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In the Forum: Melquiades Amplifier
In the Thread: More power from Melquiades? More powerful tube?
Post Subject: The alternative output tubes.Posted by Romy the Cat on: 3/1/2010
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 cv wrote:
Consider a triode connected 13E1. 95W dissipation, will probably work beautifully with the existing OPT if you adjust the gap down and if you can rewire your arrays to present a somewhat higher impedance.
Something like 400V-450V / 200mA-ish will give you a plate impedance of about 300 ohms, and it probably wants to see a load of around 1k5.

Yes, CV, I might very much look in those B7A tubes. I have seen a few of them at MIT fleemarket but I never tried them. I am taking about all of those CV2377, CV6045, 13E1, VX6094. I think if I driver them with low voltage that I have in Milq (240V) but will use high current then I will drive the plate impedance down and will be able to use them. The all have 4.5 times amplification that is considering slightly higher plate impedance will be competitive to 6C33C. I think I will be able to get out of those beam tubes 35W. Will it be enough – hard to say and I do not know how much power I would need in new place.

My biggest concern with those tubes is not power but that they run at relatively low bias voltage. The 6C33C can run at 80V-90V that with 32 times of driver stage amplification would make a sub 3V allow on the amp’s input. That is good. However, those beam tube run at 30V bias that would make 1V one the amp input to switch the output tube into A2 operation. Yes, I understand that those tubes might be fine to run with positive bias but I do not know if I want to go in there. The coupling capacitor in Melquiades will be changing polarity – very ugly for Sound.  The 6E5P driver will begin to battle the grid currents. A tube that runs in A2 effectively stops to be a triode - something that I would need to consider.  The most important – it will be bass channel and the tube will be running almost all time on the right side into deep A2. All the amps that I have heard, when they are in A2 kill bass’ quality first (because multiple reasons). So, I think it need to be very careful evaluated if the bass from the beam tube family on the B7A socket is worse to pursuit.

Rgs, Romy the Cat

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