Members D Aussie Posted September 26, 2007 Members Share Posted September 26, 2007 Im actually on the look out for a 2nd hand all tube geetar amp of around 30-60 watts and Ive never owned a tube product before. Amps that come to mind are Peavey Classic 30, Peavey Triumph 60, Traynor 40, Fender Blues Jnr 15. What is some things for me to know? What is bias? When do tubes need changing? Is there a good way to look after them? Link to comment Share on other sites More sharing options...
Members Thumper Posted September 27, 2007 Members Share Posted September 27, 2007 You're dead right on wanting a tube amp. IIRC biasing adjusts individual power amplifier tubes to run at the proper voltage. I'll let other HCBFers get into the specifics. Preamp tubes do not require biasing. Tube life varies depending on application. A Marshall 50 watt head that's always cranked to 10 will need new tubes sooner than an Ampeg B-15 used as a low-volume studio amp. If you're buying used, take the amp to a knowledgeable tech and have him sort the amp out for you. A well-maintained tube rig is just as reliable as an ss rig. Never power up the amp without connecting a speaker cab first. Use the standby switch to let the tubes settle in before turning on the main power. Keep the chassis clean---dust, crap and crud can insulate the tubes an cause excessive heat build-up. As for specific amps, keep your eyes open for a Peavey Delta Blues (40 watt 1x15 combo) or a Fender Bassman 10 (50 watt 4x10 combo---huge, but sounds wonderful). Good luck. Link to comment Share on other sites More sharing options...
Members rummy Posted September 27, 2007 Members Share Posted September 27, 2007 I own a 50W tube head. They're fun! Biasing is adjusting how much juice you get out of the power tubes. You can bias them hot for early breakup, or bias them cold for head room and clarity. Obviously, if you bias your tubes hot, your amp will run hot, and the tubes will die quicker. You'll know when your tubes are shot, 'cause it'll sound very different. To look after them? THere's not much to it other than common sense. Use ventilation, try not to get vibrations/shocks into the frame, etc, etc Link to comment Share on other sites More sharing options...
Members bikehorn Posted September 27, 2007 Members Share Posted September 27, 2007 by the sound of the amps your'e considering, it doesn't sound like you're looking for massive gain, but not a completely clean amp either. Bias is comparable to setting the idle on a car. Set too low, the car will sputter and perform roughly. Too high and the car will start running away the second you put it in gear. In the same way bias has to fall into a range that is suitable to the tube ratings and the amplifier's circuit design. When tubes are biased 'cold', aka low bias, the life will be extended but the amp may not sound as 'warm' or 'alive'...and you could get crossover distortion. This is hard for me to explain, but many people find this type of distortion unpleasant and harsh so you should probably look at it as undesirable. If the tubes are biased 'hot' they will sound the opposite, but the tube life will be shortened. How much depends on how high they are biased and the type of tube. Usually a good balance can be struck between good sound and life expectancy. Some amps are designed to use a method known as cathode biasing, which effectively means the amp biases itself. This method is inefficient and does not extract as much power from the tubes as a regular bias setup, but is used in many great amps, most notably the Vox AC30. I think the Peavey Classic 30 and many low-wattage amps are cathode biased. With these you can just stick in a new set of power tubes and you'll be ready to roll. Also, preamp tubes don't require biasing. Link to comment Share on other sites More sharing options...
Members OneBassNut Posted September 27, 2007 Members Share Posted September 27, 2007 Very good, useful info here! Link to comment Share on other sites More sharing options...
Members fretless Posted September 27, 2007 Members Share Posted September 27, 2007 Tube power rocks m/ Link to comment Share on other sites More sharing options...
Moderators Kindness Posted September 27, 2007 Moderators Share Posted September 27, 2007 preamp tubes don't require biasing. Because they are cathode biased. Link to comment Share on other sites More sharing options...
Members bikehorn Posted September 27, 2007 Members Share Posted September 27, 2007 Because they are cathode biased. Word. I tried to make it sound simple though although, i guess it wouldn't have made it that much more complicated if I had added that. Link to comment Share on other sites More sharing options...
Moderators Kindness Posted September 27, 2007 Moderators Share Posted September 27, 2007 Link to comment Share on other sites More sharing options...
Members Kontra Posted September 27, 2007 Members Share Posted September 27, 2007 Im actually on the look out for a 2nd hand all tube geetar amp of around 30-60 watts and Ive never owned a tube product before. Amps that come to mind are Peavey Classic 30, Peavey Triumph 60, Traynor 40, Fender Blues Jnr 15. What is some things for me to know? What is bias? When do tubes need changing? Is there a good way to look after them? Excellent site for second hand amps in Aus http://www.guitargear.net.au/discussion/index.php Link to comment Share on other sites More sharing options...
Members D Aussie Posted September 27, 2007 Author Members Share Posted September 27, 2007 thanks Kontra. I didnt know about that site. Link to comment Share on other sites More sharing options...
Members bholder Posted September 27, 2007 Members Share Posted September 27, 2007 I have a tube bias. Link to comment Share on other sites More sharing options...
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