Kofi Annan in: "Push and Pull with Me"

[zobsky]

a few points to consider (in no particular order) given the posts so far:

* using an input tranny, .. make sure your preamp can drive it
* re. the 807, .. 6bg6 should work in an octal socket, and maybe be cheaper .though it still has the funky top cap. i've had a 6bg6 pp project in the pipeline for the past year or so, but its one of those cursed projects that never gets off the ground (hint, ... UN)

* re. 300B, .. IMHO, i think the sound is nice but overhyped. YMMV

i think your best low power bet will be a push pull 2a3, ... use an interstage tranny if you want to make things real simple.

else, 6v6 amps rock, can't beat that tone

[Jaap]

Some people have gone the PP lane and never return to the SE path. But do not simply replicate old pp designs I would suggest. You do not fly those old choppers so why not use state of the art PP:

http://home.pacifier.com/~gpimm/1624.gif

http://www.vacuumstate.com/schematics/pp-1c_s.gif

[Jaap]

This is something Kofi can certainly afford:

[Gluca]

If I were mr Annan I would:

1) allow people ride my helicopter
2) build a PP 2A3, as you like these bottles, working in class A1 (6-7W into 5K) possibly IT coupled and hopefully with a splitter transfomer at the input.

If I were me I would:
1) buy the biggest helicopter
2) upgrade my class A1-transformers all the way-2A3 PP using a splitter autoformer by MQ.

I am very happy with it.

Ciao.
Gianluca

[ThorstenL]

Konnichiwa,

Originally posted by Kofi Annan
but having never heard a push pull tube amp in my short, sweet life, I thought I'd try to build one of those thingees.

Well, my first advise is to stick to SE, unless you must have loads of power. I make quite excellent sounding PP Amp's but I keep comming back to SE. I equally keep coming back to the 300B, well implemented it does not add much coloration, it has just the right sort of power to manage medium efficient (eg 95 - 100db/W/m) speakers, for 45, 10Y etc you really need huge high efficient (105db/W/m +) speakers and they get well big.

If however you are absolutely bent on trying PP, all the best sounding PP Amplifiers I know use the EL84. I would build such an amp strictly as excercise in frugality, this means using the classic sansui 500 style circuit with an ECC83 (or better 12DW7 - the ECC82 halve as phasesplitter, the ECC83 halve as input Amp), probably the output stage in ultralinear or triode. You'll get no more power than a 300B SE can do that way, but cost is a fraction.

As an aside, the EXTREME frugalphile PP Tube Amp uses a 6AS7 and due to the very low anode impedance you can get away using a dirt cheap mains torroidal transformer as output transformer and two more at higher power for mains. It even looks like an SE Amp.... ;-)

Google and Search DIY Audio for Maurits if you want more details (you find some comments of mine there).

If you live with even less power, the 6AS7 can be used as SRPP with around 550V +B and a 100V Line Speaker transformer as parallel feed output that way it is pretty much a SE Amp.

Sayonara

[mr mojo]

Heya Kofi,

I'm pretty new here so assign what value you will to my opinion

I think in some ways I've come at DIY tube amps from a different direction than a large portion of builders and went PP from the start.
I started out restoring old Scott units and thought the sound was really special.

For a purely subjective opinion, I think PP sounds like really good solid state with a good dose of the "tube sound" we all like thrown in. Think clarity, detail and good base of SS with the ability to reproduce the human voice, soundstage and dimensionality of tubes-and most of all for me, no listening fatigue even at high volume for extended periods.

As far as distortion-whether you build SET or PP, with distortion levels below 1% chances are unless you're a bat you won't hear it.

I think if you're gonna go PP then go all the way. 20-40wpc, using either a pentode/triode or dual triode for gain and phase splitting, resistor coupling for best frequency response. Accept that a PP amp will be more complicated, more resistors, more caps etc. Embrace it and be proud of the complicated beast you've built.

Remember a PP amp will operate at almost class A at low levels which is where most of us listen anyway.

Depending on your comfort and experience level I'd be willing to share the circuit I've been building. Stereo single chassis, PP 7591s, dual 5AR4s, dual 0A3s for screen regulation and 6AN8s in a cathodyne arrangement for gain/phase splitting. Separate bias control for each channel, separate DC and AC balance for each channel as well. 35-40 wpc, less than .3% distortion at a full 35 watts from 20-20khz. Less than 1% ripple. At 20 watts absolutely flat from 20-20k and @ .1% distortion.

Circuit was drawn by the tube engineering department at Westinghouse. I love the 7591 tube and I figure if anyone could come up with a great circuit using this tube it would be the engineers who helped design the tube itself.

Is it complicated? Relatively. But if a monkey like me can build it anybody can. It is a vintage PP circuit in all its glory-and since there hasn't been any earth-shattering improvements in PP tube circuits for a long time-there's no shame in building it.

Just my $.02. Probably worth less.

Best,
mr mojo

[Andrewbee]

http://www.meta-gizmo.com/Tri/sunschematic.html

http://www.meta-gizmo.com/Tri/interstage.html

Kofi, here you go. The top one uses 300bees but throw some Sovtek 2A3's in there with the fixs (filament etc)

The bottom one uses 6B4G's which is the 6v version of the 2A3.

I built the pp300Beeee version and then changed to 2A3s.

They use transformers for phase splitting.
Not my cup of tea but .......


