• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Vera Audio Class-D Amp Build Quality

Armand

Member
Audio Company
Joined
Jun 25, 2018
Messages
96
Likes
321
Is is a 20kHz 3,1V sine wave mixed with a 440kHz 0,3V sine wave.
There are small amounts of unavoiadable remaints of the switching frequency left on the output on class D amplifiers. It cannot be heard and it does not affect tweeters. Let me explain why.

The switching frequency current and power
A typical tweeter inductance is 30uH and that alone will represent an impedance of 80 Ohms. Adding the tweeter DC resistance of typical 6 ohms we end up with 86 ohms resistance to the 440kHz signal. The current in the tweeter will then be 0,3v/86= 0,0035A (3,5mA). Calculating the power we get 0.0035*0.0035*86=0,001W
On top of that I don't think it is neccassary to say that 440kHz is very very far from being audible either.

The high frequency audio signal
The 20kHz signal is 3,1V and the AC resistance (impedance) of the 30uH coil is 3.8 ohm. Adding the DC resistance og 6 ohms we get 9,8 ohms.
The current in the tweeter will be 3,1/9,8=0,316A. Calculating the power we get 0.316*0.316*9,8=1W

To sum up the math in words.

The signal we see in the oscilloscope does not look that nice. The 440kHz frequency is only about 10 times smaller than the 20kHz auido signal.
But because of the inductance in the tweeter the power delivery of the high frequency is 1000 times smaller. Even when a fairly small 3,1V 20kHz signal. At higher sound levels it will be many thousands time smaller. Its neglible.

0,001W power is way to little to matter at all. Also understand that this power is continous from the moment the amp is turned on. It is not something that changes. It is constant and independant of the music signal. It will heat up the tweeter by something like 0,01 degrees. I haven't seen anyone claim that a 0,01 degree constant temperature difference has a huge impact on the sound yet.

This supposedly damaging high frequency noise is the last grasping at straws to disqualify class D amplifiers.
I have here explained why it has no effect.
Why cannot you explain why it is so bad?
 

tmtomh

Major Contributor
Forum Donor
Joined
Aug 14, 2018
Messages
2,844
Likes
8,421
I am sure that John does not speak about audibility, he rather speaks about technical accuracy.

BTW, is this a sine wave or something else? And we are sure it does not matter?

View attachment 159494

The entire point of this part of the discussion - and the point @amirm and @Armand are trying to make - is precisely that one cannot answer the question "are we sure it does not matter" simply by looking at that waveform and saying, "oh, that looks ugly, therefore there must be a problem."
 
OP
maty

maty

Major Contributor
Joined
Dec 12, 2017
Messages
4,600
Likes
3,181
Location
Tarragona (Spain)
 

Bjorn

Major Contributor
Audio Company
Forum Donor
Joined
Feb 22, 2017
Messages
1,369
Likes
2,699
Location
Norway
The Vera Audio P400/1000 is back in stock now. Only a few for now, but numbers will gradually increase in the weeks to come.
 

Feyire

Active Member
Joined
Mar 9, 2019
Messages
272
Likes
314
Location
Netherlands
The Vera Audio P400/1000 is back in stock now. Only a few for now, but numbers will gradually increase in the weeks to come.
Safe to assume that the latest NCOREx amplifier range from Hypex will be available in the future, right?
 

Bjorn

Major Contributor
Audio Company
Forum Donor
Joined
Feb 22, 2017
Messages
1,369
Likes
2,699
Location
Norway
Safe to assume that the latest NCOREx amplifier range from Hypex will be available in the future, right?
We need more information before we can make decision.

The new NCx500 comes with an internal buffer, something Vera Audio doesn't need since VA has developed its own buffer with world class performance. The new module offers somewhat better cooling. However, great cooling no matter how the amplifier is being used is already take care of in the P400/1000 unit. So we're primarily left with sligthly more power with very low impedances. We need to weigh that against the cost and see what more is coming.
 

Bjorn

Major Contributor
Audio Company
Forum Donor
Joined
Feb 22, 2017
Messages
1,369
Likes
2,699
Location
Norway
A teaser of our next amplifier.
Vera Audio 4 ch. Power Amp_top 10.png
 

Bjorn

Major Contributor
Audio Company
Forum Donor
Joined
Feb 22, 2017
Messages
1,369
Likes
2,699
Location
Norway
Top Bottom