Return-Path: Received: (qmail 14961 invoked from network); 22 Oct 2002 17:23:57 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 22 Oct 2002 17:23:57 -0000 Received: (qmail 4675 invoked from network); 22 Oct 2002 17:23:17 -0000 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 22 Oct 2002 17:23:17 -0000 Received: from majordom by post.thorcom.com with local (Exim 4.10) id 1842jO-0008Kk-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 22 Oct 2002 18:22:14 +0100 Received: from [194.247.47.231] (helo=mailout.zetnet.co.uk ident=mail) by post.thorcom.com with esmtp (Exim 4.10) id 1842jO-0008Kb-00 for rsgb_lf_group@blacksheep.org; Tue, 22 Oct 2002 18:22:14 +0100 Received: from irwell.zetnet.co.uk ([194.247.47.48] helo=zetnet.co.uk) by mailout.zetnet.co.uk with esmtp (Exim 3.35 #1 (Debian)) id 1842jO-00057p-00 for ; Tue, 22 Oct 2002 18:22:14 +0100 Received: from a7j7r2 (bts-0074.dialup.zetnet.co.uk [194.247.48.74]) by zetnet.co.uk (8.11.3/8.11.3/Debian 8.11.2-1) with SMTP id g9MHMCE15000 for ; Tue, 22 Oct 2002 18:22:13 +0100 Message-ID: <004901c279ef$a8d6f6c0$4a30f7c2@a7j7r2> From: "John Rabson" To: rsgb_lf_group@blacksheep.org References: <3DB0C203.A90691A6@verizon.net> <000801c279ad$b339adc0$f530f7c2@a7j7r2> <3DB55E79.50901@usa.net> Date: Tue, 22 Oct 2002 18:13:10 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Re: Vacuum tubes on Motherboards... Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-0.6 required=5.0tests=QUOTED_EMAIL_TEXT,REFERENCES,SPAM_PHRASE_01_02, USER_AGENT_OEversion=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group I believe the Hallicrafters used several pairs of lightly coupled tuned circuits. The 1960s receiver, a GEC RC411, had crystal filters. There is of course another advantage to the thermionic device. It is more robust than a large number of transistors. One of my colleagues described the power transistor as "the fastest fuse known to man". John Rabson ----- Original Message ----- From: "Alberto di Bene" To: Sent: Tuesday, October 22, 2002 3:19 PM Subject: LF: Re: Vacuum tubes on Motherboards... > John Rabson wrote: > > >A few years ago, I was restoring an ancient Hallicrafters receiver and > >noticed the crisp quality of the audio compared with that of a 1960s > >transistorised communications receiver. I spoke to one of the experts at BT > >Labs, who suggested that the output transformer might have something to do > >with it. Also, the characteristics of a bipolar transistor audio output > >stage are _not_ identical to those of a pentode or beam tetrode. > > > > > > > IMHO, the main reason for the more pleasant sound is the IF > filter...supposing the '60s receiver > uses a crystal filter, while the Hallicrafters not. > Crystal filters are wonderful in the frequency domain, but terrible > performer in the time domain, > while LC filter just the opposite... > > 73 Alberto I2PHD > > > > >