) than standing directly in front of the amp.

That said, the response with the tweeter disconnected might well be sufficient for you, depending on your tastes.

That said, I'd rule out other issues before modifying the amp.

(@Doner Designs was one of the folks to try the Monacor mod - he details his experience here: Markbass Tweeter Upgrade. How'd that end up working out long-term?)

 

[Bright Midnight]

Browsing on my phone just now, I don't see a clip of the sound to play.

If the sound you're talking about is the usual high-frequency static/hiss emitted to varying degrees by most amps, it makes sense that it would show up more in some cabs than others, as some are more and some less sensitive in that range.

If it is something else, as "whine" seems to imply, I'd investigate further - if there's an issue with the amp, you might cover it up by disconnecting the tweeter but you won't address the root cause.

I'm curious as to whether the level of the noise varies with gain and volume or whether it's fairly constant, even with those dialed down. Does it come through the DI as well? If you have another amp, it might be instructive to hook it up to the combo cab in place of the Combo Head.



As for disconnecting the internal tweeter, it can be done pretty easily - on my older, Italian-made CMD 121P combo, there isn't a "true" crossover - the woofer runs full range and the piezo is high-passed (and perhaps padded back).

There are some threads that discuss this as well as a mod some folks have performed, replacing the stock tweeter with a Monacor HT-30 horn - I had the mod done to mine, along with adding an on/off switch for the tweeter. Haven't yet played the amp that way at gig volume and am not yet ready to say it's a good idea, but I can confirm that, at home-practice volumes, output from the Monacor is lower than that of the stock tweet and that the impact of the tweet is more apparent off-axis than directly on.

Ditto for the stock tweeter - when I thought that there might be an issue with it (ended up being the amp, recently repaired) and tried running with it disconnected, the difference in high-frequency response between tweet/no tweet was more apparent off to the sides (where the woofer would start to beam higher frequencies more narrowly) than standing directly in front of the amp.

That said, the response with the tweeter disconnected might well be sufficient for you, depending on your tastes.

That said, I'd rule out other issues before modifying the amp.

(@Doner Designs was one of the folks to try the Monacor mod - he details his experience here: Markbass Tweeter Upgrade. How'd that end up working out long-term?)

Hey Mark, thanks for the reply, much appreciated! We disconnected the speaker and hooked up a Mesa Boogie with the tweeter almost turned down to zero. The noise was still there, but less profound....

The noise is consistent. No matter what knobs turned on or off the noise remains the same.

What I found strange was when we disconnected the Markbass speaker, the noise stopped completely. So it only appears when a cab is hooked on....

 

[MarkA]

Hey Mark, thanks for the reply, much appreciated! We disconnected the speaker and hooked up a Mesa Boogie with the tweeter almost turned down to zero. The noise was still there, but less profound....

The noise is consistent. No matter what knobs turned on or off the noise remains the same.

What I found strange was when we disconnected the Markbass speaker, the noise stopped completely. So it only appears when a cab is hooked on....

Well, to produce a sound that we can hear, the amp has to produce and transmit to us vibration through some medium (usually air). Barring something like a humming transformer (which physically vibrates), this usually requires a speaker to be hooked up to the amp (electrical noise then becomes amplified along with the musical signal from your instrument).

Depending on where in the signal chain the noise occurs, it might or might not be affected by EQ, Gain, or Master Volume controls.

Noise can have both mechanical and electrical components -- I had an amp with a noisy fan -- it produced an annoying, high-pitched whine mechanically (audible with no speaker connected) and electrically (noise from the fan motor was transferred to the cab and increased with turning up the volume control).

I've never had an amp that was completely immune to electrical noise -- the quietest I can recall were a couple of Glockenklang amps, and even those had some audible tweeter-hiss (though orders of magnitude lower than the musical signal) when turned up quite high -- but it's important to distinguish between the usual type and amount of "between radio stations" hiss and something else.

The (now repaired) head in my combo amp doesn't produce any unusual or distracting amount of noise whether plugged into the combo speaker or my other cabs with high-frequency drivers.

 

[woodworm_dan]

To the OP.

Did you ever get this thing sorted out? I'm having a very similar problem on a italian made LM250 head.

High pitch noise coming from inside the amp, even when no speaker is connected.

Anyone could help?

 

[MarkA]

To the OP.

Did you ever get this thing sorted out? I'm having a very similar problem on a italian made LM250 head.

High pitch noise coming from inside the amp, even when no speaker is connected.

Anyone could help?

Yeah, @Bright Midnight, how'd it turn out?

@woodworm_dan, your issue appears to be different in that there is noise when no speaker is connected, whereas @Bright Midnight's only happened with a speaker connected.

