80dB now but still needs improvement at 1KHz

Nov 04, 2024 Last reply: 1 year ago 45 Replies
E

Simulation isn't fast but if you let it complete and do an FFT on the last 30 seconds, it's 80dB down at all unwanted harmonics. There do however seem to be unwanted sidebands close in either side of 1KHz Any suggestions for improvement?



Version 4 SHEET 1 2196 932 WIRE 400 -704 368 -704 WIRE 608 -704 464 -704 WIRE -80 -624 -176 -624 WIRE 16 -624 -80 -624 WIRE 112 -624 96 -624 WIRE 128 -624 112 -624 WIRE 240 -624 208 -624 WIRE 336 -624 240 -624 WIRE 368 -624 368 -704 WIRE 368 -624 336 -624 WIRE 400 -624 368 -624 WIRE 512 -624 464 -624 WIRE -80 -608 -80 -624 WIRE 240 -592 240 -624 WIRE 336 -576 336 -624 WIRE -176 -544 -176 -624 WIRE -208 -496 -288 -496 WIRE -80 -496 -80 -528 WIRE -80 -496 -112 -496 WIRE 0 -496 -80 -496 WIRE 240 -480 240 -512 WIRE 288 -480 240 -480 WIRE 336 -480 336 -512 WIRE 336 -480 288 -480 WIRE 112 -464 112 -624 WIRE 288 -448 288 -480 WIRE 320 -448 288 -448 WIRE 320 -432 320 -448 WIRE 288 -400 288 -448 WIRE 288 -400 240 -400 WIRE 336 -400 288 -400 WIRE -288 -368 -288 -496 WIRE -192 -368 -288 -368 WIRE 0 -368 0 -496 WIRE 0 -368 -112 -368 WIRE 240 -368 240 -400 WIRE 336 -352 336 -400 WIRE 416 -336 384 -336 WIRE 608 -336 608 -704 WIRE 608 -336 480 -336 WIRE -80 -256 -176 -256 WIRE 16 -256 -80 -256 WIRE 112 -256 112 -400 WIRE 112 -256 96 -256 WIRE 144 -256 112 -256 WIRE 240 -256 240 -288 WIRE 240 -256 224 -256 WIRE 336 -256 336 -288 WIRE 336 -256 240 -256 WIRE 384 -256 384 -336 WIRE 384 -256 336 -256 WIRE 416 -256 384 -256 WIRE 512 -256 512 -624 WIRE 512 -256 480 -256 WIRE -80 -224 -80 -256 WIRE 512 -224 512 -256 WIRE 608 -224 608 -336 WIRE -176 -176 -176 -256 WIRE -288 -128 -288 -368 WIRE -208 -128 -288 -128 WIRE -80 -128 -80 -144 WIRE -80 -128 -112 -128 WIRE 0 -128 0 -368 WIRE 0 -128 -80 -128 WIRE 176 -128 0 -128 WIRE 288 -128 256 -128 WIRE 320 -128 288 -128 WIRE 448 -128 400 -128 WIRE 288 -16 288 -128 WIRE 288 -16 -80 -16 WIRE 320 -16 288 -16 WIRE 448 -16 448 -128 WIRE 448 -16 400 -16 WIRE 48 48 48 32 WIRE 448 48 448 -16 WIRE 512 48 512 -144 WIRE 512 48 448 48 WIRE -80 96 -80 -16 WIRE 16 96 -80 96 WIRE 448 96 448 48 WIRE 448 96 176 96 WIRE 16 160 -80 160 WIRE 592 160 176 160 WIRE 608 160 608 -144 WIRE 608 160 592 160 WIRE 736 160 608 160 WIRE 832 160 736 160 WIRE 512 192 512 48 WIRE 592 192 592 160 WIRE 48 224 48 208 WIRE -464 256 -544 256 WIRE -400 256 -464 256 WIRE -80 272 -80 160 WIRE 16 272 -80 272 WIRE 224 272 16 272 WIRE 304 272 288 272 WIRE 448 272 448 96 WIRE 448 272 384 272 WIRE -80 288 -80 272 WIRE 16 288 16 272 WIRE 736 288 720 288 WIRE 832 288 816 288 WIRE 912 288 896 288 WIRE -544 304 -544 256 WIRE 512 304 512 272 WIRE 592 304 592 272 WIRE -400 320 -400 256 WIRE -80 384 -80 368 WIRE -32 384 -80 384 WIRE 16 384 16 352 WIRE 16 384 -32 384 WIRE 768 400 768 384 WIRE -32 416 -32 384 WIRE 592 416 592 368 WIRE 720 416 720 288 WIRE 720 416 592 416 WIRE 736 416 720 416 WIRE 816 432 800 432 WIRE 912 432 912 288 WIRE 912 432 896 432 WIRE 448 448 352 448 WIRE 512 448 512 368 WIRE 512 448 448 448 WIRE 736 448 512 448 WIRE -544 480 -544 384 WIRE -544 480 -624 480 WIRE 592 480 592 416 WIRE 592 480 512 480 WIRE 768 480 768 464 WIRE -624 496 -624 480 WIRE -544 496 -544 480 WIRE -400 496 -400 384 WIRE -400 496 -544 496 WIRE 352 512 352 448 WIRE 512 512 512 480 WIRE 448 528 448 448 WIRE 592 528 592 480 WIRE -544 576 -544 496 WIRE 912 576 912 432 WIRE -400 592 -400 