[Amps] [ham_amplifiers] Re: Sensible filter Cap sizing

Leigh Turner invertech at frontierisp.net.au
Wed May 23 03:35:07 PDT 2012


Nah Jim; although 60 uF is plenty adequate to achieve more than ample
regulation and low ripple on the B+ plate supply, a 116 uF reservoir
capacitance is at the upper limit of what I reckon is sensible, and is
erring on the side of overkill and pandering to the lunatic fringe and
purists :-)

The HV transformers in Rex's two versions of DX3 amplifier have serious
gravitas with massive kVA proportions comprising heavy Cu wire gauge on the
primary and secondary windings that's akin to fencing wire; plus there's a
huge core/window area to yield superb xfmr performance.

With a stiff no-sagging AC mains feed from the building's distribution
panel, the B+ rail DC voltage will hardly quiver at full rated load. 

Increasing the C in these amplifiers to the excessive values you suggest
will yield no practical benefit in these already well designed amplifiers.

By way of comparison we can note the Ameritron flagship AL1500 amp has only
26 uF or 33 uF (depending on year of manufacture) of B+ filter capacitance.

Squeezing an extra hundred watts or so Pout in a large multi-kilowatt output
amplifier due to the hugely increased Joules of stored energy and stiffer B+
are neither here nor there.  It's a case of erroneous Fool's Gold logic.

Cheers,

Leigh
VK5KLT

________________________________________
From: ham_amplifiers at yahoogroups.com [mailto:ham_amplifiers at yahoogroups.com]
On Behalf Of jim
Sent: Wednesday, 23 May 2012 3:07 PM
To: ham_amplifiers at yahoogroups.com
Subject: [ham_amplifiers] Re: Supply voltage/ current


--- In ham_amplifiers at yahoogroups.com, Rex MacRae <cathar.gnostic at ...>
wrote:

>
> Hi,

> On thing that bugs me is that my DX-3 has 116 mf on B+ but my DX-3SP has 
> only 58 mf which is noticeable. The DX3 has 2 X DX-2 B+ power supplies but
> the SP only one.
> 
> ZL4IV
> Rex.

### shhh ! Don't let Leigh hear that. He will go nuts...and give you the
lecture about too much filter C. Increase it to 200-400 uf... and you will
really get an eye opener. 

Jim VE7RF 






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