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SE vs. PP

Hey.

I am wondering; what is really the sonic difference between a triode SE amp. and a triode PP amp. More or less bass? Details and perspective etc...?

I am considering to buy the Klipch KF-3 (or whatever it was named) with a sensitivity av 98dB at 1W/1m! This will allow me to use a SE amp with 8-10W. I am just conidering what to build. A SE amp would be cheaper...(relatively...)


- Stig
 
SE VS PP

In my opinion, a pp triode connected amp will give you a taste of what se triode has to offer. I have a narrow point of reference, having only used a Dynaco st-70 wired in triode mode, compared to a full fledged 2a3 se triode amp.
Before I bought my 2a3 set's, I wired up my Dynaco into triode mode to see what the fuss was all about, I was impressed. First off, I would have thought bass would be lessened due to the lower power; Just the opposite occurred. The bass was full and detailed, and seemed to "bloom" out into the room better than before. Instruments sounded more like there live counterparts, and it was as though the were almost in the room. As I heard it described once; "There was more "there" there". Imaging was better, and the slight bit of "softness" to the upper treblemade you relax and listen to the music.
As for my se 2a3's, they have all of the above to a much larger degree. Your choice of speakers is limited which can be a drawback, or a blessing depends on how you look at it. I am very happy with my 104 db/1w/1m Klipsch Lascalas and 2a3 triodes.
I will never go back to inneficient speakers and 200 wpc solid state amps.
mg16
 
PP vs SE

If you are getting 98db efficiant speakers you can easily use a 3 watt SE amp. I have used SE 3.5 watt amps with 92db speakers with great results. PP can sound very good and often will have a greater dynamic range than SE in the lows but our ears are tuned the best to the range of the human voice and in that area nothing can touch SE for clarity. With good speakers your system will disappear and you will be listening to the performance. You will also find yourself sitting in the dark because the soundstage seems better. Get some of those great old tube analog recordings of Ella, Frank etc and you can tell your friends "I see dead people."
 
Hmmm, so SE is the way then... thats just wonderful! I have found that Andrea Ciuffoli's SV572-3 amp suits just fine for me! I've heard many great impressions of this tube. 13W will give me some headroom too.
I have read about the Amithy amplifier by Lynn Olson... This was the article that got me going into tube amps in the first place, and realy got me wondering about PP vs SE.
 
SE vs PP

Single Ended amps are for those who are pure in heart and mind. For they shall listen to heavenly music.

A properly designed and built SE amp will be more musical than a Class A PP amp.

The difference to my ears is mainly in terms of tonal purity, real dynamics as opposed to the ‘slam’ of most PP amps and the ability to present a wealth of low level information that is simply not there with PP amps.

To enjoy the maximum benefits that Single Ended amps are capable of, we need speakers without crossovers. This means that the voice coil of the driver should be connected to the output transformer. In the old days, Philips made 600 ohm voice coils to suit their OTL amps. I wish a few of the present manufacturers would consider making full range (well, almost full range should be adequate for 90% of recorded music) drivers with 600 ohm voice coils. Some 5 years ago, I did take up the matter with Lowther and when I replied that I am willing to purchase 10 pairs, there was a brief silence at the other end of the telephone line and the discussion topic changed!

A less puristic approach will be to engineer the front end and output transformers of SE amps to roll off at frequencies appropriate for a selected driver. This means that we need separate amps for each driver and the drivers should be capable of operating over a wide frequency range to suit 6dB/octave roll off. This is going to be an expensive affair and could be outside the domain of most DIY enthusiasts. Besides, the wife would not like all those wires and ugly cases taking up more than their deserving share of the room. I hope that I have not offended some of our members.

Yes, paralleling output tubes and increasing the current drive to these tubes is an option to increase power output at the expense of loosing a puristic approach. Bottom line is that no two tubes would act alike. Full stop. We will need to match the tubes regularly and adjust the bias at each listening session. This is the story of PP amps.

Yes, there are ways of forcing the tubes (shared cathode resistors is a simplistic and effective approach) to be more consistent and follow each other more closely under signal conditions. The tubes then become rather restricted in their voltage and current swings because one tube may not exactly like what its neighbour is forcing it to do. The net result is somewhat diminished transient response (pulse rise time) than otherwise would have been possible with a single tube.

My opinion is that SE is for purists and single driver systems. PP is a more practical approach for systems with multiple drive unit systems. Yet again, some of my friends with ESL 57 say that parallel SE is more musically satisfying than their PP amps.

Mohan
 
PP vs SE

This big tube will handle 2 channels? My question is why would you want to stray off the beaten path for enjoyment? Wattage is not worth it. Your SE tube amp can't take it? You bi-amp and increase your power more tham 2 fold. If your speakers can't get it for you then, well, it is you or your speakers. One or the other aint working right.
 
PP and SE sonics can be married ...

