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Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Bill Sloman <bill.sloman@ieee.org> Newsgroups: sci.electronics.design Subject: Re: The not-all-that-low distortion sine wave oscillator in a faster simulating version Date: Fri, 20 Dec 2024 15:01:45 +1100 Organization: A noiseless patient Spider Lines: 83 Message-ID: <vk2q7n$3949i$3@dont-email.me> References: <vjtgnp$24ubg$1@dont-email.me> <vjv658$16ls$1@nnrp.usenet.blueworldhosting.com> <vk00um$2i900$1@dont-email.me> <vk02qm$18bb$1@nnrp.usenet.blueworldhosting.com> <vk0ehh$2o9dc$1@dont-email.me> <vk1c0g$392$1@nnrp.usenet.blueworldhosting.com> <uoj8mj9t5vc84kl4mdr01n3spqtnra2u6v@4ax.com> <vk1kpc$57k$1@nnrp.usenet.blueworldhosting.com> <lo79mjp9m4ohk7cq99gonaiihf95bcoakq@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Fri, 20 Dec 2024 05:02:00 +0100 (CET) Injection-Info: dont-email.me; posting-host="ec3070724bfd06020732b17d836f2053"; logging-data="3445042"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18yeogTWAVme4nBNji9112tO6BFgRGpP88=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:4HT5booa5/4BUog8y57cQuo5px8= Content-Language: en-US X-Antivirus-Status: Clean In-Reply-To: <lo79mjp9m4ohk7cq99gonaiihf95bcoakq@4ax.com> X-Antivirus: Norton (VPS 241219-8, 20/12/2024), Outbound message Bytes: 5405 On 20/12/2024 9:34 am, john larkin wrote: > On Thu, 19 Dec 2024 12:22:51 -0500, "Edward Rawde" > <invalid@invalid.invalid> wrote: > >> >> "john larkin" <JL@gct.com> wrote in message news:uoj8mj9t5vc84kl4mdr01n3spqtnra2u6v@4ax.com... >>> On Thu, 19 Dec 2024 09:53:03 -0500, "Edward Rawde" >>> <invalid@invalid.invalid> wrote: >>> >>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vk0ehh$2o9dc$1@dont-email.me... >>>>> On 19/12/2024 2:10 pm, Edward Rawde wrote: >>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vk00um$2i900$1@dont-email.me... >>>>>>> On 19/12/2024 6:00 am, Edward Rawde wrote: >>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vjtgnp$24ubg$1@dont-email.me... >>>>>>>>> I've been playing with the circuit, and have got rid of one op amp, which made the simulation run much faster, but didn't >>>>>>>>> help >>>>>>>>> the >>>>>>>>> distortion performance. >>>>>>>>> >>>>>>>>> Swapping the LT1115 for the LME49710 speeded up the simulation a bit more, but didn't make any difference to the distortion >>>>>>>>> either. A few of the ferrite beads have gone too. >>>>>>>>> >>>>>>>> >>>>>>>> I got a simulation speed of about 30us/s so I didn't wait the nearly 4 days it would take to complete. >>>>>>>> I did an FFT on the first few cycles and it does look 100dB down up to 1.5MHz. >>>>>>> >>>>>>> It rans at 68msec/sec for me and takes a couple of minutes to run the full ten seconds. >>>>>> >>>>>> I used the circuit from your third post. One op amp had to be moved down a bit into position and then I hit simulate. >>>>>> To be sure we're talking about the same circuit I've reposted it below. >>>>>> I'm using LTSpice 24.0.12 with no new model updates available as of this post. >>>>> >>>>> And I'm using LTSpice XVII(x64)(17.0.37.0) up-dated recently. >>>>> >>>>> I finally got your version to work. As you say, U1 had to be moved into place, but I also had to change C10 on the output of U4. >>>>> I'd specified the capacitance as 3.3u. but the "u" symbol had vanished. When I specified the capacitance as 3300n everything >>>>> worked fine. >>>> >>>> C10 is definitely 3.3u here. I tried changing it to 3300n but still less than 30us/s when I start the simulation. >>>> >>>>> >>>>>>>> If building this for real then ten turn trimmers would be used for: >>>>>>>> R14 2.2k >>>>>>>> R3 68 ohm >>>>>>>> R16 100k >>>>>>>> And I'd also want R19 or part of it variable. >>>>>>> >>>>>>> Why a ten turn trimmer? >>>>>> >>>>>> Can be 100 turn if you want. The point is only that fine adjustment would be a good idea. >>>>> >>>>> Lots of turns don't always equate to fine setability. >>>> >>>> Yes I agree. You might easily have the kinds of problems which were solved with anti backlash couplings in the days of drive cords >>>> and tuning capacitors. >>> >>> The long multi-turn trimpots are hard to adjust and expensive, and are >>> no better than single-turns for settability. >> >> Yes particularly if the resistive element is the same length, it may as well be single-turn. >> Single-turn also has the advantage that you can see where it's set before you adjust it. >> Multi-turn is usually enclosed so hard to know where it's set before adjustment. >> >> https://www.google.com/search?&q=multi+turn+trimpots&udm=2 >> >> So I'd probably go for good quality open single-turn if I ever build the 120dB circuit. Not a wise choice. >>> Single-turns have much lower HF parasitics too. Sometimes. > The rectangular multi-turn trimpots have a lot of backlash. A good > single is actually more settable. A heap faster too. You should be able cope with the backlash. A good multi-turn pontentiometer can be set a lot more precisely than any single turn part, but you have to know what you are buying to get good parts. -- Bill Sloman, Sydney