Output Relays

[ostripper]

mjl or njw X302/281's have about 2X the Hfe as their X21193/4 counterparts. They don't push the limits on the mje's/properly heatsinked. If I used 6 or more pairs , I would go with the OP's as drivers. 21193/4's are at best 50Hfe (often less) , 3 pair drawing up to .5A @ 2-4R. The mje's are at best 300ma @ 75v soa.
Some on the forum will "pile" up a dozen OP pairs on a EF2 w/mje's - bad . Not I.... Electrically , njw0281/0302 is identical to the mje's , just a bigger die - a bit more Cob.

You are fine as is , but if you build a new amp - why not ?

[Michael Bean]

Here's what I use - simple, reliable, easily scalable, and quiet.

[PMA]

Well - SSR is almost perfect, when properly designed. Standard relay is almost incapable to interrupt high current DC arc, that may occur in a high power amplifier. And, even if it succeeds, you have to change it after 1st interruption

[Michael Bean]

What do you mean "almost" perfect?

[PMA]

High supply voltage of amplifiers like Bonsai's dictates to use MOSFETs with very high V(br)dss. Then you get Rdson of some 20 milliohms per device, 40 milliohms per pair. So you reduce DF a bit. I do not think this is crucial, but just realize it.

[ostripper]

Originally Posted by PMA

Well - SSR is almost perfect, when properly designed. Standard relay is almost incapable to interrupt high current DC arc, that may occur in a high power amplifier. And, even if it succeeds, you have to change it after 1st interruption

WOW - simple. Looks like some of the opto-coupled big industrial SS AC switches I've seen. 3uS turnoff - 100's of ac volts. .01R Rdson !
ASSR-1611 (halfway down the page) - ASSR-1611 datasheet, Pinout ,application circuits High Current, 1 Form A, Solid State Relay (MOSFET).
That's a small one - 30-60A units run $100usd and up.
Would be much cheaper to build one.

OS

[PMA]

As you have guessed, I speak about the built circuit.

Attached.

[ostripper]

Originally Posted by PMA

As you have guessed, I speak about the built circuit.

Attached.

I can reverse engineer that by just seeing it - just kidding (the SS relays are essentially the same circuit minus the DC detect).

No heatsink ? With super low RDSon not needed ?
I was thinking a tda-xxxx protection IC triggering opto X2 (stereo) ... much better than contacts .. regardless.


OS

[Art M]

Originally Posted by Michael Bean

Here's what I use - simple, reliable, easily scalable, and quiet.

What about the steering diode voltage drop and the minimum photo detector supply voltage requirement. Looks like a very distorted solution for Audio use ?

[digits]

Originally Posted by Andy5112405

Auto (car) relays work flawlessly (for a few years anyway) in a hostile DC environment.

It's easy to obtain 16A - 30A auto relays which are great for speaker protection.

Sorry for the double post - my internet connection is playing up - some bugger riding on the wireless connection I expect.

Which is why I said, generaly. Just like ordinary switches, there are ones designed to switch DC, normally at lowish potentials, the downside is the costs.