Single Ended vs. Push Pull: Pros & Cons

[rtsyrtsy]

Can someone please evangelize the non-technical Pinoydiophiles in layman's terms of course the principles behind single-ended and push pull operation as well as their pros and cons?

Are there other configurations?

Thanks in advance.

[Aylwin]

I seem to remember someone (most likely John Marco) explaining something about that old e-group.

One thing that confused me is that my amplifier is a push-pull design but it's solid state. How does that work? I'd appreciate an explanation on that too.

[rtsyrtsy]

Hi Aylwin,

Welcome back, long time no see.

Are you back in Manila now?

--Russell

[Aylwin]

Hi Russell,

Thanks for the welcome! WiredState looks great!

Unfortunately, I'm still in Japan and I'll be here at least until the end of the year. So no chance to attend your nice get togethers.

Regards,
Aylwin

[arnoldc]

after making and hearing the 2A3 integrated that i did, the sonic qualities over push pull is simply amazing. the level of detail, articulation and resolution that a single-ended amp like the 2A3 can produce is magical. and this is just DIY, quite proud of my work.

[vintage_dog]

after making and hearing the 2A3 integrated that i did, the sonic qualities over push pull is simply amazing. the level of detail, articulation and resolution that a single-ended amp like the 2A3 can produce is magical. and this is just DIY, quite proud of my work.

When I first got my 2A3, I too was captivated by the SET magic...but that is not to say that the PP amps can not deliver the musicality we all look for. In fact, throughout the years, I've learned to love both PP and SET, each one with its strengths.

But to really get the most from your 2A3 amp, you have to match them with the right speakers....

[arnoldc]

i'm not selling my Anthem Amp 1 (ultra-linear push pull)

i like them both, and owning a SET and PP gives me flexibility and choices!

on the Anthem, i have the volume at 9-10 o'clock driving the Kappa 200. on the 2A3 driving the same speaker it's around 1-2 o'clock (no pre-amp just ALPS volume pot), not bad at all for a 89dB speaker. of course a higher sensitivity speaker will give me more pleasure to enjoy the SET amp.

cheers.

i am sorry if i sound offensive to PP owners. sori po!

[rajan]

eh, if you are feeling kinda nice, pahiram niyan and i will audition it with my 90dB speaks

[arnoldc]

rajan, which one? if you mean the 2A3, hindi pa ngayon... he he he

[mozilla]

From Vaccum Tube Valley

Class A means that the power tube conducts the same amount of current all the time, whether idling or producing full power. Class A is very
inefficient with electricity but usually gives very low distortion.

* There are single-ended class-A, or SE, amplifiers. They use one or
more tubes in parallel, which are all in phase with each other. This is
commonly used in smaller guitar amps and in exotic high-end amplifiers.

Many audiophiles prefer the SE amplifier, even though it has relatively high levels of even-order distortion. Most 300B high-end amplifiers are SE.

Negative feedback, which can be used to decrease the distortion of an
amplifier, is felt by some people to sound inferior. Most SE amps have no feedback. Unfortunately, the high saturation currents in SE-amp output transformers tend to limit the bass-frequency response of such amps.

Unless you use a subwoofer with a separate driver amplifier, the SE amp will tend to give inferior performance. We also feel that keeping distortion down is important (though not as important as engineers tend to think).

SE amps made with low-mu triodes can have very low distortion, IF they are properly designed. Beware of some SE amps that are designed entirely "by ear", especially those made by small companies run by audio-guru egomaniacs.

The amps made by such firms might NOT do everything well, and might not be the sound you would prefer.

* Push-pull class-A amplifiers also exist--they use two, four or more
tubes (always in pairs) which are driven in opposite phase to each other.
This cancels out the even-order distortion and gives very clean sound.

Push-pull Class A operation usually involves low plate voltages and high plate currents, compared to Class AB operation below. The high currents might tend to wear out the tube cathodes faster than in an AB amplifier
.
* There are two kinds of class-A operation, which can apply to
single-ended or push-pull.

--Class A1 means that the grid voltage is always more negative than the cathode voltage. This gives the greatest possible linearity and is used with triodes such as the 300B, and sometimes with audio beam tetrodes and
pentodes. (Such amps are rare in the modern trend-driven and ego-ridden
world of high end audio today--most gurus lean either toward
Class AB beam-tube amplifiers, or toward SE triodes.)

--Class A2 means that the grid is driven MORE POSITIVE than the cathode for part or all of the waveform. This means the grid will draw current from the cathode and heat up. A2 is not often used with beam tetrodes, pentodes or triodes like the SV300B, especially in audio. Usually a class-A2 amplifier will use tubes with special rugged grids, such as the 811A or SV572 triodes.