Andrew

[Andrewbee]

Kofi,

Problem solved

http://euphoniaaudio.netfirms.com/ea...roducts_id=101

This driver board will drive your PP pentode / tetrode or triodes 2A3 /6B4G.
It uses a Sowter tranny up front for splitting duties.

more here http://www.pmillett.com/push-pull_kt...driver_pcb.htm

So, wire up a pair of these boards and then set up the output stage to be individually swappable / mountable (new words) and make octal and 4 pin output boards so you can swap to your hearts content.
The driver stage remains the same so you can make a convertible output stage amp and when you make the output boards all the same size you simply swap the output stage only, same mounting and add some barrier strips or plugs for your connections and voila!
Thats going to cost you some more heli rides since I don't get to fly them anymore

[arnoldc]

frank de grove posted a complete PP 2A3 in this forum... it goes to around 7 wpc

angela instruments also has a PP 2A3 with 6SN7 driver/splitter.

thorsten's comment on the EL84 supports most of my friends who's into vintage gear that the EL84 is hard to beat (subjectively) in sonics. i was thinking of making a Dynaco ST-35 clone myself.

[Kofi Annan]

Whew! Tried to reply earlier, but I've had a helluva day. So, I burned out a resistor de-soldering it and I was waiting for some new wirewounds to arrive so I could finish the Thorsten Phono Pre which, if you've been following my soap opera, has been a long time coming.

I finally got them today and was all set to start soldering when I couldn't find the remaining components for the PSU. I did, however, find a bag not dissimilar to the bag in which I have been keeping the other components. This bag did not contain any components, however; but it did contain a pocket pizza, chips, diet cola and a granola bar.

Being the detective that I am, I arrived at the conclusion that Mrs. Annan's afternoon meal likely consisted of five 47uF, 450V electrolytics, four 1.2K 12W wirewound resistors (one damaged), eight ultrafast rectifier diodes in the TO-220 package and some tinned copper 22AWG wire.

I the meantime, I was left trying to solder a pocket pizza and a granola bar together in parallel for PSU smoothing. *******' mess.

Nice girl, really.

Anyway, I am really, really grateful for all the responses.

Well, my first advise is to stick to SE, unless you must have loads of power. I make quite excellent sounding PP Amp's but I keep comming back to SE. I equally keep coming back to the 300B, well implemented it does not add much coloration, it has just the right sort of power to manage medium efficient (eg 95 - 100db/W/m) speakers, for 45, 10Y etc you really need huge high efficient (105db/W/m +) speakers and they get well big.

Jeez, I knew this would be the case. I really like the SET sound, but let's see what else was added to the response queue while Mrs. Annan was choking down wirewonds with a side of Fairchilds.

Some people have gone the PP lane and never return to the SE path. But do not simply replicate old pp designs I would suggest. You do not fly those old choppers so why not use state of the art PP:

Sounds reasonable, but ixnay on the opperschay.

For a purely subjective opinion, I think PP sounds like really good solid state with a good dose of the "tube sound" we all like thrown in. Think clarity, detail and good base of SS with the ability to reproduce the human voice, soundstage and dimensionality of tubes-and most of all for me, no listening fatigue even at high volume for extended periods.

OK-- I like this description. This is what I need to know. Thanks.

Depending on your comfort and experience level I'd be willing to share the circuit I've been building. Stereo single chassis, PP 7591s, dual 5AR4s, dual 0A3s for screen regulation and 6AN8s in a cathodyne arrangement for gain/phase splitting. Separate bias control for each channel, separate DC and AC balance for each channel as well. 35-40 wpc, less than .3% distortion at a full 35 watts from 20-20khz. Less than 1% ripple. At 20 watts absolutely flat from 20-20k and @ .1% distortion.

Errr... Aahhh... I like dogs!

If my comfort and experience are the contingency, its probably best you don't expose your this design to my ignorance. I can handle some intermediate stuff, but I'm a-scared of what you described. Maybe its easier than it sounds?

Problem solved

http://euphoniaaudio.netfirms.com/e...products_id=101

This driver board will drive your PP pentode / tetrode or triodes 2A3 /6B4G.
It uses a Sowter tranny up front for splitting duties.

If you say, "very interesting" in your best Artie Johnson voice, you'll get my general reaction to this. This looks good and will be a real consideration, should I stay with the push-pull concept.

frank de grove posted a complete PP 2A3 in this forum... it goes to around 7 wpc

angela instruments also has a PP 2A3 with 6SN7 driver/splitter.

thorsten's comment on the EL84 supports most of my friends who's into vintage gear that the EL84 is hard to beat (subjectively) in sonics. i was thinking of making a Dynaco ST-35 clone myself.

OK. This is good news. I'll check these out.

Here's my overall feeling, though: I think I may be too enticed by an SET 300b design to actually go with a push-pull for the following reasons:

- More than one poster has mentioned that they keep going back to SET designs.
- SETs would mate will with my Fostexseseses (206Es in the 208EZ backhorn)
- 300bs are cool
- More power, same SET sound
- 300bs are cool
- Hail yeah

So, do I have a dynamic personality or am I fickle?

See? You thought this would be easy, but I made it hard. Story of my life.

So, since I enjoy the SET sound, can anyone trump the 300b SET with a good push-pull? If not, can anyone recommend a relatively inexpensive 300b SET design that sounds nice? Any experience with the Angela Instruments 300b design?

Do you feel ripped off yet? You will. I have that effect on people.

Sorry for all the confusion, as always.

Yours in indecision,
Kofi