MM phono preamp made by myself with ha12017 and ad797,the circuit diagram is also designed by me. The power supply part uses LM317 / LM337 to stabilize the voltage, and the power filter capacitor uses Germany's Mundorf capacitor, which has good performance, but I haven't found a decoupling capacitor on the amplification circuit board with good sound quality until I use Audio Note STD capacitors of various specifications. I made all the holes on the chassis by hand. The final sound quality is very good. Next, I want to use LT1963 and LT3015 as regulated power supply to see how the sound quality and timbre change
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I use Gotham of Switzerland for all the wires in the machine. My dealer here only has orange and gray wires. In order to pay attention to safety, I use orange for high-voltage 220V wires. Later, I used enough epoxy glue to firmly stick the switch to the chassis
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The input resistance is about 32 kohm now, is that intended? I mean the equivalent parallel resistance at audio frequencies.
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Hi,
the wire ends look like soldered and screwed to the connector blocks.
You know that soldering ends and screw connectors are considered a nogo not without reason?
It might not matter much in low current application like a preamp, but I´d rather twist together the power supplying wires, especially when you run signal wires in close proximity.
Was there a special reason to use AD797 as second gain stage?
The AD797 is optimized for low source impedances.
At 1k and above other OPAmps surpass it noisewise.
jauu
Calvin
the wire ends look like soldered and screwed to the connector blocks.
You know that soldering ends and screw connectors are considered a nogo not without reason?
It might not matter much in low current application like a preamp, but I´d rather twist together the power supplying wires, especially when you run signal wires in close proximity.
Was there a special reason to use AD797 as second gain stage?
The AD797 is optimized for low source impedances.
At 1k and above other OPAmps surpass it noisewise.
jauu
Calvin
This MM phono preamp is designed as an amplifier circuit board and a power circuit board. Each board may have its own improved version. In order to easily and quickly replace the circuit board, I use screws to fix the connecting terminals of the connecting lines. I am designing PCBs with as few connecting lines as possible, which may adopt plug-in connection. The external electronic components of ha12017 are determined according to the official drawings of Hitachi. Only ha12017 is used to amplify, and the volume of the power amplifier is turned to the maximum. The sound is not very good. I add one level of ad797 amplification to increase the output level so that the power amplifier can play with the normal volume value, and the sound quality is improved
Thank you for your prompt. I define the input impedance as 47K. According to the official data of ha12017, it is recommended not to exceed 100k. I forget that this 47K resistor is connected in parallel with the later 100k resistor. The resistance value of this 47K resistor needs to be increased.
I'm very excited to see the Chinese compatriots, and you also wrote simplified Chinese characters. It's very kind!🙂
Well done both for DiyAudio endeavors transcending geo-political boundaries...🙂
More than 20 years ago, I used HA12017 for tape head NAB amplification. The sound quality is very good, but later I accidentally lost it when I moved. Now many people in China are recycling electronic components. I see the recycled HA12017, which is very cheap. You can buy two for $1.I bought a lot and can make many sets
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Hey, I bought a bunch of those HA12017 op amps also out of China, they are all original Hitachi components, some are new, some are recycled. The only trouble is I cannot seem to test them to see if they are working or not, I have used a commercial op amp tester, as well as trying to get a voltage follower to read same voltage out as going in, but no tests have given any positive results. The op amp tester, jut reads that all the chips are dead, and yet I tested 2 known working chips from an audio circuit and both also read as dead op amps. As for the voltage follower that works fine with other op amps for reading same out as going in, I get nothing coming out from the HA12017 op amps.
Any help on how to effectively simply test these ic's would be greatly appreciated.
Cheers,
Any help on how to effectively simply test these ic's would be greatly appreciated.
Cheers,
Just found today a Hitachi HA-2700 containing 2 of those chips at a scrap metal yard...payed like 4 bucks on the amp...I think it was intended to give a high quality sound for mm carts, but never heard it.Can't wait to see it in action after a little bit of refurbishment.I first heard of this chip 18 years ago...never saw it until today.I just hope it was a good bid.