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Failed to connect to MySQL: (1203) User howardkn already has more than 'max_user_connections' active connectionsPath: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Bill Sloman Newsgroups: sci.electronics.design Subject: Re: 1kHz 130dB distortion sinewave oscillator. Date: Mon, 3 Feb 2025 12:37:10 +1100 Organization: A noiseless patient Spider Lines: 55 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Mon, 03 Feb 2025 02:37:11 +0100 (CET) Injection-Info: dont-email.me; posting-host="00c7990bbb317234de994dd49c3ca3ec"; logging-data="995322"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+kGtkLNNOngs3w3c6iBXIdSWvwCRqygmc=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:Ioq9jIOYt3iPghp95Judmaw9VaY= X-Antivirus-Status: Clean Content-Language: en-US In-Reply-To: X-Antivirus: Norton (VPS 250202-4, 3/2/2025), Outbound message On 3/02/2025 5:40 am, Edward Rawde wrote: > "john larkin" wrote in message news:tk6vpjp7tn5hct35jo5ue4846p9vt8ggt1@4ax.com... >> On Thu, 30 Jan 2025 13:47:31 -0500, "Edward Rawde" >> wrote: >> >>> Approaching 130dB now. Any suggestions for improvement? >>> It wouldn't be hard to add another four rectifier phases but then I'd have more components than Bill. >>> >>> This circuit was simulated in LTSpice 24.1.1 with all component updates as of 30th January 2025. >>> >>> Take a sample near 20s and FFT on current zoom extent with Blackman-Harris window. >>> It's approaching 130dB at 2kHz and approaching 140dB everywhere else. >>> >>> I do not know why C13/R28 and similar are needed but without them the simulation speed goes down to us/s >>> It appears that LT1115 doesn't like being simulated with very little load on its output. >>> Whether or not that's true in reality I've no idea and it may not be the case in earlier versions of LTSpice. >>> >>> Simulation speed in 24.1.1 appears to be about twice as fast as earlier versions for this circuit. >> >> If you actually build one, how would you measure the distortion? >> >> (I can think of one way) > > I'd probably ask you what you thought the best way of measuring it would be. > >> >> I'd expect it to be worse than the sim, even ignoring noise. > > I would too. > >> >> There is a hobby of playing with LT Spice as a sort of video game, >> never building or even needing the circuit. Nothing wrong with that I >> guess, except that the pay isn't very good. It can be a long term investment. > I wasn't expecting to get below -120dB in a simulation but the current circuit is approaching -140dB in a simulation. > I have definitely found it fun to do and also to improve it using suggestions from people here. > And I have learned a lot about how to use LTSpice which makes it much quicker and easier to simulate anything I might get paid for. > > From a sinewave oscillator point of view the original objective was to find out whether it's really necessary (at least at one fixed > frequency) to use lamps, thermistors or opto devices to get the lowest possible distortion. > That question seems to have been answered. But it's the wrong question. The real questions are "can you stabilse the output of an oscillator without using a non-linear device", to which the answer is that you can't, and "which non-linear device gives you least distortion in the output" to which the answer is "it depends on exactly what you are trying to do". -- Bill Sloman, Sydney