Members Jopop Posted June 3, 2008 Members Share Posted June 3, 2008 On a serious note it would be entirely possible and simple to build a circuit that switches the OT out and a resistor in when no plug is connected to the output jack. However it only guards against powering up with no cab.. Link to comment Share on other sites More sharing options...
Members Angry Grimace Posted June 3, 2008 Author Members Share Posted June 3, 2008 Ok, my answer was tongue in cheek here's my serious reply... Why equip an amp with an expensive add on that replaces a $7.97 multimeter http://www.radioshack.com/sm-pocket-sized-8-range-analog-multimeter--pi-2103534.htmlwhen the add on will cost 10x's as much and be subject to failure? You know your automatic impedance selector is gonna screw up, detect the wrong impedance and blow up the OT. It'll do exactly what it was meant to prevent. Plus the $7.97 mulitmeter will do ALL you amps, all your life. It's an expensive answer to a problem that doesn't exist. Because the average person doesn't understand teh concept that matching impedeance or having a load makes a difference at all. If everyone knew the difference, they would probably have enough sense to plug it into the right tap. But go down to GC and find out...they don't.Cost is a reasonable answer. I did figure it might have been prohibitevely expensive. Although, tube amps are prohibitively expensive in general. I was wondering whether that's just an impossibility or cost-prohibitive. If it wasn't, I imagine they WOULD do that. Link to comment Share on other sites More sharing options...
Members .homewrecker. Posted June 3, 2008 Members Share Posted June 3, 2008 See, but that's a poor choice of comparison because they DO do something about htat; Diesel pumps are physically imcompatible with gasoline gas inputs and vice versa. I personally know a person who tried it, and yes she is stupid. But they stuipid proof things becuase people are stupid. Women and cars... {censored} all this stupid people bull {censored}, I've had amps get knocked off of a cab and come unplugged at a show before, someone make something that will not have my amp blow up if that happens. Link to comment Share on other sites More sharing options...
Members Weathered Posted June 3, 2008 Members Share Posted June 3, 2008 Why do you direct keep directing sarcastic crap about breathing and eat at ME like I said I couldn't do it or don't want to...it's a question of interest becuase I would think that companies would do this to avoid having to pay out warranty costs. I can bias my tubes and match my amps impedance loads just fine. I mean, I've been to my local GC and seen people wondering why the DSL they were playing wasn't producing sound numerous times? You're telling me you've never met a dolt? Most people are dolts. Basic business - if you add a part that costs $125 to an amp, and are only able to pass on a certain % to the end user, you accept the small % of failures that come back on warranty claims. Regardless, anyone who is purchasing a tube amplifier should RTFM. Link to comment Share on other sites More sharing options...
Members Johnny'sGotTheBlues Posted June 3, 2008 Members Share Posted June 3, 2008 Because the average person doesn't understand teh concept that matching impedeance or having a load makes a difference at all. If everyone knew the difference, they would probably have enough sense to plug it into the right tap. But go down to GC and find out...they don't. I'll concede that the world is generally ignorant (not stupid). But, when you learned to play guitar you learned how to tune it right? And that's a TON more complex than figuring out your impedance. You can't make the whole world idiot proof. Cuz you know the saying, they just come up with a better idiot. And I for one, wouldn't want to pay a premium on my amp for a device I would never use and would never want. Link to comment Share on other sites More sharing options...
Members Angry Grimace Posted June 3, 2008 Author Members Share Posted June 3, 2008 Basic business - if you add a part that costs $125 to an amp, and are only able to pass on a certain % to the end user, you accept the small % of failures that come back on warranty claims.Regardless, anyone who is purchasing a tube amplifier should RTFM. As I said, I'm sure cost plays a part. If they could do that for $1.00 in parts, I would imagine they WOULD. I'm aware it won't "Blow up" if you just mismatch it. But I could reasonably see guys stacking two 8ohm cabs, setting it to 16 and cranking that bitch until it stops working. Link to comment Share on other sites More sharing options...
Members thinkpad20 Posted June 3, 2008 Members Share Posted June 3, 2008 Many of you are missing the point. He's not talking about impedance mismatch so much as he's talking about running a tube amp with no load (speakers) at all. It's quite easy, especially if you're setting up in a hurry, to forget to hook up a cable. For any of the cables (guitar cable, effects, power, et cetera) you can forget to hook it up, and the worst that will happen is that you'll look like an idiot and go "oh, yeah" and hook it up. That is, except for one cable, the speaker cable, for which the worst that will happen is that you'll kill your OT and have a several hundred dollar repair on your hands. Now if you're new to tube amps, it's quite possible (as happened to me) that you will be unaware of the dangers associated with this - and everyone who uses tube amps was new to them at some point. And even if you've been playing for 20 years and know this rule backwards and forwards, you could have a faulty speaker cable and have the same thing happen. So in either case, it seems like a worthwhile thing to put in, unless there's something physically prohibitive or cost prohibitive in doing so. I'm not saying I can't be wrong, but I'm with AG in wondering why this might be the case. Link to comment Share on other sites More sharing options...
