FFT and Sine Waves Question

Jerry Avins wrote:


> 2. Why are push-pull amplifiers standard for low-distortion
>    applications?

BTW, the push-pull amplifies are no-no for the real low distortion 
applications.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

Vladimir Vassilevsky <nospam@nowhere.com> wrote:

> Jerry Avins wrote:

>> 2. Why are push-pull amplifiers standard for low-distortion
>>    applications?

> BTW, the push-pull amplifies are no-no for the real low distortion 
> applications.

It would seem to depend on what kind of distortion you were
looking at.  

-- glen

On 9/1/11 3:18 PM, dvsarwate wrote:
>
> On a semi-related matter, I have no problems
> with the FIRST overtone being the same as the
> SECOND harmonic.  After all, one cannot have
> an OVERtone unless one has a tone to begin
> with!  But, I do worry that r b-j and Dijkstra will
> want to call it the zero-th overtone.....   :-)
>

damn straight!  maybe i'll call it the minus-oneth overtone just to fuck 
with your brains.

Edgar Dijkstra will have to speak for himself (from the grave).

speaking of graves, Hurricane Irene caused a bunch of acute flooding at 
various places in the mountains of Vermont (not *my* place, thankfully). 
  these flash floods washed out roads in scores of places in the state. 
  besides that, in the town of Rochester VT, part of the cemetery was 
washed out:

   http://www.csmonitor.com/CSM-Photo-Galleries/In-Pictures/Hurricane-Irene

the Burlington Free Press had a closer ground-level pic of the washed 
out cemetery (coffins strewn about), but i can't find it on their 
website and my DSL is too slow to look any more.



-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

glen herrmannsfeldt wrote:

> Vladimir Vassilevsky <nospam@nowhere.com> wrote:
> 
> 
>>Jerry Avins wrote:
> 
> 
>>>2. Why are push-pull amplifiers standard for low-distortion
>>>   applications?
> 
> 
>>BTW, the push-pull amplifies are no-no for the real low distortion 
>>applications.
> 
> 
> It would seem to depend on what kind of distortion you were
> looking at.  

I thought I made it clear: real low distortion :-)

Whether it is in the audio or in RF, small signal or power 
amplification, the single ended amplifiers achieve the topmost specmanship.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

Vladimir Vassilevsky <nospam@nowhere.com> wrote:
 
(snip) 
>>>BTW, the push-pull amplifies are no-no for the real low distortion 
>>>applications.
 
>> It would seem to depend on what kind of distortion you were
>> looking at.  

> I thought I made it clear: real low distortion :-)

> Whether it is in the audio or in RF, small signal or power 
> amplification, the single ended amplifiers achieve the topmost 
> specmanship.

That should be true, but is it always true?  

Are higher power output devices naturally less linear?  

As I understand it, the usual problem with push-pull amplifiers
is at smaller signal levels.  If you know you always have large
signals, does that change the decision?  

Now, to be even less obvious, how about a push-pull class A
amplifier, such that both drivers are always on.  It will
dissipate a lot of power, but might be even lower distortion
than a single ended class A.

-- glen

glen herrmannsfeldt wrote:

> Vladimir Vassilevsky <nospam@nowhere.com> wrote:
>  
> (snip) 
> 
>>>>BTW, the push-pull amplifies are no-no for the real low distortion 
>>>>applications.
> 
>>>It would seem to depend on what kind of distortion you were
>>>looking at.  

>>I thought I made it clear: real low distortion :-)
> 
>>Whether it is in the audio or in RF, small signal or power 
>>amplification, the single ended amplifiers achieve the topmost 
>>specmanship.
> 
> That should be true, but is it always true?  
> 
> Are higher power output devices naturally less linear?  
> 
> As I understand it, the usual problem with push-pull amplifiers
> is at smaller signal levels.  If you know you always have large
> signals, does that change the decision?  
> 
> Now, to be even less obvious, how about a push-pull class A
> amplifier, such that both drivers are always on. 

The real life signals aren't symmetrical; as such, there is no inherent 
distortion advantage in the push-pull.

There are specific difficulties with the availability of the true 
complimentary devices and with the accurate splitting of the signal and 
then adding it back.

> It will
> dissipate a lot of power, but might be even lower distortion
> than a single ended class A.

It depends; We are down to the details here. Questions about particular 
applications are welcome.

VLV