Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=0.5 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_SORBS_SPAM,SPF_PASS,T_HK_NAME_DR autolearn=no autolearn_force=no version=3.4.0 X-Spam-DCC: EATSERVER: mailn 1166; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id v74FSd5U011315 for ; Fri, 4 Aug 2017 17:28:41 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ddeRw-0007z0-NI for rs_out_1@blacksheep.org; Fri, 04 Aug 2017 16:23:40 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ddeRt-0007yr-T5 for rsgb_lf_group@blacksheep.org; Fri, 04 Aug 2017 16:23:37 +0100 Received: from mailout10.t-online.de ([194.25.134.21]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ddeRr-0003ze-3L for rsgb_lf_group@blacksheep.org; Fri, 04 Aug 2017 16:23:36 +0100 Received: from fwd21.aul.t-online.de (fwd21.aul.t-online.de [172.20.27.66]) by mailout10.t-online.de (Postfix) with SMTP id 6200941F671A for ; Fri, 4 Aug 2017 17:23:34 +0200 (CEST) Received: from [192.168.1.4] (E2IHniZYZhR+QGHiWTUM1nm45w-MJojBg3JdmDz0AvEGn622bR+HnXsIaagmMDVZmW@[31.212.58.226]) by fwd21.t-online.de with (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384 encrypted) esmtp id 1ddeRl-0EoAIi0; Fri, 4 Aug 2017 17:23:29 +0200 To: rsgb_lf_group@blacksheep.org References: <791401561.20170803151834@gmail.com> <9eb8f313-3b17-9da7-7e3e-3d77b2137080@t-online.de> <42526801.20170804153406@gmail.com> From: "Dr. Wolf Ostwald" Message-ID: <0694e0a6-7bc0-9f8d-c11c-0ba18bc93155@t-online.de> Date: Fri, 4 Aug 2017 17:23:31 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <42526801.20170804153406@gmail.com> X-ID: E2IHniZYZhR+QGHiWTUM1nm45w-MJojBg3JdmDz0AvEGn622bR+HnXsIaagmMDVZmW X-TOI-MSGID: f55481ad-7e85-440d-a4f3-6d8ff4c73247 X-Scan-Signature: 59677119386dcf9f1872cb454dc1331d Subject: Re: LF: RE: LPF for a valve based (tube based) LF amp? Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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 2.75 Status: O X-Status: X-Keywords: X-UID: 12323 Hi Chris and Clemens, surely a Pi-circuit provides a much greater selectivity than an ordinary push-pull amp by itself. Which resembles a frequency multiplier. If one does not need many bands to cater to, a so called Pi-L circuit does an extra 10db attenuation of harmonics on the average. it does consists of a series L with output of the traditional Pi-circuit forming an extra selctive component with the output C , which is to ground. All commercial RF amps by Collins Radio Corp. had Pi-L outputs. A bit tricky to adjust on multi band amps, but on a monoband amp its just a fixed inductivity. Needles to say that an outboard 5-7-or even 9 pole Tchebycheff filter does much better. I use a 3 and a 5 pole in series. Just as it was developed. And here working on the tube amp as well. 73 de wolf df2py