Double Bass Clarus sounds like old radio... what's that?

[bonaventura]

I got a new Clarus 2R III back in January 2007. It is a fine amp, and I'm very happy. Now once in a while, not every time I use it, but at least three or four times in the past year, the Clarus 2R III emits a funny sounding distortion -- all by itself!

I'm not necessarily playing when it does this. It sounds sort of like an old shortwave radio, the ascending or descending whistle-like thing as you would dial in and out of a particular frequency. There is also some distorted background noise.
I first noticed it in August 2007, and have heard it several times since. Usually, it goes away by itself. Once I turned the Clarus off and then back on, and it was gone.

Does anyone know what this could be? Could it be interference from something else? Or could it be some defect in the wiring? Does it need cleaning? Do I need to do anything? Could it be harmful to the Clarus?

 

[DaveKirkpatrick]

Do you have your cellphone in your pocket? (or are you just happy to see me?, Sorry--OLD JOKE) Sometimes that can make some odd noises through an amp.

 

[MingusAmongUs]

Yes, sounds like some kind of interference. Either electrical or RF. When I lived in Brooklyn I used to hear all kinds of taxi cab CB radio chatter through every speaker in my apartment. What fun!

 

[Basicbassist]

I agree - it's probably radio interference. In the 90's when I had occasion to play at Windows on the World at the top of one of the the ill-fated World Trade Center towers, my amp would pick up the audio component of TV broadcasts from the huge antenna on the roof of the building just above us. Nonetheless, I suggest that you contact Rick Jones of AI and speak to him about your concern. No doubt, he'll be glad to give your Clarus a very thorough examination and address any technical issues that might be afoot. Let me be quick to add that, in the two instances when I had bizarre issues with my AI amps and sought RJ's intervention, the AI equipment was never faulty.

 

[robgrow]

This is probably an internal problem with your amp instead of a case external interference. It sounds like you are hearing a heterodyne frequency, which is being produced in the class D power amp section. The class D amp uses a very high frequency, which is essentially RF. I would highly recommend contacting Acoustic Image directly about this problem.

 

[Chris Fitzgerald]

I have a Clarus series I that used to do this. I asked Rick Jones about it, and he told me to clean the inputs with some contact cleaner. I did, and it's never done it since. YMMV.

 

[robgrow]

I have a Clarus series I that used to do this. I asked Rick Jones about it, and he told me to clean the inputs with some contact cleaner. I did, and it's never done it since. YMMV.

The effect you are describing here is called audio rectification. The dirty input jack becomes a detector, much like the cat's whisker in a crystal radio set. I can't be sure of course, but it sounds like bonaventura is describing an audible frequency that's being created from the very high frequency (well above the range of human hearing) used in the class D amp. This new frequency is called a heterodyne frequency, which has the characteristic whistling sound. Audio rectification usually manifests itself by a radio transmission (such as a broadcast station) actually being heard through the speaker. I'm sure Acoustic Image knows what's going here, and they're the ones to talk to.

 

[fdeck]

The effect you are describing here is called audio rectification. The dirty input jack becomes a detector, much like the cat's whisker in a crystal radio set. I can't be sure of course, but it sounds like bonaventura is describing an audible frequency that's being created from the very high frequency (well above the range of human hearing) used in the class D amp. This new frequency is called a heterodyne frequency, which has the characteristic whistling sound. Audio rectification usually manifests itself by a radio transmission (such as a broadcast station) actually being heard through the speaker. I'm sure Acoustic Image knows what's going here, and they're the ones to talk to.

+1

A nice explanation for something I have experienced, but never fully understood the cause.

About input jacks, it could be a dirty jack, or a jack that has wriggled loose from the printed circuit board. The cable gets tugged on, this flexes the jack, and eventually the solder connections break. If you are comfortable opening an amp, and know how to do it safely, the fix could be as simple as re-melting the solder joints with a bit of new solder added as a libation to the gods.

Of course, the fix could also be as simple as getting it fixed.

 

[robgrow]

+1

A nice explanation for something I have experienced, but never fully understood the cause.

About input jacks, it could be a dirty jack, or a jack that has wriggled loose from the printed circuit board. The cable gets tugged on, this flexes the jack, and eventually the solder connections break. If you are comfortable opening an amp, and know how to do it safely, the fix could be as simple as re-melting the solder joints with a bit of new solder added as a libation to the gods.

Of course, the fix could also be as simple as getting it fixed.

Thanks. In such a high-gain, high-impedance circuit, almost anything can become a point-contact diode (and then you have a cat's whisker RF detector).

My concern however is the whistling sound that bonaventura described is being created in the class D amp itself. I could be wrong of course.

 

[bonaventura]

I have a Clarus series I that used to do this. I asked Rick Jones about it, and he told me to clean the inputs with some contact cleaner. I did, and it's never done it since. YMMV.

Chris, thanks. What kind of input cleaner is that? Is there a specific product you have in mind?

Bill

 

[bolo]

What kind of input cleaner is that? Is there a specific product you have in mind?

I've used Caig DeoxIT D5 spray to clean input jacks and output jacks (cable ends) before. I think I read about it in an old issue of BP magazine.

And check this out too. robgrow's recommendation (also a Caig product) is probably an even better one.

 

[bonaventura]

I have a Clarus series I that used to do this. I asked Rick Jones about it, and he told me to clean the inputs with some contact cleaner. I did, and it's never done it since. YMMV.

The effect you are describing here is called audio rectification. The dirty input jack becomes a detector, much like the cat's whisker in a crystal radio set. I can't be sure of course, but it sounds like bonaventura is describing an audible frequency that's being created from the very high frequency (well above the range of human hearing) used in the class D amp. This new frequency is called a heterodyne frequency, which has the characteristic whistling sound. Audio rectification usually manifests itself by a radio transmission (such as a broadcast station) actually being heard through the speaker. I'm sure Acoustic Image knows what's going here, and they're the ones to talk to.

+1

A nice explanation for something I have experienced, but never fully understood the cause.

About input jacks, it could be a dirty jack, or a jack that has wriggled loose from the printed circuit board. The cable gets tugged on, this flexes the jack, and eventually the solder connections break. If you are comfortable opening an amp, and know how to do it safely, the fix could be as simple as re-melting the solder joints with a bit of new solder added as a libation to the gods.

Of course, the fix could also be as simple as getting it fixed.

Thanks everyone for the comments. Glad to hear that wiser and more experienced minds than mine had already heard this sound coming from an amp or know what it is. At least it's nothing to really be concerned about...

I did write to Rick at AI and he wrote back:

"Since the problem is intermittent, my guess is that it is a dirty connector. Take the top portion of the chassis off and get access to the ribbon cable that connects the preamp and power amp. Remove the cable and clean the headers on both boards with contact cleaner and then reassemble. Also, spray a little of the contact cleaner into the input jacks and plug and unplug a few times."

I guess I'll try first to clean the input jacks. If it recurs, I'll have to go in and clean the headers.

Thanks again for the good replies.

Bill