[Berndt]

I want to build a custom case for a pre amp kit and would like to go above and beyond the existing design.
I want to build a mapletree linestage, as I like my current mapletree quite well.
I am a prototype machinist and have access to an interesting assortment of canvas base 3/8" phenolic sheet, most types of aluminum, and some very pretty mohagany.
I was thinking of doing a one box solution (instead of Dr Lloyds p/s, driver tube 2 box solution). Would it be suitable to seperate the p/s from the driver section with aluminum?
I am thinking that I would use the mohagany for the front and sides, aluminum for the top and back opanel and the phenolic for the bottom.
Any viewpoints or suggestions would be much appreciated.
TIA, Bill

[Gordy]

Hi Bill,

You'll want to use a grounded to earth mild steel (not stainless) for separating the ps and driver/signal sections.  Depending on the layout, just shielding the transformer should be fine.

Enjoy!
Gordy

[Berndt]

I was thinking of mounting the transformers on top of the pre.
Why do I want to use steel for the mid-baffle?
For grounding purposes? I thought Al was a better Rf sheild?
What is the prpose exactly of a seperate ps?
Thanks for your thoughts, Bill

[Daryl]

Using a separate case for the PS is a good idea.

It also is a good idea to completly shield the amplifier by surrounding it in a metal enclosure.

Higher electrical conductivity is better (copper or aluminum).

[Gordy]

I suggested mild steel as a shield against emi, which is what I tend to be concerned with when AC lines and transformers are in close proximity to signal lines and circuits.  Daryl is correct about rfi shielding, though I've  yet to have a need for it in my location 

[GBB]

I suggested mild steel as a shield against emi . . .

Ah,those evil EMI folks - I hate what they do to the music too. aa

All kidding aside, I think what Gordy means is magnetic coupling.  Transformers have pretty strong magnetic fields which can couple into some circuitry and cause hum.  The fields drop off in strength as the square of the distance from the transformer, so a remote power supply will tend to be quieter in terms of magnetic coupling.  Daryl's suggestion of full metal shielding seems like overkill, since your preamp seems to work fine right now without that type of shielding.

You can do a simple experiment to see if the idea of one chassis with the power supply right next to the amplification stage will have problems or not.  Just put the power supply on the shelf physically next to the main part of the preamp and see if you hear any problems.  If not then you are probably going to be fine.  Note, that the coupling can be dependent on the exact location and orientation of the transformer, so move it around as you listen for problems.

By the way, I've built quite a bit of equipment in wooden boxes and it works fine.  If I feel the need for a good ground plane, I'll line the inside of the box with some thin copper.  Copper clad PC boards are easy to get or some copper flashing.

---Gary