Clock tick amplifier - Electronic Circuits Projects Diagrams Free

romosco · 13th June 2007, 07:47 PM

Hi I repair clocks and watches to enable me to listen to the tick tock sound the clock or watch makes I use an amplifier made by L&R T300, the unit is very small and is powered by a 9v battery, you attach a sound pickup lead using dbl sided tape (I think it is a quartz pick?) as close as possible to the area of the clock\watch that is making the tick sound, this then allows me to set the clock\watch in beat.
My problem is the above unit producing a very loud feed back sound and a low volume tick sound. The electronic circuit is based around the LM386n-1 IC with an amp gain of 200 the power switch automatically turns off after 60 seconds.
Can any one suggest a solution other than bin it, that being the case I would like to build a circuit that would allow me to use a crocodile type clip as the sound detector, instead of the dbl sided tape method. Can you recommend a circuit with diagram.
Thank you for any assistance that you are able to offer.

audioguru · 13th June 2007, 08:05 PM

Acoustic feedback is caused when the microphone can hear the speaker.
Turn down the volume.
Separate the mic and the speaker.
Enclose the mic so it can't hear the speaker.
Wear closed headphones instead of using a speaker.

romosco · 13th June 2007, 08:33 PM

Hello
Thank you for response. I have just disconnected the 8 Ohm speaker and connected a mono headphone set, unfortunately the continues humming sound is still there and the sound level is controled by the volume slider. The lead to the pickup is 1/2 meter long, half the pick up head is encapsulated. The unit was working ok and then suddenly produced the continues humming sound?
Regards Roger

audioguru · 13th June 2007, 08:41 PM

Humming is not acoustic feedback. Humming is caused when the shield on the microphone cable is broken or disconnected and the very sensitive amplifier picks up hum from the surrounding AC mains.

romosco · 13th June 2007, 09:02 PM

The shield on the microphone cable is broken adjecent to the pickup, am I correct in thinking that this is a Quatz pick up as the pickup head has a very thin wire coil with a very small metal center encapsulated between two pieces of plastic. When the piece of metal in the pick up was taped the sound was produced by the amplifier.
Roger in Essex in the UK

audioguru · 13th June 2007, 11:01 PM

The hum will disappear if you fix or replace the damaged shielded cable.

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13th June 2007, 07:47 PM	(permalink)
romosco	Clock tick amplifier Hi I repair clocks and watches to enable me to listen to the tick tock sound the clock or watch makes I use an amplifier made by L&R T300, the unit is very small and is powered by a 9v battery, you attach a sound pickup lead using dbl sided tape (I think it is a quartz pick?) as close as possible to the area of the clock\watch that is making the tick sound, this then allows me to set the clock\watch in beat. My problem is the above unit producing a very loud feed back sound and a low volume tick sound. The electronic circuit is based around the LM386n-1 IC with an amp gain of 200 the power switch automatically turns off after 60 seconds. Can any one suggest a solution other than bin it, that being the case I would like to build a circuit that would allow me to use a crocodile type clip as the sound detector, instead of the dbl sided tape method. Can you recommend a circuit with diagram. Thank you for any assistance that you are able to offer.

13th June 2007, 08:05 PM	(permalink)
audioguru	Acoustic feedback is caused when the microphone can hear the speaker. Turn down the volume. Separate the mic and the speaker. Enclose the mic so it can't hear the speaker. Wear closed headphones instead of using a speaker. __________________ Uncle $crooge

13th June 2007, 08:33 PM	(permalink)
romosco	Hello Thank you for response. I have just disconnected the 8 Ohm speaker and connected a mono headphone set, unfortunately the continues humming sound is still there and the sound level is controled by the volume slider. The lead to the pickup is 1/2 meter long, half the pick up head is encapsulated. The unit was working ok and then suddenly produced the continues humming sound? Regards Roger

13th June 2007, 08:41 PM	(permalink)
audioguru	Humming is not acoustic feedback. Humming is caused when the shield on the microphone cable is broken or disconnected and the very sensitive amplifier picks up hum from the surrounding AC mains. __________________ Uncle $crooge

13th June 2007, 09:02 PM	(permalink)
romosco	The shield on the microphone cable is broken adjecent to the pickup, am I correct in thinking that this is a Quatz pick up as the pickup head has a very thin wire coil with a very small metal center encapsulated between two pieces of plastic. When the piece of metal in the pick up was taped the sound was produced by the amplifier. Roger in Essex in the UK

13th June 2007, 11:01 PM	(permalink)
audioguru	The hum will disappear if you fix or replace the damaged shielded cable. __________________ Uncle $crooge