Sound Quality Vs. Measurements

[M Gregg]

I still think,

That a pair of speakers should be in a public room and the amps and equipment in another..Then keep the same source and play all different amps and topology of SS and tube and hybred and ask them to pick the one they would buy after 15 Mins periods..over a day..Including SMPS etc etc Krell...all types home made..And measure each of them for fidelity and match the results

Perhaps at a HIFI convention ...a big one! Don't let them see the equipment or whats playing...no list either

Just for fun of course

Regards
M. Gregg

[CopperTop]

Isn't an SMPS just a class D amplifier with a DC input signal?

[abraxalito]

No, normally a bit simpler in its switching (e.g. just one switching transistor rather than two) because it only needs to source current, not sink any.

<edit> But there are topologies which are more akin to class D amps - forward converters for one.

[Wavebourn]

Originally Posted by CopperTop

Isn't an SMPS just a class D amplifier with a DC input signal?

No. SMPS contains rectifier and switches working on high frequency in order to make transformer smaller and lighter. However, as the result they contain much more parts that generate HF, filter, protest, cool down transformers and transistors. If to fit 60 Hz transformers, rectifiers and linear regulators, in the same enclosure with the same cooler, you may get something in the middle in terms of size and weight per power, but of higher quality than SMPS.

[suntechnik]

Originally Posted by CopperTop

Isn't an SMPS just a class D amplifier with a DC input signal?

Trafo is a key component of a switching power supply still. Mister Faraday was really good at Physics without his invention we gonna stay in Middle Ages forever.

However due to higher frequency a trafo could be very small relatively to one that operates at 50/60Hz. Means huge savings on metal and labor for mass production manufactures & big bonuses for upper management guys.

[210]

Originally Posted by godfrey

I tend to feel sorry for the input stage, because it gets blamed for everyone else's mistakes.

Internal mutterings of a feedback amp:
Feedback network: Oh look; the output stage is clipping. Let's go beat up the input stage again, that should fix it.
Input stage: sigh....
2'nd stage: O no! What they gonna do this time, switch me off or saturate me so bad it hurts?

Happy weekend, everyone!

Output Stage to Feetback Network: Here you have all the junk!

Feetback Network to Input Stage: Here you have a signal, that will correct your misbehaviour!

Input Stage to Second Stage: Here you have a signal, that is already corrected from my misbehaviour
and will correct your misbehaviour!

Second Stage to Output Stage: Here you have a signal, that is already corrected from
the misbehavior of the Input Stage and mine, and finally will correct your misbehaviour.

[ThorstenL]

Hi,

Originally Posted by M Gregg

I still think,

That a pair of speakers should be in a public room and the amps and equipment in another..Then keep the same source and play all different amps and topology of SS and tube and hybred and ask them to pick the one they would buy after 15 Mins periods..over a day..Including SMPS etc etc Krell...all types home made..And measure each of them for fidelity and match the results

Funny thing, this precise test was done by Juergen Ackerman in germany as part of work on a habilitation in psychology. Stereophile had an article including extended information on this, use google.

The outcomes (statistically speaking) of this test are quite telling on many levels.

I would also recommend to e-mail John Atkinson for the text if his Richard C. Heyser Memorial Lecture: “Where Did the Negative Frequencies Go?” (or PM me if you don't want bother JA, which he may appreciate) as this contains some very crucial points relating to behavioural psychology and audio, that made me sit down and exclaim "Grass Mud Horse".

Of course, NON of this proves anything worth all the tea in china, but it may "change your mind".

Ciao T

[a.wayne]

So no wire with gain ...?

[Wavebourn]

Output stage: Current increases, I loose Beta! Driver, give me more!
Driver: Can't give you more, I have my own limits! Well, can give little bit more, don't ask too much!
LTP: Hey, where is feedback voltage, output stage?! Input signal increases pulling my left leg, give me more voltage on right leg or I will... Ooohhh...Oooohhh... (All together): FFFARRRTTT!

[abraxalito]

Originally Posted by a.wayne

what is plitron doing differently ...?

I went over to Plitron's site and took a peek at their offerings. The transformers which have the lowest interwinding capacitance are those they market for medical applications (as hinted at by Thorsten above). They say:

Leakage Current: Special design and winding techniques unique to Plitron allow this series to have leakage currents well below international medical safety requirements. This allows margin for line cords and other peripheral components. Measurements are made between the primary windings and all other leads (secondary windings, and ground screen, where used) normal polarity, neutral closed. See ratings table for nominal values.

Capacitance: Low interwinding capacitance provides good high frequency common mode noise rejection. Measurements are made using the same method as for leakage. See ratings table for nominal values.

The results of all this? Well scrolling down, these are the only trafos I've so far found on there where they quote the interwinding capacitance. For a 750VA isolation trafo, its 1500pF. At 200VA, its 710pF.