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Why has single ended output become popular

kodabmx

Member
Paid Member
2011-10-31 1:00 am
Toronto
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.

I built this instead :)

The "Hum cancel" circuit is only a thought, I didn't build it in. I might have ditched R16 for a short, too.

D3 is REQUIRED or blow up your MOSFETs
 

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Hard to beat a mosfet follower for SE. I've played with tube SE in the past and vastly prefer push pull.

My first real finished amplifiers were IRF510 mosfet followers with large resistor arrays for load resistors. I got into tubes primarily for the gain on these, with a lot of the sijosae inspired low voltage stuff. The 6111 subminiature tube with a 36 volt supply worked surprisingly well with a mosfet follower for efficient speakers.
 
PP has phase splitting problem. Perfect symmetry in the audible range is difficult to achieve, and requires considerable effort and expense. SE does not have this problem. However, the trade-off is that SE has its own problems that PP doesn't have: DC-carrying output transformer, high second order distortion, and requirement of a very high quality power supply.

When done right, Class A PP sounds like SE, but better. 2nd harmonic distortion is what it is - distortion. There is nothing pleasing in it.

As posted above, SE is only good for certain kinds of music - "girl and guitar". It is not good for complex music, particularly orchestral and choral.
 
As posted above, SE is only good for certain kinds of music - "girl and guitar". It is not good for complex music, particularly orchestral and choral.

I think you'll find several guys who disagree with that! I do know what you mean, though. A PP on the face of it sounds cleaner and better damped, so complex music seems to sound more tidy.

But...... vocals have always been better with good SE amps and in particular DHTs. PP is thinner, SE is richer. And individual instruments have better timbre - more reediness to woodwinds, more boing to the skins in a drum kit and so forth. So put all that together and you do in fact get better reproduction of orchestral and choral music. But........ this requires certain things of your SE amp.

In my 12 years experience of building mainly SE amps, but also some comparable PP ones, I've realised that a good SE amp requires plenty of power, an OPT with good inductance and IMO a higher value primary than usual. So for 300b I like 5K. By power I also mean plenty of current in the driver stage, not wimpy high mu tubes. And DHTs everywhere they can be used. All his cleans up the sound. And lots of attention to parts - teflon coupling caps, polypropylene PSU caps, loads of chokes, mesh rectifiers, amorphous core plate chokes etc etc. All this makes a SE amp that is truly clean, airy and competitive. Just throwing together stuff like EL34s and 12AX7s with basic parts won't really get you into the ballpark unless you're a genius designer.
 

invaderzim

Member
2015-10-07 4:07 am
I'd probably replace the "good for" with "better for" since it isn't like either is terrible with the other music unless you expect the SE amp to shake the walls.

At low to medium volumes I prefer my SE to the PP amp I built with any kind of music. Even with not-so-efficient speakers the performance seems to be speaker dependent.

It is funny that the PP crowd looks down on second harmonics and the A/B SS crowd looks down on the distortion of a PP and the class D crowd looks down on the....

But then again if we didn't all like something different there would be one class D amp manufactured and we'd all buy it.

....In my 12 years experience of building mainly SE amps....

Any recommended designs or are they proprietary?
 
At low to medium volumes I prefer my SE to the PP amp I built with any kind of music.

Any recommended designs or are they proprietary?

I agree - low to medium volume is SE territory. Higher volumes aren't impossible but you're up against the ceiling - high voltage B+, parallel tubes, OPT problems when you put high currents through them, and so on. Normally girl + guitar doesn't require much volume unless the poor girl is shrieking. But orchestral and opera in a large room at realistic volumes is something else. Opera and orchestral at lower volumes is very pleasant indeed.

No - I'm an experimenter. I use a modular system and I'm always swapping over stuff like input and output stages to see if the sound floats my boat. Amps get assembled and taken apart then re-assembled in another configuration. Goes on forever pretty much. There's always a new combination.
 
There is vocal and vocal. Bonnie Raitt and Kiri Te Kanawa. One requires close miking, the other fills a huge concert hall without amplification, flying above the sound of full orchestra. #1 is good with SE, #2 with PP.


I understand the appeal of SE. It is easier for an average DIYer to make it right than PP, and it sounds good with most popular kinds of acoustic music, like singer-songwriter, small group, or jazz.
 
A DIY design that was rather popular here in the 1950's used a single-ended output stage because it was simpler and cheaper and the output power was high enough for domestic use, according to its designer L. V. Viddeleer. Distortion was kept low by heavy feedback from the primary side of the output transformer - feedback from the secondary side was too hard to keep stable at high loop gains.
 
There is vocal and vocal. Bonnie Raitt and Kiri Te Kanawa. One requires close miking, the other fills a huge concert hall without amplification, flying above the sound of full orchestra. #1 is good with SE, #2 with PP.

Yes, but practically speaking, nobody is going to listen to an opera at its correct theatre volume in an average listening room. Or if they do they live in a mansion. It's all going to be at a reduced volume. Since this is the case anyway, I prefer my opera on a SE amp because I want to bring out the full vocal colour of the singers and the timbre of the orchestral instruments. I know very well what orchestral instruments sound like because I'm a musician trained in a conservatoire and played in orchestras for years. It's all about timbre for me.

And yes, I regularly listen to the Ring Cycle, Meistersinger, Parsifal, L'Enfant et les Sortileges, all the Janacek and R.Strauss operas and so on.

And I have to say that the loudest live music I've witnessed is all amplified jazz and rock rather than opera. The Duke Ellington or Basie bands aren't trivial at full volume. Probably louder than most of Debussy's Pelleas and Melisande.
 

Brinkman

Member
Paid Member
2007-08-17 5:48 pm
Oakland, CA
Why does a SE amplifier at reduced volume bring out the colour and timbre better?

Just going to spitball here and say that a SE amplifier being used at reduced volume is more than likely being paired with a high sensitivity speaker, also being used far below its rated power handling. Both the loudspeaker and amplifier are being used at levels where distortion of both devices is extremely low and in the case of the SE amplifier, the harmonic distortion spectra minimizes more audible distortion (odd- and high-order) by theory of operation.
 
There is no substantial power difference between SE and Class A1 PP using the same output tubes. A pair of 2A3 will yield the same 6 W in parallel SE as it will in PP. PP virtue is not more power, it is less distortion, in quite audible way.

The bad reputation of PP comes out of topologies that squeeze more power from a pair of tubes (Class AB), but introduce crossover distortion.

"Timbre of instruments" betrays the simple kinds of music. Nobody is talking about timber of instruments in a symphony orchestra, what matters is resolution, so that you hear real complex texture, and not some kind of homogenized sound. Good PP does it better than good SE.

To SE afficionados, could you tell about your experience with PP when you did your comparisons of the two topologies? What was the PP amplifier? Model, output tubes, class of operation, stage coupling, driver?