496 WIRE 352 624 352 592 WIRE 448 624 448 592 WIRE 448 624 352 624 WIRE 512 624 512 592 WIRE 512 624 448 624 WIRE 592 624 592 592 WIRE 592 624 512 624 WIRE 352 656 352 624 WIRE -544 752 -544 656 WIRE -464 752 -544 752 WIRE -400 752 -400 656 WIRE -400 752 -464 752 WIRE -288 752 -288 -128 WIRE 400 752 -288 752 WIRE 512 752 400 752 WIRE 624 752 512 752 WIRE 736 752 624 752 WIRE 832 752 736 752 WIRE 912 752 912 656 WIRE 912 752 832 752 WIRE 400 800 400 752 WIRE 512 800 512 752 WIRE 624 800 624 752 WIRE 736 800 736 752 WIRE 832 800 832 752 WIRE 912 800 912 752 WIRE 400 912 400 864 WIRE 512 912 512 864 WIRE 624 912 624 864 WIRE 736 912 736 864 WIRE 832 912 832 864 WIRE 912 912 912 864 FLAG -624 496 0 FLAG 768 384 V+ FLAG 48 224 V- FLAG -464 256 V+ FLAG -464 752 V- FLAG -32 416 0 FLAG 736 160 output FLAG 48 32 V+ FLAG 768 480 V- FLAG 352 656 0 FLAG 320 -432 0 FLAG 912 912 0 FLAG 832 912 0 FLAG 736 912 0 FLAG 624 912 0 FLAG 512 912 0 FLAG 400 912 0 SYMBOL voltage -544 288 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 12 7 Left 2 WINDOW 3 15 104 Left 2 SYMATTR SpiceLine Rser=0.01 SYMATTR InstName V1 SYMATTR Value 6 SYMBOL res 400 256 R90 WINDOW 0 -7 54 VBottom 2 WINDOW 3 37 50 VTop 2 SYMATTR InstName R1 SYMATTR Value 10.5k SYMBOL cap 288 256 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 15n SYMBOL cap 32 352 R180 WINDOW 0 -33 54 Left 2 WINDOW 3 -49 18 Left 2 SYMATTR InstName C2 SYMATTR Value 15n SYMBOL polcap -416 320 R0 SYMATTR InstName C4 SYMATTR Value 100µ SYMBOL res 272 -144 R90 WINDOW 0 -1 46 VBottom 2 WINDOW 3 35 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 6.34k SYMBOL res 416 -144 R90 WINDOW 0 -4 61 VBottom 2 WINDOW 3 39 55 VTop 2 SYMATTR InstName R8 SYMATTR Value 13k SYMBOL njf -112 -176 R90 WINDOW 0 -37 23 VRight 2 WINDOW 3 -9 -3 VRight 2 SYMATTR InstName J1 SYMATTR Value J112 SYMBOL voltage -544 560 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 10 0 Left 2 WINDOW 3 15 104 Left 2 SYMATTR SpiceLine Rser=0.01 SYMATTR InstName V2 SYMATTR Value 6 SYMBOL polcap -416 592 R0 SYMATTR InstName C5 SYMATTR Value 100µ SYMBOL res -96 272 R0 SYMATTR InstName R2 SYMATTR Value 10.5k SYMBOL res 496 -240 R0 SYMATTR InstName R9 SYMATTR Value 4.7 SYMBOL pjf -112 -544 R90 WINDOW 0 -34 29 VRight 2 WINDOW 3 -9 -1 VRight 2 SYMATTR InstName J2 SYMATTR Value J175 SYMBOL schottky 464 -720 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D3 SYMATTR Value BAS40HY SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 416 -240 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D5 SYMATTR Value BAS40HY SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 464 -640 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D2 SYMATTR Value BAS40HY SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 416 -320 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D1 SYMATTR Value BAS40HY SYMATTR Description Diode SYMATTR Type diode SYMBOL res -96 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 68 SYMBOL OpAmps\\LT1994 80 128 R0 WINDOW 3 10 -65 Left 2 WINDOW 0 11 -95 Left 2 SYMATTR InstName U2 SYMBOL OpAmps\\LT1057 768 368 R0 WINDOW 0 19 104 Left 2 WINDOW 3 18 130 Left 2 SYMATTR InstName U1 SYMBOL schottky 496 304 R0 WINDOW 3 53 -28 VRight 2 WINDOW 0 53 91 VRight 2 SYMATTR Value BAS40HY SYMATTR InstName D4 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 576 304 R0 WINDOW 3 50 -51 VRight 2 WINDOW 0 48 74 VRight 2 SYMATTR Value BAS40HY SYMATTR InstName D6 