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LF: RE: LPF for a valve based (tube based) LF amp?

To: <[email protected]>
Subject: LF: RE: LPF for a valve based (tube based) LF amp?
From: "Clemens Paul" <[email protected]>
Date: Fri, 4 Aug 2017 14:10:32 +0200
In-reply-to: <[email protected]>
References: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Thread-index: AdMMY8KZ2MZzctl4QkS96zqVwx329gAtXsBg
Hi Chris,

at the risk to state the obvious:
A LPF of a solid state PA has 50 Ohms in- and output impedance.
A tube type PA needs a LPF which transforms from several kOhms on the tube side
to 50 Ohms at the output.
Therefore the values for the lumped reactances differ considerably from the 
non-transforming LPF.
Moreover design parameters like optimum loaded Q for the needed flyweel effect 
etc. come into play.
The ARRL Handbook,also old versions, cover this subject in depth.


>-----Original Message-----
>From: [email protected] 
>[mailto:[email protected]] On Behalf Of Chris Wilson
>Sent: Thursday, August 03, 2017 4:19 PM
>To: [email protected]; [email protected]
>Subject: LF: LPF for a valve based (tube based) LF amp?
>Hello LF'ers,
>My next contemplated project is a GS35B valve based LF amp. I have the
>HT supply, a couple of GS35B's to play with and a suitable filament
>supply. My question is can I build an air wound LPF based on exactly
>the same values as the one I use on my W1VD FET based Class D amp?
>That gets pretty warm and I use a small PC processor fan on the centre
>toroid, but I am unsure if the filter characteristics are specific to
>a FET based amp in some ways?
>W1VD  amp  schematic here:    (1
>kW amplifier)
>W1VD LPF details here:
>Best regards,
> Chris                          mailto:[email protected]
>Diese E-Mail wurde von AVG auf Viren geprüft.

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