joessportster Posted August 21, 2018 Share Posted August 21, 2018 I Know this sounds nuts but here goes anyway I want to keep 2 different amps hooked up to the 1 pre-amp and the 1 pair of speakers, At times I prefer 1 amp over the other and it is a PITA to keep swapping out all the cables My pre has 2 sets of output so no problem there as long as I only power up 1 amp. My question is on the speaker connection, My idea is to make a jumper that will go from 1 amps speaker terminals to the other amps speaker terminals and have the speakers hooked to either amp again only 1 amp will be powered on at a time. Will this cause any issues with the speakers being connected to both amps ie...backflow into the amp that is powered off. These are tube amps I would rather not get into a switch another link in the chain is not what I want. Quote Link to comment Share on other sites More sharing options...
rplace Posted August 21, 2018 Share Posted August 21, 2018 Curious to see what others have to say. I do exactly what you want but with a Niles switch which you do not want....and I totally understand that. I don't want it either. In the end I decided to have the Niles Break before Make switch so no issues. Seemed safer to me. I know enough to be dangerous, but not much more. So My pre outs go to both sets of amps SET Mono blocks and VRD Mono blocks. I switch the switch, power up the preamp, then power up amps in question so they have something connected to them. My gut tells me as long as you never have them powered up at the same time you should be good. After all it is just the signal going form one to the other following the copper wires. I also wondered if the Niles switch could actually degrade the signal more or less than an extra connection between amps and all they bring to the table when powered down. Quote Link to comment Share on other sites More sharing options...
babadono Posted August 21, 2018 Share Posted August 21, 2018 Tube amps have a transformer on the output. You will be feeding signal from the live amp into your speakers and into the output transformer of the amp that is off. I am by no means a tube amp expert(or any other kind of expert for that matter) but I don't think this is a good idea. I don't think you will harm anything but it will put an extra load on the amp that is on. A great general rule of thumb in electronics: Never tie two outputs together. 2 Quote Link to comment Share on other sites More sharing options...
Coytee Posted August 21, 2018 Share Posted August 21, 2018 Cripes... I don't remember my setup. I had a situation where I had either two preamps in the system (with a splitter) or two amps. I THINK it was two amps (along with a Niles A/B box) None the less.... the solid state amp would go into protection mode every now & then. Finally figured out that if I had the tube amps on, turned solid state on and then tubes OFF, it would go into protection mode. If I turned the SS amp off, everything would be fine with the tubes. It's been 12'ish years...so I don't fully remember. None the less.... Mark Deneen was the one that figured it out. Because I was using the splitter, remember that the signal travels both ways. When the tube amps were turned off, they emitted a slight bit of DC current as they died (spitting it back out the RCA input). Since that wouldn't go to the speakers, it was fine. Since however, I had a splitter, that DC current would back-peddle and become part of the input to the solid state amp, pushing it into protection mode every time. I figured out the process on how to power things so that would never happen but it was annoying as anything. Point being, when you are putting a splitter in the system, things can bite your ankles that you didn't think about so just be aware. 1 Quote Link to comment Share on other sites More sharing options...
rplace Posted August 21, 2018 Share Posted August 21, 2018 14 minutes ago, Coytee said: Cripes... I don't remember my setup. I had a situation where I had either two preamps in the system (with a splitter) or two amps. ….. Point being, when you are putting a splitter in the system, things can bite your ankles that you didn't think about so just be aware. Interesting and thanks for that input. So you are saying your preamp only had one pre-out and you used a splitter to go to both amps, correct? Either a RCA Wye Cable or something like the picture below? I have a preamp that has two sets of pre-outs so I would not think that would be an issue. However I have another preamp with just one set of outs and I use the solid Audio Quest thing below. I swap the preamps less frequently, but when I do I still use both sets of amps. Quote Link to comment Share on other sites More sharing options...
Coytee Posted August 21, 2018 Share Posted August 21, 2018 Yes, I had a piece of wire "Y" shaped but did same thing as in your picture. I'm not an EE nor did I stay at a Holiday Inn last night....so take comments with grain of salt. None the less, what I was told by Mark was if they're connected, they'll still "see" each other. Even though we (or at least speaking for myself) think of the signal going "from" here "to" there.... when the amps had their little DC exhaustion thing go on....it fed back through the amps input which would otherwise be irrelevant but, since I had the "Y" adapter in there, it would also shoot over to the SS amp and freak it out, putting it into protection mode. It ONLY happened when I turned the tube amps off first. If I left them on, no issues. If I turned them off second, no issues. 1 Quote Link to comment Share on other sites More sharing options...
rplace Posted August 21, 2018 Share Posted August 21, 2018 31 minutes ago, Coytee said: It ONLY happened when I turned the tube amps off first. If I left them on, no issues. If I turned them off second, no issues. Did you ever have both amps on at the same time? I'd think the order of operation would be: To listen to amp 1 and only 1 for say a couple of hours Turn on pre Turn on amp 1 Listen Turn everything off To listen to amp 2 only for a couple of hours, same except in step 2 turn on amp 2 To listen to one then the other, say amp 1 then amp 2 Turn on Pre Turn on amp 1 Listen Turn everything off Turn on Pre Turn on amp 2 Listen Turn everything off Quote Link to comment Share on other sites More sharing options...
