I’m interested to build a universal variable loudness to use with any amplifiers. The idea is to put it in between pre-out and main-in link of any integrated amplifiers. I had the schematics of Nakamichi 410 preamplifier as attached. Could anyone help to educate me whether I can build this circuit with or without any modifications, please? I'm not an electrical engineer but have some soldering skills. Thank you in advance
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I would start by driving it with a low impedance source, and having a high impedance buffer on the output.
I went down this road. I tried many different configurations and I was quite dissatisfied with the results. The best one was based on the Nakamichi circuit from the TA2A receiver.
That doesn't mean you can't do it.
I went down this road. I tried many different configurations and I was quite dissatisfied with the results. The best one was based on the Nakamichi circuit from the TA2A receiver.
That doesn't mean you can't do it.
You have to find one in good shape from an old unit.
I have a few NOS units from Radio Shack I bought around ten years ago. When I saw them I figured I better grab them, since the Loudness feature has been absent since the 1990s at the latest. I experimented with one and it worked pretty good.
You could try to find a circuit that doesn't use the center tap. That's where I was going. I was trying to develop an active circuit that didn't change the volume, only the contour. I'm pretty sure the Nak TA2A has a circuit that works like that, even without an op amp. It might be worth a look.
Nakamichi TA-2 High Definition Tuner Amplifier Manual | HiFi Engine
I have a Nakamichi TA3 receiver, hope the preamp section will be the same as TA2A. There are contour knobs separately from the volumes for both TA-3 and 410. They seem that there are no center tapped pots used since they both have their own pots for the contour circuit. The reason I choose the circuit from the 410 is that the operating frequency is centered at 3kHz while the TA3 is centered at 1kHz. The 3kHz would more satisfied me.
Here is the TA2A & TA3 Loudness cuicuit, luckily, they are alike.
Another difference between 410's and TA's loudness is the 410's was placed at the final stage before going out to pre-out terminal, and after the volume & tone control while the TA's was placed at the first stage, directly after input selector, and before the volume & tone control.
So, another question is which one is more suitable for building a plug-in unit?
Another difference between 410's and TA's loudness is the 410's was placed at the final stage before going out to pre-out terminal, and after the volume & tone control while the TA's was placed at the first stage, directly after input selector, and before the volume & tone control.
So, another question is which one is more suitable for building a plug-in unit?
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