Amp switcher

[soundmasterg]

Any news on Weber's re-engineered FourHead? Is it just a bunch of relays controlled by a simple logic circuit?

I would just email TA and ask him about it. He borrowed mine to blueprint it, but they probably didn't reissue the product yet. You might be able to get him to make you a one off if that is what you are looking for....I dealt with TA through email on it though so just ask him about it and he should be able to tell you the status. I have no idea about the circuitry of it...I never bothered to open it.

Greg

[R.G.]

On the thread topic, my only concern would be hot switching valve amps to speakers. Either each valve amp needs very good internal over-voltage protection to cope with fast turn-off of speaker load, or the switching mechanism needs to ensure some make-before-break loading on the valve amp prior to disconnection from speaker.

If I were doing a design today, I'd do it with a microcontroller. A $1.50 chip can be programmed to scan footswitches, then do even complicated switching and timing. Easy enough to have a few microseconds of make before break.

[trobbins]

If I were doing a design today, I'd do it with a microcontroller. A $1.50 chip can be programmed to scan footswitches, then do even complicated switching and timing. Easy enough to have a few microseconds of make before break.

The make-before-break would need to be making a connection of the valve amp output to a load-dump, prior to disconnecting the speaker and then reconnecting the speaker to another amplifier. Luckily the input signal to the amp would then be muted so that the load-dump didn't have to continue to dissipate.

Trying to coordinate such a hot switch would be interesting, as the phasing of the amp outputs would need to be assured to be correct if a speaker was fast switching between one amp and another whilst going flat chat.

[Gregg]

If I were doing a design today, I'd do it with a microcontroller.

That's best for more complicated designs. For simple switching you can use "fast" switching relays (1-2msec) for amps' inputs muting and "slow" switching (5-15msec) bigger relays for speakers/cabs or use a channel mute circuit as found in Engl amps for example.

[soundmasterg]

If I were doing a design today, I'd do it with a microcontroller. A $1.50 chip can be programmed to scan footswitches, then do even complicated switching and timing. Easy enough to have a few microseconds of make before break.

I'm taking a microcontroller class right now and from what I'm learning in it, I would use a microcontroller too.

Greg

[loudthud]

If the microcontroller goes bad in a couple of years, will you be able to find a replacement and program it? Or will you just throw the whole thing away? So many of the things we buy today can't be repaired. The parts are obsolete by the time it breaks.

[NateS]

If the microcontroller goes bad in a couple of years, will you be able to find a replacement and program it? Or will you just throw the whole thing away? So many of the things we buy today can't be repaired. The parts are obsolete by the time it breaks.

If the micrcontroller goes bad in a few years, my experience suggests you can still buy it, but you can probably buy a PSOC which can with your original microcontroller core for cheaper, or ridiculously more pwer for less

[R.G.]

If the microcontroller goes bad in a couple of years, will you be able to find a replacement and program it? Or will you just throw the whole thing away? So many of the things we buy today can't be repaired. The parts are obsolete by the time it breaks.

\
What "the microcontroller"? They're $1.50.

Make two. Or three. Save one or two in a static-sheltered box glued inside the amp. If you have to lager more than a half dozen, it's a bad design and should be redone. Likely, the thing will outlast most of the parts in the rest of the amp ASSUMING GOOD DESIGN PRACTICE.

If you use all of the spares, then go to whatever is available for $100 each then, $100 being the then-current value of the dollar; the actual part will cost the same or less in constant dollars.

[loudthud]

If you use all of the spares, then go to whatever is available for $100 each then, $100 being the then-current value of the dollar; the actual part will cost the same or less in constant dollars.

By that time, the parts will be long obsolete. You'll be looking at counterfeit parts on ebay. The life cycle of semiconductors is getting shorter and shorter. I'm not saying it's not a good solution to handle the relay logic and timing. It's probably the lowest cost solution. But if you put such a part into a product, that product will be thrown away at some point when it can't be repaired due to lack of parts.

In the future car collectors will have cars that don't run because the engine computers are long dead. If you swap the engine computer Mercedes, the car won't run because all the computers in the car talk to eachother and the car won't start if one computer has a new serial number. You'll have to find the guy with the computer and software that can talk to the car's computers to get it running.

[NateS]

The Z80 sells more volume today than it did during it's heyday as a personal computer proc, a couple DECADES ago.

[Gregg]

Don't be afraid of uCUs. They are here to stay and will be available for a long time. If we're talking problems it's not the part itself but the software which might not be available.

In the future car collectors will have cars that don't run because the engine computers are long dead.

Most consumer electronics these days are made to last no longer than 3-4 years. For some the projected lifespan is even shorter.