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Post by mahons on Aug 14, 2008 7:34:28 GMT -7
I know almost nothing about amp design/electronics, but I was just wondering...
Is it possible to build an amp with two different power sections?
What I mean is, could you have one channel running 6L6s and another channel running EL34s and switch between the two with a foot switch, etc.?
I would be pretty cool to combine amps that share the same preamp (z28 kt45 rt66 delta 88). It's probably not very practical (if even possible) and the tone would probably be better if you just bought the two amps separately, but I was just wondering it it is possible electronically.
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Post by benttop (Steve) on Aug 14, 2008 8:40:51 GMT -7
It's possible, but there are a lot of tradeoffs. One is weight, another is cost. Mesa Boogie did an amp like that a while back - Roadstar or some such. That thing had more tubes, knobs, switches and jacks than any amp I've ever seen. And it weighed about the same as a '59 Cadillac.
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Post by mahons on Aug 14, 2008 14:44:23 GMT -7
Thanks for the reply Benttop. I guess 2x the power section would mean 2x the transformers (maybe?), so it surely would be a weighty contraption. Cool to know that it is in fact possible thoough. I guess we'll just have to buy two amps instead (yay! An excuse to buy more amps!)
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Post by JumpMarine on Aug 17, 2008 21:22:45 GMT -7
The Divided by 13 JRT 9/15 is just that, 2x6v6 and 2xel84.
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Post by Phil (aka Phil) on Aug 18, 2008 16:33:13 GMT -7
Well, first- there's more differences in the 28/45/66/88 than just the power tubes. There are differences in the preamp circuits, phase inverters and most importantly the power supply sections of those amps. Also the 66 and 88 run ultralinear where the 45 and 28 do not.
I had an EL84/6V6 amp about 12 years ago that I ordered unseen and unheard and thought was going to be the holy grail for me- the Mesa Boogie Blue Angel. That is, until I played it for a while. It never seemed "right" to me. That was back when I was learning more and more about amps and started building my own.
When I started looking at the BA from an engineering point of view it was pretty obvious that some "compromises" had been made in the design to get the four EL84 and two 6V6's to play nice together and share an output transformer while being able to switch between each set or combine both. I think the bigger problem with the BA was probably that the bias with the stock Mesa tubes was pretty cold though, and the fact that Mesa used all Sovteks back then. I retubed it with some nicer tubes selected to be on the "hot" end of things but it didn't help much. When I got my Ghia a couple of years later (1998) it blew the BA's EL84 voice away and a few years later I got a Z28 and that was an even bigger murdering of the BA's 6V6 section. It also had that '90s Mesa midrange emphasis that you couldn't dial out and no bass response even though it was a 4X10. I sold it to a friend who loved it at first but later got a beautiful MAZ 38 hardwood front 2X12 combo. He'd be the first to say that the MAZ is 100x the amp the BA is (apples to oranges, but I'm jest sayin').
I haven't played the /13 or the Kendrick.
The Kendrick is a dual single ended design (like the THD Bivalve) not a dual push/pull amp. That's a lot easier to do.
The /13 guys know what they're doing; I'll bet that amp sounds great. Also, I don't believe the /13 can do both EL84 and 6V6 at the same time like Mesa tried to do.
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