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Each AES / Cary SixPac monoblock has a 12BZ7 input tube but Cary says that the 12AX7 or 12AU7 can also be used.
12AX7 and 12AU7 tubes are easy to find in NOS and several new brands are available. This is not so much the case with the 12BZ7. The 12BZ7 is credited with giving the SixPacs excellent dynamics and drive for more power output and less distortion vs the 6922 that it replaced (in the original prototypes).
Will the 12AX7 or 12AU7 type be a better replacement for the 12BZ7 if I'm looking for excellent dynamics (high gain?) for the SixPacs?
In what ways do the 12AX7 or 12AU7 differ from the 12BZ7?
Thanks, ...Abe
Follow Ups:
The general consensus on 12BZ7s is the early 1960's GE. I just tried a NOS matched pair of Raytheon's circa 1960. Cost me over $75 to win the pair off ebay. Man, they really punch the vocals out front. They are very quick, punchy, and add alot of HF detail. They lift the soundstage, but also make it less deep, as the mids are brought so prominently forward. They are still a suprisingly musical tube... vocals and strings sound great.
I also just picked up a brand new set of the early 60's GE's. After burning them in for 100 hours, they still are my favorite. A little snappier than my 2 year old ones, but not so fast and in your face as the Raytheons.
What power tubes have you tried, and what are your thoughts on them?
Scott T.
Very surprised if that sounded lifeless...
Abe,
The 12BZ7 isn't too hard to find as yet - you had one suggestion from another poster, I have some, and I'm sure others do too.
What is hard to find is a non-microphonic one. Those large plates tend to be microphonic, no question about it. I reject about 25% for microphonics issues.
The low plate resistance and high mu of the 12BZ7 really makes it kind of unique, I'd get a few for spares as they aren't expensive, and I'd use them instead of the subs for as long as I could.
and I would get pairs of different makes and get as early of manufactured as I could find. I preferred the 12BZ7 to my fine smooth plate nos TEles, 1949 RCA 12AX7's and others. I never tried the 12AU7's since, although I have many, I am not crazy about them.
Balanced the 6 Pacs do a very find job, which is how I converted mine. I also totally rewired them and put DC on the heaters vs AC but I like AC as well. I also changed out most of all the resistors for Kiwame and Mills but again, stock the 6 Pacs are fun and a great bang for the buck if they are still around 2400.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
see images at: www.pbase.com/jamato8
FWIW...I had very good results replacing the stock 12BZ7's with some RCA 12BZ7's from Kevin at Upscale Audio. Not too expensive either.
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