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In the Forum: Melquiades Amplifier
In the Thread: To drive the 6C33C...
Post Subject: Re: Cooking the 6C33C.Posted by Romy the Cat on: 3/22/2006
Yes, Jim, you put it very well. Still in case of the 6C33C it only possible to cool the glass and I made experiments blowing a strong flow to the glass and it did cool down the plates. The problem is that it is not a good idea to apply a strong flow juts to one side of the tube and the entire balloon should be cooled down. To do it with sufficient flow it would need a very powerful blower and consequentially a lot of noise. It would be possible to engineer something effective for the 6C33C cooling but the real question that I always ask myself: why would I need it? It the end, leaving aside my foolish desire to deal with imaginary problems, the 6C33C does not need cooling…. In the case of the 3 tubes in a relatively small chassis (the Super Melq’s gain chassis is 14x20), and considering that the chassis is staffed the forced airflow to the tubes socket is really necessary, at least in my case.
 hagtech wrote: |
| As far as soft start, I believe that is where your choke rectified heaters come in. Such an arrangement is extremely gentle. |
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Actually I use choke-rectified heaters in my phonostage not in the power amps. Melquiades has both stages filaments powered by AC. The 6C33C filaments never fail and the only thing that should be a reason of concern with 6C33C is its anode. Actually it is funny but I know a guy who use 6C33C at barbarian power and fixed bias (good for sound), So, he monitors the plate temperature and if it goes up then he lower voltage on the filaments…. He is loosing power this way but… hey… whatever makes him happy… So in my case I soft-start the plate supply. The filaments do off. In 100 sec I apply bias voltage and the voltage on the B+ of the first tube. In 20 sec I turn on B+ on the 6C33C. The voltage begin to charge the last large cap for ~3 sec and then reaches the cruse voltage of the 230V. If the nominal plate current is 200mA then it reaches approximately 110mA after the voltage is set. Then within next 10 minutes the current gradually rises to 200mA and stay there forever.
In the end… all of this is not really important as getter on the 6C33C burns out sooner then any other danged take palace on this tube…. Pretty much a year of operation and you need to pay another $10 for a new 6C33C....
Rgs,
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