Fantastic! Thank you for following up. It looks like the lowest THD you'll be able to measure with that setup is around -110 dBc 0.0003%, which is considerably lower than the THD of most DIY amps. That's excellent!
"...that I can measure with this setup." I agree with your assessment otherwise, though. The THD contribution of the SSR is below -110 dBc. That's excellent.
Should you wish to further improve your measurement capabilities, I suggest looking into twin-T notch filters. If you notch out the fundamental, your measurement becomes less limited by the dynamic range of the sound card. Of course, should you choose to do that, you'll likely just find the harmonics of the oscillator itself. Should you wish to further improve the oscillator, contact Victor (vicnic). I have one of his oscillators underway by mail. It's supposed to get me below -150 dBc THD. That'd be nice.
I'm not suggesting that you go through all this trouble to characterize the SSR - at least not for my sake. Measuring low THD takes some real work. I'm just throwing it out there in case you'd like to satisfy your technical curiosity.
A twin-T is easy to build. Just make sure to use metal film resistors and polypropylene caps so you don't get appreciable distortion from the filter itself. You'll need to match the resistors and caps to get a good notch. Don't forget to characterize the filter response, as it'll attenuate the harmonics some. You'll need to compensate for this when you calculate the THD.
Most should be able to look at the data points at 2k, 3k, 4k ... and see that there are no harmonics sticking up above the noise floor of the measurement. What you'd get from clicking the THD button is the THD+N. I suggest pondering the internal validity of such experiment.
Ahh... Life in the precision lab. Your instruments may lie to you.
Tom
Hey X, I need to cancel my order of the RTR SSR. I did order the SLB psu which is what I needed more. Sorry bout that but am excited to get the SLB!
No problem, Ripcord. Thanks for ordering the SLB - destined to be a staple of Class A amps.
For other folks on the fence about the RTR SSR Protection board: $80 is a very fair (even a bargain) price for a built and tested state of the art solid state relay protection and startup delay circuit. How much does the woofer or tweeter on your speaker cost to replace? Do you worry what would happen if full-rail DC was released on your speaker when you are not watching? Do you have an issue with amp startup thump? These worries will all be solved with a super easy to install RTR SSR protection board.
60 units still available. We are still waiting for delivery of the first build checkout unit from the assembly house.
For other folks on the fence about the RTR SSR Protection board: $80 is a very fair (even a bargain) price for a built and tested state of the art solid state relay protection and startup delay circuit. How much does the woofer or tweeter on your speaker cost to replace? Do you worry what would happen if full-rail DC was released on your speaker when you are not watching? Do you have an issue with amp startup thump? These worries will all be solved with a super easy to install RTR SSR protection board.
60 units still available. We are still waiting for delivery of the first build checkout unit from the assembly house.
My settings appear to be the same as jhofland’s as shown on his plot. I am using ASIO driver and 96kHz data rate. The data rate may be 2x higher than default 48kHz.
Attachments
"Yes": Low-distortion Audio-range Oscillator
Actually. If you go to above thread and search for "victor schematic" you'll find the schematic. There's sadly not a website that I'm aware of. Contact Victor directly via PM (vicnic).
His earlier versions reached below -140 dBc. The new ones are even better. They're ~$60, so money shouldn't be the greatest limiting factor. For a while, Victor sold his oscillators on eBay. I couldn't find his listing last I looked, so either he's stopped or the listing has drowned in all the mediocre crap advertising itself as "high-end" or "precision".
Tom
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Hi Darr,
We are still waiting for the verification unit. We were told it would take about 3 weeks but that’s already been exceeded I think. Perhaps Jhofland can give a Status Update.
X, I contacted Vicnic through the PM on this site. He apparently takes in orders then will list them on Ebay for sale.
I first contacted him in April of last year and it was several weeks before he sent me the Ebay link to place my order.
So I would say reach out to him, and get on the list or maybe you will be lucky and he has some ready.
Tnx
David
I first contacted him in April of last year and it was several weeks before he sent me the Ebay link to place my order.
So I would say reach out to him, and get on the list or maybe you will be lucky and he has some ready.
Tnx
David
What are the oscillators like? Fixed or variable frequency? Can I read about them somewhere? The RX6001 thread is too long...
I contacted him. I'm getting 95Hz, 1K and 10K oscillators from him. Slurrrp! Thanks.