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6P15P Tubes: Push Pull Possible?

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#61
Wavebourn said:
Mu > 20, rp < 1k5

6p15p_vah24.GIF
Click to expand...

Thanks very much. Eyeballing your curves (midpoint) mu is about 20 - high as I would expect, so a typical Ra is about 1.2k. I guess you'd have to run them quite hard then Ra would be below 1k.

A very nice valve I'd say. And in parallel push-pull triode mode, an easy-to-drive output stage for a high-quality ten watts or so.

Paul
 
#62
Right. I used them to drive Gu-50 in Pyramid-VII amp, to drive MOSFET stage in Tower hybrid amps, now I use one more Russian TV tube, 6P41S. One more sleeper, more powerful. Pentode curves have relatively high 2'nd order error, but trioded it is nice, and pentode with local feedback it is much better.

6p41stwax.jpg
 
#63
The reason I was suggesting not applying voltage to g2 was to bring the power down to levels the output transformers can handle < 25 watts.
Click to expand...

about power handling, that is a function of the B+, lower it and you get lower power......

power is also a function of turns ratio or reflected primary impedance....say your OPT has and 8k a-a resistance at 8ohm secondary with a pair of output tubes....now using 2pairs, the same OPT can be used to reflect 4k a-a load using the secondary's 16ohm tap to connect an 8ohm load...

i wouldn't worry about the output transformers, though rated for 25 watts, they can handle much more....read the post of tubelab.com and you will see...

dynaco_4.jpg
 
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#71
Hey All,

I just found my transformers for the ppp 6p15p amp. I bought a transformer set from a Harmon Kardon A500. The original amp used a pair of 7355's per channel and was rated at 25 watts with a p-p of 4k. Eli once told me that HK transformers were overbuilt and very stout. I plan to use the HK power transformer for the HT. With a separate transformer for the grid supply. Now all I need is an appropriate front end. Since the grid 2 current is so low would it make sense to use a voltage doubler for the grid supply?
 
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#74
Hey All,

I want to run four 6P15P's into a pair of 4k Harmon Kardon output transformers. I recently built an amp using a Floating Paraphase front end using 12AX7's. Its a nice simple design. But I'm not sure if the 12AX7 can drive four EL84 type tubes?

If the 12AX7 has a mu of 100 and plate current of 1.2ma and the other tube mentioned on the schematic is a 6SL7 which has a mu of 70 with 2.3ma of plate current either of which can drive a pair of EL84's. Can I assume a pair of 6GK5's with a mu of 78 and a plate current of 11.5ma could drive four EL84 type tubes? I've tried to find an explanation of 'drive' and not found one. But I assume it is based on the power output of the preamp tube?

Does anyone know of a good explanation of drive? I think it involves some complex math?
 
#77
mr2racer said:
Does anyone here have a good source for 6P15P data? I found a couple datasheets but none mention the output impedance. I need to know what the output impedance is at about 300 volts B+
Click to expand...

What do you mean by 'Output impedance?'

The output resistance of a device depends upon the circuit in which it operates and with a valve this is further variable since the anode resistance depends upon the operating point chosen.

7N7
 
#80
Duncan labs lists it as Z OUT. Reflected impedance? And having read Gogol, Turgenev, Dostoyevsky and Tolstoy I really wish I could read Russian, but alas I can't.

I'm a Berk. Just looked on Duncan labs again. He doesn't list 6P15P but on the EL84 page he lists an alternate, 6N15 as 8k at 300 B+
 
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