Members chakosh Posted June 3, 2008 Members Share Posted June 3, 2008 Basic business - if you add a part that costs $125 to an amp, and are only able to pass on a certain % to the end user, you accept the small % of failures that come back on warranty claims.Regardless, anyone who is purchasing a tube amplifier should RTFM. Parts wise, I don't think it'd be that expensive. The digital potentiometers aren't that high, and a stub is literally just a thicker trace of a certain length on the PCB. The R&D to get it to work might be the source of the "cost prohibitive"-ness of the idea. While I think it'd be an interesting experiment, I only see the benefit for people who use multiple cabinets that are different impedance. Usually you set it once and don't have to worry about it unless you change your cab. Link to comment Share on other sites More sharing options...
Members RCC Posted June 3, 2008 Members Share Posted June 3, 2008 Many of you are missing the point. He's not talking about impedance mismatch so much as he's talking about running a tube amp with no load (speakers) at all. It's quite easy, especially if you're setting up in a hurry, to forget to hook up a cable. For any of the cables (guitar cable, effects, power, et cetera) you can forget to hook it up, and the worst that will happen is that you'll look like an idiot and go "oh, yeah" and hook it up. That is, except for one cable, the speaker cable, for which the worst that will happen is that you'll kill your OT and have a several hundred dollar repair on your hands. Now if you're new to tube amps, it's quite possible (as happened to me) that you will be unaware of the dangers associated with this - and everyone who uses tube amps was new to them at some point. And even if you've been playing for 20 years and know this rule backwards and forwards, you could have a faulty speaker cable and have the same thing happen. So in either case, it seems like a worthwhile thing to put in, unless there's something physically prohibitive or cost prohibitive in doing so. I'm not saying I can't be wrong, but I'm with AG in wondering why this might be the case. Didn't think about that scenario.... this is actually a good point. Especially for those who are new to tube amps and/or for faulty speaker cables Link to comment Share on other sites More sharing options...
Members TheAmazingBlob Posted June 3, 2008 Members Share Posted June 3, 2008 I think that an amp that will automatically adjust it's own impedence to match whatever it's plugged into is a little farfetched, but I can't think why an amp that will shut itself down if loadless or mismatched would be impossible Link to comment Share on other sites More sharing options...
Members newholland Posted June 3, 2008 Members Share Posted June 3, 2008 well, grim.. the OTHER option in regards to losing your power cord is just to put a dummy load in every head.. which ain't THAT expensive.. but it'd bring the cost of everything up.. and i hear what you're saying -- most people ARE dolts... but it's like anything else-- they know the economic imperative for {censored} to COST less is more important than IDIOT proofing... i'm certain the amp companies DON'T care about that, cause they don't cover your OT most times if you've done something negligent and not read your manual. i think most of them have big disclaimers in them... besidedly.. for the cost associated with the development and implementation of the autosensor-transformer, it's just cheaper to warrantee a few knuckleheads.. Link to comment Share on other sites More sharing options...
Members chakosh Posted June 3, 2008 Members Share Posted June 3, 2008 He's not talking about impedance mismatch so much as he's talking about running a tube amp with no load (speakers) at all. That's not how I read the OP at all, but that would be easy. Just have it so that unless there's continuity in the cable to the cab, you have it match to a power resistor or something at 4 Ohms. I wonder if the thing that makes this not a viable solution is the heat generated from the power resistor. Power resistors can get really hot, and if you're running 100W of power to get discharged into this resistor, it's going to get really hot. Maybe even hot enough to melt your face, Raiders of the Lost Ark style. Link to comment Share on other sites More sharing options...
Members Weathered Posted June 3, 2008 Members Share Posted June 3, 2008 Parts wise, I don't think it'd be that expensive. The digital potentiometers aren't that high, and a stub is literally just a thicker trace of a certain length on the PCB. The R&D to get it to work might be the source of the "cost prohibitive"-ness of the idea. While I think it'd be an interesting experiment, I only see the benefit for people who use multiple cabinets that are different impedance. Usually you set it once and don't have to worry about it unless you change your cab.What you're forgetting is that there are secondary windings on the OT that need to be switched. The high voltage nature of this means that the switch needs to be heavier duty. It's not a continuously variable thing - you're switching windings at high amperage.This is the impedence switch I use in my amp builds - it's rated for 6 amps of power. 3 position rotary impedance selector switch. Very heavy duty. 6 amps at 125volts with silver plated contacts. Able to handle speaker switching loads no problem. It comes with a stop pin to make the switch into a 2 way switch. Link to comment Share on other sites More sharing options...
