Have you guys seen this:
Ultrapure reference 1kHz sine oscillator bare circuit THD 0.000015% (-135dB) | eBay
Opinions/experiences?
Jan
Ultrapure reference 1kHz sine oscillator bare circuit THD 0.000015% (-135dB) | eBay
Opinions/experiences?
Jan
What passive notch does not need gain correction (second picture 2nd and 3rd harmonics are read directly off of screen). I might have missed one of Samuel's musings.
The 2nd may be a few dB optimistic due to the passive notch, but still 1st class performance I think.
Frex, if I would build this I would make it switchable for a couple of spot frequencies, make sure the level control is a good quality pot with a knob rather than a trimpot, and also include a balanced output connector, an XLR or better yet a combination XLR/TRS.
And of course power it with a SilentSwitcher ;-)
Any chance you will make an alternative packaging for some standard box with panel drawings for such a 'deluxe' version?
Jan
Frex, if I would build this I would make it switchable for a couple of spot frequencies, make sure the level control is a good quality pot with a knob rather than a trimpot, and also include a balanced output connector, an XLR or better yet a combination XLR/TRS.
And of course power it with a SilentSwitcher ;-)
Any chance you will make an alternative packaging for some standard box with panel drawings for such a 'deluxe' version?
Jan
Composite op-amps, Jim Williams and I exchanged a few mails on this and the original "distortionless" claim. B. Oliver described the problem in wonderful maths when the original HP oscillators sometimes failed to stabilize when the distortion was too LOW. The trade off is difficulty in trim as the distortion is reduced, indeed getting the parts per billion in AN67 would be difficult to hold.
EDIT - Dave and I crossed. I might add that few people realize that the light bulb oscillator has two mechanisms working and it's stability is due to the frequency independent voltage coefficient of resistance not the obvious thermal one. That's why a couple of years ago I showed the Christmas tree bulb oscillator which gets 20dB better than the common instrument bulb usually used.
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That's LT's super gain block oscillator. Nothing new here. Someone just packaged it up.
Victor's does better at a lower cost. This oscillator can be rather unstable.
Is this to say the higher voltage lamps have a lower voltage coefficient? I never looked so don't know.
Hi Frex,
I was very careful to build it following your BOM. Mostly Digikey parts. Needless to say, I was surprised to see 5 KHz. That's not a welcome frequency since I use an HP 339A, and switching a decade in frequency is easy. 5 KHz isn't.
They both work, but the 2nd harmonic is higher than it should be as Jan noted.
Jan, you could do that with a normal board. Just run the wires to your switching assy from the PCB, same for the level control.
-Chris
I was very careful to build it following your BOM. Mostly Digikey parts. Needless to say, I was surprised to see 5 KHz. That's not a welcome frequency since I use an HP 339A, and switching a decade in frequency is easy. 5 KHz isn't.
They both work, but the 2nd harmonic is higher than it should be as Jan noted.
Jan, you could do that with a normal board. Just run the wires to your switching assy from the PCB, same for the level control.
-Chris
Red
I have to check the number, but it's the standard 2" or so high one shaped like a candle flame.
Hi Chris.
If you go back a zillion posts ago you can read about my lamp multiplier. I don't know if you where involved with this thread that long ago.
It might be possible to use higher voltage lamps. The key is to keep the temperature of the filament down to avoid the sensitivity of a hot lamp.
It does require a descent R delta to work though
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