|
Tubes Asylum Questions about tubes and gear that glows. FAQ |
|
|
|
Tubes Asylum Questions about tubes and gear that glows. FAQ |
|
In Reply to: And they say guitar ppl push their amps! posted by FenderLover on May 2, 2010 at 06:49:21:
Mike's post isn't clear and the numbers got confused.
The original Citation II biased at 100 ma. and had 450 volts across the tube. That was 45 watts - that was really pushing it, agreed. But back then tubes were relatively cheap and plentiful so it wasn't as big a deal. In spite of that, Stu Hegeman & Harman-Kardon later reduced the bias current spec to 90 ma., which dropped the dissipation to 40.5 watts.
With my kits I recommend 80 to 85 ma. With today's higher line voltages, etc., that gives 37-39 watts dissipation.
No amp I know of ever (deliberately!) ran 600 volts and 100 ma per tube.
One thing Mike pointed out is definitely worth remembering - in a pentode or beam power tube the screen voltage has much more influence on current than the plate voltage does. You can run very high plate voltages with lower screen volts and it'll work well (if it's done right obviously).
Finally, keep in mind that when you measure cathode current you are measuring the sum of the plate current AND the screen current. So 85 ma. cathode current on a Cit II is actually (it varies from tube to tube some) about 78 ma plate current and about 7 ma-ish screen current. That means you have a plate dissipation of 78 ma. x 460 plate volts, or about 36 watts; and you have screen dissipation of 7 ma x 460 screen volts, or about 3.2 watts. Do keep in mind plate and screen current varies some from full load to idle - I chose sort of a "mid-point" above.
A 6550A or KT88 typically have a plate dissipation limit of 42 watts and a screen limit of 8 watts using the Absolute Maximum rating system, the least conservative rating. The next more conservative rating is the "Design Maximum". The Design Maximum rating for the plate is 35 watts.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: And they say guitar ppl push their amps! - Jim McShane 07:12:04 05/03/10 (1)
- RE: And they say guitar ppl push their amps! - PakProtector 14:39:19 05/03/10 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
