[Roger A. Modjeski]

An interesting editorial by Robert Harley on Single Ended (SE) Amplifiers. http://www.enjoythemusic.com/tas/223/editorial.htm.  It is also interesting to note that in the review of the very expensive Constellation amplifier and others he often mentions that these amps come close to having the magic of SE midrange.

What he does not mention, which I think is important from an engineering perspective is that:

Most SE amps have very simple circuits and fewer stages than Push Pull (PP) amplifiers. Compared to complex tube amps from ARC, CJ and many others they have about one tenth the parts in the signal path and are often hand-wired which eliminates the sonic ill-effects of circuit boards.

Most SE amps set the magnetic flux at half the saturation flux (north or south) and never go through zero flux, where PP amps are going from full north to full south through zero all the time.

SE output transformers do not suffer from the fact that most PP output transformers have un-equal coupling from each half of the primary to the secondary at high frequencies. SE transformers have a whole primary rather than two halves.  This is something I have worked hard to correct in my output transformers.

Triodes used in SE amps are selected for having "inherent damping" which is good enough to require no feedback in order to get reasonably good damping factor. These triodes also are fairly linear and require no feedback for reasonable distortion if played at levels at least 6 dB below clipping.

Although most practical SE amps are just a few watts, my research in talking with many customers leads me to believe that most listeners use far less power than they think. Many of us listen at 80-90 dB max which requires less than one watt with most speakers. The 2.5 watt EM7 playing an 85-90 dB/watt speaker is quite sufficient for most of my listening.

[poseidonsvoice]

Roger,

Regarding the sensitivity vs. wattage required debate, I think you must take into the consideration, the listening position distance and whether the speaker in question is a point source or line source. I believe many audiophiles have woefully inadequate amounts of power combined with inefficient loudspeakers.

See this from Daedalus Audio (I do not own Daedalus speakers, the article just puts this issue into perspective). FWIW, the 2.5 watt design you have would be only useful  for background listening or for a pair of headphones (My speaker's sensitivity is 95dB/1watt/1m with an 8 ohm average impedance and no lower than 6 ohms). A 2.5 watt design should not be used with any speaker less than 100dB efficient and maybe even 105 dB, imho, unless you are willing to forgoe dynamics and peak SPL levels.

I listen at levels of 80-100dB depending on the recording/program material.

Best,
Anand.

[sebrof]

A 2.5 watt design should not be used with any speaker less than 100dB efficient and maybe even 105 dB, imho, unless you are willing to forgoe dynamics and peak SPL levels.

I listen at levels of 80-100dB depending on the recording/program material.

Peak SPL levels maybe, but certainly not dynamics.
I run a 3-watt 2A3 SET with DIY speakers in the 97db range and they play plenty loud for me (70 - 90 db-c). If I wanted to play louder than my SET amp can go I have a vintage 150-watt Yamaha receiver I can hook up in minutes. But I never have. I feel that what I give up in max SPL is more than made up for in sound quality over the SS and PP amps I've owned.
But it all depends on what you're looking for. Some people like loud, others focus on SQ.

[poseidonsvoice]

Some people like loud, others focus on SQ.

I focus on both. Just because something is loud doesn't diminish its sound quality, imho. Of course, my room is treated, etc...It's not that I can't use a 10-20 watt amp with my speakers, but 2.5 watts? Please. I can hear the compression. On top of that, recording volume level, varies wildly as well. When that drum hits, it has to wack you in the chest, so while your recording is loafing along at 80dB, suddenly there is a 20dB peak and guess what? The 2 watt amplifier croaks. 

With a 95dB speaker, and sitting 10 feet away, you are now down to 85dB at 1 watt/1meter, add the other speaker (assuming a point source) and you are at 88 dB. So at 1 watt, you are getting 88dB. Which is fine MOST of the time. To feel the full face of an orchestral peak, say 105dB (and I mean recreating what is heard live) your 2 watt SET will not hack it even with 95dB sensitive speakers. 105dB - 88dB places you with a 17dB difference...and that requires 50 watts!

The unfortunate truth is, amplifier that put out 100 watts and are clean, detailed, etc...are few and far between. Borrow an NCore sometime, your thoughts may change...you won't get rid of your SET, but you may not play it as often 

Think of all the fellas with 85dB 2 ways and 3 ways on this circle. They shouldn't even approach an amplifier that is less than 100 watts. Unfortunately, most of those speakers can't play 100+dB peaks anyway, because of poor design.

Sensitivity and controlled directivity are two mantras I follow religiously.