Class A2 also requires a special driver circuit, that can supply power to the grid.

Class AB applies only to push-pull amplifiers. It means that when one tube's grid is driven until its plate current cuts off (stops) completely, the other tube takes over and handles the power output. This gives greater efficiency than Class A. It also results in increased distortion, unless the amplifier is carefully designed and uses some negative feedback. Most guitar amps are push-pull Class AB. The biggest high-end amplifier manufacturers love to build big Class AB amplifiers using 6550s or KT88 type beam tubes--primarily because their wealthy customers often have very inefficient speakers, such as electrostatic panels or Magnepans.

(There are class-AB1 and class-AB2 amplifiers; the differences are the same as were explained above--the tube's grids are not (AB1) or are (AB2) driven positive. AB2 is
rare in today's high end market, primarily because the egomaniacs who often design such amps do not how to design a reliable and good-sounding AB2 amplifier....)

3. Class B applies only to push-pull amplifiers in audio; it SOMETIMES applies to RF power amplifiers with one tube. It is like Class AB, except that the tubes idle at or near zero current. This gives even greater efficiency than Class A or AB. It also results in increased distortion,
unless the amplifier is carefully designed and uses some negative feedback.

If careful design is not undertaken, the result may be crossover distortion,
which appears at the midpoint of the output waveform and has very
bad-sounding effects in audio. Most solid-state audio amplifiers use class
B, because the transistors undergo less heat stress when idling. Class B
amplifiers can sound very good, if well-designed. The classic Altec 1570 is
an example.

4. Ultralinear operation is usually considered to be invented by David
Hafler and Herbert Keroes in 1951. It uses only beam tetrodes or pentodes,
and special taps on the output transformer. The taps connect to the screen
grids of the tubes, causing the screens to be driven with part of the output
signal. This lowers distortion considerably. It is usually seen only in
hi-fi amplifiers that use power tubes such as the 6L6GC, 6550/KT88, EL84 or EL34. All classic Dynaco amplifiers used ultralinear connection. It is VERY
hard on the screen grid of the tube, especially the EL34 type. So good-quality EL34s are critical in such amplifier circuits.

Misc Notes:

Triodes were all that existed at the beginning (or at least the 20's and 30's), so were the only tube of choice to power those old radio sets. Since single-ended is the cheapest to implement, most were that, but there were some attempts to get more power, either SE parallel or PP. Pentodes and beam power tubes came in the 40's and took over by the early 50's, virtually eliminating the SE circuit. By the 50's, virtually everything was push-pull in the consumer market.

The SE circuit was revived in the late 80's, although it never completely disappeared. There are still today far more PP amps than SE amps.

SET stands for Single Ended Triode meaning only one tube of a triode configuration is used for the output power tube. The SET is usually very low power requiring more efficient speakers.

Push Pull means two tubes are used for the power output tube. They work together. A signal consists of a sine wave. The signal is split and one tube handles one side of the sine and the other handles the other side. The push pull can be either both pentodes and triodes. Push pull is usually higher power.

[rtsyrtsy]

Thanks, Moz.

My interest was most stimulated by vintage SETs, those from the pre-push-pull ear.

Are those pre-40's stuff still obtainable?

[ambel]

If you're pocket is deep sure why not. Vince Gallo's Western Electric 91A
SET 300B amp is up for ante at $40K a pair. Vince used to write for Sound
Practice and a B rated actor.

[rtsyrtsy]

ambel, thanks so much for saving me the US$40k that I don't have on those vintage SETs.

Vintage Dog,

You mentioned yesterday that as a SET and push-pull user, there are moments when you look for a certain sound on push pull that is missing from SETs.

Mind sharing more details on the differences you perceive being both a SET and psh pull user.

Thanks!

[vintage_dog]

Vintage Dog,

You mentioned yesterday that as a SET and push-pull user, there are moments when you look for a certain sound on push pull that is missing from SETs.

Mind sharing more details on the differences you perceive being both a SET and psh pull user.

Thanks!

well, my romance with PP amps has really been driven by my love for the vintage amps. although we didn't get to listen to the vintage PP gear (except for the tweaked st70 and st35), these amps (vintage PP) provide a very musical (?&*$!!) experience that just stops me from being too critical a listener and just enjoy the music. they have the aplomb, weight and grandeur i sometimes find missing in my SET amps. again, perhaps i don't have the best SET amp-speaker combinations. i enjoy my SET amps but i find myself oftentimes dissecting the music more than enjoying them. they sound too clean and "perfect", i miss out the "soul" sometimes.

when i want to relax and appreciate a good performance, i turn on the SET amp. but if i want to have a "good time" and dance to the music, i let go my vintage PP amps.

again this is a matter of personal taste. listening to the Cachaito CD yesterday, the PP amp brought out the music and musicians at their best, but for JEsmilla's violins, the SE was king.

