hi octane wire gauge

[Marcos - Munky]

I'm building a Hi Octane, bought everything and done the board. But since I don't have too much experience on building tube amps, I don't know the wire gauge I have to use. The ones I have here are thin, something about 0,8mm2 and 1mm2 (wire gauge, without the insulation), so I think they can't be used - well, maybe I can use them for the wirings but heater wirings. What's the recommended wire gauge for tube amps?

[J0K3RX]

16 to 18AWG on the heaters and 20 or 22AWG on the rest... should be fine. The length of each wire, routing and how they intersect is important!

[Marcos - Munky]

Thanks for the info! I will try to find the the wires today. The ones I have are 21 and 19 I think, so I just need the wires for the heaters.

[thermionix]

I'm not familiar with the Hi Octane, the layout, or how many tubes it has...but usually there is enough extra wire coming from the power transformer that you can use your trimmings for heater wire between power tube sockets.  Then 22 AWG is plenty heavy for the preamp tube heaters.

If you're wiring heaters in an amp with two power tubes in push-pull, run the wires "parallel" like pin 2 to pin 2, pin 7 to pin 7 (twisted of course).  This makes the power amp humbucking with respect to heater supply hum.

If you're wiring heaters in an amp with two power tubes in parallel single-ended (not likely), wire them in a cross pattern (pin 2 to pin 7, pin 7 to pin 2) to get the same humbucking effect.

If you're wiring heaters in an amp with four power tubes in push-pull amp, wire the two outside pairs in a cross pattern, then "parallel" between each pair, for a double humbucking effect.

If that makes sense.

[davent]

If i recall, two 12ax7's and a single  EL84 or i suppose 6V6 so not much total heater current.
dave

[Hatredman]

If i recall, two 12ax7's and a single  EL84 or i suppose 6V6 so not much total heater current.
dave

For reference, this one:

http://www.ax84.com/hioctane.html

.

[Marcos - Munky]

The current it's something like 1,5A. Actually, 760mA for the EL84 and 340mA for each 6N2P, which I'm using instead of the 12AX7s.

If you're wiring heaters in an amp with four power tubes in push-pull amp, wire the two outside pairs in a cross pattern, then "parallel" between each pair, for a double humbucking effect.

This will be useful for an 4 power tubes amp I'll rebuild soon. To make the wirings shorter, can I wire tubes 1 and 2 in parallel, tubes 2 and 3 in cross pattern and tubes 3 and 4 in parallel?

[thermionix]

No, that would be maximum hum, no bucking at all.  If you want the shortest wires* go straight across all the sockets (I really shouldn't say "parallel", electronically all these heaters are in parallel, but seems you understand what I meant).  That would be humbucking once over, good enough hum reduction.

= X =    maximum hum
= = =    low hum
X X X    low hum
X = X    minimum low** hum

This is one of those things that was "unlearned" by Fender during the 70's.  Many silverface amps have their power tube heaters wired randomly, and it's worth straightening out if you wind up with one.  I think the 50s and 60s 4-tube Fenders were wired = = = (good enough).

12Ax7 preamp tube heaters are automatically wired humbucking when connected for 6.3v operation.  I'm not familiar with 6N2P tubes.

*Edit:  On second thought, either way you connect them the wires are twisted, so no real difference in wire length.  Number of twists counts for more than which socket pin.

**Edit #2:  Oh jeez, where is my mind.  On THIRD thought...probably no real difference in options 2-4 above.  You would only get "double humbucking" with X = X in certain specific situations.  Probably easiest to just go straight across  for any push-pull power amp.  But you still don't want = X = or something unbalanced.

[PRR]

> Number of twists counts

Point of diminishing returns past about 2 twists per inch.

I see wires twisted like the rubber-band on a model airplane and I cringe. Just make it so, if the wires were black and white, and the tube had poor eyes, it would see "grey" not white or black.

[thermionix]

and the tube had poor eyes

[Marcos - Munky]

Thanks a lot for the lessons!

= = =    low hum

I'll probably go this way.

12Ax7 preamp tube heaters are automatically wired humbucking when connected for 6.3v operation.  I'm not familiar with 6N2P tubes.

6N2Ps are used instead of 12AX7s because they're cheap at least here in Brazil. The heaters are internally wired in parallel, with pins 4 and 5 powered by 6.3V and pin 9 connected to ground.
https://tubedata.altanatubes.com.br/sheets/113/6/6N2P.pdf

[thermionix]

I'm not sure what you'd call the electrode connected to pin 9 (I bet Paul knows).  I guess it provides some shielding between the triodes, from the way it's depicted in the datasheet pinout.

[Marcos - Munky]

I too believe it's some kind of shielding.

[Marcos - Munky]

Just finished it right now. I didn't tested it yet, but here's two pics of it. It was a repurposed chassis, so that's the reason of the extra tube and switch holes.

[thermionix]

Nice!  Those are some big ol' honkin' transformers for a SE EL84!

[Marcos - Munky]

Thanks. Yeah, I thought they're pretty big for a SE EL84 too. The power transformer looks like it haves the same size as Hammond 269EX (the one suggested by AX84). For the output transformer, the guy who made it said it's oversized - and I believe in him . Still thinking on using 3mm green leds under the tubes, as it have a green switch and will have green knobs, but I'm still not sure if I'll do the leds.

Last question before I plug it, I don't have any 1A slo-blo fuse. Does a regular fuse do the job, or it's better wait until I find a slo-blo one?

[thermionix]

A "fast-acting" fuse should be fine, I guess it offers just a hair more protection than the slo-blo, but at 1A shouldn't blow under normal operation.  What is the mains voltage in Brazil?

[Marcos - Munky]

Some regions (like mine) uses mainly 127V for almost everything but air conditioners , showers and other high consumption electrics, those are powered by 220V. Other regions uses 220V for everything.

I'll try the fast-acting fuse this weekend.

[thermionix]

Remind me to never take a shower in Brazil!

[PRR]

> never take a shower in Brazil!

That seems odd to US folks.

In England they have point-of-use water heaters, one on the shower. I assume this is like he has.
https://www.tritonshowers.co.uk/electric-showers/t80z-fast-fit-electric-shower.html

It says an RCD (GFI) is required.


There's not a huge difference between that and my 240V water heater in the cellar. Until recently, the hot water pipes were copper, great conductors. (Now plastic in my place, but copper is still common.)