Hey Jaap,
This could be something. Checked the Mazda paper. Triode looks quite linear. Pentode looks good at over 150V/10mA, could be something for a Schade driver.
This could be something. Checked the Mazda paper. Triode looks quite linear. Pentode looks good at over 150V/10mA, could be something for a Schade driver.
Great Schade and Blumlein are my "heroes" (as is Turing, although my tube amps failed the Turing test))
I have used ECF801 and 802 as driver/phase splitter to drive small pentode/bpt output stages and they work well. My favourite is ECF802 as driver/cathodyne-pi into PP EL84. Very nice sound.
Gary
Gary
Hi Gary, any chance for a schematic of how you use the ECF801 and the 802? Brought some and want to do a PP amp with those.
BTW: Heard that McIntosh users use ECF802 to replace the 6U8 (ECF82) in their amp,
BTW: Heard that McIntosh users use ECF802 to replace the 6U8 (ECF82) in their amp,
Doesn't the ECF801 have a common cathode for the triode and pentode?
The ECF802 is a great tube, so is the ECF80. The latter works great as first stage and phase splitter, it was used for many years by Klein + Hummel in their studio amps and active monitors, also in 'civilian' guise as Saba. They used very low currents through the pentode to get the maximum possible gain, but IMHO it works far better with a more substantial current and gains around 100. Also works great as a driver for Schade pentode outputs, either SE or PP. ECF802 differs mainly in the triode gain. ECF82 sadly is not as linear. In all cases there are a few tricks to get around tube tolerances, as proper choice of operating point is crucial to get low (actually very low) distortion. One of the trick is not to use active G2 regulation, rather a simple resistor to drop voltage, and a capacitor to cathode (also to ground will work for high gain even when NFB is applied to the cathode because of very small swing WRT G2 voltage).
The ECF802 is a great tube, so is the ECF80. The latter works great as first stage and phase splitter, it was used for many years by Klein + Hummel in their studio amps and active monitors, also in 'civilian' guise as Saba. They used very low currents through the pentode to get the maximum possible gain, but IMHO it works far better with a more substantial current and gains around 100. Also works great as a driver for Schade pentode outputs, either SE or PP. ECF802 differs mainly in the triode gain. ECF82 sadly is not as linear. In all cases there are a few tricks to get around tube tolerances, as proper choice of operating point is crucial to get low (actually very low) distortion. One of the trick is not to use active G2 regulation, rather a simple resistor to drop voltage, and a capacitor to cathode (also to ground will work for high gain even when NFB is applied to the cathode because of very small swing WRT G2 voltage).
Thanks ilimzn, just checked and you are right.. I got 10 PCF803 coming in, was using ECF801 data sheet they seems to have a seperate cathode (was thinking i brought a load of junks...)
http://www.tubebbs.com/tubedata/sheets/124/p/PCF801.pdf
An externally hosted image should be here but it was not working when we last tested it.
Thanks for the head up on the ECF82 and the 802, will draw a load line later this week.
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Got here after a search:
How does that work?? I'm also curious to hear what the other tricks are.
I'm designing a stage with ECF80 and I was looking at ECF802 as well.
Thanks.
How does that work?? I'm also curious to hear what the other tricks are.
I'm designing a stage with ECF80 and I was looking at ECF802 as well.
Thanks.