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Old 7th August 2009, 06:35 PM   #1
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Default tubelab simple se 6.3v close to output

I know this is a very successful amp, but I have a question about the circuit board and what if anything should be done about the proximity of the 6.3 v winding to the speaker/output wires going to the circuit board.
Is it recommended to use shielded wire or anything for the speaker/output connections?
Thanks,
Paul
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Old 7th August 2009, 09:08 PM   #2
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Default Re: tubelab simple se 6.3v close to output

Quote:
Originally posted by pforeman
...what if anything should be done about the proximity of the 6.3 v winding to the speaker/output wires going to the circuit board. Is it recommended to use shielded wire or anything for the speaker/output connections?
Simply twisting the leads of the AC wiring will be perfectly adequate. There is no need for shielded wiring. If your output transformer already has leads attached to the secondary, they should be sufficient to make the connection to the speaker binding posts. If the leads are too short or the output transformer does not have leads, I would use any decent quality hookup wire (18~20 gauge). I have some silver plated, teflon jacketed stuff that strips easily and solders well. Look for something with 600V insulation rating if you plan to use it on the primary side of the OT.

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Old 7th August 2009, 09:13 PM   #3
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I remember raising an eyebrow when I saw that as well. However if you think about it, most of the current from the 6.3V winding is going to the output tube heaters. Only a small amount travels to the input/driver tube. So by locating the inlet for that supply as close to the output tubes as possible it decreases the length of the traces between them and possibility that 60Hz will be induced into other parts of the circuit.
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Old 8th August 2009, 12:50 AM   #4
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The 6.3 volt filament windings carry a great deal of current. They should indeed be lightly twisted and kept away from sensitive wiring. The speaker wires and OPT primary wires are just not that sensitive. The secondary leads are operating at a very low impedance (8 ohms) even if there was 100 pF of capacitance (a lot) between the green wires and the hot speaker lead, the coupling would be microvolts. The OPT primary leads operate with hundreds of volts of signal. A few millivolts of coupling here would be stepped down to microvolts by the OPT.

You must keep all of the power transformer wires away from the input wiring. This is why they are on opposite ends of the board and typically routed off in opposite directions.

The routing of the traces on the board is optimized to keep the high currents somewhat balanced with respect to the input to afford some hum cancellation. This is why the connection is in the middle of the rear of the board.

The Tubelab SE has no AC in the signal area of the PC board, and the Simple P-P uses a similar layout to the Simple SE. The 6.3 volt wiring is in the middle on the back.
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