Hi,
while looking for schematics for my High power twin build, I found two versions: 5f8 and 5f8a. They mainly differ in the grid stoppers (5f8 has 1k5 for each of the 4 6L6's, while 5f8a only uses 1k5's for one of the pairs, while the other pair is left w/o any resistor), and screen resistors (5f8 has 100R, while 5f8a has 470R).
5f8 schem:
http://ampwares.com/schematics/twin_5f8.pdf
5f8a schem:
http://ampwares.com/schematics/twin_5f8a.pdf
Apparently most Fenders from that era do not use grid stoppers (e.g. Bassman). I would like to add the grid stoppers to improve the stability of the circuit.
Bassman schem:
http://ampwares.com/schematics/bassman_5f6.pdf
The question is: do you guys have any personal experience with these amps oscillating? Would the 1k5 have major impact on the sound?
Thanks
Fender High Power Twin (5f8a) grid stoppers
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Re: Fender High Power Twin (5f8a) grid stoppers
1k5 might remove some 100.000hz
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Super 100 amps: 1202-119 & 1202-84
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Super 100 amps: 1202-119 & 1202-84
JTM45 RS OT JTM50 JMP50 1959/2203/34/39
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Re: Fender High Power Twin (5f8a) grid stoppers
Yeah, the question is, why has fender used grid stoppers for only one of the pairs... Cost?
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Re: Fender High Power Twin (5f8a) grid stoppers
sloppiness perhaps?
http://www.myspace.com/20bonesband" onclick="window.open(this.href);return false;
http://www.myspace.com/prostitutes" onclick="window.open(this.href);return false;
Super 100 amps: 1202-119 & 1202-84
JTM45 RS OT JTM50 JMP50 1959/2203/34/39
http://www.myspace.com/prostitutes" onclick="window.open(this.href);return false;
Super 100 amps: 1202-119 & 1202-84
JTM45 RS OT JTM50 JMP50 1959/2203/34/39
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Re: Fender High Power Twin (5f8a) grid stoppers
My 5F8A copy had uncontrollable feedback at any volume setting over 9 with the 1K5 on each pair. I installed 5K6 on each tube sounds great now.