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 Post subject: Re: Vacuum Tube Question
PostPosted: May Thu 09, 2019 5:11 pm 
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Location: Thornhill, Ontario, Canada
Jim Mueller wrote:
... Just because those are "transmitting" tubes doesn't mean that that is the only thing they can be used for.
Agree, Jim. I designed and built a 60 watt rms audio amplifier with two 7534 "transmitting" tubes. AFAIK, they were not used for the RF, rather as audio modulators. I would have used four in parallel P-P for 120 watts, but I ran out of heater amps! The 7534 in audio is a bit tricky... screen voltage is quite low (not equal to B+) and needs regulating, at least in the fixed-bias, class AB2 design that I used.
Yes, the 6146 is good for audio, too, but I've not looked into the design issues.
Cheers,
Roger

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Ontario Vintage Radio Assoc. http://www.ovra.ca


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 Post subject: Re: Vacuum Tube Question
PostPosted: May Thu 09, 2019 10:40 pm 
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As I remember (since I don't remember where I saw it so I can't look it up) the 6146 amplifier I mentioned above also had some sort of primitive screen voltage regulator. That seems to be pretty much required with any tubes if you are trying to get the most possible power from them without exceeding their ratings. If you don't mind pushing them beyond their ratings it's a different story.

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 Post subject: Re: Vacuum Tube Question
PostPosted: May Sun 12, 2019 5:38 pm 
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Location: Thornhill, Ontario, Canada
Jim Mueller wrote:
As I remember (since I don't remember where I saw it so I can't look it up) the 6146 amplifier I mentioned above also had some sort of primitive screen voltage regulator. That seems to be pretty much required with any tubes if you are trying to get the most possible power from them without exceeding their ratings. If you don't mind pushing them beyond their ratings it's a different story.
I'm not surprised about screen voltage... these tubes seem pickier than 6L6's!
A short war-story... a while back I picked up a small box of old tubes and in it were two boxed 6146's that looked NOS. My eyes lit up with thoughts of yet another P-P amplifier (how many do I need?!) Anyway, putting them in the tube tester, one tested "very good+" and the other... dead, open heater! Project shelved... probably a good oiutcome!
Cheers,
Roger

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Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


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