Members kinggeoff Posted June 3, 2008 Members Share Posted June 3, 2008 failsafes are generally a good idea. I agree with the op that this could be useful for n00b amps like crates and {censored} that all teh n00b players buy without thinking anything about it. But i mean how far do you go? you could develop standby and power into a single switch that delays 30-45 seconds before turning to "on" ...simple enough procedure, but n00bs are always asking and complaining about it I'll stick to learning about my gear and applying that knowledge to proper use Link to comment Share on other sites More sharing options...
Members chakosh Posted June 3, 2008 Members Share Posted June 3, 2008 What you're forgetting is that there are secondary windings on the OT that need to be switched. The high voltage nature of this means that the switch needs to be heavier duty. It's not a continuously variable thing - you're switching windings at high amperage. This is the impedence switch I use in my amp builds - it's rated for 6 amps of power. This is true. I didn't take that into account. I was more of an E&M/RF/Semiconductor guy than a Power Electronics guy. I wonder if there'd be a way to put the transformer in stand-by... Dunno. Thinking out loud (?) I guess. Link to comment Share on other sites More sharing options...
Members teemuk Posted June 3, 2008 Members Share Posted June 3, 2008 Well, one could sample the output current over a low-ohm resistor in series with the speaker load and then convert the current to a voltage signal that is Link to comment Share on other sites More sharing options...
Members Angry Grimace Posted June 3, 2008 Author Members Share Posted June 3, 2008 failsafes are generally a good idea. I agree with the op that this could be useful for n00b amps like crates and {censored} that all teh n00b players buy without thinking anything about it. But i mean how far do you go? you could develop standby and power into a single switch that delays 30-45 seconds before turning to "on" ...simple enough procedure, but n00bs are always asking and complaining about it I'll stick to learning about my gear and applying that knowledge to proper use I wouldn't go that far. I mean, for one, a standby switch isn't a necessity at all; they make amps that don't have them. The standby switch does more than just keep your tubes from getting a ton of electricity put on them. Lots of people put their amps into standby between sets, etc. Link to comment Share on other sites More sharing options...
Members Angry Grimace Posted June 3, 2008 Author Members Share Posted June 3, 2008 Well, one could sample the output current over a low-ohm resistor in series with the speaker load and then convert the current to a voltage signal that is Link to comment Share on other sites More sharing options...
Members chakosh Posted June 3, 2008 Members Share Posted June 3, 2008 Besides, most output jacks already contain an internal switch mechanism that could be used for protective purposes, for example to connect a dummy load when no plug is in the jack. I Link to comment Share on other sites More sharing options...
Members Weathered Posted June 3, 2008 Members Share Posted June 3, 2008 I wouldn't go that far. I mean, for one, a standby switch isn't a necessity at all; they make amps that don't have them. The standby switch does more than just keep your tubes from getting a ton of electricity put on them. Lots of people put their amps into standby between sets, etc. If the amp has a tube rectifier, you can sometimes get away without a standby switch, as the B+ will come up to voltage slowly. If it's a SS rectifier, you need a standby to avoid cathode stripping as the B+ will come up to full voltage very quickly. Link to comment Share on other sites More sharing options...
Members Angry Grimace Posted June 3, 2008 Author Members Share Posted June 3, 2008 If the amp has a tube rectifier, you can sometimes get away without a standby switch, as the B+ will come up to voltage slowly. If it's a SS rectifier, you need a standby to avoid cathode stripping as the B+ will come up to full voltage very quickly. True, but cathode stripping probably doesn't matter to the manufacturers because it negatively affects the tubes's lifespan...but valves are considered consumables anyways by amp manufacturers. Link to comment Share on other sites More sharing options...
Members sled Posted June 4, 2008 Members Share Posted June 4, 2008 Here's several thoughts... Add a separate Ohm Indicator Jack that displays the load. Basically a Digital Ohm meter, user then manually selects the amp OT tap Add a separate jack to sense the load, that selects the OT tap based on the load value. User then moves load to the output jack. No Load plugged in and a relay opens the signal to the OT/Power Section Add ohm sensing to the output Jack that switches/selects the proper OT tap Link to comment Share on other sites More sharing options...
Members potaetoes Posted June 4, 2008 Members Share Posted June 4, 2008 what's so hard about using eyeballs and brains to plug it into the correct hole? is one extra thought really an inconvenience? i feel sorry for anyone who actually thinks that's a feature worth paying more money for... because they probably have to wear velcro shoes and a helmet every day. Link to comment Share on other sites More sharing options...
Members potaetoes Posted June 4, 2008 Members Share Posted June 4, 2008 Besides, most output jacks already contain an internal switch mechanism that could be used for protective purposes, for example to connect a dummy load when no plug is in the jack. I Link to comment Share on other sites More sharing options...
Members subsea Posted June 4, 2008 Members Share Posted June 4, 2008 Don Link to comment Share on other sites More sharing options...
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