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Post subject: Mismatched power tubes are a GOOD THING?
Posted: Thu Mar 31, 2011 9:46 am
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Aspiring Musician
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I've been taught that matched sets of power tubes are essential and almost mandatory. Apparently there is an opposing school of thought. see link below. what say you guys? true/false?

http://www.stephensonamps.com/old/dpt.htm


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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Thu Mar 31, 2011 9:56 am
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True.

But you'll never catch me playing one.

Arjay

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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Fri Apr 01, 2011 8:27 am
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Retroverbial wrote:
True.

But you'll never catch me playing one.

Arjay


You got me wantin' to learn sumpin'.

Why?


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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Fri Apr 01, 2011 9:07 am
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Because the very essence of a Class AB amp design is a symmetrical output stage, with matched-but-opposing duty cycles for the output tubes. The EL84 typically runs hot -- the 6V6, substantially less so. Guess which bottle will fail first?

Arjay

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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Fri Apr 01, 2011 11:50 am
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I agree. If you want to mix power tubes, get an Egnater Rebel 20, 30 or any other Egnater amp that was designed to do it. That's what I did. I can blend a pair of 6V6 and EL84's to any degree I wish. Great amps. And yes, EL84's do run pretty hot. More so than 6V6's.It's another example of just because it CAN be done, doesn't really mean it Should be done.
Learn sumpin? :mrgreen:

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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Fri Apr 01, 2011 12:01 pm
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63supro wrote:
I agree. If you want to mix power tubes, get an Egnater Rebel 20, 30 or any other Egnater amp that was designed to do it. That's what I did. I can blend a pair of 6V6 and EL84's to any degree I wish. Great amps. And yes, EL84's do run pretty hot. More so than 6V6's.It's another example of just because it CAN be done, doesn't really mean it Should be done.
Learn sumpin? :mrgreen:


+1

Bruce took a novel design tack but hedged his bets (wisely so IMO) by integrating two separate Class AB stages (each, with its own pair of matched output tubes). It's not as revolutionary as the Stephensons cited by the OP but I believe the Egnator will deliver more consistent and reliable performance than a pair of single disparate jugs.

JMO

Arjay

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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Fri Apr 01, 2011 12:21 pm
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I'll tell you Arjay, my Egnater Rebel 20 is one of the most versatile and unique sounding amps I've had in a long time. Bruce Egnater and his son Ian, answer questions on the Egnater forum section on Rig Talk. The nice thing is, the switches and knobs on his amps are not just bells and whistles, they actually do things. There is no fizz and more fizz channels. And yes the power tubes are matched. When you set the tube mix dial at 12:00 all foru power tubes are cooking and you get a nice volume bump. What's nice is if say an EL84 takes a dump, if you turn the dial back to the 6V6 side you're still in business as long as a fuse wasn't taken out.

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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Sat Apr 02, 2011 5:19 am
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I think the Egnater amps are a very good design. The next amp I get will be one of the Egnaters or a Mesa Lonestar Special. I want an amp with EL84's next. I got the Fender tone covered with my DRRI.

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Post subject: Re: Mismatched power tubes are a GOOD THING?
Posted: Sat Apr 02, 2011 10:06 am
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Thanks for the replies, guys! Now I know more than I did before.


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