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Why has single ended output become popular

Hello
Can anyone explain to me why has single ended output has become popular. In my day it was push pull output with its distortion cancelling. My Quad 2 amp is push pull.
I have wondered this for a while, I must have missed it.
Explanation appreciated.
Thanks
thyristor44
 
I have built push pull and single ended I have used tubes and transistors and MOSFETs.

I really like the sound of single ended tubes when played through the right speakers. but my best amplifier by far is a class ABC push pull solid-state. I don’t think one topology guarantees a good sound. and without thinking about the interaction between your amplifier and its power supply and between your amplifier and your speaker you will only have part of the story.
 

kodabmx

Member
Paid Member
2011-10-31 1:00 am
Toronto
There are amplifier projects that are just a MOSFET and a Resistor. Thats it.

I tried this approach - the resistor being 2x120V 200W incandescent light - but the sound was not very good at all. To fix it, I just turned it from common source into a source follower and built it a voltage gain stage with tubes. It's the only amplifier I have that's single ended - mainly because the entire amplifier cost me less to build than buying a pair of good SE transformers. 8WPC out from over 400W in from the wall though - I only use it in the winter but it sounds wonderful for what it is.
 
The distortion your push-pull is cancelling is the "sweet" second harmonic - and all the increasing even order harmonics. The single ended amplifier doesnt do this, hence the sound of the distortion it has is pleasing to listen to, for some -

I'm sure the OPT (output transformer) is contributing something to the sound as well - just as it is in your push-pull amp. It may be DF (Damping Factor, or ratio of output impedance to speaker impedance) or other stuff going on through the primary-secondary magnetic coupling. Particularly when considering the magnetic bias resulting from the DC current flowing through the primary winding. This core magnetization is cancelled in the push-pull arrangement.

In other words, the OPT has a sound to it that's part of the overall amp's sound. That'll be different for the single ended amp, by matter of fact. Apparently, a lot of people like it and could fall into the "measures so-so; sounds great" phenomena that does exist.
 
Factors that are involved in their popularity include:

  • Cult status
  • Lack of crossover distortion
  • Excellent midrange performance
  • Simplicity (minimalistic circuit design and minimalistic triode tubes)

Ad Price to your list. I see lots of posts where someone wants a cheap SE amp, but doesn't have much of a budget. It's usually an EL34 amp running UL (or something similar). Like a Boyuu A9 for ~$300.

jeff
 
I tried this approach - the resistor being 2x120V 200W incandescent light - but the sound was not very good at all. To fix it, I just turned it from common source into a source follower and built it a voltage gain stage with tubes. It's the only amplifier I have that's single ended - mainly because the entire amplifier cost me less to build than buying a pair of good SE transformers. 8WPC out from over 400W in from the wall though - I only use it in the winter but it sounds wonderful for what it is.


Should give the MoFo in the diyaudio Store a try. MOSFET Follower amp which is... SE. The sound is actually quite nice and what an easy and relatively inexpensive build. You will need a voltage pre-amp with gain, but mine worked nicely driven by an old pre-amp.
 
As BigUn suggests, with the right speaker…

A typical SE amp has a higher output imedance which means that the speaker impedance, to some extent, is imposed on the FR.

This often leads to the bass & treble changes suggestted by stocktrade, often works well to extend teh response, happens because we typically have an impedance rise at impedance and often in the top. This kind of speaker impedance is most often seen in single FR speakers. Multiways all to often have a big midrange impedance peak due to the XO that directly affects that region.

No crossover distortion — SE is always Class A, and in a tube SE amp, unless parafeed, the transformer goes not have a zero crossing in the transfer curve of the OPT. So at low levels they tend to be more seemless.

The nature of SE means a distortion spectra with diminishing amounts as the order increases. Predominantly 2nd order, with assymetrical clipping. In a PP amp the 2nd harmonic mostly cancels out as do other even order harmonic products. A PP typically has much lower numbers, but the ear/brain finds the continually decreasing harmonic producs with order sounds more natural and anything over 3 is not something we hear often in nature so adds information tha is unnatural.

At this point i would like to nite that this is not fixed in stone, a few PP amps, like the AKSAs, have been fine tuned to have a distortion profile closer to typical SE. Mine is still parts but they are highly respected amplifiers.

Human perception of these kinds of things can be significantly different, as well as a huge range of implementation, means you have to try and se ewhat works for you

dave
 
Ad Price to your list

Both the PS and in particualr the OPT in an SE amp are more fiddly and ore expensive. The simplicity of the actual circuit can be deceiving, the PS is in the circuit, and the OPT has to hadle DC so needs to be much larger, with an air-gap, and trickier to make.

dave