Members DaveJes1979 Posted July 29, 2003 Members Share Posted July 29, 2003 I am looking to switch between 3-16 various amplifiers into 2-8 speakers cabinets. Is there a matrix switcher that will handle the high current loads AND protect the amps with a "safety load" when not in use. I am not a "live sound" guy, so I don't know if such a product exists (my search has led me to believe that it may not). Link to comment Share on other sites More sharing options...
Members flanc Posted July 29, 2003 Members Share Posted July 29, 2003 I wouldn't want one of my speakers hooked to that! Link to comment Share on other sites More sharing options...
Members DaveJes1979 Posted July 29, 2003 Author Members Share Posted July 29, 2003 Hmmm...perhaps I was not clear. I am looking for a matrix switcher that will output a SINGLE AMP to a SINGLE CAB at one time - NOT multiple amps into a single cab. I assume this confusion was the cause for your objection? Link to comment Share on other sites More sharing options...
Members Scodiddly Posted July 29, 2003 Members Share Posted July 29, 2003 Would be tricky to do. I assume you're talking about guitar amps, probably tube-based. Those tend to be rather finicky about having a load, so the matrix would have to be smart enough to always switch in the right dummy load. It would also be noisy to switch, since we're talking inductive loads. Dunno if a stomp-switch in the middle of the song would be doable. However, if I was to start looking for such a beast I'd look at ham-radio antenna switching products. They've got similar issues with needing a constant load and having high power signals. Link to comment Share on other sites More sharing options...
Members flanc Posted July 29, 2003 Members Share Posted July 29, 2003 I understood, but question how graceful the handoff would be between amp(x) and amp(y). I guess some a well-designed switching circuit would be fine....I'd still be scared switching between amps! Link to comment Share on other sites More sharing options...
Members DaveJes1979 Posted July 29, 2003 Author Members Share Posted July 29, 2003 Scodiddly, Hmmm...ham radio, eh? That's a very interesting idea. I'll have to look into it. Thanks for the creative tip. Yes, it is for guitar amps. As for the amp loading/switching issue, I know that it can be done. Soundsculpture (www.soundsculpture.com) has a unit that does it called the Head Trip, but it only accepts 3 amps (input) to 2 cabs (output). I just have too many amp heads I need to switch! I should also note that when the particular amps are not in use, the input signal to the amp heads will be cut. Really, the loading of the amp is just a failsafe (although a necessary one). Link to comment Share on other sites More sharing options...
Members IsildursBane Posted July 29, 2003 Members Share Posted July 29, 2003 I feel bad for your roadies! -Dan. Link to comment Share on other sites More sharing options...
Members tlbonehead Posted July 29, 2003 Members Share Posted July 29, 2003 Originally posted by flanc I understood, but question how graceful the handoff would be between amp(x) and amp(y). I guess some a well-designed switching circuit would be fine....I'd still be scared switching between amps! No doubt. There's no way I would risk my amps that way. Link to comment Share on other sites More sharing options...
Members chugheshc Posted July 30, 2003 Members Share Posted July 30, 2003 I saw an ampeg switch on ebay that would dowhat you are talking about.probably came from a store display.C. Link to comment Share on other sites More sharing options...
Members ashivraj Posted July 30, 2003 Members Share Posted July 30, 2003 you'd probably want to try something that runs guitar-level. i.e. something between your guitar and the multiple amps. active split into each amp head. that way, the load always stays connected, and the input signal to all the other amps will be cut. i know whirlwind, mebbe even morley, make 2-way and 3-way switchers. mebbe some esoteric combination of these? you'd still have to tap dance to switch heads, unless you plan your wiring (and tone selection) such that each song gets two or three tones that can be accessed on one switch itself. i dunno. or, if you cant find anything, build (or find someone to build) a device based on these switchers. just tossing out mindfarts here. generously disregard anything that doesnt make sense. AS Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 30, 2003 Members Share Posted July 30, 2003 Originally posted by ashivraj you'd probably want to try something that runs guitar-level. i.e. something between your guitar and the multiple amps. active split into each amp head. that way, the load always stays connected, and the input signal to all the other amps will be cut. i know whirlwind, mebbe even morley, make 2-way and 3-way switchers. mebbe some esoteric combination of these? you'd still have to tap dance to switch heads, unless you plan your wiring (and tone selection) such that each song gets two or three tones that can be accessed on one switch itself. i dunno. or, if you cant find anything, build (or find someone to build) a device based on these switchers. just tossing out mindfarts here. generously disregard anything that doesnt make sense.AS A guitar pick-up will not drive so many inputs without loading down and affecting the tone in a negative way. You would definately need a signal buffer to do this successfully, and then switch-selecting the drive to the amps would be trivial, but this doesn't address the load side of the power amps. I would also be concerned about ground loops... connecting a bunch of guitar amps together would be a crapshoot at best. Link to comment Share on other sites More sharing options...
Members ashivraj Posted July 30, 2003 Members Share Posted July 30, 2003 andy, i stand corrected. i should've thought about the grounding issues, as well as the p/u loading issues. i mean, it's not like i've never heard such things before... geez... ::slaps forehead:: could you explain the load-side-of-poweramp thing? i was assuming that a cab connected to the poweramp is sufficient load, even if there is no input signal? tia! AS Link to comment Share on other sites More sharing options...
Members rocksld Posted July 30, 2003 Members Share Posted July 30, 2003 Davejes, Mesa boogie makes an amp switcher(this is the same one John Petrucci of Dream Theater uses) http://johnpetrucci.com/equipment.html http://www.mesaboogie.com/Product_Info/Accessories/Amp-Switchers/AmpSwitches.html rocksld Link to comment Share on other sites More sharing options...
