He does. Its a photovoltaic coupler (think solar cell and LED in a DIP package) that generates a floating 7 volt supply.
The one I used was from Avago, but like everything else they get superseded.
Back to the Hg-wetted relays: Aside from the regulatory issues of Hg-wetted relays, you're no likely to find ones with sufficient current rating to be suitable for switching speaker loads. I don't recall one that wasn't some variant on a reed relay.
Neat! I think ADI has some isolators that are based on magnetism and hall effect sensors (or some similar kind of voodoo).
I like that idea! Thanks!
Tom
Looks like we can have something to look forward to. I like the idea as well.
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Tom, see spart 2 of Scott Wurcer's condenser microphone preamp articles in Vol 3 of Linear Audio for more on using opto-isolating MOSFET drivers as (very low current) floating DC bias circuits. (unrelated application)
Support
I gotta say that the tech support that Tom provides is excellent.
Better than excellent.
It is better than I've experienced before from any other supplier or vendor.
Thank you Tom
tim
I gotta say that the tech support that Tom provides is excellent.
Better than excellent.
It is better than I've experienced before from any other supplier or vendor.
Thank you Tom
tim
Hi soongsc,
No, that is a bit simplified. A P and N channel are connected in parallel to equalize the transfer characteristic. They are larger than DIP style devices.
-Chris
No, that is a bit simplified. A P and N channel are connected in parallel to equalize the transfer characteristic. They are larger than DIP style devices.
-Chris
Hi Chis,
I am lost in the discussion. But if there is a good idea out there, I certainly would try it first hand. We can worry about the measurements later. Since speaker driver motors and suspension mostly have highly nonlinear characteristics some where along the road it needs compensation anyway.
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No harm in chiming in and give credit where it due - Tom is very responsive and provides great support.
Also his product documentation is top notch.
I have considered building the Modulus-86 — Rev. 2.0 amplifier; but I cannot find on his website the specifications for THD at full 20-20KHz bandwidth. He appears to only quote his ultra-low THD specs at 1KHz. Why is this?
He includes a multitone test, which no manufacturer dares to do. Also if you go here https://www.neurochrome.com/modulus-86-rev-2-1/ and scroll down you will see a graph of THD+N vs frequency.
What is missing that you need and what are you comparing to? I am not sure exactly sure.
What is missing that you need and what are you comparing to? I am not sure exactly sure.
Because I don't have a precision oscillator that covers the entire audible frequency range.
You can see the THD+N sweep from 20 Hz to 20 kHz about 3/4 down on the Modulus-86 Rev. 2.1 page. The THD+N is limited by the -112 dB THD+N of the Audio Precision APx525 analyzer.
In order to measure the THD of the Modulus-86 from 20 Hz to 20 kHz, you need an oscillator that provides better than -135 dB THD across that frequency range. This oscillator would also need to be able to provide this low THD at a wide range of output amplitudes. This is a rather tall order.
The $12.5k APx525 that I use reaches -112 dB THD+N. The $32k (for the base model) APx555 gets down to -125 dB. Neither is good enough to measure the true THD of the Modulus-86. They're both state of the art pieces of test equipment.
If you know of a commercially available audio oscillator that can hit -135 to -140 dB THD across 20Hz-20kHz and 10 mV - 10 V with differential outputs, please let me know. I'd love to own one.
Tom
There are different ways of measuring ultralow distortions. Also you can use low or band pass filter with AP sig gen.
True. It'd have to be a rather steep filter to provide any meaningful attenuation at H2, though.
I think the precision oscillator is the way to go. I may have to build one... The "Victor" oscillator I'm currently using is good but has grounding issues.
Tom