resistors to ground at outputs

[Larpy]

I've got what I suspect is a silly question and a serious question about the 60.4 ohm resistors that tie the signal and ground signal at the output of the Kaiju to ground.

Silly question: does it matter is the resistor is 1/8 watt (spec) or 1/4 watt?  I broke the lead of the one of the resistors at the body of the resistor and the only replacements I could find on Digikey were 1/4 watt.

Serious question:  what is the function of these resistors?  I can understand the signal output needing a reference to ground, but why the ground output as well?  Is this a parallel feed issue?  And why 60.4 ohms?  That's suggests a value that was calculated precisely.  Why does it need to be so precise?

[Paul Birkeland]

The resistor power isn't particularly important. Technically if you ran the amp at full power you would dissipate 1/4W across each resistor and eventually you could fry them.  In practice it's difficult to run the amp that close to clipping for much time.

These resistors provide the secondary of the output transformer with a ground reference.  Having the set of four makes the output a balanced output.  Another option is to just run a wire from each speaker - binding post to the chassis solder tab by the IEC power entry module, then use none of the 60.4 ohm resistors.

[Chris65]

Hi Paul, could explain the technical aspects a little more. The reasons for doing this & how the resistor value is determined?
Thanks.

[Paul Birkeland]

The reasons for doing this

If there is a short between primary and secondary of the output transformer, you'd like the fuse to blow.  It won't blow if it's floating.

how the resistor value is determined?

It's not really crucial. If you use a value that's too low, it will load down the circuit.  You could use anything between about 50 ohms and a couple hundred ohms and they will do the job.