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 432 528 R0 SYMATTR InstName C7 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL res 336 496 R0 SYMATTR InstName R11 SYMATTR Value 220k SYMBOL res 496 496 R0 WINDOW 3 29 83 Left 2 SYMATTR Value 220k SYMATTR InstName R12 SYMBOL res 224 -608 R0 WINDOW 0 -62 49 Left 2 WINDOW 3 -66 84 Left 2 SYMATTR InstName R13 SYMATTR Value 100k SYMBOL cap 320 -576 R0 WINDOW 0 -31 5 Left 2 WINDOW 3 -36 50 Left 2 SYMATTR InstName C6 SYMATTR Value 22µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0028 Lser=544p mfg="Würth Elektronik" pn="885012107005 WCAP-CSGP 0805" type="X5R" SYMBOL res -96 -624 R0 WINDOW 0 36 45 Left 2 WINDOW 3 33 76 Left 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL res -96 -240 R0 WINDOW 0 36 45 Left 2 WINDOW 3 34 76 Left 2 SYMATTR InstName R6 SYMATTR Value 100k SYMBOL res 224 -640 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R14 SYMATTR Value 100k SYMBOL res 240 -272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 100k SYMBOL res 224 -384 R0 WINDOW 0 -53 15 Left 2 WINDOW 3 -61 47 Left 2 SYMATTR InstName R17 SYMATTR Value 100k SYMBOL cap 576 528 R0 SYMATTR InstName C8 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL res 416 -32 R90 WINDOW 0 -4 61 VBottom 2 WINDOW 3 39 55 VTop 2 SYMATTR InstName R5 SYMATTR Value 680k SYMBOL res 592 -240 R0 SYMATTR InstName R10 SYMATTR Value 4.7 SYMBOL res 112 -640 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R19 SYMATTR Value 100k SYMBOL res 112 -272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R20 SYMATTR Value 100k SYMBOL res 896 560 R0 SYMATTR InstName R16 SYMATTR Value 100k SYMBOL cap 896 800 R0 SYMATTR InstName C10 SYMATTR Value 100µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C575OX5ROJI07M" type="X5R" SYMBOL cap 816 800 R0 SYMATTR InstName C12 SYMATTR Value 100µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C575OX5ROJI07M" type="X5R" SYMBOL cap 720 800 R0 SYMATTR InstName C13 SYMATTR Value 100µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C575OX5ROJI07M" type="X5R" SYMBOL cap 896 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C9 SYMATTR Value 10µ SYMATTR SpiceLine V=16 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61C106KAAL" type="X5R" SYMBOL res 832 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R18 SYMATTR Value 220 SYMBOL cap 96 -464 R0 SYMATTR InstName C15 SYMATTR Value 1µ SYMATTR SpiceLine V=16 Irms=0 Rser=0.007 Lser=0 mfg="TDK" pn="C3216X7RIC105K" type="X7R" SYMBOL cap 608 800 R0 SYMATTR InstName C11 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL cap 496 800 R0 SYMATTR InstName C14 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL cap 384 800 R0 SYMATTR InstName C16 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL res 496 176 R0 WINDOW 0 36 27 Left 2 WINDOW 3 39 52 Left 2 SYMATTR InstName R21 SYMATTR Value 4.7 SYMBOL res 576 176 R0 WINDOW 0 38 27 Left 2 WINDOW 3 40 51 Left 2 SYMATTR InstName R22 SYMATTR Value 4.7 SYMBOL res 912 416 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R23 SYMATTR Value 100 SYMBOL cap 320 -352 R0 WINDOW 0 -27 5 Left 2 WINDOW 3 -35 47 Left 2 SYMATTR InstName C3 SYMATTR Value 22µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0028 Lser=544p mfg="Würth Elektronik" pn="885012107005 WCAP-CSGP 0805" type="X5R" TEXT -584 840 Left 2 !.tran 0 300s 0s startup TEXT -400 -720 Left 2 ;Edward Rawde's high purity sinewave oscillator. 3 Nov 2024