Best,
Anand.

[wushuliu]

I focus on both. Just because something is loud doesn't diminish its sound quality, imho. Of course, my room is treated, etc...It's not that I can't use a 10-20 watt amp with my speakers, but 2.5 watts? Please. On top of that, recording volume level, varies wildly as well. When that drum hits, it has to wack you in the chest, so while your recording is loafing along at 80dB, suddenly there is a 20dB peak and guess what? The 2 watt amplifier croaks.

With a 95dB speaker, and sitting 10 feet away, you are now down to 85dB at 1 watt/1meter, add the other speaker (assuming a point source) and you are at 88 dB. So at 1 watt, you are getting 88dB. Which is fine MOST of the time. To feel the full face of an orchestral peak, say 105dB (and I mean recreating what is heard live) your 2 watt SET will not hack it even with 95dB sensitive speakers. 105dB - 88dB places you with a 17dB difference...and that requires 50 watts!

The unfortunate truth is, amplifier that put out 100 watts and are clean, detailed, etc...are few and far between. Borrow an NCore sometime, your thoughts may change...you won't get rid of your SET, but you may not play it as often 

Best,
Anand.

You know I here what you're saying, but there are a lot of people who are not listening to orchestral, opera, audiophile classical with large dynamic swings. Some of them are just listening to Rumours, Elvis Live from Hawaii, and Bill Evans. 2.5w could certainly be considered pushing it but if there are people who are happy with fewer watts despite lower efficiency who are we to say likewise.

[poseidonsvoice]

You know I here what you're saying, but there are a lot of people who are not listening to orchestral, opera, audiophile classical with large dynamic swings. Some of them are just listening to Rumours, Elvis Live from Hawaii, and Bill Evans. 2.5w could certainly be considered pushing it but if there are people who are happy with fewer watts despite lower efficiency who are we to say likewise.

Sure, we can agree to disagree, in that peaks for me are maybe 105dB (uncompressed), but for somebody else, it may be just 90dB (uncompressed). To each their own. I do believe that many audiophiles turn the volume down, not only because of poor recording quality, but poor design, both in the amplifier AND most definitely speaker domain.

However, when they hear 105dB peaks without compression, the realism takes on a whole new level. I do get my hearing checked about every 6 months however, and there is always an SPL meter in the room. But when I want to hit that pedal, I don't want my amp holding me back. 'Nough said.

Best,
Anand.

[wushuliu]

I do get my hearing checked about every 6 months however

  hardcore!

[Carl V]

I am no expert, but aren't we taking about 'crest levels' or 'crest factor'?
and isn't Voltage swing or Current delivery more applicable than the usual Watts?

I have owned some low watt amps...Bottle head...Fi....Welbourne  AN-england(some DIY) et. al.
When I listened & bought two AT-211 amps I was amazed at both tonality & dynamics.
I bought a pair of HT-88 Hyperion Sound parallel SET mono blocs after listening to a friends
Tube Distinctions SOUL mono blocs -again paralleled kt88 amps. I couldn't swing the MSRP.
Again it was both dynamics & tonality.  And the speakers used were not low efficiency/sensitivity
types. I had Lowther based speakers, Fostex, AN-E, Pi & an SP tech/Bella Wave guide hi-eff M-T-M design.

I listen in a moderately treated room-quiet, 8-10 feet away. 70-75db with peaks of 90-95dB.

I'd like to consider this new DIY offering.
But I have some reservations. I've built 300B, 45 & A23
amps.  Lovely tone.

Any guidelines & minimum requirements?

Basic specs for each are as follows:

Frequency Response - 48Hz to 20kHz +/- 2dB  -3dB at 43Hz
4pi Sensitivity - 92.5 dB @ 2.83V/1M
Long Term Power Handling - 150 Watts
Impedance - 4-Ohms
Dimensions - 30.75"H X 12.5"W X 16"D
Another AC member asked for the specs of the SP tech Speakers

[sebrof]

Sure, we can agree to disagree...

I don't believe it's a matter of agreeing to disagree as much as your statements may be true for you but not for others.

When you say, " would be only useful  for background listening and " should not be used with any speaker less than 100dB efficient " you are stating these as facts.
Unless you are talking about yourself, these statements are not true because for me and many others, a 2.5 watt amp is useful for much more than background music, and a 2.5 watt amp should absolutely be used with speakers with sensitivities less than 100db.
I've had as much as 325 wpc SS and 100 wpc PP tube. I did play louder but always missed what I get from SET. I seriously doubt that an NCore amp will make me unplug my SET for more than a few minutes.
Funny how people who have and love SET amps are often told they don't have enough power. The truth is you don't have enough SET   

[cheap-Jack]

 Many of us listen at 80-90 dB max which requires less than one watt with most speakers. The 2.5 watt EM7 playing an 85-90 dB/watt speaker is quite sufficient for most of my listening.

