Why does Onkyo A-9010 sound so good?

Oneminde

Member
2014-06-22 11:14 pm
I am yet to build my first amplifier and to make a long story short, I will need something in the next couple of months since I am developing a Transmission Line loudspeaker and the Onkyo A-9010 popped up as a supposedly fantastic amplifier considering its price. 44-70 watt of useful energy (8-4 ohm's). Comparing the 9010 to other Onkyo amps such as 9050, 9150 etc, people who have listened to these state that non of them sound as the 9010.

Now, I have not auditioned the 9010 or the other Onkyo amps, but I trust the general consensus about this amp. So my question is this;

What exactly is the reason for the sound signature of the 9010 ?

Another thread was created with a similar question and a member relied with this:

Quote:
Originally Posted by Klangwelt
Just bought this amp and it sounds better than it should at this pricerange. Can anyone tell me what kind of topology this is? I'm a complete noob, and would appreciate some input. Apologies for the schematic, the screenshot from the service manual didn't work out well in terms of sizing.

Thanks!


vzaichenko: Well, it's rather simple yet efficient. CCSed long tail pair, feeding a balanced (mirrored) push-pull VAS with simple EF2 output stage, based on BJT Darlington pairs (Sanken) - good ones, by the way. Class AB operation.
Thread: Noob Question - Onkyo A-9010 - what kind of topology?

Since I am trying to learn and understand, what is required for this circuit to be expanded to say, 150, 250 watt etc ?
 
It's easier to design an amplifier of such moderate power (44W).
Scaling it up would sacrifice much of the sound quality.

That's not necessarily the case. It depends on how it is scaled, voltage increase behaves much different than parallel-ing more darlingtons or different ones. To generalize it that much is simply wrong.

Could also suggest that your 'quality threshold' experience may not be as high as it could be ;)

:tongue:

But ofcourse you are right. At first we have to define what 'better' means and I tend to repeat myself at this topic, 'different' is not always better. What kind of improvement or difference does it give and while one might like it, it could still be a kind of effect which could be nice at first but might run stale and annoying on the long run. Not to mention if it's really closer to the original than other amplifier concepts - I mean, High Fidelitys ultimate goal is per definition to be as close to the original as possible.

Measurements are very important there, at first it has to be checked if the judgement might be founded on a emphasis (or dip) somewhere in the frequency response or harmonics or if the comparison to other amps is realistic, and repeatable, the human ear very quickly judges louder sounds as better, that means, exact level adjustment in a comparison is very important. Are there any measurements of the Onkyo A-9010 available?
 

Oneminde

Member
2014-06-22 11:14 pm
Could also suggest that your 'quality threshold' experience may not be as high as it could be ;)
You are judging me, that's not fair .. LOL. Bear in mind that we are talking about roughly $250 aka budget amplifier. Yes yes I know, there are many kits for that price who can compete and probably beat it, but if we are talking ready made amplifier from a OEM, then it will be very difficult to beat. The next lvl up for me would be the NAD C388 which is beating many amps that cost twice or more.

Measurements are very important there, at first it has to be checked if the judgement might be founded on a emphasis (or dip) somewhere in the frequency response or harmonics or if the comparison to other amps is realistic, and repeatable, the human ear very quickly judges louder sounds as better, that means, exact level adjustment in a comparison is very important. Are there any measurements of the Onkyo A-9010 available?
I can't find any in depth measurement, but I would be interested in doing one.

Personaly, I would not look for it in the shophisticy of the schematic architecture, but probably just vas has low noise... somehow... power supply is good, ground and power planes are well traced,
etc
Well, isn't a good (quiet) power supply, proper grounding etc a given ? What I mean is this: An amp that has noise coming from the power section will introduce audible artifacts and is a completely isolated topic which should be treated separately as a whole (read between the lines :)) but which often is expensive and left out.

Since people are talking about the PWR possibly being a reason to the sound quality, here is that section from the service manual.
 

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Oneminde

Member
2014-06-22 11:14 pm
Which is fine. If it is not broken, why fix it.

I am a firm believer in that a good circuit is a combination of excellent components, good layout and good grounding plane. But could there be, lets say, physical damping attributes in transformer that reduce the electrical interference and audible sound. They are certainly using a EI transformer just like Yamaha and many others.
 

Oneminde

Member
2014-06-22 11:14 pm
Without being able to measure ripple, EM, RF etc etc, besides only two complementary transistors in the output per chn, what could - hypothetically - be the reason for the clarity and low noise people report ? I have attached the amplification section of this amplifier, discarding the input section for now.

- EDIT -
Since I am learning I want to ask if anyone can see DC Servo. I know such a circuit is important and signify a good amplification.
 

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Last edited:
some observations -
1 large emitter degen resistors on input diff pair will minimise "hard" slew induced distortion
2. symmetrical VAS with local feedback (just an observation, not necessarily a factor)
3. connecting the base of the centre PNP transistor in the differential VAS circuit to the driver collector common-mode cancels Early effect distortion (this is a potential factor)
4. Phase lead compensation reduces high frequency distortion (around 2-20kHz) compared with Miller compensation
Overall gain however will be low and distortion figures could be around 0.02%- not as low as can be achieved but nevertheless this would be OK (if it is that low).
 

Oneminde

Member
2014-06-22 11:14 pm
Is this a commercial speaker or just something for your own use? If the former, it is a false economy to buy a cheap amp.
Both. This amp will get things started. As for a reference amplifier - which I will assume is what you are talking about - the NAD C388 is a good contender. But as we both know, reference amplifier is a never ending debate, so lets just leave it at that.
 

Oneminde

Member
2014-06-22 11:14 pm
some observations -
1 large emitter degen resistors on input diff pair will minimise "hard" slew induced distortion
2. symmetrical VAS with local feedback (just an observation, not necessarily a factor)
3. connecting the base of the centre PNP transistor in the differential VAS circuit to the driver collector common-mode cancels Early effect distortion (this is a potential factor)
4. Phase lead compensation reduces high frequency distortion (around 2-20kHz) compared with Miller compensation
Overall gain however will be low and distortion figures could be around 0.02%- not as low as can be achieved but nevertheless this would be OK (if it is that low).
Point 1; Harsh as in steep ?
The others are also interesting observations.