Return-Path: X-Spam-DCC: paranoid 104; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,SUBJ_RE_NUM autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id tAEK505k002157 for ; Sat, 14 Nov 2015 21:05:00 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Zxh1V-00077C-NC for rs_out_1@blacksheep.org; Sat, 14 Nov 2015 20:02:09 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Zxh1V-000773-Ek for rsgb_lf_group@blacksheep.org; Sat, 14 Nov 2015 20:02:09 +0000 Received: from smarthost03b.mail.zen.net.uk ([212.23.1.21]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1Zxh0V-0006XD-Eu for rsgb_lf_group@blacksheep.org; Sat, 14 Nov 2015 20:02:08 +0000 Received: from [82.70.254.222] (helo=OfficeWin7.lan) by smarthost03b.mail.zen.net.uk with esmtp (Exim 4.80) (envelope-from ) id 1Zxh0F-00039H-OF for rsgb_lf_group@blacksheep.org; Sat, 14 Nov 2015 20:00:51 +0000 Date: Sat, 14 Nov 2015 20:00:51 +0000 From: Chris Wilson Organization: Gatesgarth Developments X-Priority: 3 (Normal) Message-ID: <825751561.20151114200051@chriswilson.tv> To: Andy Talbot In-Reply-To: References: <4510637253.20151114190626@chriswilson.tv> MIME-Version: 1.0 X-Originating-smarthost03b-IP: [82.70.254.222] X-Scan-Signature: ce0e5a4ae990e5a63db3ab7aea21191b Subject: Re[2]: LF: Valve LF amps and tank coil size / voltage rating? Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 5075 Hello Andy, Saturday, November 14, 2015 OK, but what about wire breakdown voltages? In all the big air cored LF tanks I have seen the windings are well spaced on ceramic, or Paxolin type grooved formers, how do I know a close wound toroidal coil won't break down? I have built a few HV supplies using decent industrial quality iron cored transformers, the biggest is 5kV at 1.5 Amps, which can also be fed from a 40 Amp Variac, to drop the primary down. I use that in my workshop for running a glue drying machine. I was also gifted some NOS ceramic triodes, some US, some Russian, and would consider having a bash at a valved LF amp, just "because" :) I have to say my limited experience of ceramic triodes has shown no unreliability, in fact a zero failure rate so long as they are gettered before use, if they have lain dormant for years. I do have a reasonable collection of failed FET's though :) In fairness user error was the demise of most of them. Thanks Andy. > I'll say it againV = 4.44.F.N.A.B  (all SI units) > THAT is how you size ferrite cores.  It tells you more or less > everything you need to know to make ferrite transformers.  Keep B to > less than 0.1 at these frequencies > But.. why would you want to use valves? > Expensive, unreliable, high voltages... > 'jnt -- Best regards, Chris 2E0ILY mailto:chris@chriswilson.tv