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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Final final 1kHz oscillator
Date: Thu, 28 Nov 2024 02:08:03 +1100
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On 27/11/2024 7:48 pm, JM wrote:
> On Tue, 26 Nov 2024 15:32:38 +1100, Bill Sloman <bill.sloman@ieee.org>
> wrote:
> 
>> On 25/11/2024 1:02 pm, Bill Sloman wrote:
>>> On 24/11/2024 5:10 pm, Edward Rawde wrote:
>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message
>>>> news:vhue9h$243sl$1@dont-email.me...
>>>>> On 24/11/2024 5:11 am, Edward Rawde wrote:
>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message
>>>>>> news:vhs1ea$1kbt4$1@dont-email.me...
>>>>>>> On 23/11/2024 4:12 pm, Edward Rawde wrote:
>>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message
>>>>>>>> news:vhrma8$1io30$2@dont-email.me...
>>>>>>>>> On 23/11/2024 3:32 am, Edward Rawde wrote:
>>>>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message
>>>>>>>>>> news:vhp713$12bnt$2@dont-email.me...
>>>>>>>>>>> On 21/11/2024 1:00 am, Bill Sloman wrote:
>>>>>>>>>>>> On 20/11/2024 2:03 pm, Edward Rawde wrote:
>>>>>>>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message
>>>>>>>>>>>>> news:vhjj2v$24eu4$3@dont-email.me...
>>>>>>>>>>>>>> On 20/11/2024 1:29 pm, Bill Sloman wrote:
>>>>>>>>>>>>>>> On 20/11/2024 12:59 pm, Edward Rawde wrote:
>>>>>>>>>>>>>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message
>>>>>>>>>>>>>>>> news:vhibce$1t7v2$1@dont-email.me...
>>>>>>>>>>>>>>>>> On 18/11/2024 2:58 pm, Edward Rawde wrote:
>>>>>>>>>>>>>>>>>> "JM" <sunaecoNoChoppedPork@gmail.com> wrote in message
>>>>>>>>>>>>>>>>>> news:n7iijjdeqecl0kmub0bq5in0dbm60m7qam@4ax.com...
>>>>>>>>>>>>>>>>>>> On Thu, 14 Nov 2024 11:14:28 -0500, "Edward Rawde"
>>>>>>>>>>>>>>>>>>> <invalid@invalid.invalid> wrote:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> "JM" <sunaecoNoChoppedPork@gmail.com> wrote in message
>>>>>>>>>>>>>>>>>>>> news:t5fajjdteskfftvkf84iqsp2vc4b9ta5kj@4ax.com...
>>>>>>>>>>>>>>>>>>>>> On Fri, 8 Nov 2024 15:43:41 -0500, "Edward Rawde"
>>>>>>>>>>>>>>>>>>>>> <invalid@invalid.invalid> wrote:
>>
>> <snip>
>>
>> The current version has been running overnight and has got to three
>> seconds, and the DFT from 2.8 to three seconds shows third harmonic
>> about 90db below the fundamental. The noise floor is about 100dB down
>> and the other harmonics are barely visible above it.
>>
>> Here's the .asc file. There are extra components put in to make it
>> simulate faster - L1 and L14 are the obvious examples, but L10, L11 and
>> L12 got put in for the same reason. I suspect that if I had put in
>> equivalent series resistance and inductance for C22 as well as for C6
>> and C15 I might not have needed some of them.
>>
>> There is some other tidying up I could do, and that should get get the
>> simulation speed up. I got a new circuit from John May last night, and
>> it not only spits out a very clean sine wave but also simulated very
>> fast. I forgot to put it on solid state disk before I ran it, and it
>> took as long to get one of the waveforms off the spinning hard disk as
>> it had done to run the simulation.

<snipped LTSpice .asc file.>

> When evaluating architecture there's little to be gained by using a
> complicated opamp model.  Use a simple 1 or 2 pole model to begin
> with.
> 
> Try the attached file, I've used a simple model to speed up the
> simulation, and made a slight circuit change.  This shows the
> harmonics due to the control loop to be sub 130dBc.  Of course the
> amplifier harmonic distortion is not simulated, but neither was it in
> the simulation by Mr Rawde.

Thanks for that. I've got it into a form that my copy of LTSpice 
recognises as a .asc file, so I have looked at it.

I haven't run it yet because I'm running yet another variant of the 
circuit, which has got to 2.4 seconds, and I'll leave it running overnight.

I'm currently curious about the effect of the phase of the 2kHz 
component in the control signal (coming from my full-wave rectifier), 
and a fast simulating version of the circuit is just what I need to get 
that sorted out. I had thought that that it would be trivial to get the 
phase right, but my first attempt didn't get close.

I could go mad and put a version of the circuit into KiCad and create a 
printed circuit layout and get some Chinese firm to make and load the board.

It would be an extravagance, but nothing dramatic.

-- 
Bill Sloman, Sydney