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SET v. Pushpull

I did a search and didn't find any threads on this topic.  I am a newbie to tubes - I have a Tavish Adagio phono stage, and I am looking to add an integrated tube amp into the analog chain in my system - I have never owned one, so my knowledge level is low.  Right now I am running KEF LS50 speakers, but they are a little small for my listening area so possibly looking at larger speakers - I was very impressed by the Joseph Audio Pulsars I recently heard, as one example.

Anyway, most of the integrated tube amps in my price range are seem to be push pull, although the Line Magnetic is SET.  At a high level, I understand the push pull design gives higher output power than SET, but also higher potential for distortion.  

Any practical experience with the pros and cons of each?  And how important is this in the overall scheme, in real world applications?  Say, compared to the choice of output tube?

Thanks,


Tom 
tgr
glennewdick's avatar
glennewdick
1,500 posts
 

SET’s are max’ish 25wch most are in the 2-8wch range so not really practical for your KEF’s 85db sensitivity.

SET one tube amplifying the whole sine wave. usually 2-8-25wpc

SET Parallel same as above but two or more tubes in parallel so they both do the full sine wave just added together to get double ’ish the power as the SET.

Push Pull you can get much more power. these run two or more tubes each pair splits the sine wave in half one amplifying the plus side the other the negative side of the sine wave hence the push pull (very general as there is other configurations but you get the idea). its when you put the plus and negative together is where you get the distortion.

If your thinking tubes (I love tubes myself) you will need a push pull amp for sure. your KEF’s are 85db sensitivity so more then the SET 25wch probably closer to 100wpc min.

i’m sure others will have run the KEF’s on tube amps and will give some suggestions for amps and what power ranges work for them. If your replacing the KEF's as well then your whole world of tubes amps opens up

remember the lower the power the more efficient your speakers will have to be. if your going to dip into the lower then 25wch SET world (more realistically 8 wpc for the 300b for example) you will need to look for speakers that are 94-95db min the higher the better here. anything below 90db and your really looking at push pull amps anything below 2wpc (45tube is an example) and your in the 100db and up efficiency area.

Oh SET they are so wonderful but harder to find a speaker but worth the effort IMO. SET are very seductive in the midrange but can if not done well be rolled off a bit at the highest top and lowest bottom. they are very musical.

Parallel sounds the same as the SET just more power, well more as in a parallel 300b amp gives you 16wpc lol.

Push Pulls can give you same power as SS so no issues but more power is more money and more tubes to replace. Push Pull amps are big and dynamic sounding but don't have as a seductive midrange as the SET. They do extend further in the bottom and top though and generally have better bass (that's a bit price dependant).

I've had SET and PP and like them both, if you want a more intimate, seductive musical experience go SET if you want a bigger louder, slightly more detailed and better bass control (price dependant) sound then PP.

geek101
284 posts
 
At 85 dB sensitivity I wouldn't even go with any tube amp, at-least in my case. 

Not sure when people say SET watts are more than SS watts, but watts are watts. It is just that when driving to spec SET distortion is more pleasant then SS. But why listen to distortion (I prefer not to)?.

Pulsars are 83 dB efficient?. Not sure why specs on website does not talk about Pulsars sensitivity?. At least it says impedance does not get lower than 6 ohm that is good.

50 Watts will get you to 95 dB at 8 feet for 83 dB speakers.

If you get a good amp that puts out the watts your speaker needs for your listening needs without breaking a sweat you should not hear a difference. Basically non-existent distortion for all the watts your music needs. This is difficult at loud levels for fair moderately efficient speakers. What I have learned is to not to drive an amp to its spec.

If you want to go in the SET direction then may be pick a speaker that is close to 98 dB or even 100 dB sensitivity?. Then 10 to 20 watts SET will get you there given impedance does not swing. It is a bad idea to pick speaker after choosing an amp, in my limited opinion.

I do own Line Magnetic 508ia and it puts out 48 Watts for a price that is hard to imagine!. It sounds great at moderate levels on 92 dB paradigm studio 40v3 (when compared to Marantz SR7005). It seems it may not be good enough for new set of speakers I got myself, so I am on the fence with this class A tube thing.

If you can do true A/B test of AMPs, after level matching the SPL level,  you should not hear any difference at normal listening levels for good amps SET/Push-pull/Class A/ClassAB or Class D etc.

wolf_garcia
6,608 posts
 
To claim all types of "good" amps adjusted for level sound the same is ridiculous. A 5 point penalty is charged.
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