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B

He did. The .asc file is a circuit diagram. I've looked at it and run the simulation - if only for 200 seconds rather than 300 seconds.

The FFT says that sine wave is as good as he claims.

The circuit diagram doesn't make it clear what it's various parts are there to do - it makes sense to group the components in a way that lets somebody looking at the circuit diagram get some feel for what the components are doing.

And it you are using the LT1994 it makes sense to read the data sheet carefully enough to notice that the Icom pin 2 should be bypassed with at least 100nF to ground.

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John May's circuit makes it clear that the second FET isn't strictly necessary. There are cheaper ways of getting rid of the even-order harmonics.

I've managed to dig out the precision, full wave rectifier that I used in my circuit, which is a half-wave rectifier to which you add just enough of the full sine wave to deliver both halves of the sine wave (one of them inverted) at it's output, which calls for a couple 10k 0.1% thin-film precision resistors on a common substrate, which you can buy off the shelf.

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E

If you mean ASCII art, no thanks in the case of this circuit.

Assuming Windows, Download this:

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Yes Windows is crap but you still need the right tools for the job.

Make a something.asc file (You'll need file extensions turned on) and open it with notepad++ Paste the contents of my post. The second file I posted has the best performance.

The first and last lines are shown here: Version 4 (many other lines) TEXT -400 -720 Left 2 ;Edward Rawde's high purity sinewave oscillator. 3 Nov 2024 V2

Now check that all lines except the first begin with a word in capital letters. If not then it's likely that line wraps need to be corrected.

Go to Encoding and choose "Convert to ANSI". Save the file.

Download this:

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After installing it make sure it's fully up to date in Tools, Update components and Help Check for updates.

Close it and open the asc file which should now open with LTSpice.

Press the green Run/Pause button and another window should open. Click in the schematic where it says output and watch the output as it simulates.

After a while you can select a clean part of the trace and right click to choose View then FFT. Select "use current zoom extent and run the FFT".

Now you can turn your lab into a bedroom or livingroom or something useful.

To answer Bill's comments, I do read data sheets in detail and I was aware that I should have added an 0.1uF but I just hadn't got to it due to the excitement of getting below 80dB :)

If I was going to build this I'd read the data sheet in a lot more detail because that may turn up other parameters which matter in reality such as maximum supply voltage. It seems that you're not supposed to go over 5V these days.

It's not possible to count the number of circuit diagrams I've seen where there was a part or subcircuit and no-one had a clue what it was doing.

The feedback system through U1 seems to be necessary to keep all four diodes making equal contribution all the time. Otherwise it can slip into only two diode mode and distortion increases.

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E

Yes there's no way I would use a part without reading the data sheet. Pass 1 fount the 0.1uF but I hadn't got around to adding it. Pass 2 found that I couldn't go above +/- 6V Pass 3 which I haven't done yet would take a lot more time and I probably won't do it because I doubt I'll be able to build this for real.

Please see also my reply to Jan.

Does his circuit have better performance? Just curious, it's not a competition.

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B

The version I got privately certainly did.

Actually, I've decided that the second FET is a bad idea. Two different FETs need two different gate drive voltages to give the right channel resistance, and the only guide you've got to that is the amplitude of the single sine wave you are producing. A large number of different pairs of FET gate drive voltages could give you the same stable amplitude.

If you monitored the second harmonic component of the output you would have a second independent output which could let you optimise both gate dries at the same time, but that would be an unnecessary refinement.

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E

These appear to be LTSpice, so why can't you use it to view my circuits?

In any case if you can't simulate my circuits you won't be able to appreciate how brilliant a designer I am like Bill does.

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E

"Bill Sloman" snipped-for-privacy@ieee.org wrote in message news:vgbv7l$177js$ snipped-for-privacy@dont-email.me...

Now approacing 90dB if you believe the simulation with with this experimental circuit. You'll want to find something else to do while it simulates. How to inprove it further?