High-pitched noise from inside the amp -- my uneducated guesses: mechanical noise from the fan motor, some electrical fault that's allowing noise from the fan motor to bleed into the signal path, some sort of vibrating transformer (though I wouldn't expect the frequency to be that high), or capacitor discharge (though I wouldn't expect it to be ongoing)... Maybe the power is noisy where you are or there's some electromagnetic interference?

I am reaching, here. Wiser and more experienced heads invited.

 

[woodworm_dan]

Here's a quick video with the noise in question. It still makes the noise if I unplug the fan.

https://youtube.com/shorts/dUCLbZM7jvk?feature=share

 

[MarkA]

Here's a quick video with the noise in question. It still makes the noise if I unplug the fan.

https://youtube.com/shorts/dUCLbZM7jvk?feature=share

The sustained "E" note sounding just before you start playing and in the intervals between? That's a new one to me (and deeper that I thought, from the term "high pitched") -- or is that just a ringing harmonic from your bass?

Or are you referring to the distorted "chirp and rattle" (room noise? distortion in the recording?) that's audible when you are playing?

 

[Bright Midnight]

Here's a quick video with the noise in question. It still makes the noise if I unplug the fan.

https://youtube.com/shorts/dUCLbZM7jvk?feature=share

Hey guys, sorry for the late reply! We asked a local repair instrument shop what it would cost and estimates were at 150€! Their explanation being it had to be returned to Markbass as they themselves were unable to anything about it. Pretty bad news....

Then we found a local electronics engineer to give it a look, but then the guy that has the amp got sick with the rona, and that's the last I heard. Gonna contact him now to see if anything has been done already to the amp.

In short, it didn't look good. Keep you posted

 

[MarkA]

Hey guys, sorry for the late reply! We asked a local repair instrument shop what it would cost and estimates were at 150€! Their explanation being it had to be returned to Markbass as they themselves were unable to anything about it. Pretty bad news....

Then we found a local electronics engineer to give it a look, but then the guy that has the amp got sick with the rona, and that's the last I heard. Gonna contact him now to see if anything has been done already to the amp.

In short, it didn't look good. Keep you posted

In deciding whether to repair the amp or look for something else, I would weigh the likely reliability of/your confidence in the repair and how much you like the amp against the cost of a suitable replacement.

In my case, the repair cost was about twice what I initially thought it might be, but still a little less than a comparable used example of the same amp in good condition -- my amp got mostly-new guts and a professional checkup before heading out to me, so should be a better gamble than a decade-old use amp. It was hard to swallow the cost of the repair, but still made sense to me vs. the alternatives.

You could also, if you don't want to repair the amp, sell the combo cab and the amp (separately or together) as a project -- someone might want to get the amp repaired, or someone might have a Little Mark 2 or 3 that they'd like to mount in a combo.

Good luck!

EDIT: If your local electronics engineer is not confident working on the amp (if he can get documentation from Markbass, that might be helpful), then sending it in to the company might be your best bet for repair.

 

[chadds]

High pitched noise? Get a new guitarist.

 

[woodworm_dan]

Yeah, @Bright Midnight, how'd it turn out?

High-pitched noise from inside the amp -- my uneducated guesses: mechanical noise from the fan motor, some electrical fault that's allowing noise from the fan motor to bleed into the signal path, some sort of vibrating transformer (though I wouldn't expect the frequency to be that high), or capacitor discharge (though I wouldn't expect it to be ongoing)... Maybe the power is noisy where you are or there's some electromagnetic interference?

I am reaching, here. Wiser and more experienced heads invited.

Very good points sir. Thanks for the input.

Just to try and rule things out.... mechanical noise from anything fan related, it's probably not that because the noise is there even with the fan unplugged.

Vibrating transformer...maybe, because the noise seems to come from a very specific area inside the amp.

Noisy power...maybe. I tried different outlets around the house and the noise is still there. The thing is...I haven't changed houses, I bought the amp a few years ago at it was always sitting on top of the cabinet ever since. never gigged.

The only whing that changed recently was that I plugged a MarkBass compressore on the effects loop. Could that have fried something???

The sustained "E" note sounding just before you start playing and in the intervals between? That's a new one to me (and deeper that I thought, from the term "high pitched") -- or is that just a ringing harmonic from your bass?

Or are you referring to the distorted "chirp and rattle" (room noise? distortion in the recording?) that's audible when you are playing?

Chirp and rattle thats surely from the room. It's the electrical type noise at the beggining of the reccording.

Attached is a reccording of the noise without any instrument plugged in.