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Old 18th June 2004, 05:59 PM   #1
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Default 12ax7 > 6sn7 > 300b

Hi,

I am just a newbie in DIY and need help.

I got a DIY set of 300B SE integrated amp.

The circuit design is

Volumn > 12AX7 > 6SN7 > 300B (SE) > Output Transformer

On the manual just mention the 6SN7 should be connect in parallel to push the 300B, but how about the 12AX7?

Do I need to use both triodes in the 12AX7 together to push the 6SN7 (connected in parallel for both triode), or just use one single triode in the 12AX7 tube and leave another triode un-connected?

Thank you for your help before hand.

Tuna Fish
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Old 18th June 2004, 08:35 PM   #2
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What do you need so much gain for, phono? 20dB NFB? Usually, the two 6SN7 triodes are cascaded. No need for any additional drive, a 6SN7 alone is fine.

Tim
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Old 21st June 2004, 09:52 AM   #3
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It is a DIY Parts Set.

The circuit is 12AX7 > 6SN7 (two triode in parallel) > 300B SE.

The parts set and the chasis got two 12AX7, but the circuit diagram does not mention is using one single side of the 12AX7 or connect both triode in parallel.

Any one can help??

Thank you in advance.
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Old 21st June 2004, 12:09 PM   #4
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Hi,

Quote:
but the circuit diagram does not mention is using one single side of the 12AX7 or connect both triode in parallel.
Can you tell us the anode and cathode resistor values for the 12AX7?

Cheers,
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Old 21st June 2004, 05:43 PM   #5
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Quote:
Originally posted by TunaFish
It is a DIY Parts Set.

The circuit is 12AX7 > 6SN7 (two triode in parallel) > 300B SE.

The parts set and the chasis got two 12AX7, but the circuit diagram does not mention is using one single side of the 12AX7 or connect both triode in parallel.

Any one can help??

Thank you in advance.

If it's stereo and doesn't have any additional preamp type stuff, they'd have to be in parallel. As Frank sez, what value are the grid, cathode, plate resistors?

Tim
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