Marvel Posted November 19, 2006 Share Posted November 19, 2006 In other words, the box doesn't care what input the amplifiers see. The box doesn't care, but the amps might when there is no load. Yes, an incredibly small period of time, and as you say, it may not matter at all. I have had amplifiers, where the documentation said don't provide an input signal with no load (no speaker attached to the output terminals), or damage to the device may result. I have often had SS amps with no load and no input signal present, with no damage. I haven't wanted to try the other way. I've also put a 10k dummy load on an amps output terminals, just so there would be a load if I screwed up. It can be a low wattage device (you can do the math). A SS amp with no load, though, means no current will flow through the output transistors. On a tube amp, the current flows through the primary. The load present to the output tubes is due to the turns ratio of the secondary related to the speaker load. The design is so totally different compared to SS amps. Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 19, 2006 Share Posted November 19, 2006 ...which is the purpose of having the dummy resistors [] The question is if a max time of 20ms is too long for the transition to occur. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 20, 2006 Share Posted November 20, 2006 "Wow. Amp A and amp B are seperate "inputs" and never connect to each other - what you propose would be an absurd and even impossible design" You obviously don't understand my question, Who. However, having the means to switch an input signal from one amp to the other is actually a very simple thing to do, and would provide a redundant measure of safety. Here's another way to ask the same question: When one switches between one amp or another, is it also necessary to manually reroute the input signal to the chosen amp, or is the signal already common to both? Erik Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 20, 2006 Share Posted November 20, 2006 I have to many questions about what is going on when this switch is thrown!! Believe it or not Erik and I are in agreement twice in the same thread in less then a week! Hard to believe........ Erik's point about the input impedance is also a good one although it will not cause harm to either amplifiers in my estimation it surely is not the best thing for sonics. Let's start here. What resistance value/wattage are those load resistors? I'm worried about the possible input sensitivity difference of the two amplifiers. If the SS HT amplifier is say 2V RMS to full power while the VRD's are 1.1V to full power and your switching to the SS amp and turning the volume up while the signal is still being presented to the VRD amplifier the amp could be over driven!! Or having music blasting through your VRD's and then instantly switching amps while the music is still being presented to the VRD's is indeed not a good idea. I have never tested for this scenario but having any tube amp blazing away playing music and then abruptly removing the load for even 20ms can not be a good idea. It could easily cause a tupe amplifier to become unstable. All so you can compare some HT amp to a VRD instantly? Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 20, 2006 Share Posted November 20, 2006 Craig's concerns are precisely the same as my own on this. I was just concerned about the possibility that the switch box, depending on its design (which is what I was trying to figure out), might be presenting some impedance/load issues that might have been a contributing factor to some of the problems that were mentioned above. Bruce/Fini: Thanks for helping to clarify some of that. Erik Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted November 20, 2006 Author Share Posted November 20, 2006 Well I guess I'll wait until you guys figure out whether otr not this box will be ok with the VRD's before I power them up again. I know others that are using the Niles Box with tube/SS amps... is it not the same design? Mike Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 20, 2006 Share Posted November 20, 2006 It's a similar to this design (but using a wider relay to provide a dummy load to the "off" amp and not sharing the same ground - as you can see from the circuit diagram): http://sound.westhost.com/absw.htm Valve and transistor amps may be compared as long as the valve model has a damping factor greater than 25. The dummy load is a non-inductive 10-Ohm 50W resistor. The Mills MRC-50: http://www.partsconnexion.com/catalog/resistors.html (I provided a picture because you have to click on a link at the bottom of the page) Ya know, I've brought this issue up twice before on the forum and there has been never been any contention on the design. Not to mention every textbook and website I read says it's ok too. I am 99% confident it's not the switchbox causing the problem with the tubes, but I wanted to bring it up just to make sure and take responsibility if I need to. And I hesitate referring to the westhost design because it's completely different and I know tube amps don't like "no loads" (and his design is doing just that...). Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 20, 2006 Share Posted November 20, 2006 Mike: I would follow Craig's advice on this one -- but that's just me. I'm not saying your switchbox is a 'bad' device per se', just that there is the chance, depending on it's design and how it's used, that it may have something to do with performance. That's why I was asking questions about both input and output aspects of it. From what I gather, it seems that in order to use one amp or another, one has to BOTH throw the switch on the box PLUS manually reroute the interconnect cable from preamp/source to the selected amplifier. I am also curious about the value of the dummy loads, but maybe I just missed that detail. Another way to accomplish the same thing would be to: turn the amps off, unplug the interconnect and speaker cables, and then reconnect them to the amp you want to use. I am truly not intending to sound -- whatever...impolite, or something -- it's just how I would prefer to switch from one component to another. I would just rather power both amps down and then make the necessary connections instead of trying to do it with both components already running full steam ahead. The Niles product: Are you talking about the Niles speaker selector box? Erik Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 20, 2006 Share Posted November 20, 2006 He's talking about the Niles Amp Selector box - which is essentially the same thing but no banana plugs. The purpose of the switcher is to provide convenience for those that don't have easy access to the rear panel of their electronics - or who simply don't want to move speaker cables back and forth all the time. Ya know, I can think of a lot more reason for having a selector than running fragile amps...but let's not go there. [6] Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 20, 2006 Share Posted November 20, 2006 Dr. Who: Thanks for providing that link to the original schematic. Since there was no description concerning the input aspect of the device, I checked the web page and found the information I was looking for: I quote: "Make "Y" leads to connect the left and right input signals to both amplifiers." That's what I was originally asking you about. Certainly I understand how such a box would be useful in making immediate comparisons of two components, and it probably isn't causing problems. However, I was curious about how the input to the amplifiers was handled, and your link answered my question. I would like to submit again that it would be possible to provide a means of switching the input signal independently from one amp to another, which would eliminate the need for 'Y' jack connections. I would like to suggest that doing so would be neither absurd nor impossible. Erik Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 20, 2006 Share Posted November 20, 2006 It would just increase the cost about $30, and require a much larger bigger box (and this is the largest these aluminum enclosures go). And even then - you're not guaranteed that the relays fire at exactly the same time. And worst case scenario you could assume you reduce the maximum size of the gap to around 10ms. Quote Link to comment Share on other sites More sharing options...
