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Push Pull & Single ended , please help, newbe here

G

Gertrude0076

New Member
So , who out there has the desire to teach along with the patience to deal with a newbe? I have a couple of years with solid state but still very limited in audiophile knowledge although I never stop trying to learn ( pretty challenging when you’re born with a learning disability) . Now. . . Tube amps , can a few of you explain the push pull & single ended verbiage? Are they two types of circuitry? What are the pros & cons for each ? I’d like several opinions. Every one explains things a little different, but that could be of help to me . Thank you in advance .
Se’an from NJ 4/12/23
 
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Gertrude0076 said:
So , who out there has the desire to teach along with the patience to deal with a newbe? I have a couple of years with solid state but still very limited in audiophile knowledge although I never stop trying to learn ( pretty challenging when you’re born with a learning disability) . Now. . . Tube amps , can a few of you explain the push pull & single ended verbiage? Are they two types of circuitry? What are the pros & cons for each ? I’d like several opinions. Every one explains things a little different, but that could be of help to me . Thank you in advance .
Se’an from NJ 4/12/23
Click to expand...

Basically, a single-ended amp uses a single power tube for the output. The advantages are (by general consensus) a "purer" sound, more realistic presentation of voices and instruments, and higher 2nd harmonic distortion, which many feel is "euphonic" and pleasing to the ears. All SE amps run in Class A, which many feel improves the sound quality of an amplifier. And the circuits can be extremely simple with a low parts count. The disadvantages are:

1) Low power. 20 wpc is about the most you can get from an SE amp, and that's with a high-voltage transmitting tube like the 845 or 211. Such tubes require more complicated circuits and power supplies. More typical is 3-10 wpc.

2) Generally high construction costs. You must have a very good-quality output transformer. It has to be constructed properly to handle the standing current produced by the output tube. You also need a heavily filtered power supply, which adds more heavy components like filtering chokes.

3) Relatively limited frequency response, depending on the quality of the output transformer.

Push-pull uses two tubes operating in opposite phase to produce 2x or more the power output of an SE circuit. The two phases are combined in the output transformer and sent to the speaker. The advantages are:

1) Much more power available, and generally better control of speakers.

2) Wider frequency response due to the construction of the output transformer, because the tube current is balanced between the two primary windings, allowing for better bandwidth.

3) Lower harmonic distortion, cancellation of 2nd order harmonics.

4) Generally lower construction costs. Simpler power supply, since most noise is cancelled at the output. Output transformer is (generally) cheaper and easier to manufacture.

The disadvantages are:

1) More complicated circuitry, including a phase splitter stage to split phase to the two output tubes.

2) Crossover distortion, which can be inherent to a PP design but minimized to varying degrees.

3) Less of the "immediate" or "intimate" sound offered by SE amps.

Hope that helps!
 
just as a mention about the power, since single ended are typically lower power, you need efficient speakers to make good use of them. If you don't already have a set, plan on buying some if you want to use a flea watt amp. I recently banged together one that does all of 4 watts, and while it sounds better than I think it should given how low effort and low budget I went with it, my speakers really aren't efficient enough to make proper use of it
 
I've built three stereo SE amplifiers so far ranging from 3.5wpc to 7wpc. I like them and they do sound good.
But as Gadget stated, you do need efficient speakers. I have a 3.5wpc SE amp that sounds nice with a pair of 91db speakers I have in a small room, but in a larger room I would need more efficient speakers.
 
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Gertrude0076 said:
So , who out there has the desire to teach along with the patience to deal with a newbe? I have a couple of years with solid state but still very limited in audiophile knowledge although I never stop trying to learn ( pretty challenging when you’re born with a learning disability) . Now. . . Tube amps , can a few of you explain the push pull & single ended verbiage? Are they two types of circuitry? What are the pros & cons for each ? I’d like several opinions. Every one explains things a little different, but that could be of help to me . Thank you in advance .
Se’an from NJ 4/12/23
Click to expand...

This article may help. Skip the intro, as it kind of meanders. Goes to "How SE works," page 2 and read from there. :)
https://www.x3mhc.no/dokumenter/SE-v-PP-Part1.pdf
 
I’m a tube dummy, so maybe my simplistic and not wholly-understood attempts will help you:

Single ended tube amp: one tube per channel, as simple as an amp gets (the original electronic amplifier design).

Push-Pull: one tube for the upper half of the signal wave, and another for the lower half. The circuitry has to put the two half signals back together again. SE fans feel these two signal halves are never put back together quite right, so there is always something a bit off about the sound (my favorite amp is a PP tube amp, and it sounds much better to my ears than the SE tube amp in my bedroom. But that is probably because it can power quite nice and inefficient planar speakers. SE tube amps are called “flea watt” amps because they are pretty much limited to 2-8 watts per channel, and need VERY efficient speakers to really sing at loud volumes).

Single ended [typicall] uses no feedback to cancel distortions, so it oftentimes has lots of distortion (which many tube fans like the sound of). Push pull generally uses feedback to deal with distortions. Some like this, others do not.

Not sure about this, but single ended might always be a Class A design, which means the amp is always running at full power, which means full power output is always available, instantaneously, but it is very inefficient. Push pull can be class A or not.

Now let’s see how much of this I got wrong!
 
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doctor fuse said:
Single ended uses no feedback to cancel distortions, so it has lots of distortion (which many tube fans like the sound of). Push pull generally uses feedback to deal with distortions. Some like this, others do not.

Not sure about this, but single ended might always be a Class A design, which means the amp is always running at full power, which means full power output is always available, instantaneously, but it is very inefficient. Push pull can be class A or not.
Click to expand...

Yes, single-ended output stages for audio use are mostly Class "A" topology.

But, many SE amps do use global negative feedback. Usually from primary tap on the OPT back to the last gain stage.
 
feedback v no feedback is not really related to single ended or not. There are plenty of single end triode designs that do not use any feedback but plenty do. Pentode single ended amps especially tend to need it. My SE amp is a single ended pentode with global feedback.

Same is true with push-pull, though finding a no feedback push-pull amp is not super common. They do exist though.
 
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