anyone ever use el86/6cw5?

[mctavish]

there is an interesting otl circuit in the phillips datasheet for this tube, just wondering if anyone has built it or has worked with this tube?

[Tweeker]

Be aware this OTL is for 600ohm speakers IIRC.

[Johan Potgieter]

As Tweeker said.

That circuit was there for a while using Philips 600 ohm loudspeakers as counter-performance to the "vicious" uquibitious output transformer of the day. As I recall, it did not stay for long - the loudspeakers did not 'make it'.

As for EL86, they are rather similar to the EL84, but not so sensitive (needing a somewhat higher g1 drive voltage). They had a higher maximum plate voltage (600V), and was mainly employed in voltage regulators of the day. Unless there is economical advantage, I would stay with EL84 in normal circuits.
(To answer your question, I did occasionally use them.)

[Tubes4e4]

Hi Tweeker,

Originally posted by Tweeker
Be aware this OTL is for 600ohm speakers IIRC.

Actually, the nominal load for that circuit as spec´d is 1k.

Regards,

Tom Schlangen

[Tubes4e4]

Hi mctavish,

Originally posted by mctavish
there is an interesting otl circuit in the phillips datasheet for this tube, just wondering if anyone has built it or has worked with this tube?

Actually both. Be prepared not to get anyway near the Po as stated in the spec sheet. Besides that, EL86/6CW6 or PL84/15CW5 are very nice pass regulator tubes There are quite some circuits out there using it in HiFi apps (and instrumental amplification, too) if you really look for them.

BTW, you can get the triode-strapped curves here. Also, don´t miss the General Electric spec sheet recommendations if you are heading for sheer Po (20W and up from a pair).

Regards,

Tom Schlangen

[tubelab.com]

I have several 6CW5 tubes and have used them in a few designs. Beware that they are NOT interchangeable with the 6BQ5 / EL84 even though the pinout is the same.

They had a higher maximum plate voltage (600V),

In my books (GE, RCA) the 6CW5 carries a 250 volt maximum plate voltage. The screen grid is rated for 200 volts. These can be violated a little, but plugging one into an EL84 amp will cause a bright red glow, for a short unhappy time.

I have used them in a Simple P-P board. They like 3000 to 3500 ohm plate to plate load with about 275 to 320 volts of B+ MAX! That is cathode biased so the tube sees 260 to 300 volts. Any more than that and the death glow comes on quickly. Some tubes don't even like that much. Given these limitations I can still get 15+ watts out of a pair.

The 6CW5 will work well on lower B+ voltages (150 to 200 volts) where the EL84 goes limp. This makes them good for hybrid amps with the output tube and a BIG mosfet are wired together in "darlington" configuration.

[RE 604]

Hello ,
Klein + Hummel used the EL86 in their TS 60 amps , with ECF 80 as driver tube .
I rebuild one of these amps many , many years ago and used him every day .
Regards , Alexander .

[Johan Potgieter]

Not to belabour; the 1970 RCA Tube Manual sometimes show different voltages for max. plate voltage and plate supply voltage, sometimes the same. The latter is where I got the 600V from (former = 275V there). But nowhere do they say what exactly plate supply voltage is supposed to mean.

Also not to hi-jack the thread, but perhaps someone here can elucidate on the difference for everybody's benefit.

[Tweeker]

Phillips and Mullard EL86 give limit values of 250V anode, 550V anode cutoff.

Tung Sol 6CW5 also gives limit values as maximum plate voltage 250V,
maximum plate voltage without plate current 550V.

I'm guessing this is what RCA's 275V and 600V are getting at.

[mctavish]

thanks for the posts guys. think i will try this circuit over the

weekend and see how it goes. i was really interested in using it

with some hi-q fullrange speakers, hoping that the output

impedance wouldnt be too big an issue. ive heard of those 600

ohm phillips speakers, and i wonder what their construction was

like...