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Arny Krueger
 
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Default Should I build this simple Mosfet follower amp?

"Bob-Stanton" wrote in message
om
"Arny Krueger" wrote in message
news:N8udnSIGNbzHVLeiU-


I guess, but....

If we go back a number of posts, I provided a means that works with
a lot less fooling around.


Which is what?



"Arny Krueger" wrote in message


If you want to try to hear high frequency nonlinearities, pick a test

signal
with lots of high frequency content (say the keys jangling from
www.pcabx.com ) and high pass filter it at say 6-8 KHz. Then record the

say
8-22 KHz slice of sound at a high level (CD burner) and play it back on

the
suspect CD player.


If the CD player is good, then this becomes a test of the power amp and
speaker. Power amps are the topic of the thread.

I don't know if anything could be simpler than what I proposed.


Sure, no equipment at all is simpler than any equipment.

The best test signal is music.


Hence the reference to test sounds from pcabx.com

The best test instrument is the human ear.


That's what I recommended using.

I think I might build this distortion tester. If someone elso wants to
build it, here is the schemetic:

DISTORTION TESTER


| Dummy Load | Highpass Filter | L-pad |Speaker

Amplifier-----------------------10 uF-----22uF---10 Ohms--
(D.U.T.) | | | | | |
10 Ohms 10 Ohms 10 Ohms | -10 Ohms----------
| | | 0.55 mH | | |
| | | | 10 10 Spk
10 Ohms 10 Ohms 10 Ohms | | | |
| | | | | | |
--------------------------------------------------------------------

All resistors are 10 Ohm, 10 Watt, from Radio Shack ($0.99)
Capacitors are 50 V, N.P., from Radio Shack ($0.99)
Speaker is any small speaker the goes up to 8 kHz or 9 kHz.
Inductor is approximately 120 turns, 22 gage wire, on 1.5 in dia form.


I don't know what could be simpler, anyone could built it. (Even me.)


My solution requires building nothing at all.



  #42   Report Post  
Bob-Stanton
 
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Default Should I build this simple Mosfet follower amp?

"Arny Krueger" wrote in message

I don't know what could be simpler, anyone could built it. (Even me.)


My solution requires building nothing at all.


Like the great man once said: "Things should be as simple as possible,
but not simpler."

Bob Stanton
  #43   Report Post  
Arny Krueger
 
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Default Should I build this simple Mosfet follower amp?

"Tony Pearce" wrote in message
u
"Bob-Stanton" wrote in message
om...

The best test instrument is the human ear.


A quaint notion, but not able to be substantiated these days.


Admittedly not the most sensitive solution, but still unbeatable in terms of
evaluating audibility.

Which is? (Don't say, "slew-rate")


How about Slew Induced Distortion?


How about nonlinear distortion at high frequencies?



  #44   Report Post  
Bob-Stanton
 
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Default Should I build this simple Mosfet follower amp?

"Tony Pearce" wrote in message . au...
"Bob-Stanton" wrote in message
om...

The best test instrument is the human ear.


A quaint notion, but not able to be substantiated these days.


Yes, a test instrument, such as a spectrum analyzer, can measure
things that are beyond the threshold of human ear. It can measure
noise , distortion, flatness, and transient response, beter than any
human ear.

Test instruments are more sensitive than human ears, but they don't
understand what they "hear". Can test instruments tell us the best
place to put a microphone, for the most muscically balanced sound? No.

Test instruments can "hear" the reverb of concerts halls. Can they
tell the difference between a great concert hall, and a less than
great concert hall? I don't think so. I don't think we have developed
our understanding of reverb data to that point. If we did, we could
make every hall concert hall, a "great" concert hall, with just a few
measurements and a few tweeks.

A spectrum analyzer can record all the data defining how something
sounds. But with a complex signal, such as an orchestra playing in a
concert hall, the data is overwelming. We simply can't look at the
data and tell if the orchestra sounds good or bad. But the human ear
"can". So, the human ear remains the best *overall* test instrument.

Bob Stanton
  #45   Report Post  
Tony Pearce
 
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Default Should I build this simple Mosfet follower amp?


"Bob-Stanton" wrote in message
om...
"Tony Pearce" wrote in message

. au...
"Bob-Stanton" wrote in message
om...

The best test instrument is the human ear.


A quaint notion, but not able to be substantiated these days.


Yes, a test instrument, such as a spectrum analyzer, can measure
things that are beyond the threshold of human ear. It can measure
noise , distortion, flatness, and transient response, beter than any
human ear.

Test instruments are more sensitive than human ears, but they don't
understand what they "hear". Can test instruments tell us the best
place to put a microphone, for the most muscically balanced sound?


Yes. But first you have to define "most musically balanced sound".

Test instruments can "hear" the reverb of concerts halls. Can they
tell the difference between a great concert hall, and a less than
great concert hall? I don't think so. I don't think we have developed
our understanding of reverb data to that point. If we did, we could
make every hall concert hall, a "great" concert hall, with just a few
measurements and a few tweeks.


Even using ears you will not get complete agreement on that, but test
equipment will show you what the differences are.

A spectrum analyzer can record all the data defining how something
sounds. But with a complex signal, such as an orchestra playing in a
concert hall, the data is overwelming. We simply can't look at the
data and tell if the orchestra sounds good or bad. But the human ear
"can". So, the human ear remains the best *overall* test instrument.


But YOU specifically use the term "TEST instrument" which the ear is NOT.

For determining a persons SUBJECTIVE audibility, their ears/auditory system
cannot be beat. Of course the result only applies to that particular person,
which is why OBJECTIVE test measurements are so much better for many
purposes, but not all I agree.

TonyP.





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Arny Krueger
 
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Default Should I build this simple Mosfet follower amp?

"Tony Pearce" wrote in message


For determining a persons SUBJECTIVE audibility, their ears/auditory
system cannot be beat. Of course the result only applies to that
particular person, which is why OBJECTIVE test measurements are so
much better for many purposes, but not all I agree.


I see other strong advantages to test equipment-based evaluation:

(1) Fast.

(2) Useful for testing equipment that is used repetitively or in cascade,
and therefore must have performance that is integer multiples better than
merely sonically transparent.


The test suite at my PCAVTech web site was designed to detect both *normal*
equipment deficiencies and also a wide range of pathological deficiencies
like relatively narrow-band performance problems.

The "Audio Rightmark" test suite cuts the PCAVTech test suite down somewhat
further, and in the process leaves a few more doors open to more
pathologies, but remains complete enough to be useful and interesting.


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