Electra-Print L-3500 line OPT with 5k driving impedance

[mike stehr]

Last Saturday in a visit, I had these bench tested.

This is a quote:

"The primary impedance is rated at 10 kohms,

but when driven with that impedance they roll off a fair bit on the top

end, about 3, or 4 dB at 20 kHz, from memory, plus they roll off a bit too

much on the low end. Reducing the driving impedance to 5k improves the top

end response considerably, giving substantially flat response to 20 kHz. A

lower driving impedance causes a rise in the output at 20 kHz. There is

some ringing, but it is sufficiently above the audio band such that it

should not be a problem. A 5k driving impedance improves the low end

response as well, but there is still some roll off on the low end. I forget

exactly how much, but several dB at 20 or 30 Hz. They seem to be pretty

picky about the driving impedance, which seems to be the trademark of

inexpensive transformers; the driving impedance needs to be just right to

get acceptable performance. The secondary was unloaded, with a short piece

of coax to the ac voltmeter and a X10 scope probe. We didn't listen to

them."

I'm trying to find a triode or dual triode with a 5k plate resistance than can be used with these L-3500 line OPT's.

I do have a pair of 801A's, a 7.5 volt thoriated tungsten triode with 5k rp at 425 volts.(DC heated, more than likely...)

But now I'm not too certain if these line-out transformers can withstand over 400 volts on it's B+.

Any ideas?

[leok]

Mike,

You might consider the E88CC (6922). It has an anode resistance of 2.65kOhm. 12AU7, in comparison has 7.7kOhm "resistance." I use the E88CC to drive KT66s, and they do very well. Svetlana specs 6N1P at 4.4kOhms.

Leo

[3dzapper]

How about the 45? Data from Duncan's:

Va 250

Vg1 -50

Ia 3.6

Ra 1600

Rk 1500

Zout 3900

Pout 1.6w

Rick

[mike stehr]

Anode resistance is 1600 ohms, Rick.

That 6N1P seems close.