Version 4 SHEET 1 2196 932 WIRE -160 -752 -208 -752 WIRE 16 -752 -80 -752 WIRE 128 -752 16 -752 WIRE 288 -752 208 -752 WIRE -208 -688 -208 -752 WIRE -128 -688 -208 -688 WIRE 80 -688 -64 -688 WIRE 128 -688 80 -688 WIRE 288 -688 288 -752 WIRE 288 -688 192 -688 WIRE 80 -656 80 -688 WIRE 16 -640 16 -752 WIRE 16 -544 16 -576 WIRE 80 -544 80 -576 WIRE 16 -464 16 -480 WIRE 80 -448 48 -448 WIRE 288 -448 288 -688 WIRE 288 -448 80 -448 WIRE -208 -432 -208 -688 WIRE -16 -432 -208 -432 WIRE 192 -416 48 -416 WIRE 240 -416 192 -416 WIRE 368 -416 320 -416 WIRE 432 -416 368 -416 WIRE 512 -416 432 -416 WIRE 624 -416 512 -416 WIRE -208 -384 -208 -432 WIRE 16 -384 16 -400 WIRE 368 -368 368 -416 WIRE 80 -352 80 -448 WIRE 192 -352 192 -416 WIRE 432 -352 432 -416 WIRE 512 -352 512 -416 WIRE 624 -352 624 -416 WIRE -208 -272 -208 -304 WIRE -208 -272 -304 -272 WIRE -208 -240 -208 -272 WIRE 80 -240 80 -272 WIRE 192 -240 192 -288 WIRE 432 -240 432 -288 WIRE 512 -224 512 -288 WIRE 624 -224 624 -288 WIRE 368 -192 368 -288 WIRE 368 -192 -16 -192 WIRE -304 -176 -304 -272 WIRE -336 -128 -368 -128 WIRE -208 -128 -208 -160 WIRE -208 -128 -240 -128 WIRE -192 -128 -208 -128 WIRE 144 -128 -192 -128 WIRE 288 -128 224 -128 WIRE 352 -128 288 -128 WIRE 512 -128 512 -144 WIRE 512 -128 432 -128 WIRE -368 -48 -368 -128 WIRE -320 -48 -368 -48 WIRE -192 -48 -192 -128 WIRE -192 -48 -240 -48 WIRE 288 -16 288 -128 WIRE 288 -16 64 -16 WIRE 352 -16 288 -16 WIRE 512 -16 512 -128 WIRE 512 -16 432 -16 WIRE -368 0 -368 -48 WIRE 144 48 144 32 WIRE 64 96 64 -16 WIRE 112 96 64 96 WIRE 512 96 512 -16 WIRE 512 96 272 96 WIRE -32 128 -112 128 WIRE -16 128 -16 -192 WIRE -16 128 -32 128 WIRE 112 128 -16 128 WIRE -336 144 -416 144 WIRE -272 144 -336 144 WIRE 624 144 624 -144 WIRE 656 144 624 144 WIRE 768 144 720 144 WIRE 848 144 768 144 WIRE -112 160 -112 128 WIRE 112 160 64 160 WIRE 624 160 624 144 WIRE 624 160 272 160 WIRE -416 192 -416 144 WIRE -272 208 -272 144 WIRE 144 224 144 208 WIRE 848 240 848 144 WIRE -112 256 -112 224 WIRE 64 272 64 160 WIRE 160 272 64 272 WIRE 256 272 160 272 WIRE 352 272 320 272 WIRE 512 272 512 96 WIRE 512 272 432 272 WIRE 64 288 64 272 WIRE 160 288 160 272 WIRE 512 320 512 272 WIRE 624 320 624 160 WIRE -416 368 -416 272 WIRE -416 368 -496 368 WIRE -496 384 -496 368 WIRE -416 384 -416 368 WIRE -272 384 -272 272 WIRE -272 384 -416 384 WIRE 64 384 64 368 WIRE 160 384 160 352 WIRE 160 384 64 384 WIRE 64 416 64 384 WIRE 848 416 848 320 WIRE -32 448 -32 128 WIRE -416 464 -416 384 WIRE 144 464 96 464 WIRE 256 464 224 464 WIRE 368 464 320 464 WIRE -272 480 -272 384 WIRE 512 480 512 400 WIRE 624 480 624 400 WIRE 288 576 288 560 WIRE 368 592 368 464 WIRE 368 592 320 592 WIRE 624 592 624 544 WIRE 624 592 368 592 WIRE -32 608 -32 528 WIRE 32 608 -32 608 WIRE 96 608 96 464 WIRE 96 608 32 608 WIRE 144 608 96 608 WIRE 256 608 224 608 WIRE 432 624 320 624 WIRE 512 624 512 544 WIRE 512 624 432 624 WIRE 624 624 624 592 WIRE 704 624 624 624 WIRE -416 640 -416 544 WIRE -336 640 -416 640 WIRE -272 640 -272 544 WIRE -272 640 -336 640 WIRE 288 656 288 640 WIRE 512 688 512 624 WIRE 704 688 704 624 WIRE 432 704 432 624 WIRE 624 704 624 624 WIRE 432 800 432 768 WIRE 512 800 512 768 WIRE 512 800 432 800 WIRE 624 800 624 768 WIRE 624 800 512 800 WIRE 704 800 704 768 WIRE 704 800 