Here is schematic.
I used a small PIC micro to look at inputs.
It does a 4 second power up anti thump delay.
Then if it sees DC for 250mS it shuts off the relay.
The PIC code is pretty simple.
I have done various other designs since with SSR's and mains failure detect and over current detect.
I used a small PIC micro to look at inputs.
It does a 4 second power up anti thump delay.
Then if it sees DC for 250mS it shuts off the relay.
The PIC code is pretty simple.
I have done various other designs since with SSR's and mains failure detect and over current detect.
Hmmm, surprised this thread hasn't taken off.
Audio-wise, would have to say my DBR TB W3-871's. Not perfect by any means, but just SO useful because of their small size.
Non-audio-wise, hmmm, many contenders. My utility trailer, built from a kit, keeps growing with add-ons gradually over the years. My 6' computer desk, made of MDF with angle iron bracing to hold multiple CRT's. My experience has been to ignore advice to not overdo it if you want to build something DIY and truly durable.
Audio-wise, would have to say my DBR TB W3-871's. Not perfect by any means, but just SO useful because of their small size.
Non-audio-wise, hmmm, many contenders. My utility trailer, built from a kit, keeps growing with add-ons gradually over the years. My 6' computer desk, made of MDF with angle iron bracing to hold multiple CRT's. My experience has been to ignore advice to not overdo it if you want to build something DIY and truly durable.
A bird feeder with bifilar wound bare wire electrodes on the perches. These were attached to a 60 foot cable that led to a shock generator box (9V + 555 + transformer) in the house. Box had a large red pushbutton switch. When parent's favorite small birds came to eat: no button push, no shock. When bluejays or squirrels came: zap, owwie, get away. Parents were thrilled.
My service bench has a simple device I made to protect the two "monitor" speakers on it.
Just in case an amp being tested should have DC on its output
Just a small box, with binding posts and two switches, oh, and a headphone jack.
To protect the bench speakers one switch connects in a blocking capacitor - 500uF/150V non-polarized.
Simple, elegant, it works.
It's the little black box pictured just above the tape deck, fastened to the shelf.
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My 0-500V 0-500 mA regulated power supply is pretty handy, I have to say. Current limiting is really nice to have when you're powering up very old tubes.
Really though, I think the most useful is the line stage with transformer balanced inputs and outputs. It sounds good, sure, but it's a fantastic line stage for testing equipment. It has about 6dB of gain (more than enough for most things). It's all class A too, and it measures pretty good as well. Ironically, it was never supposed to be a finished project- just a test application of some mic preamp boards that I trimmed down to have 6dB of gain rather than 60.
It's been so useful I wish I had two of them, so that's gotten me working on a new digitally controlled line stage for the shop that will have differential input and outputs, programmable gain control using an AD5452, mutes on both channels, etc. This one uses an INA for the input, mostly to save a few bucks on transformers.
Really though, I think the most useful is the line stage with transformer balanced inputs and outputs. It sounds good, sure, but it's a fantastic line stage for testing equipment. It has about 6dB of gain (more than enough for most things). It's all class A too, and it measures pretty good as well. Ironically, it was never supposed to be a finished project- just a test application of some mic preamp boards that I trimmed down to have 6dB of gain rather than 60.
It's been so useful I wish I had two of them, so that's gotten me working on a new digitally controlled line stage for the shop that will have differential input and outputs, programmable gain control using an AD5452, mutes on both channels, etc. This one uses an INA for the input, mostly to save a few bucks on transformers.
One of the best things I ever made was a copy of an Ampex 351 recorder in the early 70's.
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