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Single ended vs. push-pull

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I loved it Maynard thanks for re posting it . Now here a few years latter in my search for 'the sound " the article was way more understandable & enjoyable having tried out most of the various build types  as one of the "The Brotherhood Of The Firebottle " . 

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Maynard, 

 

Thank you for posting that.  Very good, extremely well written and comprehensive.

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I really enjoyed the article. For someone like me who isn't an EE, this explained a lot of technical jargon in easy to understand layman's terms. Thanks

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Great article. 

 

Now as far as I can tell, in his conclusions he seems to be saying the way to go is to develop a high efficiency push-pull amp with low power of about 15 watts using triode (either 2a3 of 300b) power tubes.

 

So Maynard, is there such a beast or have you designed such a critter? Or somebody else.  Might be an interesting build if so.

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1 hour ago, thebes said:

Great article. 

 

Now as far as I can tell, in his conclusions he seems to be saying the way to go is to develop a high efficiency push-pull amp with low power of about 15 watts using triode (either 2a3 of 300b) power tubes.

 

So Maynard, is there such a beast or have you designed such a critter? Or somebody else.  Might be an interesting build if so.

 

Love my Cary CAD 2A3i

 

It’s a 2A3 PP designed by Dennis Had 🙂

 

 

F8C53726-2BA2-403D-8D61-9597BC6AFE90.jpeg

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2 hours ago, thebes said:

Great article. 

 

Now as far as I can tell, in his conclusions he seems to be saying the way to go is to develop a high efficiency push-pull amp with low power of about 15 watts using triode (either 2a3 of 300b) power tubes.

 

So Maynard, is there such a beast or have you designed such a critter? Or somebody else.  Might be an interesting build if so.

Frank Ng makes one... 

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On 4/15/2019 at 7:15 PM, thebes said:

Great article. 

 

Now as far as I can tell, in his conclusions he seems to be saying the way to go is to develop a high efficiency push-pull amp with low power of about 15 watts using triode (either 2a3 of 300b) power tubes.

 

So Maynard, is there such a beast or have you designed such a critter? Or somebody else.  Might be an interesting build if so.

 

I have designed just such a critter a couple of months ago.  It is as simple as can be.  Only two audio stages, no coupling caps, direct-coupled.  NO solid state parts in it, a rectifier tube, and input tube, and P-P JJ2A3-40s.

 

Thebes, right now, I do not need 10 Watts, so the 2019  KT88 SE Direct-Coupled amp build has my time, money, and attention. 

 

I'd suggest, forget a 300B, I find the JJ2A3-40 is the better sounding Finals tube and design.  You CAN USE AC heating on the 2.5 VAC 2A3's filament, but the 300B has a 5 VAC filament, and AC heating  ( which IS better sounding ), can't be favorably employed.  2A3s rule, overall.

 

My 2019  " experiment "  is to see if I can build a KT88 DC amp, that exceeds what the best JJ 2A3-40 DC amp can do.  Don't know, no one does, till it gets built and listened to.  Single Ended amps, Direct Coupled stages with LSES supplies, I am referring to.

 

Jeffrey

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Interesting to see that it explains, quite well, how  PP can be Class A or B or AB. 

 

There  has often been the explanation that PP is inherently Class B. 

 

Of course  Nelson Pass presents PP Class A transistor amps.

 

WMcD

 

 

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My 2A3 PP amplifier, designed and built by Jeff Lessard will be my last amp.  

8147269F-D919-443D-9494-D80468CCDB22.jpeg

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22 hours ago, sunnysal said:

My 2A3 PP amplifier, designed and built by Jeff Lessard will be my last amp.  

8147269F-D919-443D-9494-D80468CCDB22.jpeg

As I recall you have had this amp for a few years. So nice to settle in equipment that just encourages a person to buy and listen to music.

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I also run a ss 7t into tubes. I am happy to see you do as well on your "forever" system. I have had problems with the on/off switch which is a bit of a pain but otherwise, I think it serves very well as a phono stage. 

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I have a pair of Brook 12A clones PP 2a3, PP EL37s triode wired, Luxman 50CA10 triode PP, and they sound good but my lil 45/2a3 direct couple two stage SET beats them all. I plan on building one with a bit more oomph for 50/300B triodes. 