[arnoldc]

i guess it's about the type of music you play. in my case, i have never enjoyed classical music this much until i use my 2A3. having said that, the 2A3 can't do justice to my other music which is heavy metal. in cases like these, it's a job for a push-pull. BUT, and a big BUT, is that i don't have an efficient speaker (with the Kappa at only 89dB). I played Metallica on the 2A3 using JM's Voigt, and it does rock.

When you go down to 4W or less of power, the speaker sensitivity has the most impact.

[ambel]

I feel your pain you need at least 94 db to hear the glory of your
2A3. For me It's the orig. WE 300B from 50's or older vintage driving the JBL L200 speakers. Every music genre this the only combo that I
had that can play any music bar none. Just like what they say diffr'nt strokes for diffr'nt folks.
From SET amps based on 2A3, 45, 10Y, 211, 845, 71A, 811A SET.
To speakers Altecs, Lowther, EV, Tannoy, and every countless of DIY
experiments.

[johnmarc0]

Just to politely dispel some misconceptions, SE is not an exclusive domain for triodes and PP for pentodes. Like the TS34.1 is actually an SEP single ended pentode while the ongaku is a PPT a push pull triode.

My point here is this, the most dominant sonic characteristics we hear is not the amp configuration (SE or PP) but most importantly the character of the tube and tube type. For example, a 300B have different coloration from the 2A3 from the 45/VT52 and so forth which are all triodes.

On the other hand, A triode is significantly different in coloration and audible distortions from a pentode. And from an EL34, to a KT66, to 6L6 to a KT88 will have significant coloration and distortion variance from each other.


Thus, An SE 300B and PP 300B will sound really close except for degree of imbalance (more dominant on PP) and static distortion i.e. hum (more on SE) but coloration will almost be the same and the power to drive your speakers will be at least double on the PP (can influence bite and attack).

While a Pentode whether SE or PP will have significantly audible distortion over SE/PP triodes.

That is why, pentodes in SE/PP mode is usually the domain of high distortion material (some classical pieces, rock music, heavy guitars) or people people who prefer equal amount of harmonics and fundamental tones.

While Triodes in SE/PP is usually the domain for dominant fundamental tones and less harmonic tones (or sometimes we describe as slow sub tones). Materials that qualify to this are most classical pieces, operas in tenor or soprano, bossa, instrumentals and less harmonic material or it can be a listener where harmonics can be annoying.

Case in point that I have observed is Racio and Edrich (to my sincerest intent not to offend them).

Racio prefers fundamental tones, less harmonics unless required but with a twist which is "bite". That makes his listening envelope to my opinion really thin and it demands a lot from the reproduction infrastructure.
Bite can be a achieve electrically through compression and power but fundamental tones are driven by dynamics and less coloration. These are mutually exclusive and diametrically opposite criteria. His compromise point is somewhere in between that only he knows, may God bless his soul.

Edrich on the other hand to my opinion is indiscriminate, he loves fundamentals as his preference for harmonics dependent on the material he plays, that makes his listening envelope wide but some weird thing he has preference to a few key tones that I can not decipher, his system requirements is looser but his in the safe side and he is sticking with SE 2A3. But I bet once in a while he hooks up a pentode to play his eric clapton,eagles or grunge LPs

Racio on the other hand will never go back to pentodes but I reckon will definitely appreciate Push Pull triode maybe in 300B or 211/845 it will definitely give him more bite than he needs. PP pentodes, will only have nostalgic impact on him not out of preference.


To conlcude, Vintage dog is correct, each one of us reaches our soul through the material we listen for a specific equipment we use and there is no clear cut equipment solution. His compromise is he switch gears to the mood he wants to listen. But just like life, we make, live and love our own compromises.

Me, I switching hobbies, I will be basketweaving, this thingamajig is getting expensive.

[rtsyrtsy]

Steve Deckert answers the question:
http://www.decware.com/paper16.htm

[johnmarc0]

Russ,

Very good article, so funny in the end part, about the 5Y3, and it's old 4 pin equivalent, the type 80. I use them more than 5U4 and the GZ34. Good to see someone share my views on this rectifier. I have tons of them, with me and Ed gave me a few pairs of the type 80. If you guys want to check this rectifier out, I can spare a few pairs.

JM

[vintage_dog]

i think he was also referring to the EL84 tube, which in my opinion is one of the sweetest tubes around. the magnavox SET amps i have use similar circuit as the Zen...