Members RickJ Posted July 30, 2003 Members Share Posted July 30, 2003 Any of 16 amps into either of two cabs? Sounds like the band "Jucifer", except there are 16 cabs as well -- all for just one guitarist. With a little time & research, you could build this yourself. Do you need this to be a stomp box? Or just be able to switch between songs? If the latter, a multi-pole make-before-break rotary switch will do. (Plus one DPDT to switch the cabs.) If you need a stomp box, the low-level signal side isn't a big problem. Even a transistor matrix switching circuit will work -- or flip-flop chips. It can also be used to drive the high-level side, since both always need to be switched simultaneously. For the high level side, you'd need to use relays, preferrably solid state relays. If I had to build one of those puppies, my guess is we're talking $750 - $1,000. What about two simple patch fields (a.k.a. patch bay)? They could be normalled to provide a short at the unused amps' inputs while feeding a dummy load to the outputs. When you plug in, you break the "normalled" connections to activate the amp. Still, two good, beefy 1/4" patch fields will cost you at least $250. Plus the cab switch. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 30, 2003 Members Share Posted July 30, 2003 Originally posted by ashivraj andy,i stand corrected. i should've thought about the grounding issues, as well as the p/u loading issues. i mean, it's not like i've never heard such things before... geez... ::slaps forehead::could you explain the load-side-of-poweramp thing? i was assuming that a cab connected to the poweramp is sufficient load, even if there is no input signal? tia!AS You would still need to manage the switching of the amps to the speakers. You would also need to terminate the amps with a dummy load to prevent output transformer insulation breakdown due to flyback voltages of an unlaoded output. I think (I may be mis-reading this a bit) he wants to be able to switch various speaker cabinets around across various amps. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 30, 2003 Members Share Posted July 30, 2003 Originally posted by RickJ For the high level side, you'd need to use relays, preferrably solid state relays.What about two simple patch fields (a.k.a. patch bay)? They could be normalled to provide a short at the unused amps' inputs while feeding a dummy load to the outputs. When you plug in, you break the "normalled" connections to activate the amp. Still, two good, beefy 1/4" patch fields will cost you at least $250. Plus the cab switch. Solid state relays would deliver a non-linear loading to the amps, and there are usually crossover notches due to the switching (commutation) of the SCR's. Also, losses can be a problem in some models, though that's not probably much of a problem. The crossover problem will really become a problem as the audio frequency increases, plus at some frequency, there will be a point the the relay may switch on by itself (or not switch off) due to the dV/dT limitations of the SCR's or triacs. Then there's the issue of the internal snubber capacitors on the SSR's, typically .1uf across the load terminals which may cause some "less than manley" amps to spill their smoking guts. Not mine of course since they are designed to drive a capacitive load, but many are not too forgiving in this respect! The patch bay idea is a good solution. Reliable, sonicly transparent and cheap (relatively!) Link to comment Share on other sites More sharing options...
Members ashivraj Posted July 30, 2003 Members Share Posted July 30, 2003 Originally posted by agedhorse I think (I may be mis-reading this a bit) he wants to be able to switch various speaker cabinets around across various amps. Aah. I misread (possibly) and interpreted that he only needed to switch the amps, i.e. each amp had its own cab, already hooked up. My bad. AS Link to comment Share on other sites More sharing options...
Members RickJ Posted July 31, 2003 Members Share Posted July 31, 2003 What would you use as a dummy load? Resistors? Rack of small radio speakers? Before posting, I didn't think about the electronic properties of SS relays. Bad choice, I guess. I thought they would be more reliable than standard mechanical relays. But I guess as long as the mechanicals were normalled to the dummy load/shorted input, no harm could be done. There is also the video routing switcher, available in just about any configuration of crosspoints. But they are much more expensive than the other options. Plus, their current handling would probably not be enough to handle speaker switching. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 31, 2003 Members Share Posted July 31, 2003 Yes, load resistors, and I would use something around 16-20 ohms. Matching to any amp, even a tube amp is not exact, the reason is to reduce the flyback voltage that could damage the winding insulation on an output transformer on a tube amp. Solid state amps do not need this precaution, but I think he was talking about tube amps??? Link to comment Share on other sites More sharing options...
Members RickJ Posted August 1, 2003 Members Share Posted August 1, 2003 agedhorse wrote:Solid state amps do not need this precaution, but I think he was talking about tube amps??? Yes, the lowest common denominator. The reason I raised the Q about resistor v. small radio speaker v. coil: Is there a difference between loading the tubes with a pure resistance, a loaded inductance, or a pure inductance? Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 1, 2003 Members Share Posted August 1, 2003 Originally posted by RickJ Yes, the lowest common denominator. The reason I raised the Q about resistor v. small radio speaker v. coil: Is there a difference between loading the tubes with a pure resistance, a loaded inductance, or a pure inductance? Yes, there needs to be some resistive component (all real inductors do have this, DCR) in order to damp out possibilities of ringing. For tjis purpose, it's to protect the output transformer, so a pure resistor will do the job cheaply. Link to comment Share on other sites More sharing options...
Members DaveJes1979 Posted August 5, 2003 Author Members Share Posted August 5, 2003 Actually...I did some more research. These guys may have just the ticket... http://www.matrixsystems.com/techs/K61057.htm Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 5, 2003 Members Share Posted August 5, 2003 Originally posted by DaveJes1979 Actually...I did some more research. These guys may have just the ticket...http://www.matrixsystems.com/techs/K61057.htm Not unless you use this to drive external relays... contact limits are 2 amps MAX. You will also need to provide the logic to prevent inadvertent cross-connecting of amplifiers to themselves, and to protect against invalid loads. Link to comment Share on other sites More sharing options...
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