Question about potential transformer placement in K-12 Kit

[Maxwell Smart]

Hi all,

So I have built my enclosure, and I have realized that I'm not going to be able to mount the transformers on the underside of a metal top peice as I previously thought because they are too heavy. Instead, I have decided to mount them to the interior of the wood. Before I put it together though, I want to make sure this is an acceptable placement in terms of potential audio interference. I have provided a picture for reference, thanks so much for your help!

An externally hosted image should be here but it was not working when we last tested it.

 

[Soonerorlater]

Advice I've seen so far is that the two output transformers are in line and the power transformer is at right-angles to them. In your case it looks like you intend to extend the wires from your transformers so that they are further apart than normal which should help.

 

[Soonerorlater]

This might be worth a read S5 Electronics K-12M Tube Amp

 

[mctavish]

Your layout looks fine, plenty of distance between the power and output transformers. Whenever possible it is best to have the two cores of the output transformers parallel like you have in the picture, as the flux is weakest in this orientation and there is less of a chance of interaction. One note, make SURE that the frames of the transformers are connected to earth ground when using a chassis of wood. This will insure safety in case of a short in the transformers. HTH

 

[Soonerorlater]

Here's some more articles that might wet you appetite 😀


S-5 Electronics K-8, K-12 K-16 and K-502 DIY Tube Amplifier Kits

 

[Maxwell Smart]

Hah funny you mention it as I have already read over both of those links. I can't thank you both more, I just wanted to confirm that this layout would be adequate based upon what I had read about transformer placement.

 

[Soonerorlater]

I just wanted to confirm that this layout would be adequate

Can't think of anything else to add to what mctavish has said except to make sure you have adequate ventillation for your power supplies transformer.

p.s. When building my K502 I forgot to earth my output transformer frames 😱 and it caused a bit of oscillation in the amp, easy fixed, I later replaced them with Hammond 1609's and had to scrape the black paint off the lugs to get a good earth contact.

Brgds Bill

 

[Maxwell Smart]

So just to be clear, what I will now do is, as I am using a standard computer power supply cable, tap each of the 3 transformers bases into the mains ground. Is there any where else I need to ground to be safe or will this be sufficient? Thanks.

 

[mctavish]

You also want to be sure that the boards ground plane and especially the metal housing around the volume pot are grounded to avoid annoying hummmmm.

 

[Soonerorlater]

You mentioned a metal top piece, this or anything else conductive you might touch I would ground.

Brgds Bill

 

[Maxwell Smart]

Very interesting and good to know, thanks again guys, this amplifier if coming along really nicely, I'll have to post a short writeup and pics when I'm done.