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Post by guitarman31 on Aug 20, 2008 15:44:12 GMT -7
Someone I thought was knowledgeable about equipment told me they thought my amp was a Class A amp. I am not sure I know the difference between a class A and Class AB but I was curious which it is.
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Post by detuned on Aug 21, 2008 8:57:13 GMT -7
Now where did I put that can opener?
Short answer: depends on the marketing department of the manufacturer. Some would say "yes" & be correct on one level, another would say "no" & be equally correct.
Someone who understands the technical part better than I will chime in soon...
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Post by awesome on Aug 21, 2008 9:27:55 GMT -7
Most "Class A" amps arent actually class A, they are just biased close to being Class A. other than that bit of info i know nothing more.
i would have thought someone would have answered this question adequately by now.
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Post by benttop (Steve) on Aug 21, 2008 9:40:36 GMT -7
It's a red herring. For me, I would prefer to say the Maz Jr is cathode biased and leave it at that. When you start talking about Class A etc. almost everyone has a quibble or two with how to define and describe that. Cathode biased, that's the ticket. For the OP, the difference between the Maz Jr and a similar amp that is known as Class AB would be how the power tube bias is derived. The Maz Jr uses cathode bias, which means you can change tubes without rebiasing, so long as you buy a matched set. The class AB amps are normally fixed bias, which means when you change power tubes, you have to go in and reset the bias for optimum performance. There is a LOT more to it than this, but the bias question is usually the factor we're interested in. As it turns out, the two different systems respond a little differently as well, so if you want more info than you can possibly digest in one sitting, let me know and I'll point you to some references. But be ready for a lot of reading and also not a little BS on the subject.
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Post by dixiechicken on Aug 21, 2008 11:42:52 GMT -7
DC here! Doc: Maz 18 Jr is NOT a class A amplifier. It's a cathode biased class B amplifier. Such an amplifier may be biased in such a way - that both output tubes is open for almost the the whole sine wave cycle - thus coming close to work like a single ended class A amplifier. Music is basically acoustic sine wave forms (changes of air pressure) - of various frequencies and amplitudes. Fourier-analysis break down a complex signal into sine waves. In class B amplifier the music signal is split in the PI-tube into one negative part and one positive part. One power tube amplifies the positive part the other the negative part - both parts are then summed in the output transformer and sent to the speaker outs. The critical part here is the boundary between negative and positive half of the sine wave. You bias the amp to eliminate the crossover distortion here as much as possible. In a class B amp when the power tube amplifying the positive half of the signal is active - the other power tube is basically closed - no current or very little is flowing through. See this link for all the info you'd care to shake a stick at: www.aikenamps.com/Click the link Technical info - you will likely need to read it several times - hehe - I did. ;D Cheers: Dixiechicken!
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Post by Strato on Aug 24, 2008 0:52:21 GMT -7
DC here! Doc: Maz 18 Jr is NOT a class A amplifier. It's a cathode biased class B amplifier. Such an amplifier may be biased in such a way - that both output tubes is open for almost the the whole sine wave cycle - thus coming close to work like a single ended class A amplifier. Music is basically acoustic sine wave forms (changes of air pressure) - of various frequencies and amplitudes. Fourier-analysis break down a complex signal into sine waves. In class B amplifier the music signal is split in the PI-tube into one negative part and one positive part. One power tube amplifies the positive part the other the negative part - both parts are then summed in the output transformer and sent to the speaker outs. The critical part here is the boundary between negative and positive half of the sine wave. You bias the amp to eliminate the crossover distortion here as much as possible. In a class B amp when the power tube amplifying the positive half of the signal is active - the other power tube is basically closed - no current or very little is flowing through. See this link for all the info you'd care to shake a stick at: www.aikenamps.com/Click the link Technical info - you will likely need to read it several times - hehe - I did. ;D Cheers: Dixiechicken! Actually, I believe that the amp is Class AB1 push-pull in ultralinear mode. This means that each power tube operates for greater than 180 degrees, but less than 360 degrees of the sine wave. A class B amplifier would have alot more crossover distortion, and it would not sound very good. A true class A amplifier is relatively inefficient. I dont know the numbers off the top of my head, but I am pretty sure that a single EL84 operating in class A can only output about 4-5 watts. Also, a pair of power tubes operating in Class A push-pull cancels even-order harmonics, which is great for hi-fi gear, but not as good for guitarists.
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Post by dixiechicken on Aug 24, 2008 11:06:02 GMT -7
DC here! In principle quite correct - although a properly designed class B push-pulll configuration can be made to have very little ( in-audible ) cross-over and im-distortion. (true class A should not have any crossover distortion)Since taste is totally subjective - there are actually guitar players the prefer class B guitar amps for precisely a slight amount of crossover distortion - that would add a certain rash/raw character to the sound. Great for certain types of rock music. As always YMMV Cheers: Dixiechicken!
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Post by bluzman on Aug 24, 2008 22:40:37 GMT -7
At any rate it's PURE CLASS!! That's why I have so many.
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Post by myles on Aug 25, 2008 19:48:32 GMT -7
DC here! Doc: Maz 18 Jr is NOT a class A amplifier. It's a cathode biased class B amplifier. Such an amplifier may be biased in such a way - that both output tubes is open for almost the the whole sine wave cycle - thus coming close to work like a single ended class A amplifier. Music is basically acoustic sine wave forms (changes of air pressure) - of various frequencies and amplitudes. Fourier-analysis break down a complex signal into sine waves. In class B amplifier the music signal is split in the PI-tube into one negative part and one positive part. One power tube amplifies the positive part the other the negative part - both parts are then summed in the output transformer and sent to the speaker outs. The critical part here is the boundary between negative and positive half of the sine wave. You bias the amp to eliminate the crossover distortion here as much as possible. In a class B amp when the power tube amplifying the positive half of the signal is active - the other power tube is basically closed - no current or very little is flowing through. See this link for all the info you'd care to shake a stick at: www.aikenamps.com/Click the link Technical info - you will likely need to read it several times - hehe - I did. ;D Cheers: Dixiechicken! EXCELLENT answer ... it is a cathode biased amp and push-pull at that.
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Post by dixiechicken on Sept 6, 2008 12:31:19 GMT -7
DC here! Glad I finally got something right. ;D ;D ;D ;D ;D Wouldn't do to obfuscate an already murky subject now, would it? Thanks Myles. Cheers: Dixiechicken!
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Post by myles on Sept 6, 2008 13:41:31 GMT -7
DC here! Glad I finally got something right. ;D ;D ;D ;D ;D Wouldn't do to obfuscate an already murky subject now, would it? Thanks Myles. Cheers: Dixiechicken! You are welcome ... well done.
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