QQE04/5 Curves

[tricomp]

Hi,

I've found a few of these Philips dual-tetrodes made for UHF amplification.

However, I want to apply them in an audio PP/Class-B construction, driven well into g1-current with a suitable CF/CCS-driver.
I need some info on expected Plate-Load; that's not immediately available from the Philips data-sheet -> electron Tube Data sheets - Q
How to calculate?
I expect to be running the tubes at around 340V, Fixed Bias
Also, each single tube will be strapped into parallel, so in all 4 x QQE04/5 for a stereo PP-amp.
External heat-sink will be applied to the anode-pins.

rgds,

/tri-comp

[tricomp]

Of course there's the raw formula of

Zout = Va/(Pa/Va)

Va = Plate (anode) voltage
Pa = Maximum plate (anode) dissipation

Here it would be something like 340/(20/340) ~ 6K

How close will that be to an optimum plate-load?
Since I'm going to build a P-P amp. are we talking 12K anode-to-anode?

Help much appreciated,

rgds,

/tri-comp

[artosalo]

There are given two anode curves at the data pages. First with Ug2 = 200 V and the other with Ug2 = 180 V. I would use the latter, draw the load line from 350 V (extend the scale a bit) to Ia = 200 mA. This will give the anode load for a single pentode = 1,75 kohms. For push-pull stage multiply this by 4, which give you total Ra-a = 7 kohms.

I you parallel tubes, the Ra-a will be halved etc. But, by parallelling tubes, the G1-current required will be doubled too. I would use a MOS-fet driver instead of tube in such case.

By fine tuning the Ug2 and bias, you will certainly get the optimum condition.
Since you will most likely apply NFB, the load impedance will be even less critical.

[pmillett]

Ooh, this just begs to be driven by a power opamp. I have to see if I can find some...

[DF96]

Bear in mind that a UHF power valve will just love amplifying/oscillating UHF! What you see as wires it may see as linear resonators. It may need stoppers everywhere.

[tricomp]

Originally Posted by pmillett

Ooh, this just begs to be driven by a power opamp. I have to see if I can find some...

What do you think about driving the QQE's this way?
I did it before with great success driving 2C34/RK34. They gobble up around 10mA of g1 current each, exactly what a paralleled QQE04/5 requires at the max.
The enclosed schematics shows the same CF/CCS that made the 2C34's sing at 12W/8Ohm & 16W/4Ohm. You won't believe the bass they put out! Something that should be experienced, not just written about

rgds,

/tri-comp

EDIT:
I thought I'd better enclose a picture of my QQE-Pyramid.
Beats any Egyptian pyramid hands down!

[tricomp]

>>BUMP<< to the above question.

Anyone has an opinion or even first hand experience?

I have become a bit worried about running the tubes at Va=375V and Vg2=250V.
The curves stop at Va=250V I suppose for some reason even if the Class-C mode allows for up till Va=400V, see attached data.
Taking Wa into consideration and not exceeding the max, won't that be safe enough driving the tube in AB2?

I hope someone will chime in with an opinion.
If not; I'll just go ahead and build according to the schematics as the power-transformer has already been ordered. If it turns out bad I suppose I could dump some energy in a series-regulator.

Sorry, had to split the QQE-data in two because of file-size limit on forum.

rgds,

/tri-comp

[tricomp]

I read a bit, actually a lot (Seely, Romanowitz and others) and dabbled with the curves.
Some of this tube tech stuff is not easily digestable to me from the bare reading.
I'm the kind of person that need to get my hands dirty to understand.
Please give your opinion on if I did or not; understand that is.
Perhaps I'm too optimistic about what the QQE's will endure?

Thanks and regards,

/tri-comp

[nhuwar]

Its like a miniature 8d21.


Here's a link to a pic of one. Weird tube.

http://www.indianamuseum.org/museumc...6&amp;i=145544

[tricomp]

Originally Posted by nhuwar

Its like a miniature 8d21.

Apart from your link not working (Here's a link to 8D21 data: http://tubedata.tubes.se/sheets/049/8/8D21.pdf ) I don't quite follow.
They are as far apart as they could possibly be. They only share the fact that they are both vacuum tubes and being tetrodes.

Btw, a picture of the tube is in the first post in this thread.

Weird maybe yes. Low and wide (Well, short and fat! If that's weird I know a few who would fit that description ) on a chassis with drop-through transformers should look nice. And since I have a stash of 20 NOS, they should be put to work somehow.

Any reflections on the posted load-line?

rgds,

/tri-comp