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Review and Measurements of vintage Yamaha AX-396 integrated amplifier

Willem

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When I bought the 606-2 from a retired Quad nl service engineer I asked him to reduce the gain internally but he refused. I don't know why. RME told me the in line attenuation should be fine.
 

gino1961

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I am using an attenuator cable. I specified the required attenuation to an engineer who made the cable for me (I am not an engineer)....
Thanks a lot again. I have come to the conclusion that i cannot live without a remote controlled volume maybe without any V gain. But able to drive properly also low Zin power amps. I have this one in the scope ....
https://italian.alibaba.com/product...ume-hifi-tube-preamplifier-1600103060599.html
i bought already a Weiliang Audio unit that i am using at present ... but then i found the measurements on this site ... not very good indeed
https://www.audiosciencereview.com/...measurements-of-weiliang-volume-control.8348/
(I still think that using an external transformer could improve a little the measurements )
another solution could be DIY ... a motorized pot followed by a buffer ... but this will need time
I love remote controls ... i wonder how people can do without.
 
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pma

pma

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As I have some improvements in my measuring system, I have re-measured this vintage amp to get both THD and THD+N plots. The result is not bad and it would score respectably even in current @amirm power amplifier charts. Interesting.

ax396_thdnampl.png


and also in dB as used in ASR
ax396_thdnampl_dBr.png


... and THD and THD+N vs. frequency at 22W/4ohm with 40kHz bandwidth
ax396_thdnfreq.png


ax396_thdnfreq_dBr.png
 
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Interference

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Quite respectable performance. I own an AX-497 now which should be not much different.

It would be interesting to see how it behaves on difficult loads (?)
 

restorer-john

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@pma you need to talk to us about your measurement system and the improvements. I am limited with my gear to pre AP system one numbers. :)
 
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pma

pma

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@pma you need to talk to us about your measurement system and the improvements. I am limited with my gear to pre AP system one numbers. :)
Hi John, it is based on this analog interface
I will tell more later. The bottleneck is the soundcard.

BTW, this Yamaha is not bad even in the 19+20kHz IMD test
ax396_19+20kHz.png


... and the multitone
ax396_multi.png
 
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Willem

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I have a question and a request. The question is if this Yamaha amplifier shows any resemblance to the current AS501/701/801 series? The request is for a proper test of a Quad 606-2 or 909, if at all possible. Restorer John, do you have one?
 
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pma

pma

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I have a question and a request. The question is if this Yamaha amplifier shows any resemblance to the current AS501/701/801 series? The request is for a proper test of a Quad 606-2 or 909, if at all possible. Restorer John, do you have one?

If there is a link to service manual of some of the units you have mentioned, I could tell you.
 
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pma

pma

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Thank you. The circuit diagram of the power amp section is in general very similar to that of the tested AX-396. Specs look similar on the paper (with higher power of A-S801), however I have not seen any detailed measurements and did not have the amp on the test bench. I would like to believe that similar circuit topology and similar inner layout might lead to similar results. If there is a continuity at Yamaha design team, it should.
 
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pma

pma

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It looks good. I would appreciate some more plots like my favorite 19+20kHz test and multitone, but I believe it should be OK based on what I see in the schematics. If you will use it with some "normal" speaker with impedance not falling below 3ohm, it should be a good choice.
 

Matias

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As I have some improvements in my measuring system, I have re-measured this vintage amp to get both THD and THD+N plots. The result is not bad and it would score respectably even in current @amirm power amplifier charts. Interesting.

View attachment 155212

and also in dB as used in ASR
View attachment 155213

... and THD and THD+N vs. frequency at 22W/4ohm with 40kHz bandwidth
View attachment 155214

View attachment 155215
Thanks, added it to the list below. I read about 110W in 4 ohms 1% THD+N, is that right?
 
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DSJR

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The 19 + 20kHz intermod test is what killed so many amps back in the 80's, with figures around -70dB or worse.

It'd be nice to see power into 8 ohms please, admitting many speakers today average out at 6 ohms by and large. The current Yamaha amps do look to be similar on the bottom circuit board, but I gather the vertical input 'cards' have been changed around the socketry on the back and obviously the front panels are totally different.
 
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pma

pma

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Thanks, added it to the list below. I read about 110W in 4 ohms 1% THD+N, is that right?

Thank you, staying on the safe side I would leave it at 110W/4ohm, even if I measured >130W/4ohm/1% earlier. I do not like the operation in clipping area with elevated high order harmonics.

BTW good job with the chart!
 
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pma

pma

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It'd be nice to see power into 8 ohms please,

OK, give me one more day please. I use the 4ohm as a rule for the reason that almost all speakers have impedance dips down to 4-6 ohms even if their rated impedance is 8ohm. I am a friend of worst case analysis.

Yes the 19+20kHz at high power was a killer in the past, but it helped us to understand how to design a reliable amplifier. For this reason, I like to see it even nowadays.
 

Matias

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Thank you, staying on the safe side I would leave it at 110W/4ohm, even if I measured >130W/4ohm/1% earlier. I do not like the operation in clipping area with elevated high order harmonics.
Also if you have more amplifiers measured and posted publicly please let me know and I will add them to the list. Thanks in advance.
 

DSJR

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OK, give me one more day please. I use the 4ohm as a rule for the reason that almost all speakers have impedance dips down to 4-6 ohms even if their rated impedance is 8ohm. I am a friend of worst case analysis.

Yes the 19+20kHz at high power was a killer in the past, but it helped us to understand how to design a reliable amplifier. For this reason, I like to see it even nowadays.
There's still enough 'iffy' amps in use out there in subjectivist circles who still find all good measuring stuff is (benign) boring in sound, so PLEASE DON'T stop doing IMD tests
 
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