6CK4 PP Amp

[Jack Thomas]

I'm looking for some help in building a PP amp using the 6CK4. If someone has any hints or info, I would certainly appreciate some guidance what kind of load line, etc.
Tks,
Jack T.

[Sch3mat1c]

Hmm...neat tube , I want some!!

Sorta like 6W6 I guess... anywho...

For class A1: maybe 200V supply, 50mA bias (-20V grid, 400 ohms per tube if cathode bias) = 10W dissipation (I'm sure you could push 15W Pd, vertical deflection is tough so it's going to be a hearty tube).
Loadline. Go up to the zero-bias curve and choose a point.. approx. double current (i.e. 100mA) is typical. That seems a little shallow so I'll say 125mA, which happens at 100V. The flipside of the point occurs at -40V, twice the bias voltage, about 5mA/255V. Thus Imax and Imin are 124 and 5mA respectively; Io (operating) is 50mA; Vmax is 257, Vo is 200, and Vmin is 100V. The slope of the loadline is the resistance, (Vmax-Vmin)/(Imax-Imin), or about 1.3k. You can also calculate distortion, based on:

            Imax + Imin
           ------------- - Io
                 2
2nd H % = -------------------- * 100
            Imax - Imin

Which can be simplified (algebraically speaking ) to:

2nd H % = 50(Imax^2 - Imin^2) + 100Io(Imin - Imax)

(That assumes my logic unit is still working.. it tends to get faulty with sleepiness... )

Anyway. That comes to 12%, but I just remembered that 2nd H is canceled in PP amps so you can ignore it

Have fun. Wonder how many responses popped in while I typed this...(when I started there were none )...

Tim

[Sch3mat1c]

Forgot the graph I prepared..

The loadline shown is SE. For PP, each tube needs to see that - so 1.3k per half (either side of the CT). So the anode-to-anode load must be four times, or 5.2k (you needn't be so exact, a 4 or 6k would work about the same ).

Now, this is where I keep forgetting things... Do the tubes act in series, hence a-a = 4*single Rl? Or do they act in parallel, giving a-a nearer 1x? Or somewhere inbetween, say one tube is half cutoff (half Gm or Rp, take your pick) and the load is suddenly on a single tube!

Tim

[Ryder]

Scroll down this page for one idea.
http://hollowstate.netfirms.com/DIY_files/proto.htm

here is another
http://tinpan.fortunecity.com/saints...er/6ck4-pp.gif

http://tinpan.fortunecity.com/saints...mer/index.html

Something to start with anyway.

Cheers
Craig Ryder

[Sch3mat1c]

I don't recommend the second one.. 100uF on a 5U4 is liable to pop it, hearty though the tube is! That guy was probably going from his junk pile, but if you must do it like that, use a lower voltage transformer or choke input.

Tim

[Jack Thomas]

So many with so much information, so quickly. Do you guys have lives? What more could I ask for? Thanks so very much. I'll put pencil to tongue and go from there!
Tks a mil,
Jack T.

[Sch3mat1c]

Originally posted by Jack Thomas
So many with so much information, so quickly. Do you guys have lives?

No..

[planet10]

Originally posted by Sch3mat1c
Now, this is where I keep forgetting things... Do the tubes act in series, hence a-a = 4*single Rl? Or do they act in parallel, giving a-a nearer 1x?

I tried to follow a thread on the JoeList on this subject -- seemed like a thousand posts -- and there seemed to be perfectly valid arguments for both cases -- over my head at the moment.

dave

[fdegrove]

Hi,

Do you guys have lives?

We all sold our souls to DIY...no live, no pay...just helping out the newBs....maybe a small statue...if you insist.

Cheers,


/This may be an idea for the "Policies thread"...oh well we'll see ...

[EC8010]

Originally posted by fdegrove
...maybe a small statue...if you insist...

What did you have in mind? How about a 1950s communist-style statue of our worker hero striding boldly forward with soldering iron held proudly aloft?