I can't disagree under the condition that the listening area is small & the 'sweet spot' is not too far from the loudspeakers & the music being played would not be rock concerts type.

FYI, years back, I built a 2x1W SE stereo power amp (50C5 SE triode strapped, as I hate pentode sound & zip NFB), driving a pair of Westlake BBSM-6 studio monitors (91dB/M/W) (tagged for USD10,000 over). As a gift to my audiophile friend who never owned any tube amps. Auditioned vs his Swiss Physics #6A 2x100 class A dual monoblocks.

This 'Little David" tube SE amp sonically blew away the SS "Goliath" monoblocks as per the audition panel present there at the same SPLs (no rock music though).

Here was what the owner of the SS amp commented:

"Vocalwise, 50C5 is the winner, so smooth, natural & detail emotion."

c-J

[mgalusha]

Funny how people who have and love SET amps are often told they don't have enough power. The truth is you don't have enough SET   

I had a pair of the Consonance Cyber 845 and a pair of the Cyber 211 amps. They manage 24 and 16W respectively, quite a bit for a SET design. I have ~95dB/1W/1M speakers and my listening room is very quiet, distance is about 3M from the speakers. I bought a meter that would let me measure and capture peak levels, as short as 250 uS. After measuring the actual power peaks needed to play a Junior Wells track at a fairly high level, I put the amps up for sale the next day. I wasn't using the SET's when I did the measurements, they wouldn't have made this much power.

I wrote the following at the time to a couple of friends, including Anand from earlier in this thread.

I used track 1 from the Focal Demo disk 1, Junior Wells - Sweet Sixteen. I used this because it has pretty hefty dynamic swings.

Test 1, average level about 80dB with peaks a bit over 90dB, I saw 92dB a couple of times. Measured using my assuredly not calibrated Radio Shack SPL meter. Subs off. I used my Fluke 289 to record the peak and average voltage levels for the track. The average RMS voltage was 1.3V and peak-peak voltage was 24.5V. Into 8 ohms these work out to an average RMS output of .21 watts with a peak of 9.61 watts.

Test 2, average level of about 90dB and recorded peaks of 102 to 104dB (f'ing loud). Average RMS voltage was 4.14V and p-p was 81.5V. Into 8 ohms this is an average RMS output of 2.14 watts with 105 watts peak.

My observations.

    You can't have too much power. The Abbeys have a sensitivity of 95dB/1W/1M (I believe) and clearly they don't require much in the way of average power but big dynamic swings mean that little amps are going to clip or compress, there is no way around it. Perfectly explains why my 16W SET will play loud but sound strained when the level goes up. At least with tubes the clipping is usually fairly soft, not so with SS and I'm guessing a lot of most folks with SS amps just don't have enough power. Anyone need a nice pair of 211 SET's... Just think of how much power is needed with low efficiency speakers of 83/84dB. It boggles the mind.

    The OTL's seem to handily exceed their RMS power rating without going to pieces, at least on peaks. I am guessing part of this is because there are no output transformers to saturate and with 150V on the plates of the output tubes short peaks can pull enough voltage without causing grief. Also I made some measurements of Abbeys over a year ago and the impedance was over 8 ohms for most of the range and OTL's love high impedance loads.

Oh, the SPL was at my listening position, perhaps 12ft from the speakers. I sat the meter on the back of my chair, so very close to where my ears are. The Fluke was connected right at the terminals on the right speaker. The Fluke was calibrated April 8th of this year and unlike my RS SPL meter is very accurate.

All of this reinforces the demo I attended at RMAF in 2005 by Bob Cordell. His demo track would average 3W RMS and pull 250W of peak power. I have not forgotten this but my tests today gave me a hell of a reminder. My low power stuff simply has to go and I have some serious incentive to get my 200W push pull 211 amps re-designed and rebuilt. 

Obviously this is my take on this and for some folks, a low power amp is perfect and the ultimate test is if you're happy. Recently a gentleman brought over a 1.5W SET (Darling with parallel outputs). My JBL/Beyma two way's are ~97dB/1W/1M, the little amp was completely inadequate with those speakers at even low listening levels. He has Klipsch Heresy II's, which are 99dB/1W/1M and it drives them pretty well, perhaps the crossover is more agreeable to the SET, as expected, speaker matching with lower power amps is complicated and critical. My friend Scott has mentioned several times that his SET's do not work well with any sort of complex crossover but sing with his Lowther's.

