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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: Thu, 19 Dec 2024 17:29:53 +1100
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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.

>>> 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. The screw will try 
  to move the brush along the resistive element, but the brush tends to 
move in fits and starts. I once specified a rather expensive Vishay 
trimmer which had a split brush that moved more smoothly, and we knocked 
about twenty minutes off the setting up time for a rather cranky circuit 
which more than paid for the extra cost of the fancy Vishay trimmer,

>> Beckman ten-turn precision potentionmeters were designed to be used with turns-counting dials. 19mm trimmers ran around twenty
>> turns, but weren't all that precisely settable.
>>
>>> I wish LTSpice had a "Do you want to fix apparent line wraps Y/N". That shouldn't be hard.
>>
>> First define a line wrap in terms that you can program. It's a carriage return and a line feed, but so is a real new line.
> 
> There are reasons why Notepad++ has an EOL conversion option Bill but never mind.

Word salad. Of course there are reasons, but you'd indicate what they 
are if you were trying to be helpful. LTspice does seem to have a 
limited numbers of words that can be put at the start of a line, and it 
baulks if it finds anything else at the start of a new line. If it 
treated that condition as indicative of a line wrap and deleted the 
preceding new line character we might get somewhere but the fact that it 
doesn't suggests that the situation might be more complicated than that.
>>> Also is there any way in LTSpice to find a component?
>>
>> Inspection works fine for me. Professional circuit diagrams tend to get re-numbered before they are released to production so the
>> numbers run from left to right across the sheet in bands, then from top to bottom as you moved down from the top band to the
>> bottom band.
> 
> What would you do when a change is required which requires an additional component such as an additional resistor or capacitor?

I wasn't responsible for keeping production drawings up to date, and the 
people who were had a bunch of conflicting priorities to reconcile.

The service engineer who travelled internationally to keep the machines 
working were forceful personalities who needed the schematics to be 
rapidly intelligible. I got told off by them from time to time, and got 
congratulated once or twice.

>>> What I mean is let's say you have a schematic like Bill's schematic and you know that R17 is there somewhere but you don't know
>>> where.
>>
>> It's on the non-inverting input of U7.
> 
> And it was just an example.

Of your capacity to make an unhelpful meal of a minor problem.

-- 
Bill Sloman, Sydney