Hello all,





if the PP amp is built fully differential including the output stage, then the beauty of the SE is combined with the utter control and clarity in the low end a good PP amp can deliver. Yes and with the slam other posters mentioned.
With fully differntial I mean the sort of circuitry Tektronix and HP used to use in their tube oscillioscopes: long-tailed pairs with a huge reistor looking to -150V or a constant current source looking at -whatyouhave and behaving like a MegOhm resitor looking at -1000V.





I had the extended opportunity to listen to Allen Wright's EL 34 PP amp using this topology. At one of the occasions, we compared Allen EL34 with a gorgeous BorderPatrol 300B SE amp., the best classic WE300B amp I ever heard.


Allen's shitty lil'experimental thing was easily as good as the Border Patrol and it outperformed it in the low end. Speaker was Peter Bahnsens Maximator horn which is a 3way tractrix horn with passive XO and should not be a difficult load at all (SPL >100dB/W/m). And Allen had not taken care of any component choice, in the amp was what he had at hand.





For the record, I do like SE sound very much. But diff.PP is equivalent to SE, it has the same sonic beauty, maybe not the same glamour but more accuracy.


What I heard from the differential PP topology with THAT components, I decided I have to give this PP a tryout which can be called serious. AD1 output tubes, E80CC drivers, Tango XE-45-5 OPT.


I come back with results as soon as the amp is running.





Greets,
 
Re: Re: PP and SE sonics can be married ...

Originally posted by planet10
Good to hear. I have least a couple PP amps (EL95/EL84/EL34) i want to give Allen's treatment to.

Hello Dave,

I would like to limit my recommendation to the output stage and the fact all stages are differential.

Allen's experimental thing had an ECC88 as input tube.
Q: how many swing can an ECC88 / 6DJ8 handle at its grid?
A: 1.4 V p-p which is 0.5 V RMS
The gorgeous listening comparison was done with a >103dB/W/m horn speaker.
Under those circumstances 0.5V RMS applied to the amp's input will make your ears bleed.

However, I would prefer my amp to have a little bit more headroom at the input. And if I intend to use the amp at a medium-efficient speaker, possibe headroom is used up already. I would feel comfortable with 10V p--p before the input tube is drawing grid current.
 
An apologize and an opinion sustaining being different

Originally posted by dice45









Allen's experimental thing had an ECC88 as input tube.





Q: how many swing can an ECC88 / 6DJ8 handle at its grid?





A: 1.4 V p-p which is 0.5 V RMS





The gorgeous listening comparison was done with a >103dB/W/m horn speaker. Under those circumstances 0.5V RMS applied to the amp's input will make your ears bleed.











However, I would prefer my amp to have a little bit more headroom at the input. And if I intend to use the amp at a medium-efficient speaker, possibe headroom is used up already. I would feel comfortable with 10V p--p before the input tube is drawing grid current.








Hello Dave, Allen and all,







I have to correct some BS from my last post. When I wrote it, I had no schematic in mind. I apologize, Allen.



Allen informed me he had unbypassed cathode resistors in his input stage providing enough bias in differential mode, acting as current feedback and as a side effect, linearizing the stage a lot . He says he has 9V p-p input swing limit.







Let me see, as the stage is a differential pair of cascodes with a current source isolating the stage's virtual ground from a, say, -25V supply and so the input grids will float to signal ground if the preamp is connected and as the tube is running atleast at 10mA, the operating point probably is not located in the knee of the transfer characteristics.



Okay, admitted, the stage not only sounds good but also seems to work properly an to swallow the claimed 9V p-p at the input.







I stated already the amp is sounding wonderful. However, what I still do not understand:



why using a tube so badly fitting for the job and then taming it? Why not using a tube where taming is not necessary? (Allen, I am citing Manfred Huber here and I share his opinion) . Maybe there is sonic potential left in the amp? Dunno, don't have Allen's experience.






I decided for my own amp to go the way using a tube with enough bias and no linearizing current feedback. 1st stage is a differential pair of E80CC with anode chokes (although I later may settle on something like the 5687/6900), 2nd stage is a pair of cathode followers, each with a CCS in the cathode, the CFs facing an eeeezy load. This amp will sound different to Allen's amp however I presume it will suit my taste.







It does me another favour, I have a 3 stage topology and I can tuck 2 XO networks between the 3 stages: no separated speaker XO, be it active or passive. I don't have to; a common cathode stage can be DC-coupled to a following CF and then the coupling cap between CF and output stage is the only one in the whole preamp/poweramp/speaker signal path, providing the LF-rolloff necessary for my "fullrange"-speaker to cooperate with the subwoofer.
 

Denis

Member
2001-10-13 2:25 pm
P.Lacombe said:
The sound of SE is more natural, but the design of the output transformer is difficult, specially for low frequencies, because of core saturation. In multi-amplification systems, PP is used for woofers, and SE for medium and tweeters.


Doubtfully. The properly designed PP amp(and with pentodes!) will leave a SE one no chance.

The common opinion on the superiority of the SE amps may be based on the far from perfect implementation of PP circuits.