 

 

 

 

 

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1 hour ago, seti said:

I have a pair of Brook 12A clones PP 2a3, PP EL37s triode wired, Luxman 50CA10 triode PP, and they sound good but my lil 45/2a3 direct couple two stage SET beats them all. I plan on building one with a bit more oomph for 50/300B triodes. 

 

 

 

 

 

 

1 hour ago, seti said:

I have a pair of Brook 12A clones PP 2a3, PP EL37s triode wired, Luxman 50CA10 triode PP, and they sound good but my lil 45/2a3 direct couple two stage SET beats them all. I plan on building one with a bit more oomph for 50/300B triodes. 

Interesting post and comments to read  !!

 

I am with you 100% on just two stages, direct coupled SETs.  It is all I pursed the last 13 years.  

 

Very good.  Is there any way we can PM each other and talk privately over the phone on amp design? 

 

Jeffrey 

Quote

 

 

 

 

 

 

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Cool stuff and I wasn't out to hijack the informative intent of the article.  It seems that many like a PP amp of that nature (thanks for the great pic Mike and others!) and then there is the very present school of SET aficionados, which, I'm sorry to say, often sound more like proselytizers than who have already found the sound they like, and will brook no argument, rather then seekers after the holy grail of magic amplification.

 


Thanks to Maynard, I've built several SET's of various flavors, and I have a solid collection of 35 to 50 watt Push Pulls, my slightly modified Marantz8b being to me is where true magic resides. In other words, I feel it is my reference amp to paraphrase a line of Klipsch speakers.

 

Being my busy and tired all the time of the year, I've only been able to do a cursory internet search of schematics for amps that fall into this range and most seem to be cobbled together DIY which is not what I'd be seeking.  Now, the Brook schematic is intriguing, yet Ian (Seti) found it lacking somehow.  I guess I'm seeking some solid suggestion vis-a-vis commercially built and proven designs with schematics and maybe a picture or two of the undersides.  Your suggestions would be welcome for a Fall build. It's been almost 16 months since my last build and it's time for another!

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Seti, Jeff lessard posted some good 2A3 PP schematics with parts lists, etc. On the Magnequest website. But I cannot seem to find them now...btw a great small PP amp is the el84 type; a dynaco st-35 or the eico or pilot equivalents we’re both great sounding amps.    I love modern version from Roger Modjeski the Music Reference RM-10 MkII.

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On 4/24/2019 at 10:10 PM, mike stehr said:

seth_2a3_schematic_v2b_650.gif

 

Mike, and Thebes : 

 

 Seth ( above ) is mildly OK.  It is very EZ to greatly improve upon.

 

First of all, C2 above, NEEDS TO BE ELIMINATED.

 

Additionally, always have a mu of 100, as the driver, in a two stage amp.  We want our amp to be LIVELY !!  Thinking 12BZ7.  

 

Lets totally eliminate R1, C2, C4 above, and eliminate the entire L2 interstage choke  splitter /  coupling, and lets simply direct-couple stage 1 to stage 2. 

 

Lets give the amp's power supply a choke input filter with a true LSES supply, ..............so that it boggies with de music !

 

That means ( below )  L1, and the two L2s are 6 Ohms - 159ZA,  C1 is 35 uF,  C2s are 50 uF, all WIMA DC LINK 4 pins.  Here we are , I'd build this :

 

( Note)

 

L5 below is a constant current source, a choke, without the sonic disadvantages of sold state devices.   High HY Hammond  L,  whose DCR  biases the triodes. 

 

R4s below are matched to each other to 0.1% or better to avoid any possibility of sonic skewing.

 

With appropriate circuit adjustments, Final tubes should optimally be JJ 2A3-40, or GE 6005, or EH KT88. 

 

This design.... with LSES supply, will rock !!

 

 

 

 

                                          1027588037_MasterSchematic4SNIPexplained.thumb.JPG.693383455bdc55845ab300ec947d4f99.JPG

 

                                Jeffrey Medwin

 

           

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There is a Part 2 !

 

http://www.x3mhc.no/dokumenter/SE-v-PP-Part2.pdf

 

Quite interesting stuff about low listening level PP with respect to hysteresis curve induced distortion. 

Anyone with high efficiency speakers will fall in this category most of the time.

The first watt matters most, and this is where Push-Pull design relatively lacks the more.

 

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