Purifi Class D: Junk?

georgehifi8,489 posts02-17-2021 7:10pm

In my past experience with the Nord Hypex NC500 monoblocks using the Sparkos and Sonic Imagery opamps, the differences were pretty obvious.

Best is no buffer at all, direct in, as I’ve done. (you don’t need a buffer driving another buffer)
If the output buffer in your source (pre or dac) is less than <50ohm output impedance and has high enough voltage output gain to give the volume you need, you’ll have better sound than any additional buffer (regardless of how good) that’s in the signal path

Cheers George

No, it is not, especially with the Hypex amps.  The input is meant to be driven by a very low impedance source. The input of the unbuffered amp is essentially in the feedback path. Not having a local buffer is a recipe for doing it wrong.  This is the difference between people who actually know what they are doing and those who do not. People who do not make statements like this above.

I can remember how something sounded 10 years ago.....really! 

Righhhhttttttt


Most people can't pick their own speakers out of a line up once they are gain matched and frequency compensated, and often not even with frequency compensation.

You may remember a general impression, but from a comparative basis 10 years ago, sorry, that is just not true. You believing that does not make it right.

Toole showed in the Harmon tests how flaky most audio reviewers are.  Looking at the rooms many of them used, different speakers, etc. the odds of them effectively pulling the characteristics of a single unit out are slim (to none). 

Example,
i had not listened to the stereophile first test disc in 10 years.  However, my system 10 ears later was more revealing than that older system except for the fact that the original system used super highly modified original Quad electrostats.(modified by me....the most extensively modded Quads that i have ever heard of).  When I played the disc 10 years later it did not sound right at all....the orchestra, the air, the bell ringing in the backround, the guy singing in Hebrew.....just not right.  So, I removed the midrange from its box and put it on top of the speaker and propped it up with a paper back book underneath (no baffle) and changed the xover on the woofer so it now went to 300hz as i knew the midrange driver on an open baffle would not do anything below 300hz.  After listening......most all of the difference from what I had remembered 10 years before came alive.  Still not quite as good as the old super modified Quad....but now very close....the reverb was going on for ever......before it was all blunted with the midrange in the box. 

Yes, indeed you can remember what something sounded like 10 years before.  Anyone can do this.....with an open mind and open heart.

In a few more days the Weiss opamps will be at 200 hours and ready for evaluation. Also I have the amp running through a 500 watt balanced isolation transformer along with the DAC and pre; I wonder if there could be any current starvation going here.

Linear power supplies on amplifiers draw current in large peaks, much higher than the average power current draw. A 500W isolation transformer will act like an inductor with a current limiter. It may be better, it may be worse.