For instance, a 300B SE amp can be considered a good amplifier below 1W (roughly -10 dB in respect to its full output). This will be indeed enoug for the loudspeakers of about 100dB sensitivity.
It is true, the linearity at thes level and below will be remarkable, and there will be enough headroom in the output current.
But nothing prevents one from making a PP amplifier with the same or even better distortion behaviour, but with far greater dynamic range and load tolerance. It is a pity, the designers of amplifiers often make the same errors, and do not look beyound old textbooks. I'm not saying these books always lie, but they rathe tell not the whole truth.
 

Brett

Member
2002-01-07 6:02 pm
Thank Goodness

Hi Bernhard,

An oasis of sense at last. I agree with everything you've written in your posts above basically. Well implemented PP is superior to SE, ALWAYS IME. Statements like Mohans above "Single Ended amps are for those who are pure in heart and mind" strike me as a lot of crap. Note to Mohan: I'm not intending to be insulting towards you personally, but I hear this sort of statement all the time and I find it has no relationship at all to my personal experience. Or to reality. Quite the contrary, I have heard maybe two dozen different SET designs in my system, and that many again in another I was familiar with, and they just don't gel. I found a post on the Asylum recently that I'll quote as it describes what I hear in varying degrees with all SETs
<i>"The harmonics were of the "Haagen-Dazs Double-Fudge Chocolate Chunk with extra Nutella & half-bottle of liquid Nestle's Quik, topped with sugar cubes & honey" school of delightful excess, just listening to the thing too long would give you a toothache! The image, correspondingly, was HUUUUUUUGE"</i>

But hey, if you have a SET and it floats your boat, more power to you. In the end, only an individuals' chioces count, and if their chosen pathway to musical ecstacy takes them there, I bow deeply.

Even the famed low level linearity of a SE at sub watt powers is easily matched by a well implemented PP, as well as better SNR and greatly reduced susceptability to PSU generated sonic characteristics. But add in a complex load like all real world speakers present, and the performance of SETs is varying all over the place.
<i>Denis</i>
But nothing prevents one from making a PP amplifier with the same or even better distortion behaviour, but with far greater dynamic range and load tolerance. It is a pity, the designers of amplifiers often make the same errors, and do not look beyound old textbooks. I'm not saying these books always lie, but they rathe tell not the whole truth.
Amen.

FWIW, I'm building a set of Allen's PP1C's for a friend, and an RTP pre for me. My PP EL84 will be very similar. I also have most of the components (tubes and iron) for a pair of Lynn Olson's Amity amps, as this design's elegance and Lynn's articles were a large part of the impetus for me to start building amps again a couple of years ago. I just don't need 20W so I didn't build the Amity, and I have the highest repect for Allen as a designer.

<i> Bernhard</i>
Allen's experimental thing had an ECC88 as input tube.
Q: how many swing can an ECC88 / 6DJ8 handle at its grid?
A: 1.4 V p-p which is 0.5 V RMS
The gorgeous listening comparison was done with a >103dB/W/m horn speaker. Under those circumstances 0.5V RMS applied to the amp's input will make your ears bleed.

However, I would prefer my amp to have a little bit more headroom at the input. And if I intend to use the amp at a medium-efficient speaker, possibe headroom is used up already. I would feel comfortable with 10V p--p before the input tube is drawing grid current.
I asked Allen a similar question recently, and got a similar answer. He also added that the noise and distirtion at my expected power levels using 105dB horns would not be easily heard or measured. My question was based on the published performance of the PP-1C. BTW the input stage is a cascode.

SETs hold one great advantage at the moment. There are so many individuals and companies out there working on designs for SETs, and variations like the Ultrapath and parafeed, that there is bound to be an increase in performance generally for this topology. Put the same resources and effort into PP (esp DHT) and I don't think there would be any question of the superiority of PP. I think this will begin to change in 10 years or so as people begin to realise the limitations inherent in SE, and look to eliminate them by developing innovative, and refining existing PP topologies. And SE has almost become a cult.

Ciao
 
I guess I may as well check in on this one as well. While new to tubes, I recently built an older Magnavox paraphase p-p design that blew my SE 6L6 right out of my set up and into the garage. Now I don't proffess to know why, but I trust my measurment system to no end (my ears). I believe a crappy design is just that, and it does'nt matter if it's SE or PP.:eek:
 

yves

Member
2001-02-06 6:18 am
earth
regarding the PP1C output stage

Would anyone care to shed some light on the
connection of the 2x1000uF caps and the 68 ohm
resistors?
The caps create a virtual ground at the
cathodes, at ac, they are shorted together.
The 470 ohm resistors bias the EL34's.
But the 68 ohm?

On another note, imagine a
constant current source biasing the output
tubes with their cathodes connected together
without a resistor. The ccs goes to ground
or some -ve bias. If I were to connect a oil cap
(say 100uF) from B+ to the virtual ground
at the cathode junction, would that make it
a p-p ultrapath with one cap?

TIA,
Yv