Dave1290 Posted August 21, 2018 Share Posted August 21, 2018 I was always told "if ya have two amps and want to play, bi-amplify nothing more or disconnect everything and play!" Just an old EE's words of wisdom. I've never had a problem, I just dismiss the need or cravings to play with stuff cause he KNOWS sound. Quote Link to comment Share on other sites More sharing options...
Schu Posted August 21, 2018 Share Posted August 21, 2018 I still use manual disconnection... 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted August 21, 2018 Share Posted August 21, 2018 28 minutes ago, rplace said: Turn everything off Yea I don't get this. If your preamp has a STABLE output stage, turning it off when switching amps on and off should not be necessary. Now if your switching cables around that's a different story. 1 Quote Link to comment Share on other sites More sharing options...
rplace Posted August 21, 2018 Share Posted August 21, 2018 13 minutes ago, babadono said: Yea I don't get this. If your preamp has a STABLE output stage, turning it off when switching amps on and off should not be necessary. Now if your switching cables around that's a different story. Some time ago I seem to remember hearing/reading never turn on a tube amp without speakers connected. So when I've had two sets of amps and one set of speakers I figure the "switch", be it me manually or an A/B selector, can only show load to one amp at a time. Since I'm already turning the first amp off, I just go ahead and turn the preamp off as well. Nice to know I don't really have to. I don't think it is actually possible to construct the perfect test bed for A/B switching of amps is there? My dream set up would be: Source to Preamp Single Preamp to multiple amps All Amps to one pair of speakers A magic thing that keeps the dB level the same when switching between amps The ability to instantly switch between amps without a split-second of down time. Joe, so sorry for the thread hijack. You just brought up a bunch of questions from my days trying to see what I liked better SS, low power tubes, high power tubes amps. Total hijack. Did I dream it up or is there some trick for putting a small resistor on the output of your amp's binding posts just incase the tube amp is turned on with no speakers attached? Quote Link to comment Share on other sites More sharing options...
Dave1290 Posted August 21, 2018 Share Posted August 21, 2018 5 minutes ago, rplace said: Some time ago I seem to remember hearing/reading never turn on a tube amp without speakers connected. Ditto to that... I'm thunkin!!! Quote Link to comment Share on other sites More sharing options...
Coytee Posted August 21, 2018 Share Posted August 21, 2018 2 hours ago, rplace said: Did you ever have both amps on at the same time? I could leave the amps on as much as I wanted. I could turn them off as often as I wanted AS LONG as I turned the SS amp off first. The little DC drain in the tube amps is what killed everything. I was able to put a meter to it and measure it. I don't recall any numbers, but let's just say it output something like 12 volts (??) I decided that standard SS was sufficient for me since I don't sit in the sweet spot counting the shimmers of a cymbal. Sold most of the tube stuff soon after this happened and acquired my K2's and called it a day. 1 Quote Link to comment Share on other sites More sharing options...
rplace Posted August 21, 2018 Share Posted August 21, 2018 7 minutes ago, Coytee said: I could leave the amps on as much as I wanted. I could turn them off as often as I wanted AS LONG as I turned the SS amp off first. The little DC drain in the tube amps is what killed everything. I was able to put a meter to it and measure it. I don't recall any numbers, but let's just say it output something like 12 volts (??) I decided that standard SS was sufficient for me since I don't sit in the sweet spot counting the shimmers of a cymbal. Sold most of the tube stuff soon after this happened and acquired my K2's and called it a day. And no issues what so ever when playing the SS amp and having the Niles switched to it and the tube amp turned on? Hmmmm, I must be misinformed. Would not be the first time. Quote Link to comment Share on other sites More sharing options...
Coytee Posted August 21, 2018 Share Posted August 21, 2018 Perhaps I didn't leave it on long enough to produce a problem. I don't know. Everything worked fine while I had it like that other than the DC voltage draining out of the tube amp inputs. This was pre-Jubilee so was 2006'ish and prior. 12+ years ago. Oh, and that annoying little Niles box.... as wonderful as they may be.... the one I had only seemed to accept something smaller than say, 14 gauge. Since I used 12 through everything, I had to nip the ends of the wires so they'd fit. Also, regarding some comments above on hot-swapping. First, I "get" that you're not supposed to do it. I got some Neutrik Profi connectors. The negative is spring loaded and touches FIRST and releases LAST so you'd (in theory I guess) be able to hot swap without any of the pops it might create. http://www.neutrik.com/en/phono-rca/profi-cable-connectors/ Quote Link to comment Share on other sites More sharing options...
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