Can two Audio Transformers be TOO close together on a PCB????

[KMS]

I am designing a PCB for R.G. Keen's A/B/Y Transformer Isolated Splitter and I need to make the PCB as small as possible.

Does anyone know if the inductance from one T018 will affect the audio signal of the other transformer if they were mounted about 1/16 of an inch apart?

[KMS]

OK, I'll answer that question.  YESSSSSSSSSS! The transformers can be TOO close.

[R.G.]

... however, since the same signal is in both of these transformers, at the same level, and all they're being used for is ground isolation, you can put these two as close as you like.

It's a very special case. In general, yes, both spacing and orientation matter a lot.

[KORGULL]

I would really like to know more component spacing and orientation do's/don'ts when laying out a board...
Anyone have any more advice or articles you feel like sharing?

[Paul Perry (Frostwave)]

As a general rule, transformers at right angles to each other will have minimum coupling. (that is to say, both sit with their centres on a line, but one is parallel to the line and the other is at right angles to it). But the best advice, in my view, is to not use them! unless there is no way out.

[brett]

Paul's advice, as usual, is very good.  It is especially important to have power transformers at right angles (preferably *both* horizontally and vertically) to any audio transformers (as in valve amps).  Otherwise, it is very difficult to totally remove hummmmm.
cheers

[KMS]

In reply to R.G.

I understand that when the signal is the same in each transformer there will be no problem (1:1 ratio, both  transformers identical, each same impedance for primary and secondary) but when A is on and B is off I was worried that I could get some A filtering into B (or vise verse).  Kind of like my guitar string making a signal through my pickup.  I could just leave A and B on all the time (maybe) and set my chains up with clean sound when the FX for each chain are off.  However it would be nice to have the capability to switch from one amp to another (not the reason why I'm building the splitter though) and the idea of using one chain with no clean sound is something I do want.

Also, my plan (we discussed prior) is to eventually build a board with many transformers on it (all T018(s)) so there will be a rather large field of inductance ( I think)  and I guess I could plan to place this board in a steel box inside my big master stomp that I had custom built so the inductance inside the main box is reduced.

I have all the parts (sprinkled around my keyboard as I write) for the Transformer Isolated 1999 version GEO A/B/Y but I could only get TL072 (my supplier does not carry LM833). I realize the impedance is lower for the TL072 and I'm hoping that won't kill my treble too much.   I like the circuit for the updated version better, but I'm not sure how to set up a "Y" direct output.  I saw that some time back one DYIer put 5 "B" portions of your 2005 updated circuit all supplied by the first 1/2 TL072. 

I have also bought the parts for the +9V/-9V power supply for the 2005 updated version and I will just use a toggle for on/off. I don't like the power on/off with the jack and I'm not sure why anyone would like that except that it is cheap switch.

I have new board design (not like GGG) but that is because I forgot about GGG's GEO A/B/Y PCB before I designed mine, and then last night I found it again. In the end, I'll need my own anyway because it will reduce the space needed for the splitter.

I guess I just need to hook this stuff up and try it.  Problem is that my amps are 5 miles away (at our barn studio) and whatever I do here at home I have to wait and test it on the amps at some later date. This has been a real pain for experimentation purposes, but my wife is happy that the amps are not here.

R.G. your site is terrific and I can't believe all you have done for the DIYers.  Anything you can do fro me to reduce the time I spend making mistakes I would greatly appreciate (I know you can't talk my wife into letting me bring the amps home).  In fact, I'll let my PCB out for all to enjoy if I can get it working right.

My PCB is drawn using the Microsoft Word drawing tool bar, and I'm not sure how to set it up for everyone to view.  I have a few last minute changes (to the transformer part of the layout) but other than that it is finished. It is about 2.5" x 2.5" and the only thing that I like better about GGGs PCB is that he has all the hook leads on one side, mine are all on the outside edge on all four sides.


To Paul and brett:

Now that you mention it, I have noticed many circuits where the transformers are 90 degree to each other, but I have never seen the vertical 90 degree orientation (I also do not have any valve amps).

I have a Kustom 200 4 channel 100watt RMS @ 8ohm, and Peavey PA 900 9 Channel Module 800 450watt @2ohm RMS.  Both are very old so as you can imagine I've been all through he boards replacing capacitors. I like the 90 degree horizontal angle idea, and will probably lay it out like that.  The vertical angle sounds like too much work due to the complexity it would add to building it (especially with 5 or six transformers) unless brett or someone else has any ideas (tricks) for the build.