Review and Measurements of vintage Yamaha AX-396 integrated amplifier

[pma]

Hi @DSJR , below please find measurements into 8ohm load as per your request.

THD and THD+N is lower than into 4ohm, as expected.

 

[pma]

Standard IMD tests - DIN 250Hz+8kHz and SMPTE 60Hz+7kHz (repeated on Sep 29,2021)

This again remained me that we have to be humble and to perform all kinds of well established tests. This would cover THD+N vs. amplitude, THD+N vs. frequency, SMPTE IMD, DIN IMD, CCIF IMD, multitone and spectra at various output level. None of them to be omitted. If we omit some of the tests, we may overlook some hidden design issue.

 

[greeef]

Hi,

I just wanted to say thank you for all the discussion here. I have rebiased my amplifier to ~10mV by following some of the advice here and from the service manual. When i first measured the channels they were at 2.1mV and 1.5mV. I have made absolutely no objective testing but have convinced myself there is an improvement! It's good to know I don't have a junker here, i bought it new about 23 years ago.

I've never rebiased an amplifier before, I appreciate how easy you guys made it sound.

 

[capslock]

I think even permitted 10mV across 0R22 would be OK, it would make 45mA idle current. I think that the amp has now much lower bias - the service manual says 0.1mV - 10mV is OK - which is of course too big tolerance field re crossover distortion. I have not measured the idle current yet, I will do it and try to set it close to 10mV. I guess now it is about 1mV.

P.S.: I have the amp in simulation now
View attachment 43565

Did your amp not have those 2x 100 p caps loading the VAS to each rail? This is from the 396 service manual:

 

[restorer-john]

@capslock

Here's a better avatar. I took a pick of my keyboard for you.

Steal the image and use it!

 

[capslock]

Thanks You know how this nick came to be? When I was a student in the late 80s, our university had this new computer room with Unix workstations with US keyboards. IRC (internet relay chat) was new to me. Choose username? I just looked down at the keyboard.

It's rare these days to find a keyboard that spells out the function rather than just sporting a fancy arrow of some sort.

Cheers

 

[restorer-john]

Choose username? I just looked down at the keyboard.

That's cool. Lucky it was before 104 key boards with Delete, Insert and End. You could have picked a worse one...

 

[capslock]

For a brief period, German keyboards tended to sport Feststelltaste (~ set lock key) for caps lock. One of those famous compound words.

 

[nofacemonster]

I am more than happy to see this review, (the whole thread)

Why?

Because I own a Yamaha AX-397 which I believe to be a later model but looks very much similar to this one. I love the amp because it sounds super great with my Meadowlark Kestrels. It is currently being fed from my computer connected to it via a SMSL M100 MK2 DAC. Sounds super good.

Best part of this thread is I just figured out why it sounds so good with my Sennheiser HD6XX, It does support high impedance headphones well. Since my Schiit Asgard 2 died this year (sniff), I have no headphone amp at the moment, With the Yammy it sounds wonderful.

 

[nofacemonster]

Thanks for these measurements!

230mW sounds nice indeed. But 600 Ohm output impedance is way to high, isn't it? I mean my Sennheiser HD 650 have 300 Ohm. That's quite a mismatch and wouldn't almost all headphones be above a value calculated by the 1/8th rule?

Anyway, nobody would buy the amp for the headphone out. So it doesn't really matter probably.

I do, And it is the single most important Information I have seen online in a while. Thank y'all for this.

 

[nofacemonster]

Thank you.
Headphone output impedance is about 600 ohm. The amplifier is able to send clean 8.33 Vrms into 300 ohm load, that makes 0.23W/300ohm. Nice, isn't it?

Amazing information. I always wanted a Yamaha on my headphones. Since my headphone amp died out, This is simply great information. Thank you!

 

[Izaac]

I found one AX-369 at home. It wasnt used for about 25 years and i am wondering if this could be a good pair with ELAC Uni-Fi 2.0 UB52 ? I appologize, but i am not familiar with all the measurements and i dont know if this a good amp.

 

[witwald]

@Izaac The Yamaha AX-396 is a very nice amplifier, as borne out by the test results presented in this thread. It's got 60W of power into 8 ohms, which would enable it to pair very well with the ELAC Uni-Fi 2.0 UB52 loudspeakers. Of course, all of this assumes that your AX-396 is in good working condition, even after such a long period of not being used.

As the impedance of your loudspeakers dips down as low as 4 ohms in places, it's worth taking a look at the power output of the AX-396 into a 4-ohm resistive load. The plot below indicates that, using a 1kHz test tone, the AX-396 can produce around 90W into 4 ohms before high levels of distortion begin to set in (i.e., the distortion line begins to rise steeply). Over much of its normal in-use operating range, the distortion levels are below 0.02%. That's a good result, and this amplifier might therefore be considered to be an excellent example of the proverbial "straight wire with gain" amplifier design philosophy.

Please report back on your experience when you get the chance.

 

[Izaac]

@witwald Thank you for the explanation.
I found Amirm`s video, where he explains the tests and watched it today along with a nice explanation between Class A, Class B, Class A/B and Class D amps.

I will skip the ELAC Uni-Fi 2.0 UB52 and buy ELAC DBR62 .

Unfortunately i dont have room for the Yamaha AX-396 as its to wide and most likely go with 3e Audio A5 or A7 .

 

[gino1961]

Hi ! nice trhead indeed Thank you
I see some room to place bigger and better caps Like 2 x 15mF

they could lower the noise a bit and provide more energy on demand