SE (single-ended) Tube Amplifers - Page 3

 

 

 

There are several advantages to a balanced (or push-pull amp, the differentiation borders on semantics) TUBE amps. In Open-loop SS amps things work a LOT like they do with tubes. In SS amps with lots of feedback, I'm borderline unconvinced that it does anything (sorry). 

In brief:

Certain distortions cancel out without the use of global feedback

More power!

More bandwidth!

 

Certain distortions basically means even harmonics canceling in a PP/balanced amp VS not in an SET. The disadvantage is that odd order harmonics become dominant in a PP/balanced amp (when there is no even to mask them, they show up) which different people have different opinions on. The problem here is that PP/balanced amps generally have more higher order harmonics than SET amps. Some people REALLY like amps with dominant odd order harmonics, they are generally perceived as more detailed and edgier. Even order harmonics are a little smoother and softer. Until you get past about 1%THD (which you should NEVER hit with a headphone at real levels, exception for ortho...) its all personal preference. 

 

More power should be obvious. most people will go for more when given the option.... If this is adequate, imagine how much more more would be.

 

More bandwidth (primarily on transformer coupled amps) comes from how transformers work. SET transformers require a "gap" to avoid core saturation, push-pull/balanced transformers do not. There are ways around this, but prepare yourself to meet a whiny individual repeating a rule he doesn't understand if you implement them (I have and I have)

 

 

Regarding converting back to SE at the output transformer. Simply put, distortion & bandwidth are what we are looking at here. push-pull/balanced amps have certain characteristic distortions, SET have others. What you do on the headphone side of the output transformer has NO effect on whats going on in the tubes which is where the VAST majority of distortions come from! 

 

 

Regarding balanced VS push-pull. If I were to show you a simple tube push-pull output stage without its driver circuit you could not differentiate it from a balanced circuit. Sorry. The drivers in SET amps are usually williamson circuits to save money but push-pull can be balanced from end to end. Even when push-pull tube amps have SE input stages they show many of the characteristics of balanced amps...

Edited by nikongod - 5/30/11 at 8:05am

I feel the fully balanced amp thing is a marketing ploy. A fully balanced tube amp is nothing more than a push pull amp

with the phase inverter left out. So they leave out the phase inverter call it fully balanced and charge more.

  The only need for balanced lines is in recording  studios with long runs of wire from the mikes that will pick up hum and noise.

 A short run of one meter between the source and amp will not pick up much hum and noise.

f

 

There are differences between a fully balanced push-pull amp, and a more conventional push-pull amp in the williamson style. There are a few other slightly less common push-pull amps than the williamson, but eeh.

 

If you really look into how the cathodyne phase splitter works you will quickly see that it dosnt. Try it out. The balance from a cathodyne is conditional on the load. Miller capacatance in the output stage throw the balance off as frequency increases.

 

For an amp to be "fully balanced" it has to be differential from input to output (or the primary of the output transformer) which by definition includes a phase splitter in one of the long tail pairs. There are a few 4-channel "balanced" amplifers that dont have a phase splitter at all, but compared to the fully differential alternatives they are just sad.

 

There is more to life than hum. The differnt distortion spectra of the amps mean a lot. Quick, some more hand-waving, and pull the rabbit from the hat - compare a balanced SS amp with 40db of global feedback, and a SE amp with 40db of global feedback to show only nominal differences... We are talking about tubes here, and I would generally assume without global feedback.

 

The reason there are so few fully balanced push-pull amps is simply economics. A wiliamson type circuit generally requires fewer tubes to work than a fully balanced push-pull power amp. Fewer tubes cost less money.

Edited by nikongod - 5/30/11 at 7:29pm

So from what I have been learning, normally (or stereotypically), SET amps are more smooth than the more powerful Pentode tube amps?

 

 

I read Skylab's review on the Decware CSP2, and he mentioned it to be lush with the mids slightly "rich/ripe/fat", while still transparent and dynamic.  That's basically the sound signature I'm looking for, so I'm thinking of getting that for a headphone amp.

 

But...If I'm looking for an amp run some efficient speakers what would be a better choice if I want that smooth, mellow sound: the mini-Torii (pentode) or the Zen Triode (dual mono SET).

 

The thing is I also want to get the LCD2's!..so I'm thinking about the Taboo w/ the CSP2+, and I can use that to run the speakers, too.

 

Is it reasonable to be ruling out pentode-based amps due to the fact that I'm looking for a more stereotypically tubey sound? Hence, the search for the perfect SET amp!

 

 

Edited by jeust0999 - 6/17/11 at 11:31pm

Any tube can sound "Tubey", Triode, Tetrode, or Pentode.  It really just has to do with the fact that some tube amps sound more "tubey" than others, and there is such a thing as too much of a good thing is a bad thing.

Yeah, but I don't think I'm looking for a downright syrupy amp. Simply, a smooth, laid back sound. I guess pentodes can sound like this too, but my guess is the SET sound is probably more of what I'm looking for.

 

Wedge, how you briefly describe the sound of your WA22, I'm undecided b/w CSP2 and WA2.

The WA-22 will give you a simply smooth, laid-back sound.  I was never a really big fan of OTL amps so I never bothered to listen to the WA-2.

Okay, thanks for the comments, wedge.

 

If your going Decware both pieces are what makes them special. If you want to use the LCD2 especially. The CSP-2 will work best with high impedance headphones not using it for the LCD2 alone it is not a good match by itself but the two piece will give you terrific sound and when I use my Omega single drivers with my sub headphones are a big step down thats how good they work on my speakers.

 

There's a wide variety of single-ended amps. They do not all sound the same. The sound depends on the circuit and tubes used.

If you want a smooth, laid back sound, consider DHTs (directly heated triodes, like the 45, 2A3 and 300B) with output transformers. That will sound rather different from a single-ended OTL.

I've been reading up on the Cary 300sei.

 

What do you guys think about these decware speakers..

 

Yes, I've read your review and comments on the Taboo w/ CSP2 previously. There's a lot of good info there, thanks Franks.

 

 

 

I think a CSP2, Taboo, LCD2, and a pair of Decware speakers (from the video) should be a nice healthy purchase. But I do think that ultimately (and unfortunately $$$), Uncle Erik's recommendation is exactly what I;m looking for. Thanks guys.

 

(I'm really diggin' that Cary 300sei)

Edited by jeust0999 - 6/27/11 at 11:39pm

Very informative thread.  After reading everything here, along with all the links, what I gather is that a general assumption can be made (dangerous, I know) that push-pull circuits should in theory sound a little more detailed like a SS amp because of the dominant odd order harmonic distortion and single ended designs should be smoother sounding because they have more even order distortion. 

 

The very first thing that comes to my mind, as it pertains to my own interests and experience, is that this completely contradicts the opinions that are generally held about my amp (the WA6, which is considered pretty neutral for a tube amp) and the WA22 (which is widely considered to be more smooth and tubey than the WA6).  Can component choices alone completely negate or strongly affect the impact of what degree of harmonic distortion, odd or even, is present in an amp?