JFET+BJT low THD+N buffer.

[Hayk]

The circuit is invented by a Japanese audio designer, I forgot his name, close friend to Jean Hiraga.
L'Audiophile magazine, published by Hiraga, showed an active filter using this circuit with 2sk30 jfet, I forgot the PNP transistor.
I make the same circuit but using 2sk246+bc560c in parallel with their complimentary, 2sj103+bc550c.
By paralleling, I subtract the even harmonics from each other to result very low distortion and 3db less noise.
bellow is the circuit loading 3k//2.5k load for 0.0005%.

 

[Hayk]

This is an example using LM3886 with inverted and buffered.
The distortion of lm3886 is not implemented, so, the THD 0.0002%is only that of the buffer. You read, the 2nd harmonic is the main issue which can be canceled by adjusting the 6.8k resistors for minimum to get 0.00006%

 

[solderdude]

Can one really hear the difference between 0.0002% (harmonics -114dB) and 0.00006% (-124dB) and is it worth the trouble for any other reason than designing a buffer for a measurement device ?

 

[Hayk]

This website is dedicated for such purpose. See the SINAD classification of ASR.
No one can be convinced that an amplifier with 1Mhz bandwidth can sound better than 100khz one. But in matter of distortion, there are and has been audio publications pretending to hear down to -110db including this website.
For studio applications it becomes an important factor but for domestic use, it is nonsense. On the contrary, you can get more vivid, dynamic sound if you flavor with the right nonlinearty see the amps bellow.

3 transistor classA 50w/25w with variable output impedance as SE triodes.

Function description is here. https://www.eevblog.com/forum/projects/can-this-3-transistor-classa-amp-50w4ohm-with-1-3a-bias-still-be-called-classa/#msg5701985 This amp initially I designed to function with constant current, where the power CCS modulates itself to keep a constant current from...

www.audiosciencereview.com

Post in thread 'TDA7293, exempt of crossover distortion.' https://www.audiosciencereview.com/...pt-of-crossover-distortion.66453/post-2612278

 

[solderdude]

There has been a notable electronics designer claiming to hear differences in signals where only differences as low as -350dB in a filter were present.
(He did not claim to be able to hear differences as small as -350dB)

It seems not many people understand that while a signal is blasting at 120dB SPL that they can still be able to hear 10dB SPL (related) signals at the same time.
Blasting loud sounds vs barely audible sounds when having acclimated in a dead/silent room for a while at the same time... nope not audible ever.
The dynamic range of the hearing is about 70-80 dB not any better.

Pushing engineering is fine but in many cases inconsequential.

 

[Hayk]

The problem arises with 24bit ADC that became a standard in recording studios. When a consumer, convinced that his DAC can reproduce 120db dynamics, he wants all the remaining equipment follow the same specification.
With vinyl world, it was hard to make believe that it can reproduce better than 50db, with all the hiss and the cracks which made people accept 80db S/N ratio of tube amps.
Nowadays, the naive people are convinced that for high fidelity, they need studio quality equipment.
0.0000x %THD+N =excellent.
0.000x% = very good.
0.00x% = good
0.0x% =normal
0.x% = dirty

 

[solderdude]

Amir has 5 tiers. (THD+N)

Excellent < 0.002 (yep 2 zero's not 4)
Very good 0.002 - 0.005
Good 0.005 - 0.01
Fair 0.01 - 0.1
Poor > 0.1

Yet, we all know many people find gear that is even worse than that excellent sounding and love all the signal degradation on vinyl and tape.

 

[Hayk]

This was once upon a time, with 16bit cd era where minimum THD+N was 0.002%. With 24bit now we are 0.00006% or -124db and this was 7 years ago.
When I read what people speak to each other, the numbers represent how clean it sounds, the lower it is the cleaner it should.
On DIYAUDIO website, there is a very active amp to built, the Wolverine. People are interested only because it aligns 4 zeros in a row. I submitted 3 music files, they all fail to reproduce clean sound because of bad PCB layout. It doesn't matter anyone if it sounds dirty as long as it measures excellent.

 

[solderdude]

When I read what people speak to each other, the numbers represent how clean it sounds, the lower it is the cleaner it should.

Doesn't work that way... Below 0.01% there simply is no audible benefit. It is the limit of our hearing capabilities when listening to music recordings.

The number of 0's is just a numbers game for the sake of engineering and obtaining the lowest numbers in a data sheet (@ 1kHz).
That's what the SINAD 'ranking' is for and why there are a few tiers only.
Those numbers are about engineering and not about audio quality.

If an amplifier sounds 'dirty' but 'measures well' then the culprits could be:
A: the wrong thing(s) or not everything that needs to be measured is measured.
B: the combination of speaker + amp is not considered and there is an interaction.
C: the use recording quality is poor (dirty sound is in the recording and reproduced faithfully)
D: the transducer is poor quality
or.. a combination of the above reasons.