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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Low distortion sinewave oscillator without big capacitor.
Date: Sun, 6 Apr 2025 13:08:04 +1000
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On 6/04/2025 1:15 am, Edward Rawde wrote:
> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vsqeh2$1emr4$1@dont-email.me...
>> On 5/04/2025 1:48 pm, Edward Rawde wrote:
>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vsq3um$107nb$1@dont-email.me...
>>>> On 5/04/2025 5:32 am, john larkin wrote:
>>>>> On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <cd@notformail.com>
>>>>> wrote:
>>>>>
>>>>>> On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <jl@glen--canyon.com>
>>>>>> wrote:
>>>>>>
>>>>>>> On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <bill.sloman@ieee.org>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> On 4/04/2025 4:02 am, john larkin wrote:
>>>>>>>>> On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
>>>>>>>>> <invalid@invalid.invalid> wrote:
>>>>>>>>>
>>>>>>>>>> Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
>>>>>>>>>> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
>>>>>>>>>> There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
>>>>>>>>>> capacitor.
>>>>>>>>>>
>>>>>>>>>> What I have so far is below.
>>>>>>>>>>
>>>>>>>>>> Any comments?
>>>>>>>>>
>>>>>>>>> Suppose you built an oscillator and had a switch that varied the loop
>>>>>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
>>>>>>>>> flip the switch if it's too high or too low. Switch at the zero
>>>>>>>>> crossing.
>>>>>>>>>
>>>>>>>>> I wonder what distortion would be like.
>>>>>>>>
>>>>>>>> Why not measure it? LTSpice could probably give you a sine wave whose
>>>>>>>> amplitude ramped up linearly for a bit, and ramped back down again.
>>>>>>>>
>>>>>>>> Do a DFT on that and you'd have your answer. It wouldn't be good.
>>>>>>>>
>>>>>>>>> (I wouldn't really do that. It's just an idea to play with.)
>>>>>>>>
>>>>>>>> Only if you don't know what you are talking about.
>>>>>>>
>>>>>>> An idea is like a cute baby puppy. Some people want to feed it and
>>>>>>> play with it and some people want to club it to death.
>>>>>>
>>>>>> "Please don't feed the troll."
>>>>>
>>>>> The point here is that some people, especially fatheads with advanced
>>>>> degrees, are incapable of having ideas, and react by being hostile to
>>>>> ideas and to people who have them.
>>>>
>>>> I've got my name three patents, so I'm demonstrably capable of having ideas.
>>>>
>>>> I am hostile to people who tout bad ideas.
>>>
>>> Don't you think it would be better to just explain why you think an idea is bad Bill?
>>
>> I usually do.
>>
>>> And also, if necessary, to just explain how and why you think it should be done.
>>
>> I have been known to do that. You should know - I've done it to you, here, and I'm about to do it to John May whom I really like
>> and approve of.
>>
>>> Being hostile doesn't make you look good and it does the opposite of persuading others that their ideas are bad.
>>
>> Few people can ever be persuaded that their ideas are bad. John Larkin definitely isn't one of them.
>>
>>> So why be hostile at all?
>>
>> The same mechanism that persuades people that their bad ideas aren't too bad allows them to gloss over any criticism that isn't
>> thoroughly explicit.
> 
> You can be critical without being hostile.

But, as I said, making it critical enough so that people realise that 
they have been criticised, rather than settling for basking in the 
attention, does come across as hostile, particularly to people who are 
seeking flattery, rather than critical comment.--Bill Sloman, Sydney