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Old 20th April 2005, 06:25 PM   #1
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Question E810F in triode

What plate voltage/current would peple recommend to run the E810F at when triode wired?
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Old 20th April 2005, 07:00 PM   #2
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If you don't know what operating point to choose for an E810F, then you probably shouldn't be using it. There aren't an awful lot of E810F around, and those that remain should be used in circuits that really require their low noise capability - such as the input device of a phono stage for medium output moving coil cartridges without a transformer.

In the interests of conservation of scarce resources, please put your E810F in a safe, warm, dry place until you know how to fully justify their use. Oh, and don't do what I did, and accidentally drop one on the floor. They don't bounce and it was almost tears before bedtime.
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Old 20th April 2005, 07:30 PM   #3
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EC8010;
They'll be used in a DAC o/p fed by a stepup-tranny (adjustable bias on secondary-), and will be tailed by BBMCCCS/mu follower. The BBMCCCS's (3 of them, one per tube + one for a shunt) is made adjustable so current is fully optimizable.. I've just ordered a pair Telefunken E810F for this, cost wasn't too bad, and wondered wether a single 0A2 (150V) will work fine for regulator in the shunt.. I'm sure the E810F's will get a really great time in my DAC, and I really need their high mu high transconductance and low noise, but I want them to operate under *safe* conditions where they'll last long... OTOH, If I had a pair of EC8020 I'd put them in a warm dry place...

If I say 150V/20mA, what would your response be?
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Old 20th April 2005, 07:49 PM   #4
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Hmmm. Triode connected, Pa (max) = 6W, so you can afford to go up a little without damaging life. I'd say that at 2/3 of maximum dissipation you will have a very long life (so long as you keep it well ventilated). How about dropping the anode voltage a little and increasing the current (to reduce noise)? Va = 125V and Ia = 30mA might be good. It's a detail really, you look to be in the right region. And if you have a variable resistor to set anode current, you can find out whether a higher current is worthwhile...
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Old 20th April 2005, 07:59 PM   #5
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Quote:
Originally posted by EC8010
Hmmm. Triode connected, Pa (max) = 6W, so you can afford to go up a little without damaging life. I'd say that at 2/3 of maximum dissipation you will have a very long life (so long as you keep it well ventilated). How about dropping the anode voltage a little and increasing the current (to reduce noise)? Va = 125V and Ia = 30mA might be good. It's a detail really, you look to be in the right region. And if you have a variable resistor to set anode current, you can find out whether a higher current is worthwhile...
I can reach anywhere from 15mA to 50mA with my current CCS setup and dropping the 0A2 voltage to 125V is NP. Maybe a detail, but I'll take your advice for it, your name implies you have experience with tubes of this family I'll go for 125V/30mA initially and see where it takes me. Thanks for your tips!
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Old 20th April 2005, 09:35 PM   #6
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Quote:
Originally posted by EC8010
I'd say that at 2/3 of maximum dissipation you will have a very long life (so long as you keep it well ventilated).
Just a question regarding ventilation...

The tubes will be placed on PCB sockets on my "top PCB", poking up in the free world through holes in the top plate. Top plate is 0.5mm copper sheet and holes in the top plate have 1mm clearance to the tubes. 1cm of the tubes is below the top plate, this is about where the bottom mica layer of the E810F is placed. Top plate is *clean* apart from this, no transformers, nothing.. the two tubes is the only thingys poking up. Will I have a ventilation problem with E810F running at 4W Pa?
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Old 20th April 2005, 09:41 PM   #7
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I should add that the top plate also can have a quite high temperature because it dissipates heat from six IRF510 mosfets..
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Old 20th April 2005, 09:47 PM   #8
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You might have a bit of a problem with heat. Ideally, you want a free flow of air past the valve. In your situation, I would make a rather larger hole in the top plate, 1 1/2" or even 2" and fit a piece of perforated aluminium across it with a hole through which the E810F can protrude. That should allow it to cool properly. Good cooling really is about vertical airflow. Think about how air can enter from undereath and how it can depart. Think chimneys and gas-flowed engines.
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Old 20th April 2005, 09:53 PM   #9
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Can I get away with drilling say 5mm holes around the tubes?? Or increasing the tube hole to some 4 or 5mm clearance? bottom is open, all I need to get air in is some spikes to lift it from the surface...
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Old 20th April 2005, 10:03 PM   #10
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Drilling lots of neat holes is much harder than using a couple of chassis punches to bash one hole in the top plate and another in some perforated aluminium. But your solutions would work.
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