I have a Nikko Na-100 integrated stereo receiver with one or more bad op amps, i just replaced both Output OP amps with 4556's which from what i understand has a higher output current to push high impedance loads such as headphones. Is there any negative effects of using it in my application? The receiver works well now and sounds decent, unless im able to A-B between the two i cant say i hear a difference. Is there any particular reason why i shouldn't have used the 4556 and used something else instead? Im also open to Desoldering and putting something else in there for better sound quality if it would make a difference.
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Replacement JRC 4558 Op Amps
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Well it is similar, however the 4556 is newer/better and i actually pulled them from my 02 headphone amp.
I wouldn't loose any sleep on this, amp sounds good then enjoy. The higher current draw just means
the operating voltage will be slightly lower than for the original. Just for future reference, when replacing
an opamp, most will insert a socket so they can easily change/roll opamps. Again, be happy all is ok...
the operating voltage will be slightly lower than for the original. Just for future reference, when replacing
an opamp, most will insert a socket so they can easily change/roll opamps. Again, be happy all is ok...
Hmm, how would the lower operating voltage affect the sound? I've used those sockets before i just didnt have any handy unfortunately. Im not against desoldering the cheap chips i have in there already and putting something else in there also, provided its an upgrade over the JRC4580. I also have some Burson Audio V5i Chips...i just thought that they would be a waste as i think the circuit design also plays a big part . I've compared op amps before and its extremely hard to tell to the difference i find, and near impossible without a way to swap A to B.
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Don't over think this, if it sounds good then be happy.
The circuit was designed for the NJM4558 which has an operating
voltage of 4V->18V at about 3.5mA, typically running at 15V.
You have inserted a NJM4556 (2V->18V, 9mA) so you've changed the
design, possibly the NJM4556 is running at 13.5V (don't have the
service manual), the 13.5V is well within the 2-18V, expect any
sonic difference to be subtle at best.
The circuit was designed for the NJM4558 which has an operating
voltage of 4V->18V at about 3.5mA, typically running at 15V.
You have inserted a NJM4556 (2V->18V, 9mA) so you've changed the
design, possibly the NJM4556 is running at 13.5V (don't have the
service manual), the 13.5V is well within the 2-18V, expect any
sonic difference to be subtle at best.
Suggest double check that it's 60Hz, plenty of tools such as mobile phone apps and freeware like audacity.
The main filters handle rectified AC so it will be 120Hz hum, unless you have a failed rectifier or 2.
Also there is "always" a bit of hum in vintage gear, needs to be audible when 2 meters from spkrs to warrant
further action. If you need to be standing next to spkrs then leave as is. Make sure screws securing transformer
are tight. Check AC power cables, ie, from cord to fuse to switch to transformer, try to separate from any audio
wires, use something non-conductive (chopstick?) to push wires around and note any improvement...
i can give those all a shot, so are you firm believer of changing caps when they pop? I was thinking of putting some new 10,000uf power caps in hoping it would solve the problem. Yes you are right, i dont hear the noise from the listening position just when i put my ear right up the speaker.
Recapping is a hotly debated topic, IMO, if the amp is 35+ years old it is probably due. That said I've
recapped a few such amps where there was no significant improvement in sound. It may come back
to orignal cap quality (NADs used elcheapo's) and design. Worst case of distorted cap was a yamaha
CA-800, 6800uf/50V where the rail was running 51-52V. Seen other CA-800's where main caps looked
fine. Some people confuse a bulging top plastic cover as distortion, it's only a thin cover, need to press down
to check actual case.
Part of this hobby(madness?) to trying to learn something, try whatever and learn...
recapped a few such amps where there was no significant improvement in sound. It may come back
to orignal cap quality (NADs used elcheapo's) and design. Worst case of distorted cap was a yamaha
CA-800, 6800uf/50V where the rail was running 51-52V. Seen other CA-800's where main caps looked
fine. Some people confuse a bulging top plastic cover as distortion, it's only a thin cover, need to press down
to check actual case.
Part of this hobby(madness?) to trying to learn something, try whatever and learn...
David_NC
Super Member
I've got a slight hum on a 50+ year old Harman Kardon A300 tube amp. I can hear it on high efficiency speakers if I'm within a yard or so with no music playing. Fortunately, I don't sit that close to speakers listening to silence, so it's a non-issue. My Dynaco ST-70 requires me to be inches away from the drivers to hear any hiss or hum with no source playing, so not all are noisy. I like the silence of the Dynaco, but the hum from the HK isn't worth losing sleep over. I prefer my tube amps because they sound pretty amazing... even that little 12 watt HK with its slight hum.
Can only speak for myself. They sound great.
Would love the new Yamaha 5000 series but at $xxk or a luxman integrated... I can't afford it. You can
pickup near TOTL vintage gear for reasonable money, pay a little more for TOTL but still cheap. Even
the middle amps Sansui AU-505/555, Luxman SQ-505x/507X not to mention all the receivers... I'm moving
into separates since they don't have the same design constraints.
Power cables, filters, boards is another hotly debated topic. No harm in trying and form your own opinion.
Post your results.
I ended up picking up a marantz pm5005 and the sound quality is absolutely stellar. In comparison to the Nikko it’s warmer and better extended with more details, I am finding that I adjusted the midbass down a touch with the q150s. The Nikko is definitely louder, and a night and day difference compared to my kenwood AVR from a similar era. The marantz is more than loud enough though since I usually listen at 75-80DB in an effort to preserve my hearing, lol. I may still choose to change the power caps on the Nikko down the road just for fun and than report back.