Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Five transistor version of the low distortion sine-wave
 oscillator
Date: Wed, 16 Apr 2025 03:58:17 +1000
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On 16/04/2025 3:11 am, Edward Rawde wrote:
> "Edward Rawde" <invalid@invalid.invalid> wrote in message news:vtlm0g$21p4$1@nnrp.usenet.blueworldhosting.com...
>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vtl0bc$364bt$1@dont-email.me...
>>> On 15/04/2025 1:56 am, Edward Rawde wrote:
>>>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vtihob$sfdm$1@dont-email.me...
>>>>> On 12/04/2025 6:27 pm, Bill Sloman wrote:
>>>>>> Edward Rawde posted an eight-transistor low distortion sine wave oscillator circuit recently, and John May pointed out that
>>>>>> you
>>>>>> could leave out half the transistors.
>>>>>>
>>>>>> I couldn't immediately see exactly how either of the circuits worked, though I could get the simulations to run under LTSpice
>>>>>> and
>>>>>> see roughly what was going on.
>>>>>>
>>>>>> I've now dug a bit deeper. Here is a five transistor version of John May's four transistor version.
>>>>>
> 
> As a first prototype I'd build the circuit below using only through hole components except where through hole is either not
> available or not desirable such as ceramic capacitors.
> Resistors may be done with pads so that through hole resistors can be soldered on in such a way that they're rather easier to remove
> than an 0402.
> 
> In recent years I've been asked if I can repair equipment such as a music keyboard.
> If the internals are surface mount and the problem isn't an obvious one (eg wrong power adapter) I will generally decline to try.
> Find someone who can get the dried up surface mount electrolytics off without damaging the board, if it hasn't been damaged already
> by leaking electrolyte.
> There may well be equipment which can do it but I don't have it.
> 
> The second prototype for this circuit would be all surface mount.
> 
> Unless I win a lottery I won't be either building it or figuring out what I need to test it.
> 
> I'm done with sinewave oscillators except for being curious about how to design a suitable sample and hold circuit in the other
> circuit JM posted.
> Use of a comparator to obtain the sampling signal might reintroduce all the harmonics we want to get rid of.

Too true. I once got stuck with cleaning a comparator-heavy board in 
fairly old Cambridge Instruments electron microscope.

Final test hated it because the comparators tended to talk to one 
another, and burst into collective oscillation. The original prototype 
might not have done it, but as the manufacturer improved the parts and 
built them with smaller dies the design got more and more twitchy.

I worked over the layout to minimise the interactions as much as I 
could, but while final test liked what I'd done, it merely reduced the 
problem and made it easier to fix when it did show up.

-- 
Bill Sloman, sydney