Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: John Williamson Newsgroups: alt.comp.os.windows-11,alt.comp.os.windows-10,comp.os.linux.advocacy,comp.os.linux.misc,uk.tech.broadcast Subject: Re: OT - TV Date: Wed, 30 Sep 2026 11:13:15 +0100 Lines: 31 Message-ID: References: <118cshs$2v7m0$1@dont-email.me> <118o9kf$2vr36$6@dont-email.me> <118p8sb$3c3gt$1@dont-email.me> <6ab13e85$0$3230586$882e4bbb@reader.netnews.com> <11987r4$dcgn$1@dont-email.me> <11991m3$mv9t$1@dont-email.me> <119as35$18kn0$1@dont-email.me> <119bbo8$1e3hu$1@dont-email.me> <119biqk$1imfn$1@dont-email.me> <119bk3r$1glpo$9@dont-email.me> <119doj1$2bpuv$1@dont-email.me> <119e25d$2ffig$3@dont-email.me> <119g5q3$37679$1@dont-email.me> <119gmur$3e4ln$1@dont-email.me> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: individual.net vwU5roYDsaND+LtlEzt7ewT4c2qSfQ2F5ESk8I9CzXaZAfqOhw Cancel-Lock: sha1:MHWxm16cdtrGAylKJsw1yZbtcXw= sha256:BT7dX34H8mFxpcWlHOEohPJM1zQFHasrq2yFofvWAps= User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Thunderbird/50.0 In-Reply-To: Content-Language: en-GB Xref: csiph.com alt.comp.os.windows-11:35383 alt.comp.os.windows-10:196319 comp.os.linux.advocacy:723001 comp.os.linux.misc:92480 uk.tech.broadcast:70622 On 30/09/2026 10:27, Carlos E.R. wrote: > On 2026-09-29 17:54, Jan Panteltje wrote: >> Yes some tube TVs had 800 Ohm speakers without transformers. >> >> Example of a tube output stage without transformer to drive a 800 Ohm >> speaker: >> >> https://2.bp.blogspot.com/-GaJkZ9klfLw/VOecHjVgPuI/AAAAAAAAA4g/H2qcMWJ3tuA/s1600/Schema.png >> > > I'm not familiar with valves EZ80 and 6CA4, I don't understand the > drawings. :-? > The EZZ80 and BCA4 valves are full wave rectifiers in the power supply. (Equivalent to two diodes in each valve, with a tapped transformer secondary. Back when semiconductors were expensive, I've done similar with a pair of germanium diodes, as it was cheaper than a bridge rectifier.)i The relevant stage for this thread is the output stage, which is two EL504 pentodes being driven in a sort of push-pull configuration by the input triode. The EL504s each have an independent DC supply. The circuit specifies an 800 ohm load, but I first expected to see a more standard 600 ohm load... -- Tciao for Now! John.