I am still firm in my belief that most people really don't have enough power IF they like lifelike dynamics. Even with ~95dB sensitivity and high power (400W/8R) amps, I still can't get the dynamics of a live performance, close but really. At least I'm sure they are not clipping.

mike

[sebrof]

Obviously this is my take on this and for some folks, a low power amp is perfect and the ultimate test is if you're happy.

Yes, I think this nails it. It's just that oftentimes it's made to sound that somehow SET amps are wrong or somehow people who like them don't know the real deal.

Excellent write-up, btw.


FWIW - My next move (after I finish tuning these speakers) is to either bi-amp with PP on the bottom and SET up top, or to build a 211 SE amp.

[poseidonsvoice]

I don't believe it's a matter of agreeing to disagree as much as your statements may be true for you but not for others.

When you say, " would be only useful  for background listening and " should not be used with any speaker less than 100dB efficient " you are stating these as facts.
Unless you are talking about yourself, these statements are not true because for me and many others, a 2.5 watt amp is useful for much more than background music, and a 2.5 watt amp should absolutely be used with speakers with sensitivities less than 100db.
I've had as much as 325 wpc SS and 100 wpc PP tube. I did play louder but always missed what I get from SET. I seriously doubt that an NCore amp will make me unplug my SET for more than a few minutes.
Funny how people who have and love SET amps are often told they don't have enough power. The truth is you don't have enough SET   

Please don't take it personal and go on the defensive...i.e feeling "victimized" because somebody called into question the marriage of an SET amp to a speaker. I think it's obvious that I am not some authority, just another opinionated audiophile, not Floyd Toole. I did back up my opinion with a link in my first post that puts into perspective, as does Mike Galusha's latest post (a fantastic post, especially his recollection of Bob Cordell's demonstration). I know that SET's have this special sound. I've built numerous Bottlehead amps and other SET designs. They are great sounding to a degree. I still think that you trade one of set of compromises for another, that is all. Some are willing to take that trade, other's are not. That's what I meant by agreeing to disagree. I will stop posting now before the thread gets thrown into the IGWB. 

Best,
Anand.

[sebrof]

Please don't take it personal and go on the defensive...i.e feeling "victimized" because somebody called into question the marriage of an SET amp to a speaker. I think it's obvious that I am not some authority, just another opinionated audiophile, not Floyd Toole. I did back up my opinion with a link in my first post that puts into perspective, as does Mike Galusha's latest post (a fantastic post, especially his recollection of Bob Cordell's demonstration). I know that SET's have this special sound. I've built numerous Bottlehead amps and other SET designs. They are great sounding to a degree. I still think that you trade one of set of compromises for another, that is all. Some are willing to take that trade, other's are not. That's what I meant by agreeing to disagree. I will stop posting now before the thread gets thrown into the IGWB. 

Best,
Anand.

You're funny. I didn't get defensive, simply corrected you where you were wrong so others who may be contemplating SET will know the truth. But I do appreciate you not dropping the old "panties in a wad" on me.
Read your posts. You didn't say you don't prefer SET amps, you clearly implied they were no good.

I know that SET's have this special sound.

Yes they do. And it's that special sound that makes everything else you posted in this thread completely moot to people who like SET amps.
And that's been my consistent point. People who like SET amps understand they are not for everyone. But very often I'm told about something better (NCore, please). I've tried a whole lot of stuff and I run a SET. Some people just can't wrap their melons around that for some reason.

[DaveC113]

It's all about what compromises please you. For me a SET is the best match for my speakers (the most important part), and high sensitivity DOES NOT necessarily mean that a SET is ideal. High sensitivity speakers with multiple drivers and more complex crossovers will never be a good match even if the speakers are 100+ dB. I would like to also have a much more powerful amp for that 2% of the time I want it, but for a huge majority of the music and volumes I listen at a SET is, by far, the best amp for my Omega Super 3 XRS.

Now, if we could only come up with a 100+ watt SET for a reasonable cost.... 

[Quiet Earth]

I play bass in a garage band with my friends from time to time so I understand what loud is. Every one of our get togethers starts off reasonably loud, and the volume level slowly creeps up with every song until someone realizes that we're just making noise. This is pretty normal behavior for amateurs from what I can gather. I'm usually phisically and emotionally spent after a two hour band practice and cant even listen to music the next day. I have no desire to listen to my home stereo at these "realistic" volume levels.

