Ahuja Amplifier

[Ahmad T]

Greetings,

Our amplifier keeps tuning a radio program despite been troubleshooted by the technician. What is/are the problem(s) please?

 

[FvM]

More information required.
Which amplifier type? Is "radio program" local AM station?

RF is usually invading equipment through connected signal (most likely) or speaker and mains (less likely) cables and demodulated by not well designed circuits.

 

[KlausST]

Hi,

I agree with FvM: With the given informations it´s impossible to give useful detailed feedback.

It could be any type of amplifier for any kind of signals. It could be a bought one or a self made one.
It could be a wiring problem, a design problem, a shielding problem, a ground loop problem...

How can we know?
You have to tell us.... Type of amplifier, photos (100kBytes should be sufficient) of amplifier, and wiring... Any thing that is involved withe the "problem"

Klaus

 

[D.A.(Tony)Stewart]

Greetings,

Our amplifier keeps tuning a radio program despite been troubleshooted by the technician. What is/are the problem(s) please?

Greetings, diagnosis requires lots of accurate data. Do you know how to supply this?

 

[BradtheRad]

Greetings,

Our amplifier keeps tuning a radio program

Any strong AM station particularly an be heard from electronic devices just by unplannted means. I suppose a general term would be 'splatter'.
This happened to me occasionally in another locale (Philadelphia) where a strong AM news station transmitted. This was years before light dimmers were on the market. The AM radio was still popularly listened to. Nowadays there's so much interference among the AM band that it's listened to less and lea while the FM band has gotten jam-packed with stations. Here in the US anyway.

 

[D.A.(Tony)Stewart]

If you have long Mic cables , you may need a CM choke and small cap across the signal to reject AM interference.

Just like all VGA cables to prevent EMI radiation, they have a molded clamshell ferrite choke. The small distortion in high gain amplifiers can detect strong AM broadcasts without a tuner, so this sort of attenuation is possible with a filter added to the input jack.

Your technician will understand that long input cables act like antenna to AM signals. If this is true , tell him to add a CM choke and RF cap across the input.

 

[Ahmad T]

More information required.
Which amplifier type? Is "radio program" local AM station?

RF is usually invading equipment through connected signal (most likely) or speaker and mains (less likely) cables and demodulated by not well designed circuits.

Yes, local AM station nearby. It is a speaker/audio amplifier.

 

[FvM]

Next step is to identify the interference path. E.g. what happens if you disconnect the input (microphone, whatsoever) cable.

 

[Ahmad T]

Next step is to identify the interference path. E.g. what happens if you disconnect the input (microphone, whatsoever) cable.

No noise heard.

 

[D.A.(Tony)Stewart]

unless you explain the technical details of your question , no will understand

 

[Audioguru]

The cable plugged into the amplifier input MUST be a shielded cable.

 

[FvM]

The cable plugged into the amplifier input MUST be a shielded cable.

Right. But depending on the amplifier design, even a shielded cable may inject RF into the sensitive input stage.
Complete information would include
- the exact amplifier model (we just know the brand)
- kind of signal and cabling details
- signal source details if it's not a simple dynamic microphone. It's also possible that RF is demodulated in the source.

If the cable is already shielded, different kinds of filter may help, e.g. common mode ferrite core, a low-pass filter.

 

[Audioguru]

In post #9, he said that when the input cable was disconnected, "no noise heard".
Then either the shielded cable had its shield disconnected, or too much of the signal wire was not shielded, or the shielded cable was junk.

Years ago when Radio Shack was in every mall I bought an expensive shielded cable but it shielded very poorly.
Then I saw exactly the same cable at The Dollar Store for a low price. I bought The Dollar Store cable, took it to Radio Shack and got my money back.













i

 

[Ahmad T]

The cable plugged into the amplifier input MUST be a shielded cable.

Yes

I may not have the technical know-how enough to supply the information. Thank you everyone for the input.