6at6

[Andy Le Blanc]

I had a fender harvard go across my bench yesterday.....model 5f10.....the cabinet was in tuff shape but was electrically mint.... second owner .....all original.....1961 or 62...... blow speaker....cant win em all....... it had a 6at6 as a pre.... good sounding before breakup then it gets nasty like a princeton can.....any way.... have any of you any practical experience with this tube... its half a 6sl7 in a 7-pin mini .....they are cheap and plentiful.... thanks

[David Root]

Some years ago I built a tweed Harvard using all 7-pin tubes, just to prove they do sound good.

I put a 6AT6 in V1, and a pair of 6AV6s replacing the 12AX7 in Fender's design. It does the same thing as the original, clean to nice distortion with a Strat, but crank a Les Paul on it and it dissolves into massive mushy overload. And with a Mercury Magnetics OT to boot, no control even there.

So I put a 6BF6 (mu=20) in V1 and turned it into a very nice '50s blues machine with a Strat, but still a monster with the LP, but contrllable this time.

So you can tube roll with this circuit till yer git what yer wants!

BTW the other tubes are a pair of 6X4s in parallel and two RCA 6AQ5s. I can retube it with all NOS RCA for $35!

[Andy Le Blanc]

great thank you.....for some reason it seems like my world rest on 8 or 9 pins and I havent had a lot of bench time with 7 pin minies.....that 6BF6 look interesting.....it has a transconductance thats lower than 12AU7 or 12BH7A and a usable gain.... could be fun to try a phono pre with that one.... pairing the 6X4 like like that brings the effective plate supply impedance down to the range of a 5u4...... affordable and good sounding....

[David Root]

I have been a believer in paralleling tube rectifiers since I first saw the schematic for the 5E8A Twin! Low impedance power supplies have the edge.

[Andy Le Blanc]

one configuration I've been wanting to try is a bridge rectifier hybrid with a tube rec. in the positive legs.... and fast recovery diodes on the neg..... supposed sonic benifits make it worth while..... tube sound with more juice ....Graetz bridge....I think..... the description of the thing uses a much smaller value cap as first filter stage than one would assume...... fun stuff

[martin manning]

Note the Fender 5F10 schematic (F-EF) shows 6AT6 (mu=70, gm=1.2, ra=58k), but I understand later amps were equipped with a 6AV6 (mu=100, gm=1.6, ra=62k5; half a 12AX7) in V1. 6SL7 is mu=70, gm=1.6, ra=44k, so sort of a hybrid of the two with low ra.

[printer2]

Did my own version of the Harvard with a 12AX7, pair of 12AQ5's and swapped between the 12AT6 and the 12AV6. Bought more of the AT and AV tubes and will probably make one again, great tubes. As cheap as they are the 12V versions are cheaper, the 12V is not a problem if you are creative.