Twisting heater wires

[drz400]

Do you think it matters if all the heater wires go to the same pins?
For instance is it better to alternate? like 9 goes to 4&5 of the next tube, then go to 9, I'm just thing about wire length and wondering if it would give the best balance to alternate. Also anyone else like floating heaters to a positive DC voltage?

[Bob-I]

Do you think it matters if all the heater wires go to the same pins?
For instance is it better to alternate? like 9 goes to 4&5 of the next tube, then go to 9, I'm just thing about wire length and wondering if it would give the best balance to alternate. Also anyone else like floating heaters to a positive DC voltage?

I've tried both ways and can't hear a difference. Remember that for a dual triode you have 2 gain stages, and the signal inverts with each one, so any hum should be canceled out. On the output tubes it's important to NOT reverse the heaters as they'll be opposite phase. The excepetion is on a 4 tube amp, the pairs on the same side should be reversed.

All that said, I still can't hear a difference. Routing seems to matter more than phase.

[drz400]

Do you think it matters if all the heater wires go to the same pins?
For instance is it better to alternate? like 9 goes to 4&5 of the next tube, then go to 9, I'm just thing about wire length and wondering if it would give the best balance to alternate. Also anyone else like floating heaters to a positive DC voltage?

I've tried both ways and can't hear a difference. Remember that for a dual triode you have 2 gain stages, and the signal inverts with each one, so any hum should be canceled out. On the output tubes it's important to NOT reverse the heaters as they'll be opposite phase. The excepetion is on a 4 tube amp, the pairs on the same side should be reversed.

All that said, I still can't hear a difference. Routing seems to matter more than phase.

That is interesting, No major manufacturer does that do they?
Ever tried raising the CT of the heater to like 80DC? I find that really helps as long as the ground path is great and follws a nice star ground for each stage then to buss and ground one place at the chassis. If the ground path is flaky then it can make things worse. My favoriet for hi gain is DC heaters but they can be a pain

[Bob-I]

That is interesting, No major manufacturer does that do they?

I couldn't say, but amps I've worked on don't, which includes Soldano. They're very quite and very high gain.

Ever tried raising the CT of the heater to like 80DC? I find that really helps as long as the ground path is great and follws a nice star ground for each stage then to buss and ground one place at the chassis. If the ground path is flaky then it can make things worse. My favoriet for hi gain is DC heaters but they can be a pain

Not that high. I'll do the 100ohm fake CT trick if there's no CT but I prefer a simple CT secondary.

[drz400]

That is interesting, No major manufacturer does that do they?

I couldn't say, but amps I've worked on don't, which includes Soldano. They're very quite and very high gain.

Ever tried raising the CT of the heater to like 80DC? I find that really helps as long as the ground path is great and follws a nice star ground for each stage then to buss and ground one place at the chassis. If the ground path is flaky then it can make things worse. My favoriet for hi gain is DC heaters but they can be a pain

Not that high. I'll do the 100ohm fake CT trick if there's no CT but I prefer a simple CT secondary.

Wow I thought the SLO's I have worked on were very noisey especially in ground path loop and heater hum. In fact I did float the CT of the heater on one of those and twisted the heater wires, it helped BIG time! I really hate noise

And what is with the single sided board for such an expensive amp? that makes it such a pain to work on

[ElectronAvalanche]

Hi Drz,

concerning your question:

I tried it myself and I DO hear more noise when I do not follow the rule of 4,5 to 4,5 and 9 to 9.

YMMV.

On another note:

Since you worked on some real SLOs, can you describe the amount of hum a bit more in detail? Is it 60Hz or 120Hz? How bad is it? Does the Crunch/Clean show as much hum as the OD?

Cheers,

Dominik

[drz400]

Hi Drz,
Since you worked on some real SLOs, can you describe the amount of hum a bit more in detail? Is it 60Hz or 120Hz? How bad is it? Does the Crunch/Clean show as much hum as the OD?

Cheers,

Dominik

Heater hum/buzz is number 1, the heaters are not twisted at all. Also the preamp tubes are close to the pots, not sure if that is the best placement.
I didnt measure if it was 60 or 120 but it is unacceptable to me, there are hums and buzz that could be better. I even hear issues when the gains are down and the Masters up which shouldnt be there and I believe is ground path. The ground path is based on different points on the chassis, something I dont believe in, I feel you need to control your ground and not on the chassis when dealing with high gain, keep local paths grounded together as a star and run to a main buss, ground at one place on the chassis (except for the AC 3rd pin ground which should be away from audio ground, on the SLO they are tied together) input is good to eliminate RF, this would require surgery in the SLO. But if you twist the heater wires at least on the preamp tubes, float the heater CT to a positive DC voltage like 75VDC it can be quite acceptable with the correct choice of preamp tubes. I just think it could have been a quieter amp for that kind of money. I happen to be a big fan of regulated DC heaters, with that you are not choosing preamp tubes for the sake of hum but for tone, Combine that with a proper ground path and you can have a dead silent amp at any volume excluding normal hiss from gain of course. Most of this knowledge of this I have to give credit to Kevin O'Connor and his books along with Randall Aiken, but it sure works!

Why making a clone? if so choose a better loop also