Date: Tue, 23 Mar 2010 04:25:48 +0100
From: "DF3KV" <df3kv@t-online.de>
Subject: Re: [Amps] How much C in PS is too much ?
In a right built amplifier one would not use series connected electrolytic
caps in the power supply.
## What else are we supposed to be using? Oil caps are not readily
available, and are way too heavy. The 4 x 47.6 uf @ 4.5 units I have are
30 lbs each... and still have to be isolated from each other.. and the chassis.
I end up with 47.6 uf @ 9 kv. [ series parallel] The 20 x 2000 uf lytics weigh
very little, and provide 100 uf @ 9 kv.
Individual, adjustable bias for what reason?
How do you bias for best IMD with more then one tube?
## On the 2 x GS35B 6m amp, each bias was tweaked for identical idle current.
When driven full bore, the plate currents were also equal. [the individual
bias
voltages were ALMOST equal]
One tube is enough.
## The builder wanted globs of power out on 6m... and trying to put a YC-156
on 6m was not about to be easy.
## On a hf amp... yes, agreed, one tube is plenty. Cost wise, the bigger the
tube,
the bigger the bang for the buck. RF parts sells both the 3CX-3000A7, and it's
bigger brother for $659.00 [3x6] Both those tubes are used in a lot of FM
stations
world wide, and will be around for a long time. IMD is superb. [-57db]
50 w of drive= 1.5 kw out. Then it just goes up from there. The YC-156/179 is
good
too.. and cheap. The 3x3 grid diss ends being a lot more than 225 w.... once
it's
bonded to chassis. You can use it as a dummy load for your FT-1000D.
Later... Jim VE7RF
73
Peter
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