Heater socket wiring consistency

[sonicmojo]

A while ago I watched the Gerald Weber video on amp maintenance and he made a point of heater wiring being consistent and not reversed. For example, that all the leads to 2 and 7 go to the exact same 2 and 7 on the Power tube (or 4/5 and 9 for the preamp tube) socket points consistently in a Bandmaster/Twin circuit. I went through the trouble of getting this right on one '68 amp and now have another '76 that appears to have random wiring. Is there a difference you have noticed in performance on keeping these consistent? Is it worth the effort to fix? Just wondering if anyone has actually noticed a performance difference since it appears that the old Fender techs didn't seem to care.

[sliberty]

I can't answer whether or not it matters, but I can tell you how I keep them consistant without an "extra effort". I use two colors for the heater wires. Then it is simple as pie to make sure that you are consistent in the wire/pin connections.

[Phil_S]

I don't know if it is important or not. I think this is one of those things that is nice to do, but not essential. My logic is this. If it was so important to do this, you wouldn't mix pentodes and triodes on the same filament circuit. After all, a 12AX7 and 6V6 are so different, how do you know how to handle the transition? IMO, the whole idea collapses right there. I'd like to see some well documented scientific evidence explaining why it's important, and then I'll be ready to change my tune.

[rp]

I built 3 amps before I knew it mattered, they were hum free, but also ptp. I went back after I learned it 'mattered' and fixed it (big PITA). I heard no improvement, but these were all already quite.

If you have an amp that's hum free with wires crossed don't bother changing it unless it bugs you. If a new build why not just do it as recommended? Then if you do get some hum you can eliminate mixed up heater wiring as an issue and proceed looking elsewhere.

IME do your heaters diligently and test right afterwards for continuity and shorts, as the wiring is the first in and usually under everything else you want to avoid ever going back in to address it.

[ToneMerc]

I agree with all of the the above.

TM

[tubeswell]

On PP amps I wire the output socket filaments on each side of the OT primary in 'reverse' to each other, because the filaments in the 6V octals are not the balanced 'hum canceling' type. This cancels any hum (which might otherwise be present at the plates because of unbalanced filaments) in each side of the OT primary.

But I have tried it both types of ways and it would be fair to say that I have found only a small difference in hum-canceling from doing this, and I attribute that to being because the amount of gain at the output stage relative to noise-floor, is not as much as it is in (say) the V1 stage for example. However, even a small extra amount of hum canceling can help.