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Old 15th November 2009, 03:52 AM   #901
AKSA is offline AKSA  Australia
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Hi Nico,

I've had a good listen. First is sharper, quite sibilant, with a slightly forward instrumental backing, voice a little more recessed and mechanical. Second is smoother, little sibilance, with a forward vocal, recessed instruments, except for the castanets.

This is pretty much what I've come to expect from PP versus SE. However, the nested feedback mod I suggested to you earlier for the PP circuit will greatly enhance the imaging issues, render the vocal more prominent and add depth to the instruments.

Subjectively speaking, there is for me more coloration in the SE sound but it is musical. The coloration of the PP design is slight, but not as benign. The best way to describe the difference lies with the word 'fatigueing', an urgency of presentation in the PP circuit which militates against a relaxed, laid back listening experience.

This is all very subjective, and people's views vary, but a good portion of the listening public would prefer the SE sound.

Thank you for making a strong effort to show the differences. Of course, a very good compromise here is to use a high bias quasi complementary output stage - arguably the best of both worlds. But that needs a phase inverter, and in this single emitter follower output stage configuration, that's probably wasteful. Better to refine the fully complementary circuit further.

Cheers,

Hugh
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Last edited by AKSA; 15th November 2009 at 03:56 AM.
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Old 15th November 2009, 04:33 AM   #902
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Hugh, I don't know your opinion on this however:

I believe class AB is an interesting compromise sound-wise. During normal volume the output stage will be in class A - this will be conducive to even harmonics. But on rough parts, say explosions or dramatic moments which are generally not laid-back, the amplifier is pushed into B, where 3rd harmonics are injected and usually dominant. In this way, perhaps AB is more suited to movie sound. (I suppose the question is whether you want to "experience" the drama as much or more than you want to experience everything else)

If we go for a class A SE then it will be a different animal in this respect.

Do you have any comments on this?

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Old 15th November 2009, 04:43 AM   #903
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Anthony,

I agree with you!

The PP HAKSA has a monotonic decreasing distortion profile at lowish volume, no more than 1Vrms. Beyond that, and coinciding with entry into Class B switching operation, the H3, H5 and H7 artefacts start to increase sharply, particularly H3 and H5. All this is visible on LTSpice, BTW. This abrupt change in the harmonic profile is not musical, and manifests as aural unease and hardness, aka 'fatigue'. This also happens with the SE amp, of course, but only at clip when half the waveform falls apart completely.

In HT applications, we are generally only registering peaks on special effects (unless it's a musical!). Consequently, the ear/mind interface, whose powers of aural discrimination are greatly reduced owing to visual stimulus, seeks out real world sounds, lacking in any musicality however, so the loss of musical pitch harmonics is no big deal. Consequently, we can choose chip amps, and run 'em close to Class B for highest efficiency, necessary for the high packaging density of multichannel amps.

Cheers,

Hugh
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Last edited by AKSA; 15th November 2009 at 04:45 AM.
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Old 15th November 2009, 05:10 AM   #904
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Hello Hugh and all the guy's

I've read all the tests and opinions for HAKSA PP and SE amps.

I just have an old Sennheiser HD-420 headphone and few cheapo ones, there is now much better ones today, so my old HD-420 will not have the best sound compared to the newest Sennheiser.

But at close listening, like with an headphone, I think a warm SE amp sound would have my favor.

So I vote for the SE.

I will wait for the final decision of all the guy's.

Bye

Gaetan

Last edited by gaetan8888; 15th November 2009 at 05:16 AM.
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Old 15th November 2009, 05:15 AM   #905
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Okay Hugh, why not add schottkeys to the class AB's emitters? This smoothens clipping and 3rd harmonics don't rise sharply after cutoff (although they are increased in class A mode)... In fact, we could operate the OPS at as low as 6mA (I tested this on the sim with MBR745 diodes). Since prototypes have been built, why not try it?

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Old 15th November 2009, 05:30 AM   #906
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Quote:
Originally Posted by AKSA View Post

This is all very subjective, and people's views vary, but a good portion of the listening public would prefer the SE sound.
I'll say it's subjective. Hugh you do realize that you are listening to two files, one of which is inverted. Both tracks are at different levels, not only between each other but between channels.
When I had my first listen this morning, I could hear a difference. As the day progressed and I managed to get these files to where they are almost on a par, that difference has vanished. What I am listening to now is indistinguishable and I'll say it again: these files are so exactly the same, they are almost certainly from the same amp.
Look at this, left (top) and right (bottom) from both files overlaid.

117.PNG

Now, an interesting thing happened while I was getting that graph together, I noticed that the left channel looked very similar to the right from the other file and vice versa. I slide the overlay up and presto! exact match. That was the final piece of the puzzle - swap channels on sample #2.

I'm not impressed.

Last edited by MJL21193; 15th November 2009 at 05:42 AM.
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Old 15th November 2009, 05:45 AM   #907
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Hmmm. John, you are saying, I presume, that Nico has given us the same file from the one amp, inverted it and changed the level, so as to confuse?

And then, of course, perpetrated an artful dupe on all of us?

This is kinda strange. Let's ask Nico.

Nico, is this two files, modded to look different, but from the same amp? Or are they two entirely different amps?

I find it hard to believe you would do this, but this is the net, so anything is possible, so I'm asking now.

If I heard a difference, it would almost certainly be level only, and my comments are trite, and I'm a goose. If Nico did deliver two files from two different amps, then we are all smart fellas. I guess when he answers, we will know for sure!

Nico, over to you.......

Cheers,

Hugh
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Old 15th November 2009, 07:31 AM   #908
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I see some differences... Of 3db at least, if you look at the scale. Is this not enough of a difference?

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Old 15th November 2009, 08:17 AM   #909
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Hello guy's

I did rely on Nico post #842, his SE sound description say a lot to me.

I cannot download the Nico's test files since I'm in a low speed internet (5Kb download speed), so I can't check them myself, but I don't think Nico would have given us the same file from the one amp.

They can be very small differences into the harmonic content between those two files, that can not be easy to see on the images, but the resulting sound would be differents between the PP and SE test files.

Bye

Gaetan

Last edited by gaetan8888; 15th November 2009 at 08:41 AM.
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Old 15th November 2009, 08:46 AM   #910
AKSA is offline AKSA  Australia
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Yes, Gaetan, I think you are right.

Nico, I am sure this is male bovine excreta. I can't see you doing anything but being 100% genuine and helpful!

What this does show clearly is that even relatively fine measurements and graphing fail to pick distinctions which, with care, the human ear can easily detect. This says quite a lot about measurement technology, and it isn't flattering.

Cheers,

Hugh
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