624 800 WIRE 432 832 432 800 FLAG -496 384 0 FLAG 288 560 V+ FLAG 144 224 V- FLAG -336 144 V+ FLAG -336 640 V- FLAG 768 144 output FLAG 144 32 V+ FLAG 288 656 V- FLAG 432 832 0 FLAG -112 256 0 FLAG 32 608 dc-trim FLAG 16 -480 V+ FLAG 16 -384 V- FLAG -368 0 0 FLAG 432 -240 0 FLAG 192 -240 0 FLAG 848 416 0 FLAG 64 416 0 FLAG 80 -240 0 FLAG 16 -544 0 FLAG 80 -544 0 SYMBOL voltage -416 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 12 7 Left 2 WINDOW 3 15 104 Left 2 SYMATTR SpiceLine Rser=0.01 SYMATTR InstName V1 SYMATTR Value 6 SYMBOL res 448 256 R90 WINDOW 0 -7 54 VBottom 2 WINDOW 3 37 50 VTop 2 SYMATTR InstName R1 SYMATTR Value 10.5k SYMBOL cap 320 256 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 0.015µ SYMATTR SpiceLine V=16 Irms=271m Rser=0.594318 Lser=0 mfg="KEMET" pn="C0603C153K4RAC" type="X7R" SYMBOL res 240 -144 R90 WINDOW 0 -1 46 VBottom 2 WINDOW 3 35 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 6.34k SYMBOL res 448 -144 R90 WINDOW 0 -4 61 VBottom 2 WINDOW 3 39 55 VTop 2 SYMATTR InstName R8 SYMATTR Value 13k SYMBOL njf -240 -176 R90 WINDOW 0 -37 23 VRight 2 WINDOW 3 -9 -3 VRight 2 SYMATTR InstName J1 SYMATTR Value J112 SYMBOL voltage -416 448 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 10 0 Left 2 WINDOW 3 15 104 Left 2 SYMATTR SpiceLine Rser=0.01 SYMATTR InstName V2 SYMATTR Value 6 SYMBOL res 48 272 R0 WINDOW 3 36 65 Left 2 SYMATTR Value 10.5k SYMATTR InstName R2 SYMBOL res 496 -240 R0 SYMATTR InstName R9 SYMATTR Value 4.7 SYMBOL schottky 496 -352 R0 WINDOW 3 -17 -1 VRight 2 SYMATTR Value BAS40HY SYMATTR InstName D1 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 608 -352 R0 WINDOW 3 -18 1 VRight 2 SYMATTR Value BAS40HY SYMATTR InstName D2 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -224 -64 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 82 SYMBOL OpAmps\\LT1994 176 128 R0 WINDOW 3 10 -65 Left 2 WINDOW 0 11 -95 Left 2 SYMATTR InstName U2 SYMBOL OpAmps\\LT1057 288 544 M0 WINDOW 0 19 104 Left 2 WINDOW 3 18 130 Left 2 SYMATTR InstName U1 SYMBOL schottky 528 480 M0 WINDOW 3 54 -49 VRight 2 WINDOW 0 -18 3 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D3 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 640 480 M0 WINDOW 3 48 -53 VRight 2 WINDOW 0 -21 4 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D4 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 448 704 M0 SYMATTR InstName C7 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL res 528 672 M0 WINDOW 3 30 83 Left 2 SYMATTR Value 220k SYMATTR InstName R11 SYMBOL res 720 672 M0 WINDOW 3 29 83 Left 2 SYMATTR Value 220k SYMATTR InstName R12 SYMBOL res -224 -256 R0 WINDOW 0 38 42 Left 2 WINDOW 3 36 66 Left 2 SYMATTR InstName R6 SYMATTR Value 2.2k SYMBOL res 224 -400 R270 WINDOW 0 -29 23 VTop 2 WINDOW 3 -1 95 VBottom 2 SYMATTR InstName R15 SYMATTR Value 330k SYMBOL res 352 -384 R0 WINDOW 0 -57 53 Left 2 WINDOW 3 -63 90 Left 2 SYMATTR InstName R17 SYMATTR Value 100k SYMBOL cap 640 704 M0 SYMATTR InstName C8 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL res 448 -32 R90 WINDOW 0 -4 61 VBottom 2 WINDOW 3 39 55 VTop 2 SYMATTR InstName R5 SYMATTR Value 1.095Meg SYMBOL res 608 -240 R0 SYMATTR InstName R10 SYMATTR Value 4.7 SYMBOL res -192 -288 R180 WINDOW 0 40 70 Left 2 WINDOW 3 45 42 Left 2 