fini Posted November 20, 2006 Share Posted November 20, 2006 Mike, Would you mind sending or posting info on that enclosure? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 20, 2006 Share Posted November 20, 2006 Well I guess I'll wait until you guys figure out whether otr not this box will be ok with the VRD's before I power them up again. I know others that are using the Niles Box with tube/SS amps... is it not the same design? Mike Mike, If you want answers to this then your going to have to answer just how your using this and under what circumstances. I have no clue why you need to leave your tube amps on when your not using them? or are you flipping back and forth to compare? What are you doing with thius setup? Do you have to turn the source up more when using the HT amplifier as compared to the VRD's ? Since you received the new 5AR4's have you had any vibration out of the amp? To many variables for any of us to answer you properly. I just don't get the reason for this setup at all. Craig Quote Link to comment Share on other sites More sharing options...
johnyholiday Posted November 20, 2006 Share Posted November 20, 2006 Anytime a power selector switch is changed on an amp, you must power it down ,an then switch the power selection, or a chance a tube will blow, and an overall thwack to the system,sort of in the same vain, johny wouldn't use a switchbox ,on the backside, without powering down the tubes first,,just dosen't seem right, good luck Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted November 20, 2006 Author Share Posted November 20, 2006 Mike, If you want answers to this then your going to have to answer just how your using this and under what circumstances. I have no clue why you need to leave your tube amps on when your not using them? or are you flipping back and forth to compare? What are you doing with thius setup? I have one pair of speakers (La Scala's) that I share between my HT system and my 2-ch system, and it is a real pain in the a$$ to get behind my rack to plug the speaker cables into the back of the Acurus amp for HT/TV listening. Do you have to turn the source up more when using the HT amplifier as compared to the VRD's ? No. Since you received the new 5AR4's have you had any vibration out of the amp? No... but haven't played them long enough to notice at this point. I just don't get the reason for this setup at all. See my first answer. Mike Quote Link to comment Share on other sites More sharing options...
@silverfox@ Posted November 20, 2006 Share Posted November 20, 2006 this might be way above my understanding of how a switcher works, seems that the use of double pole double throw switches might be a safer and less expensive way to approach this problem. could the unit contain a quick make slow break switch, i'm using the above method between acurus 125,bottlehead -pre, and dewald , or scott 299ba .interchangable with dewald.with cornwalls sharing double duty and no issues. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 20, 2006 Share Posted November 20, 2006 Mike, If you want answers to this then your going to have to answer just how your using this and under what circumstances. I have no clue why you need to leave your tube amps on when your not using them? or are you flipping back and forth to compare? What are you doing with thius setup? I have one pair of speakers (La Scala's) that I share between my HT system and my 2-ch system, and it is a real pain in the a$$ to get behind my rack to plug the speaker cables into the back of the Acurus amp for HT/TV listening. Do you have to turn the source up more when using the HT amplifier as compared to the VRD's ? No. Since you received the new 5AR4's have you had any vibration out of the amp? No... but haven't played them long enough to notice at this point. I just don't get the reason for this setup at all. See my first answer. Mike Okay now I will ask again. If your going to stop listening to your VRD's and start listening to the HT system whether it be music or a movie why wouldn't you simply shut your tube amps off? Or are you indeed using this as a means to instant A/B your two amps to freinds or what ever. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 20, 2006 Share Posted November 20, 2006 Mike: I know you and Craig are working this out, but can I ask if there is a way you can use the VRDs for both 2-channel AND home theater? That's what I'm doing with one of my stereo tube amps. I use it for front L/R of the surround system, but can use the 2-channel bypass on my Lexicon for stereo-only listening. Your system capabilities may just not allow for something like that, but I was just thinking it would make things much more simple and you would have your best amps to use for both. I think you're also running a TT, which probably means this idea I'm suggesting is completely wrong for you. Erik Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted November 21, 2006 Author Share Posted November 21, 2006 Okay now I will ask again. If your going to stop listening to your VRD's and start listening to the HT system whether it be music or a movie why wouldn't you simply shut your tube amps off? Or are you indeed using this as a means to instant A/B your two amps to freinds or what ever. Craig Yes... I could do that, and that is what I will have to do from here on out. I generally listen to music first when I get home, but I occasionally watch TV, a DVD movie, or a DVD concert afterwards and need the use of the HT amp. When I do this I will switch the VRDs off, and if I choose to use the VRDs again later I will switch back over to them and then power them up. Mike Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted November 21, 2006 Author Share Posted November 21, 2006 Mike: I know you and Craig are working this out, but can I ask if there is a way you can use the VRDs for both 2-channel AND home theater? That's what I'm doing with one of my stereo tube amps. I use it for front L/R of the surround system, but can use the 2-channel bypass on my Lexicon for stereo-only listening. Your system capabilities may just not allow for something like that, but I was just thinking it would make things much more simple and you would have your best amps to use for both. I think you're also running a TT, which probably means this idea I'm suggesting is completely wrong for you. Erik The BlueBerry Xtreme does not have the HT bypass functionality like the Peach does, or I would go this route. Mike Quote Link to comment Share on other sites More sharing options...
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