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In a Fisher 400 which is gain 12ax7 and which is tone?

R

robster

New Member
Which 12ax7 is the gain tube and which 12ax7 is the tone tube position?, in a Fisher 400?
If facing the Fisher 400 tube receiver from the front looking over the dial glass is the tone 12ax7 on the left and gain on the right? I don't have a manual and I'm trying to decide which 2-positions to put my 2-Raytheon 5751 windmill getters in.

Many thanks,
Robert
 
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I tried putting 5751s in my Fisher 400. For me, they only worked when the were put in the two front sockets. These are the tone and voltage sockets. They didn't work in the two sockets by the transformers which are for the driver/inverter. I have the manual in .pdf format. PM me and I'll send it to u.
 
Here is a copy of the tube placement for the Fisher 400

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hi, sorry to be bumping up an old thread but i have a further question on the diagram- what's the function of audio amp section on the drawing? v100,101,102 tubes- are they also part of preamp including v10? and which 12ax7 do you think would impact the sound most by rolling if the amp's being used for line out?
 
V100,101,102 are the Multiplexer for the FM. Put a 12AT7 in the V100. For some reason it works better that way.

V11,12,13 would be the ones to roll for the amp. V10 is the Voltage amplifier for the Audio amps. Leave the 12Ax7 in there. Rolling that one doesn't do anything, Except if you roll a strong one in there in place of a weak one, then the voltage is more stable.

V8-9 are for the Phono and Tape Head section. Unless you are using them a lot and don't care for the sound leave them.

Larry
 
thanks larry, good to know. I swapped out v10 for v101 just then. v10 was a no mark but presumably telefunken and v101 a sure mullard. the surprise was that when the mullard went into v10 slot, the sound became oversaturated and grainy. i took them out after 20 min and put the mullard in v11 instead. well, that's a quite an improvement. i definitely get that mullard lushness without any significant impact on fidelity. but the mullard's gotta come out once again. i think i like the darkness of telefunks the best in this amp.
 
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Has this amp been recapped? The term "oversaturated" makes me think that there might be bias problems on the preamp tubes (which would most likely be caused by leaky coupling caps) or insufficient heater voltage to the preamp tubes (which would be caused by bad caps or rectifier in the bias supply)...

Just saying... if it hasn't been done, it's probably time...

Regards,
Gordon.
 
no it has not. i know i should take it to a techie but i'm just too busy loving every minute of the sound! :D good news is, it came with a silicone rectifier.

my only gripe with the amp is that it's not really doing that 3d imaging. i get a decent soundstage but nothing holographic. is that to be expected from this model or is there something i could tweak to improve that?
 
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I haven't found the 400 to be sensitive to the fancy triple mica 5751s in the tone and voltage sections the way the 500 (any) or 800 (any) or integrateds are in comparable positions.

Let's put it this way: They're not better enough to justify buying them at a premium price to put in these positions in a 400. But if you own them, try 'em.
Let us know.
 
Wow, this is an oldie!

This thread was originally started long before the Fisher Forum existed, so we can now move it.
 
maransansui said:
no it has not. i know i should take it to a techie but i'm just too busy loving every minute of the sound! :D good news is, it came with a silicone rectifier.
Click to expand...

More can go wrong than that bridge.
Buy yourself some insurance and at least put in cathode resistors.
 
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