SYMATTR InstName R20 SYMATTR Value 2.2k SYMBOL res -16 544 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R16 SYMATTR Value 47k SYMBOL res 128 448 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R18 SYMATTR Value 220 SYMBOL res 528 304 M0 WINDOW 0 36 27 Left 2 WINDOW 3 39 52 Left 2 SYMATTR InstName R21 SYMATTR Value 4.7 SYMBOL res 640 304 M0 WINDOW 0 38 27 Left 2 WINDOW 3 40 51 Left 2 SYMATTR InstName R22 SYMATTR Value 4.7 SYMBOL res 128 592 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R23 SYMATTR Value 100 SYMBOL cap 416 -352 R0 WINDOW 0 -27 5 Left 2 WINDOW 3 -35 47 Left 2 SYMATTR InstName C3 SYMATTR Value 22µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0028 Lser=544p mfg="Würth Elektronik" pn="885012107005 WCAP-CSGP 0805" type="X5R" SYMBOL cap 176 352 R180 WINDOW 0 -36 39 Left 2 WINDOW 3 -86 12 Left 2 SYMATTR InstName C2 SYMATTR Value 0.015µ SYMATTR SpiceLine V=16 Irms=271m Rser=0.594318 Lser=0 mfg="KEMET" pn="C0603C153K4RAC" type="X7R" SYMBOL cap -288 208 R0 SYMATTR InstName C4 SYMATTR Value 100µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C575OX5ROJI07M" type="X5R" SYMBOL cap -288 480 R0 SYMATTR InstName C5 SYMATTR Value 100µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C575OX5ROJI07M" type="X5R" SYMBOL cap 256 448 M90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C9 SYMATTR Value 10µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.001 Lser=0 mfg="TDK" pn="C3216X5ROJ106M" type="X5R" SYMBOL OpAmps\\LT1057 16 -496 M0 WINDOW 0 73 93 Left 2 WINDOW 3 18 119 Left 2 SYMATTR InstName U3 SYMBOL cap 720 128 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 1µ SYMATTR SpiceLine V=10 Irms=0 Rser=0.0065 Lser=542p mfg="Würth Elektronik" pn="885012208013 WCAP-CSGP 1206" type="X7R" SYMBOL res 832 224 R0 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL cap -128 160 R0 SYMATTR InstName C10 SYMATTR Value 1µ SYMATTR SpiceLine V=10 Irms=0 Rser=0.0065 Lser=542p mfg="Würth Elektronik" pn="885012208013 WCAP-CSGP 1206" type="X7R" SYMBOL res 112 -736 R270 WINDOW 0 34 21 VTop 2 WINDOW 3 62 88 VBottom 2 SYMATTR InstName R13 SYMATTR Value 22k SYMBOL res 64 -368 R0 SYMATTR InstName R14 SYMATTR Value 22k SYMBOL res -176 -736 R270 WINDOW 0 34 21 VTop 2 WINDOW 3 62 88 VBottom 2 SYMATTR InstName R19 SYMATTR Value 22k SYMBOL res 64 -672 R0 SYMATTR InstName R24 SYMATTR Value 10k SYMBOL cap -128 -672 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C16 SYMATTR Value 0.0082µ SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GCM155R71E822JA37" type="X7R" SYMBOL cap 32 -576 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C11 SYMATTR Value 0.015µ SYMATTR SpiceLine V=16 Irms=271m Rser=0.594318 Lser=0 mfg="KEMET" pn="C0603C153K4RAC" type="X7R" SYMBOL cap 128 -672 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C12 SYMATTR Value 0.0082µ SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GCM155R71E822JA37" type="X7R" SYMBOL cap 176 -352 R0 WINDOW 0 22 11 Left 2 WINDOW 3 21 58 Left 2 SYMATTR InstName C13 SYMATTR Value 22µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0028 Lser=544p mfg="Würth Elektronik" pn="885012107005 WCAP-CSGP 0805" type="X5R" TEXT -456 728 Left 2 !.tran 0 300s 0s startup TEXT -288 -856 Left 2 ;Edward Rawde's high purity sinewave oscillator. 5 Nov 2024

