Transformer hum

[ranchak]

I'm going to build a new version of the Real McTube. My first build sounds great other than the hum (no kidding!). I am going to use the toroidal transformer that Aron sells and I am going to add a tube compressor. My question is: am I better off placing this transformer in a separate "power supply box"? I know the EH pedals have the transformer located in the same box as the effects unit, but I don't want to deal with the hum.

[bancika]

If you have enough place to make sure that no signal wires go nearby than why not, otherwise I'd put it in separate box. My tube preamp has separate PS unit and it's very quiet.

[ranchak]

I wasn't sure about having the high voltage running through a power cable from the PS to the effect. I saw somebody had done this on a Real McTube and they said that their unit was quiet.

[Processaurus]

Isn't the deal with toroids that they put out less interference?

My EH wiggler has the same toroid in there as aron sells, I believe, it isn't hummy at all.  It is at opposite ends of the box as the input though, and the switching happens with a relay up by the jacks, presumably because it would be noisy to run wires down to the footswitch and back.  If high impedance signals (like the input) had to go by the transformer or ac input, I'd use shielded wire, which isn't that hard to do.

I wouldn't be scared to try putting it in the box, seperate power supplies are a pain, get lost, cords break, get mixed up, take time to set up, clutter the place, are generally uncool. 

[ranchak]

I think I'm going to give it a try. I wonder if one of these transformers can power three tubes? I know it can handle two. I'm going to try to keep the AC at one end of the box and the audio signal and switching at the other end.

[puretube]

I think I'm going to give it a try. I wonder if one of these transformers can power three tubes?

Yes!

[brett]

Hi
I think you will still need to pay a lot of attention to layout, earthing, etc.
The toroid will almost eliminate radiated hum, but won't do anything for earthing problems etc.  These are critical in the McTube because the potential gain is really high.  It is doubtful that it is the transformer alone that is causing the problems in your current design, so maybe you can use it as a test unit for reducing noise in the new one.
cheers

[ranchak]

I haven't messed with this layout in awhile, but I am suspecting that a large amount of the noise is coming from the AC current. I am working on an AC filter design to quiet the incoming AC line. If I have any luck I will post some results. As well any input is also welcome.

[David]

I haven't messed with this layout in awhile, but I am suspecting that a large amount of the noise is coming from the AC current. I am working on an AC filter design to quiet the incoming AC line. If I have any luck I will post some results. As well any input is also welcome.

There's always ye olde bog standard 100R resistor and 1000uF cap across the power rails...

[ranchak]

I was looking at something like this:

http://www.geocities.com/jonrisch/surge.htm

or this:

http://www.10audio.com/diy_power_conditioner.htm