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JVC A-X1

Super A Stereo Integrated Amplifier (1980)

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JVC A-X1

Specifications

Power output: 30 watts per channel into 8Ω (stereo)

Frequency response: 10Hz to 100kHz

Total harmonic distortion: 0.007%

Damping factor: 50

Input sensitivity: 2.5mV (MM), 150mV (line)

Signal to noise ratio: 73dB (MM), 77dB (line)

Output: 150mV (line)

Dimensions: 120 x 420 x 329mm

Weight: 5.5kg

Year: 1980

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Reviews

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rating
Reviewed Nov 27th, 2016 by Solophonola

I have always designed and built my own class A amplifiers, but seeing this old amp on eBay I thought I'd make a bid for it, and I won the auction for less than £10. One channel was faulty, as described.
Two quick sqirts of switch cleaner on the volume control pot and a bit of diamond filing of the complex & rusty cassette tape record/play switching mechanism put right the faulty channel and made changing the volume sound less like sandpapering the midrange speakers.
I was then astonishingly impressed by the sound. This amp was capable of delivering. Into two Clements TL 'Spatial Image' floor standing speakers, it almost matched my own 40 year old 20 wpc class A amp, inspired by my dear departed old friend, John Linsley Hood, but with slit supplies and two constant current sources defining the standing current, and no bootstrap capacitor
Give me a week with any amp and my ears tell me nearly all I need to know about its qualities and vices. This AX-1 was very good. Later, on test, I adjusted the mysterious chip that sets up the current that defines where class A becomes class A/B.
Square waves remain remarkably unaffected by being passed though this amplifier, with no visible ring shown on my HP oscilloscopes. The circuit is very stable. The bass falls off rather too soon, which may have more to do with ageing capacitors in the signal path than anything inherent in the design.
And then there's the power supply. It is truly massive, and here's some of the secret of the solid sound. It is almost possible to assess the quality of many amplifiers, as also it is for speakers and pianos, by their weight This AX-1 is no pretend class A PSU, despite the sickly 'Super Class A' flash on the front panel. This is the PSU that keeps on giving adequate current and with negligible ac ripple. There was an audible 100Hz buzz from the transformer that would not be negligible if one were sat within couple of feet from the amplifier.
I could recommend thes amplifiers to anyone, providing one recognises that they are middle-aged and cannot be guaranteed to work for ever. But the service manual and cct diagram is available from hi-fi engine, and apart from the magic chip that sorts out the class A/ class AB biassing, there is nothing very other wordly or metaphysical contained within the circuit. You get a LED strip pair of peak meters, loudness control, a very acceptable phono stage and a decent headphone output.
When these amps first became available in the UK I was a young buck of under 30. An analogue engineer for microcircuits with Ferranti and then National Semiconductors, I thought this 'new class A' amp must be a con trick, and avoided the fact that the Japanese Victor Company may actually have pioneered a clever way of solving the perpetual problems of standing current heat dissipation in Class A amplifiers and that of cross-over distortion squigglies during the times when the amplifier is running quiet passages of music - which is most of the time unless you are solely into heavy metal thrash.
The build quality and ease of servicing has been well thought out here, and this was a far cry from JVCs monstrously complicated Class B amplifiers of the early 70s of which the least said the better, having recently repaired one by the subtle method of scrapping the whole caboodle and using only the box and controls, connected to new amplifier and preamp modules. And even then one is left with a huge beast of a bling-thing. Enough said, rant over!

I have since gone on to buy two later Technics versions of the same amp, and may report in more detail at a later date. Well done JVC, and I take back most, but not all of my previous derogatory comments concerning Japanese amplifiers. This design was clearly an important pioneering step in bringing quality sound to a wider market for people who were on a tighter budget. And although it can only be whispered to few engineers, many of the top end amplifiers from this same period (1980-1995) were vastly overpriced and offered little if any audible improvement on this JVC model.

rating
Reviewed Apr 09th, 2015 by Simon Spiers

Caps 621 622 will be dry.
seems to be under biased by default.
Once set to across the two emitter followers the sound improved a bit.
Good soundstage but always a bit shrill.

 

Comments

re: A-X1

Anyone know how many Ampere [amˈpɛɐ̯] is the little fuse inside the amplifer?
Thanks a lot.
Alex.

re: A-X1

1 amp slow blow.

re: A-X1

wow...
thaks :)
Terimakasih :)

Thx

Thanks for it!

jvc A-x1 amplifier

I didant think i would ever obtain a manual for the above amp. Thanks a bunch.Mavrik

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