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Measure the audio level with no load. Then connect a rheostat or resistor decade box across the output and adjust the resistance until the audio level drops in half. Disconnect the rheostat (or resistor decade box) and measure it's resistance with a DMM. The reading will be equal to the output impedance of the old radio.I'm giving inputs from another old radio.How can I measure the source impedance.?
Suraj143 said:Can I measure them with a DMM?
You mean to give input via another op amp? can I use same TL071 for that also?audioguru said:The tone control circuit should be fed from the extremely low output impedance of an opamp. Then the new opamp can be fed audio from any audio source.
I think its poor low frequency.How do I get that to know?Does your radio or speaker have poor low frequency response that requires the bass control to boost the bass?
How did you measure that?My home speakers are flat to 55 Hz. I made a bass boost circuit that boosts 30Hz by 10dB (10 times the power). Then they sound like a sub-woofer is with them but I don't have a sub-woofer at home, only in my car.
Use a second opamp. A TL072 has two opamps in an 8-pins case.Suraj143 said:You mean to give input via another op amp? can I use same TL071 for that also?
A high quality tuner or CD player will have good low frequency response.I think its poor low frequency.How do I get that to know?
Since you ask then you don't have the test equipment to measure frequency response.How did you measure that?
Yes, because 20dB of boost from the tone controls with the bass control set to max requires 100 times more power from the power amplifier.mneary said:You'll have plenty of bass if your power amplifier can provide it.