herf
Junior Member
Posts: 80
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Post by herf on Sept 5, 2007 3:13:27 GMT -7
So which tubes do you all like to use in the PI position for the R66?
I was considering a 5751.
There are lots of discussions about the rectifier, power tubes and EF86's, but little discussion of the PI tube. Does it have less effect on tone in the R66 than in most other amps?
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Post by dixiechicken on Sept 5, 2007 3:29:13 GMT -7
Mja.. I don't know about less effect in "66" compared to other amps. I get the feeling that the PI-tube has less effect on sound compared to other tubes, rather. ( you should really check this with Myles and Doc himself - they are probably two of the most knowlwdgeable guys on this subject )But the PI-tube should definitely be balanced - i.e. the two triod halves in the PI-tube must preferraby track the same. (same idle current, same transconductance, same plate dissipation & etc etc. ) If this is NOT the case the PI-tube will drive powertubes in an unbalanced fashion , this will at least to some extent ( perhaps big extent ) ruin what your trying to accomplish by matching the powertubes. End result will be - your amp doesn't sound so good. BTW this is what Mike at KCA NOS said: www.kcanostubes.com/categories/57/1/GE.htmThese ones he can balance for you: www.kcanostubes.com/products/36/NOS-GE-12AX7-ECC83.htmCheers: Dixiechicken
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Post by zdogma on Sept 5, 2007 3:45:13 GMT -7
I'm using a balanced 12AX7 LPS. Nice PI tube. I've tried the 5751 as well, slightly less gain/more headroom and a bit less midrange with that one.
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Post by jwr on Sept 5, 2007 23:59:04 GMT -7
Another vote for the Sovtek 12AX7LPS. Tried a GT 12AX7M and didn't like it as much, mellowed out the amp too much for my taste. I want my 66 to be as aggressive as possible and the LPS seems to really make the amp bark. I like that tube as a PI in all my amps except for my Carr.
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