Products > Test Equipment
Question: Cheap pure sine wave genertor 1khz?
Fungus:
--- Quote from: innkeeper on January 10, 2020, 09:57:22 pm ---
--- Quote from: Gyro on January 10, 2020, 10:49:03 am ---You might get better than the quoted -124dB with some careful component value matching anyway...
--- End quote ---
i've actually ordered one of these .. figured its a start and maybe i can tweak it.
--- End quote ---
Ok, so -124dB is only "a start"? Got it. :-+ :-DD
innkeeper:
--- Quote from: MasterT on January 10, 2020, 10:53:54 pm --- (Attachment Link)
I've build one recently, to test my 18-bits differential AD7984 board. I changed OPA to LM4562, and use 7370-18V-0.04mA lamp. Circuits does need "manual" tuning to get the lowest THD, but accounting simplicity it's not an obstacle. Results thd-2 ~0.0004% (-110dB) and thd-3 ~0.0002 (-114dB) at 4kHz. Not sure about 100kHz, ADC itself has thd-3 ~0.002% at this frequency.
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that is amazing for such a simple circuit, i;ll have to throw that together and put it on the analyzer and check it out. thanks
innkeeper:
i've hit up victor from the diyaudio forum to see if he has any of his boards available. he is getting better then -150 Db.
MasterT:
--- Quote from: innkeeper on January 11, 2020, 03:13:46 am ---i've hit up victor from the diyaudio forum to see if he has any of his boards available. he is getting better then -150 Db.
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What circuits? I've seen link to e-b https://www.ebay.com/itm/Low-Distortion-Audio-Range-Oscillator-1KHz-Sine-Wave-Signal-Generator-PCB-Board/262844562138,
let's call it JFET-Wein, description says:
--- Quote ---Low distortion coefficient of the sinusoidal oscillator circuit board, oscillation frequency: 1KHz, low distortion, distortion factor 0.0064% (- 124dB)
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doesn't look right, in my math -120dB is 0.0001% ( or 1ppm), 0.0064% is about -84-85 dB, worse than cheapest sound card has. And NE5532 ? Common, be serious.
Or is it CdS-Wein? http://www.redcircuits.com/Page82.htm
Probably, just simplified version of
https://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/dc1858a.html#eb-overview
I trust AD, performance is outstanding, but same with a price and complexity.
Though -120 only:
Table 1. Amplitude and Offset Options for DC1858A (SNR and THD Taken at f OSC = 2kHz)
Range (V) R22 (kΩ) R18 (kΩ) C11 (μF) Sine Out (V P-P ) Offset (V) SNR (dB)* THD (dB)*
0 to 2.5 14 36.5 0.47 2.25 1.25 100 –119
0.5 to 4.5 22.6 12.1 0.47 3.6 2.5 103 –121
0 to 4.096 23.2 17.4 0.47 3.7 2.048 103 –121
0 to 5 28 12.1 0.47 4.5 2.5 104 –118
±2.5 28 ∞ 0.47 4.5 0 104 –119
±5 56.2 ∞ 0.47 9 0 107 –117
±10 118 ∞ 0.1 18 0 100 –107
page 3 https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/dc1858af.pdf
And most resistors precise 0.1% tolerance, they can't get -120dB with CdS even for single Tone generator using common 1% parts, and adjustable frequency doesn't go along with precision parts at all.
innkeeper:
@masterT
victor sells is an updated version of this:
https://www.diyaudio.com/forums/equipment-and-tools/205304-low-distortion-audio-range-oscillator-21.html#post3116055
update: i think this is the latest schematic
https://www.diyaudio.com/forums/equipment-and-tools/205304-low-distortion-audio-range-oscillator-743.html#post5873578
i am sure there is a more up to date schematic in that thread, but that thread is over 8000 messages long
here is the web page he put up just wiht the specs
https://viccc42.wixsite.com/uld-audio
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