Yaqin MC-84L Tube Stereo Amplifier Review

[Koeitje]

I agree. I would suggest broken by design. Or broken as designed.

Broken as designed has a certain charm to it.

 

[Geert]

Looks like this amp is available via different 'high-end' shops. Seems that they all did kind of a 'copy and paste' of a text provided by Yaqin:

• High-performance ultra-linear push-pull circuit bring out rich acoustic
• Srpp preamp circuit widen frequency response and lower distortions
• Output transformer is made of Japan audio-specific oriented silicon steel (0.35mm) and free-oxygen high-intensity enameled Copper Wire, to widen frequency response and better acoustic quality, transparent and powerful
• Adopt audio-grade electrolysis and Philips mkp non-polar AC capacitor make it low-noise, quite music background and durable.

This is why the world needs ASR.

 

[Saponetto]

Getting an amp of these no longer responds to the quest for hi-fi.
Look 'n feel becomes a major catch, and the hisses becomes characteristics rather than flaws.
As I wrote, it is a quest for faith.

I'm a little biased, honestly.

 

[olieb]

Thanks for the review.
With all these identical sounding top notch amps, here at last is an amplifier with a "sound signature". Harmonic and intermodulation distortion, hiss and hum, clipping, it is all there! An amp with "character". (or may be an attitude?) No wonder it gets raving reviews ;-)

 

[Blumlein 88]

Some amps give you nothing extra, this one gives you more.

It is one of those classic tube amps where there is more there... there. Certainly more there than just the input signal.

 

[Geert]

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No bias (quiescent current) adjustment for the tubes I wonder where all that distortion comes from

 

[Narrator]

When I saw 40dB I thought: that is a lot of gain!

 

[TNT]

Pure junk in any respect and a waste of resources and time.

//

 

[AndreaT]

Bad, bad, bad. At least it does not cost $ 4,500. Waste of money and waste of time listening to it.

 

[AdrianusG]

Thanks for the review.
With all these identical sounding top notch amps, here at last is an amplifier with a "sound signature". Harmonic and intermodulation distortion, hiss and hum, clipping, it is all there! An amp with "character". (or may be an attitude?) No wonder it gets raving reviews ;-)

If you look at it that way, it's actually way too cheap, a 0 is missing

 

[Wesseling Audio Lab]

Getting an amp of these no longer responds to the quest for hi-fi.
Look 'n feel becomes a major catch, and the hisses becomes characteristics rather than flaws.
As I wrote, it is a quest for faith.

I'm a little biased, honestly.

There are those consumers and not sure if there's anything we can do to change their minds and course of what they purchase. maybe a few of them will change with some HI-FI education.

I knew about a guy through a friend. His major hobby/interest was owning many turntable/cartridge combinations. His goal was to recreate various sonic signatures from different periods throughout the history of vinyl playback or something to that effect..

Anyway, the amp is garbage. Thanks for the review!

 

[pma]

1930’s design level.

 

[davmol]

It's the first watt that really matters but these guys went the extra mile and gave us two. Bravo!

 

[EdW]

This amp is so bad it’s good
Back in 1954 Mullard did a design called the 5-10 amp which with distributed feedback could approach 0.1% THD at 10W.
EDIT: distributed feedback is not strictly correct. I should have said that the middle grids of the EL84s were taken to symmetrical taps on the O/P transformer (either 20% or 43%) rather than to the power supply. This reduced the ultimate power from 15W down to 11 or 12W but reduced the distortion below 10W appreciably.
I made a few of these in the mid 60’s when I was a teenager learning valuable lessons like that is a great idea to work with one hand behind your back when debugging a powered circuit (prevents a solid current path through you to ground!)

 

[Bob from Florida]

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Thanks for the testing though @amirm... I needed a good laugh.

Pics;

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JSmith

Interesting that a transistor was chosen for the split load phase inverter instead of a tube. They should have used the second half of the 12AX7 for that instead of going for the SRPP configuration. The transistor is not rated for the voltage it is subjected to until the 12AX7 warms up - 345 volts DC until the input tube starts to conduct. Only rated for 160 volts CE max, cannot be good news for long term reliability. Also, the collector and emitter resistors are not the same value - 39K and 47K - indicating they did not get the bias correct for proper phase inversion. On the other hand, it is cheap - only positive I can see.

 

[Ajax]

I wonder what the motivation is behind, first making this amp, and second buying it.

 

[PierreV]

Bob Carver breathes a sigh of relief.

 

[Blumlein 88]

Interesting that a transistor was chosen for the split load phase inverter instead of a tube. They should have used the second half of the 12AX7 for that instead of going for the SRPP configuration. The transistor is not rated for the voltage it is subjected to until the 12AX7 warms up - 345 volts DC until the input tube starts to conduct. Only rated for 160 volts CE max, cannot be good news for long term reliability. Also, the collector and emitter resistors are not the same value - 39K and 47K - indicating they did not get the bias correct for proper phase inversion. On the other hand, it is cheap - only positive I can see.

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Broken as designed.

 

[SIY]

1930’s design level.

Not that good.

 

[SIY]

They should have used the second half of the 12AX7 for that instead of going for the SRPP configuration

Don't let the topology fool you - it's not an SRPP.