Hi All,
I am trying to build an amplifier around LA4440. There is also a preamp, which is feeding the input to the main amp. I am driving my preamp from the RCA output of a car tape.
When the input to the preamp is not connected to the car tape, if I increase the volume of the amplifier I hear loud humming.
If I connect the car tape RCA output to the preamp input and increase the volume of main amp, then there is a loud flutter.
I have been breaking my head on this!
I checked the pot meters and they are properly grounded..
Can anyone tell me what do I need to solve the problems mentioned above??
I am trying to build an amplifier around LA4440. There is also a preamp, which is feeding the input to the main amp. I am driving my preamp from the RCA output of a car tape.
When the input to the preamp is not connected to the car tape, if I increase the volume of the amplifier I hear loud humming.
If I connect the car tape RCA output to the preamp input and increase the volume of main amp, then there is a loud flutter.
I have been breaking my head on this!
I checked the pot meters and they are properly grounded..
Can anyone tell me what do I need to solve the problems mentioned above??
Hi Perry,
I am trying out the circuit using transformers right now and the humming has gone away completely. thanks to your trick - I grounded the amp & preamp to the head unit.
I have a new question for you:
The pre-amp output from my tape is basically a pseudo signal. What they have done is they have put a 22k resistor in series with 1MF electrolytic capacitor to the speaker out and provided a new RCA jack!!
Now when I am feeding this output to my preamp input, the sound is muffled..its not clear. I guess the impedances are not matching? What do I need to do for this??
I am trying out the circuit using transformers right now and the humming has gone away completely. thanks to your trick - I grounded the amp & preamp to the head unit.
I have a new question for you:
The pre-amp output from my tape is basically a pseudo signal. What they have done is they have put a 22k resistor in series with 1MF electrolytic capacitor to the speaker out and provided a new RCA jack!!
Now when I am feeding this output to my preamp input, the sound is muffled..its not clear. I guess the impedances are not matching? What do I need to do for this??
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Hi Perry - I am using the LA4440 in bridged mode, here's the schematic for the same. I got this circuit readymade from the market. The schematic just shows the LA4440 in bridged mode, I dont have the circuit diagram for the preamp & bass-treble module
Basicall the pre-amp is using a chip - HWCT35244 and 2 transistors BC548. I could not find any information or datasheet on HWCT35244
Eagerly awaiting inputs from you
Basicall the pre-amp is using a chip - HWCT35244 and 2 transistors BC548. I could not find any information or datasheet on HWCT35244
Eagerly awaiting inputs from you
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I dont see any capacitor on the input (Pin 2) in the schematic
Also I observed that when I connected the speaker out of the headunit directly to the amp pin, the sound is loud & clear - but I loose the bass-treble controls. And when I give the RCA out to the preamp, then the sound is still loud - but it is muffled.
Also I observed that when I connected the speaker out of the headunit directly to the amp pin, the sound is loud & clear - but I loose the bass-treble controls. And when I give the RCA out to the preamp, then the sound is still loud - but it is muffled.
Thanks for you valuable time Perry, I really appreciate your help. But, as I told before, I got this circuit readymade from the market..hence I dont have the schematics.
But all I know is that the preamp has a shielded wire which we are supposed to connect to tape head (deck mechanism), so I assume the input impedance would be approx 200 ohms.
I want to drive the preamp + AMP using my car tape RCA out (pre-amp) and this is a Pyramid make 1704MP radio
But all I know is that the preamp has a shielded wire which we are supposed to connect to tape head (deck mechanism), so I assume the input impedance would be approx 200 ohms.
I want to drive the preamp + AMP using my car tape RCA out (pre-amp) and this is a Pyramid make 1704MP radio
If it was to be driven by a tape head, there will be significant equalization (needed for the tape head to produce a flat frequency response).
You may want to replace the preamp you have. You could use an IC like the following:
http://sigma.octopart.com/89270/datasheet/Philips-TDA1524AN.pdf
You may want to replace the preamp you have. You could use an IC like the following:
http://sigma.octopart.com/89270/datasheet/Philips-TDA1524AN.pdf
I guess I am ok with 20Watts RMS, and my LA4440 in bridged mode can deliver upto 19W RMS to an 8Ohm load.
The preamp, which I am using is based on LA3161. I have the following questions for you:
1) What would be the impedance & output voltage of a cassette tape head?
2) Can I connect my preamp (LA3161) to the volume control of my car tape (Pyramid 1704MP)?? Schematic of the car tape attached.
Kindly advice.
The preamp, which I am using is based on LA3161. I have the following questions for you:
1) What would be the impedance & output voltage of a cassette tape head?
2) Can I connect my preamp (LA3161) to the volume control of my car tape (Pyramid 1704MP)?? Schematic of the car tape attached.
Kindly advice.
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