Hi all,
I recently bought an audio innovations 300 amp:
http://www.drtube.com/img/icon-gif.gif
The amp is push-pull 10W with phono stage thats switchable between MM and MC.
7 tubes in this thing, 4 ECL86, 2 ecc83 (12AX7) plus one other that has absolutely no markings on it. It looks like a 12AX7, but the internal structure at the bottom of the tube looks a bit different to the other 2 12AX7s .... could this just be maunfacturing differences? The tube is the same size and shape as the 12AX7 with the same number of pins.
Theres so little about this amp out there, that I though I might ask here first about the mystery tube!
Many thanks in advacne for any help that anyone can give,
Fran
I recently bought an audio innovations 300 amp:
http://www.drtube.com/img/icon-gif.gif
The amp is push-pull 10W with phono stage thats switchable between MM and MC.
7 tubes in this thing, 4 ECL86, 2 ecc83 (12AX7) plus one other that has absolutely no markings on it. It looks like a 12AX7, but the internal structure at the bottom of the tube looks a bit different to the other 2 12AX7s .... could this just be maunfacturing differences? The tube is the same size and shape as the 12AX7 with the same number of pins.
Theres so little about this amp out there, that I though I might ask here first about the mystery tube!
Many thanks in advacne for any help that anyone can give,
Fran
The 6EU7 is basically a 12AX7 with a different pinout. Do pins 1 and 2 look like they are for the heater?
Is this the schematic you were trying to link to?
http://www.drtube.com/schematics/ai/ai300mk2.gif
Is this the schematic you were trying to link to?
http://www.drtube.com/schematics/ai/ai300mk2.gif
woodturner-fran said:
No. A far better method would be to look into the valve and identify which pins are which. The anode is the big outer structure, the heaters are the white wires coming out of the centre. The cathode is the (often cylindrical) sleeve surrounding the heaters, and the grid surrounds the cathode. When you know the pin-out it becomes easier to trace the circuit around the unknown valve. The component values and working voltage will give a clue as to what the valve is.
Frankly, in an amplifier of that era, it's likely to be an ECC83/12AX7.
Yep,
as far as I can tell thats the schematic.... However, if you look at the schematic there are 4 ecl 86 - OK, I understand that the schematic shown uses "half" and ecl86 and that only one channel is shown. Then there is the ecc 82 - this is for one channel and there would be another ecc82 for the other (in mine these are the ecc83) - this would be the preamp section. What isn't shown in that schematic is the 7th tube that I have and must really be for the phono stage?
Another clue is that the ecl86 are mullard, which means they were replaced at one time, but the ecc83s are "precisa" - which were the tubes supplied originally in this amp, but the last mystery tube has no label so must have been replaced at one stage.
Will take a few photos and post them here, maybe that would give a better idea.
Can I just say thanks for all your efforts so far!
Fran
as far as I can tell thats the schematic.... However, if you look at the schematic there are 4 ecl 86 - OK, I understand that the schematic shown uses "half" and ecl86 and that only one channel is shown. Then there is the ecc 82 - this is for one channel and there would be another ecc82 for the other (in mine these are the ecc83) - this would be the preamp section. What isn't shown in that schematic is the 7th tube that I have and must really be for the phono stage?
Another clue is that the ecl86 are mullard, which means they were replaced at one time, but the ecc83s are "precisa" - which were the tubes supplied originally in this amp, but the last mystery tube has no label so must have been replaced at one stage.
Will take a few photos and post them here, maybe that would give a better idea.
Can I just say thanks for all your efforts so far!
Fran
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