Sound Quality Vs. Measurements

[tessier]

Originally Posted by Wavebourn

I agree with Jon here: when building something for high end potential flaws have to be examined under microscope. Like, apply 1 MHz triangle on full swing to see close how it behaves on 20 KHz sine. If it is subtle on oscilloscope and hard to measure, it may be well audible as "something is odd". But if it looks nice, fronts of squares are equal, that means at least stereo image would not be blurred by phase intermodulation.

Hi Wavebourn

You wrote: "apply 1 MHz triangle"

You did mean a 1 MHz square wave ?

So, you just mix that 1 MHz signal with a 20 KHz sine and send it to the amp under test ?

Thanx

Paul

[Wavebourn]

Originally Posted by tessier

Hi Wavebourn

You wrote: "apply 1 MHz triangle"

You did mean a 1 MHz square wave ?

So, you just mix that 1 MHz signal with a 20 KHz sine and send it to the amp under test ?

Thanx

Paul

Paul, I apply triangle to see how slopes are equal, and what is their form. No need for additional 20 KHz. If I remember correctly that discussion was related to phase intermodulation. Instead of measuring it directly that is hard and almost impossible I can stretch and extrapolate. Stretch and extrapolate, in most of observations. Find what causes misbehaviour and correct it.

[tessier]

Originally Posted by Wavebourn

Paul, I apply triangle to see how slopes are equal, and what is their form. No need for additional 20 KHz. If I remember correctly that discussion was related to phase intermodulation. Instead of measuring it directly that is hard and almost impossible I can stretch and extrapolate. Stretch and extrapolate, in most of observations. Find what causes misbehaviour and correct it.

Hi Wavebourn

I've done a search and found in one of your post that you linked that subject to this one:

Wavebourn Tower-III High-end hybrid amp

On the scope it's look like a bad square wave, so it's was just a triangle with a bad slope from the output of an amp with phase intermodulation ?

Thanx

Paul

[Wavebourn]

She tried to fix her TV...

http://wavebourn.com/1022.flw

[Wavebourn]

Originally Posted by tessier

Hi Wavebourn

I've done a search and found in one of your post that you linked that subject to this one:

Wavebourn Tower-III High-end hybrid amp

On the scope it's look like a bad square wave, so it's was just a triangle with a bad slope from the output of an amp with phase intermodulation ?

Thanx

Paul

No, that time it was bad square wave. The same trick: expand and extrapolate. This picture looks quite asymmetrically.



This is much better:



Now, let's check on more realistic frequency 50 KHz, 100V P-P:

[tessier]

Originally Posted by Wavebourn

No, that time it was bad square wave. The same trick: expand and extrapolate. This picture looks quite asymmetrically.

Hi

Which are best to test phase intermodulation; 50khz triangle or 50khz square wave ?

So we need to look at the best output triangle or square signal for the lowest phase intermodulation, but I've test bad sounding amps showing an almost perfect 100khz square wave on my scope ??

Thanx

Paul

[Wavebourn]

As higher as possible frequency, at full swing. Bioth triangle and squares are useful, when you know what to look for.
But of course it all depends on topology.

As you see from last picture, 50 KHz does not show very much. You barely can see if fronts are equal.

[Wavebourn]

Originally Posted by tessier

So we need to look at the best output triangle or square signal for the lowest phase intermodulation, but I've test bad sounding amps showing an almost perfect 100khz square wave on my scope ??

There may be lots of causes of bad sound that can be diagnosed by different symptoms, and phase intermodulation is just one of them.

As I said many times, there are no single recipes to test any amp independently of it's structure.

[a.wayne]

@DVV,

No worries mate, I dont get anywhere near electrons when listening , glass a wine in one hand , remote in the other .

I do on occasion touch the reel and TT , never been buzzed by them ...

[a.wayne]

The few times I have gotten buzzed were with tube amplifiers, another reason for only SS stuff ..