hellion102792 Posted April 4, 2011 Share Posted April 4, 2011 Hey ya'll! So I have a question about impedance in tube amps between the chassis and the speakers. I'm getting a bunch of conflicting info from Google, and my electronics class unfortunately got shut down so I figured I'd turn here for an actual answer. Here's my situation.. I use a 1978 Peavey Classic VT 2x12. Solid state preamp section, 50w tube power section. It is loaded with 2 Celestion Hot 100's, each rated at 16 ohms. The back of the amp has 2 outputs, a 4 ohm and an 8 ohm. I've never really payed much attention to which output the speakers were hooked into, I believe it may have been 4 ohms? So I played a show this past Friday, and while packing up from our practice space I accidentally pulled out the speaker wire. Not knowing which it was plugged into, I put it into the 8 ohm output. No problems during the gig, no problems at all as a matter of fact but I only fired her up once for a few minutes since the gig. I noticed that the tubes seem to be glowing a little brighter, but my tone/volume output seems a bit beefed up. Now here's my question: Am I supposed to have the 2 16 ohm speakers wired into the 4 ohm output? Or the 8 ohm? I read that impedance matching is important for tube amps, I don't wanna fry my speakers or my output transformer by screwing it up. Thanks! Link to comment Share on other sites More sharing options...
Tim Plains Posted April 4, 2011 Share Posted April 4, 2011 8 ohms (I hope) unless your speakers are wired together differently. You can download nearly any amp's owners manuals for free off their website. Some of them explain the ohms and where to plug into. For example, this is from a Blackheart owner's manual. SPEAKER CABINET IMPEDANCE divided by NUMBER OF CABINETS = TOTAL LOAD 4 x 16 ohm cabinets with parallel inputs = 4 ohm load. For this application use 4 ohm output jacks. 2 x 16 ohm cabinets = 8 ohm load. For this application use the 8 ohm speaker jacks. 1 x 16 ohm cabinet = 16 ohm load. For this application use the 16 ohm speaker jack. 2 x 8 ohm cabinets = 4 ohm load. For this application use the 4 ohm output jacks. 1 x 8 ohm cabinet = 8 ohm load. For this application use the 8 ohm speaker jack. 1 x 4 ohm cabinet = 4 ohm load. For this application use the 4 ohm speaker jack. Link to comment Share on other sites More sharing options...
Riverside Posted April 4, 2011 Share Posted April 4, 2011 Here's some good information: Scroll down for impedance discussion Link to comment Share on other sites More sharing options...
Guest FarnsBarns Posted April 4, 2011 Share Posted April 4, 2011 A simple answer... 2 16ohm speakers can be wired in series (32 ohms) which is extremely unlikely, or in parallel (8ohms), very likely. Assuming the latter, you should connect your cab to the 8ohm output. They should match. Link to comment Share on other sites More sharing options...
JDK Posted April 4, 2011 Share Posted April 4, 2011 Use the 8 ohms. The 4 ohm plug may be stressing your output transformer. Parallel wiring as mentioned means the + speaker wires go to each + treminal, and negative to each speakers - terminal. Link to comment Share on other sites More sharing options...
davidl Posted April 5, 2011 Share Posted April 5, 2011 Impedence...hmmm. I think there are pills for that now. Link to comment Share on other sites More sharing options...
damian Posted April 5, 2011 Share Posted April 5, 2011 Here's some good information Scroll down for impedance discussion Thank you for the link.....awesome link....... Impedence...hmmm. I think there are pills for that now. Yes, there are; I take them; I now do a lot of stuff in series.......... Link to comment Share on other sites More sharing options...
MrNylon Posted April 5, 2011 Share Posted April 5, 2011 I would say use the 8 ohm. The 4 ohm would be used for an external cab. On the back of the amp head, it should give it's ohm rating. Link to comment Share on other sites More sharing options...
Silenced Fred Posted April 5, 2011 Share Posted April 5, 2011 Impedence...hmmm. I think there are pills for that now. beat me to it Link to comment Share on other sites More sharing options...
pete c Posted April 5, 2011 Share Posted April 5, 2011 Impedence...hmmm. I think there are pills for that now. depends Link to comment Share on other sites More sharing options...
damian Posted April 6, 2011 Share Posted April 6, 2011 depends Depends........There are apps for them..... ..... Link to comment Share on other sites More sharing options...
hellion102792 Posted April 11, 2011 Author Share Posted April 11, 2011 Late response but thank you all, glad to know I won't burn it up now! Link to comment Share on other sites More sharing options...
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