I'm not sure why but I have been attending a lot of live performances lately. I notice that no matter who you see or where you see it, it is too loud. I always take earplugs with me because after about thirty minutes I feel physically assaulted and no longer enjoy the music anymore. It's a shame to be happy when the show is over just because you want to take the earplugs out and breath again. I will admit that I have actually seen a couple of shows where the players were mature enough (musically confident?) to keep the volume level civil and I didn't need the plugs at all. But for the most part, I don't have any desire to listen to my home stereo at this "realistic" volume level either. Not for more than a couple of songs anyway.

I think dynamic range is a good argument, but dynamic range shouldn't be limited to the peak maximum volume levels, it should include the peak minimum volume levels too. The information that is buried way down below is just as important as how lively and dynamic the peaks should be. This is only my opinion, or more likely my preference. Clarity, contrast, and texture. This is what a good SET amp is all about IMO, and a big reason why you would own one in the first place. I don't care if the sound is real or not, as long as I am continually mesmerized by it. This is what matters to me.

As for matching a SET with a speaker to play music in a common domestic setting, well,,, I don't see what all the fuss is all about. It's just not that complicated. We make it complicated.

[Berto]

Ironic your SN is Quiet Earth but you jam too LOUD.   

Don't blame ya. SET is so much easier to listen too and relaxing. We're def not all trying to replicate the AC/DC show they saw. There is something to be said about emotionally involving sound quality as opposed to merely great sonic attributes that rival a live rock concert. Finding what works best to attain your ultimate objectives is what this hobby is all about IMO! 

[HT cOz]

I really enjoyed Bin Folds with the Houston Symphany because it was civil and not too loud.

[G Georgopoulos]

An interesting editorial by Robert Harley on Single Ended (SE) Amplifiers. http://www.enjoythemusic.com/tas/223/editorial.htm.  It is also interesting to note that in the review of the very expensive Constellation amplifier and others he often mentions that these amps come close to having the magic of SE midrange.

What he does not mention, which I think is important from an engineering perspective is that:

Most SE amps have very simple circuits and fewer stages than Push Pull (PP) amplifiers. Compared to complex tube amps from ARC, CJ and many others they have about one tenth the parts in the signal path and are often hand-wired which eliminates the sonic ill-effects of circuit boards.

Most SE amps set the magnetic flux at half the saturation flux (north or south) and never go through zero flux, where PP amps are going from full north to full south through zero all the time.

SE output transformers do not suffer from the fact that most PP output transformers have un-equal coupling from each half of the primary to the secondary at high frequencies. SE transformers have a whole primary rather than two halves.  This is something I have worked hard to correct in my output transformers.

Triodes used in SE amps are selected for having "inherent damping" which is good enough to require no feedback in order to get reasonably good damping factor. These triodes also are fairly linear and require no feedback for reasonable distortion if played at levels at least 6 dB below clipping.

Although most practical SE amps are just a few watts, my research in talking with many customers leads me to believe that most listeners use far less power than they think. Many of us listen at 80-90 dB max which requires less than one watt with most speakers. The 2.5 watt EM7 playing an 85-90 dB/watt speaker is quite sufficient for most of my listening.

Hi Roger,I dont know how se tube amplifiers do it,sound good,with 5% distortion some times limited frequancy response limited power output etc...I like se tube amplifiers because they are simple...
I think this simplicity takes all the credit for tube amplifier design and music enjoyment...Finally i think it's something about the high voltage that people like the tubes more than ss,with hv you can make distortion
more than you can make with ss,what do you think??

kind regards

[DaveC113]

Finally i think it's something about the high voltage that people like the tubes more than ss,with hv you can make distortion
more than you can make with ss,what do you think??

kind regards

A good SET may have a lot more distortion than SS with a ton of feedback, but a good SET produces mainly 2nd order harmonic distortion which our brain isn't very sensitive to. SS amps (in general) produce more 3rd order and higher multiples which our brain is very sensitive to. So an amp that produces much more 2nd order harmonics with very little odd order or higher multiples of even order distortion may sound better than an amp that produces far less overall distortion, but of 3rd order with higher multiples. So distortion figures mean very little without seeing the FFT chart of what kind of distortion is being produced. I'm not sure the high voltage tubes run at makes too much of a difference, push-pull tube amps produce more 3rd order distortion and can be designed with feedback to lower THD to levels similar to an SS amp.