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B

The quantity of brilliance is only apparent when you can see the circuit diagram and work out what he is trying to do, which can take a while.

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J

On 11/6/24 03:39, Edward Rawde wrote: [Snip!]

You are chasing ghosts. Simulation doesn't prove anything at this level. Build it and measure it.

Jeroen Belleman

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B

Not all that different, and you can test a new idea in LTSpice a lot faster than you can cobble stuff together on the bench.

Because you don't try anything new?

Hollywood movies are expensive. LTSpice is free.

Sci.electronics.design does seem to be a genius-free space. There are quite a few competent people who post here, but genius is rare, and most of the people who are called geniuses have exploited a stroke of luck that let them look better than they deserve, though as Pasteur said, chance does favour the prepared mind.

Plowing through a lot of circuit variations quickly with LTSpice does give you more chances to win that particular lottery.

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L

Don't believe anything a politician tells you. That applies to Trump - only more so.

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B

Not if he's got a decent conmputer to run his simulations.

It does look that way. Your elation will fade as he starts implentming his silly ideas

Trump persuaded Putin that he could get away with invading the Ukraine. Biden got elected a long time after Putin had started encouraging pro-Russian insurrections in the Ukraine, and Trump was impeached for attempting to influence Zelensky by threatening to hold back military aid that the then Repulicna dominated US Congress had voted to send them. You are quie a fond of fatuous nonsense as Cursitor Doom.

Mine too. LTSpice isn't any kind of neural net.

It's quite a few words of computer program.

Of course there are - LTSpice is a simulation program, not a filter design program.

So you didn't use it correctly.

Far from it.

Been there, done that. LSpice isn't designed for that kind of work, though it does offer lossy delay line models. At high frequencies layout is all about stray capacitances, which you can model in LTSpice, but it gets very messy for anything complicated enough to be useful.

Design is a bit more than "cooking up stuff". It helps if you understand what you are doing and what you are trying to do.

Who hasn't?

It might, to you.

It's called the Monte Carlo approach. There are more systematic approaches.

Twaddle. Excessively motivated people thrash around getting nowhere.

As you say, understanding is the key, but LTSpice - in the right hands - can help you understand what's going on on the bench quite a lot faster than bench work on it's own.

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L
[...]

It can help you understand what *should* be going on but benchwork shows you what is really going on and it is up to you to understand why. learning by benchwork is slower because it is complicated by having to deal with reality.

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B

But quite a lot of what you need to understand in bench work is captured by a decent simulation, and a whole lot faster than you can capture it on the bench.

Simulations capture quite a lot of what is going on on the bench.

Sometimes the reality you have to deal with is easier to dig out of a well-set up simulation because you can fiddle with stuff in the simulation that you can't twiddle on the bench.

A great deal of electronic design is getting the right concepts together, and while bench work is usually a safer way of doing that, it can also be quite a lot slower.

The subjectivist audio people get quite sentimental about what their golden ears tell them. Peter Baxandall was an objectivist.

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E

I don't have the facilities to build and test it so I'll probably have to leave it there. I totally agree that simulation is no longer worthwhile on this circuit. The simulation time just gets longer and doesn't prove anything.

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J

Simulation won't asolutely prove what circuits would produce low THD, but it will pretty definitely show which circuits won't.

Of course, a sim like this needs good opamp models.

If one builds it and measures it, what would you use to measure the distortion?

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J

I'm now simulating a rugged transimpedance amp for capacitive oil level measurement. That would be a mess to evaluate by breadboarding, partly because the real thing needs ADCs and FPGAs and such, and it's hard to breadboard those.

Once the sim is tuned, we'll go directly to product PCB layout without breadboarding.

One nice thing about design by simulation is that we can do a schematic and PCB layout and set up to build some rev A first articles, and parallel all those time delays with code development, so we can start testing as soon as the first units are built.

So the best breadboard is the first production unit.

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J

I'm old school: A passive notch filter. It's likely to be fiddly.

Jeroen Belleman

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J

LC? Just make sure that the inductors and capacitors are all linear.

Even twin tee can generate distortion.

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L

Yes, that was the point I was trying to make, it is slower but safer and more comprehensive.

Most of the fundamental progress in quality audio has been done by objectivists. Subjectivists enjoy playing about with it, but they rarely discover more than a small part of the truth and usually misunderstand the fundamentals of the process.

When PGAH Voigt invented the moving coil cutterhead (which was later 'stolen' by Arthur Haddy to become the Decca FFRR system and then 'stolen' again by Arnold Sugden to become the Connoisseur cutterhead), he didn't have a signal generator or an objective source of sound. Rather than rely on subjective effects, he equipped a piano with a weight which could be dropped on the keys to generate a consistent sound so that he could make objective measurements.

The BBC did a great deal of objective research on loudspeakers because they found that different studios and microphones sounded better on different loudspeakers and they weren't content to just accept this as subjective audio folklore. That research gave us a step improvement in the quality of loudspeaker drive units.

I recently did a great deal of work to get the best bass response from a loudspeaker in a small cabinet. When I demonstrated it to a group of record enthusiasts, one of them complained that it was playing notes that weren't on the records. I eventually discovered that he had always listened to those records on a clockwork gramophone which, in spite of its huge exponential acoustic transformer,. lost the bottom couple of octaves.

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