Re: A variation on my current mirror low distortion sine wave oscillator - 10dB less distortion and much the same number of components

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp4ou6$29vt1$1@dont-email.me...

On 19/02/2025 11:43 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp4ibd$28rod$1@dont-email.me...

On 19/02/2025 5:40 am, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp1acj$1j5t7$1@dont-email.me...

On 18/02/2025 2:50 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...

On 18/02/2025 3:54 am, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...

On 17/02/2025 3:53 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...

On 17/02/2025 2:14 am, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...

On 16/02/2025 2:18 pm, Edward Rawde wrote:

"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...

On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:

>

>
But it doesn't matter to anyone else Bill.

>
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.

>
It strikes me as an obvious fact.

>
We can see that, and work out why.
>

I'm not expecting anyone else to offer any comment but it's interesting that they haven't.

>
Low distortion 1kHz oscillators are a pretty niche subject. It's pretty much audiophile-specific. I'm not actually an audiophile,
though I got a couple of letter into the UK HiFi News and Record Reviews back in the 1980's, but I got interested by some of the
weirder electronics they touted.
>

And it's not like this group is only for the discussion of electronic matters, as the "Cracking Speech by JDV" thread shows.
You seem to be enjoying yourself there.

>
Sending up Cursitor Doom can be fun.

Which suggests that you enjoy being unpleasant.

>

...

I think the circuit JM posted is likely to work.

>
Congratulations. You've said something  sensible for once.

>
Why do you like to talk down to other people Bill?

>
I don't especially like doing it but some comments make it unavoidable.

Which suggests that unpleasantness is just part of your personality.

>

It doesn't make you look superior, far from it.

>
I don't feel any need to look superior, and scholar google demonstrates that I'm not. My wife has racked up many more citations -
psycholinguistics papers do get cited in larger numbers than my kind of stuff, but that isn't the crucial difference.
>
https://scholar.google.com.au/scholar?hl=en&as_sdt=0%2C5&q=%22A+W+Sloman%22&btnG=
>

Two BCM61B devices would probably be fine for the current mirror.
A single LT1679 can be used for U1,5,6,8 with a cheaper device for the rest.

>
This is a less defensible observation.

>
After more simulation I agree that all devices may as well be LT1679.

>
That wasn't what I said, so "agree" isn't the right word. John May uses the cheaper LT1013 outside the oscillator signal path, as
anybody with an sense would.

Anybody with any sense would look at the economics and go for the lowest possible cost when choosing between LT1678, LT1679, LT1013,
LT1014

It's nice to have a circuit ready for practical build but I won't be building it myself.

>

Two quad op amp packages.
This produces the lowest possible distortion in simulation.

>
Compared with what?
>

U5,U6 and U8 are the phase shift oscillator. U1 should a cheap device that is part of the network that generates the amplitude
feedback signal fed into the integrator wrapped around U7 to generate the gain control signal that modulate the level of the
feedback sine wave that adjusts the output amplitude.
>

And C6 can be made from two polarized capacitors.

>
Sadly, you can't buy a pair of 940uF polarised capacitors. Two 1000uf polarised capacitors would be quite close enough

>
There have been two polarised 1000uf capacitors on my schematic for the last few days.

>
Something of an over-kill.
>

https://4donline.ihs.com/images/VipMasterIC/IC/VISH/VISH-S-A0010924709
/VISH-S-A0010924709-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0
>
are offered at +/-10% and +/-20% tolerance and 940uF is within 10% of 1000uF.
>
I(R17) runs at about 100uA and I(R21) runs at about 145uA -that is about 25mV across R17 and 36mV across R21. A single polarised
capacitor isn't going to get depolarised by 11mV of bias.
>
Putting 100uF polarised caps in parallel to R17 and R19 delivers harmonics about -135dB below the fundamental rather more
cheaply,
and won't upset people who get nervous about polarised caps.
>
As we know, LTSpice isn't all that credible when it predicts very low harmonic content, so 470uF is perhaps a a bit much.

>
<snip>
>

I've have spelled this out quite explicitly from  time to time over the twenty years I've been posting here.

>
I've been reading and posting in this and other groups for way more than 20 years.

>
These kind of groups haven't been around for "way more than twenty years". I dug my first post here out of google groups some time
ago, and it was in 1996 (some 28 years ago). User groups predate the world wide web, but not by much. I was e-mailing my wife
across Cambridge via Abingdon in the late 1980's but only by virtue of the Alvey project I was tied up with at the time.
>
--
Bill Sloman, Sydney
>