Starting Express

[Structo]

The material that the chassis cover/shield is made from raises a question from me.

I have often wondered if it matters what kind of metal the shield is made from?

Is a ferrous metal like steel sheet metal better than say aluminum for shielding?

I guess a shielded chassis is kind of like a Faraday cage which I believe can even be made from copper.
So as long as the shield is conductive it works good?

Sort of like Stratocasters that have an aluminum sheet for a pickguard shield.

On my D'lite amp I used some aluminum flashing sheet metal and since the amp is tubes down in the head cab, the shield just gets pinched between the chassis and cab.
I sanded off the powder coating around all four screw holes of the chassis so that the shield makes electrical contact with it.

[Big Jim]

Hey Ampmike,
I am currently in the inventory phase. I think I will have one more order to place with Mouser.com for some odds and ends. I will probably order the Bud Chassis cover with this order ($11.00). It is 8"x17" so it should work nicely. I do think an aluminum cover is required, mostly for its shielding qualities. As far as where to start, I will probably follow the build guide loosely (located in the "Trainwreck Files" section). I plan to familiarize my self with the layout some more before I actually start building. I'm a relative noobie to Trainwreck circuits, so I'm thinking that time spent studying the available information will pay off in the long run. I see you had the same positive experience with rj that I did. He's super helpful and a gentleman to deal with. Good luck with your build, I'm sure we will be in touch during this process! Jim

[rawnster]

Mouser has the aluminum cover:

http://www.mouser.com/ProductDetail/Bud ... hk0w%3d%3d

Also, I got a piece of aluminum from my local metal shop for about $8 cut to size. I just glued it down inside the head cab. Don't have to worry about it taking it off when opening up the amp.

[Firestorm]

Aluminum and steel both block RF interference, but aluminum does not couple magnetic fields from the trannies. On the bottom, it probably doesn't matter, but since the aluminum plate is readily available (also from AES/CED I believe), why not?

[M Fowler]

We have had this discussion in the past and no one won.

[Structo]

It depends what style the chassis is.

If it is a Marshall style amp with the tubes up then aluminum works well.
But if it is a tubes down type amp, the cover above will work better because everybody knows that electromagnetic energy flows up.

[ampgeek]

Jana: Yes indeed! One of those "simple" life's pleasures when enjoyed responsibly and in moderation.

AmpMike/BigJim: Just a quick comment based on my recent Express build. If you intend on using PEC pots and buss bar lugs with the pot spacing dimensions shown in some of the reference documents, you will find it hard to install the pot assembly in the chassis. The pot+lug width is such that they interfere "at rest". With a little muscle, the lug coming along the side of the pot flexes enought to get it together. It works...but...it just didn't "feel" right having to lean on them that much.

I would add an additional ~1/64" to 1/32" (about the thickness of the lug) in the spacing distance to alleviate that issue if (no...when!) I were doing it again.

Also, don't wait until the end to drill the holes to mount the chassis cover. That could be a real megabummer once it is all wired up. Not impossible...just a major PITA.

Good luck,
Dave O.

[Big Jim]

Amp Geek,
Thanks for the tips. I actually do plan on using ground lugs on this build. I have Clarostat pots on order. I will check the spacing closely to see if this condition is the same with the Clarostats. The more I think about it , it might be easier just to put a piece of aluminum on the bottom of the head cab. It would make biasing/amp service much easier. Jim

[ampmike]

Thanx for the info guys,Jim and I are going to do are builds together.Im going to order my pots as well.Is using a better quality pot OK,Is it safe to say a better pot will make a bettter sounding amp.We would be deviating from the KF BOM.Thanx Mike

[M Fowler]

Mike, I recently switched to mojotone CTS pots which are solderable and high quality. They have both regular CTS and mojo specially made CTS post cheaper both are good quality.

Of course PEC is great but there are other choices.

Mark

[ampmike]

Thanx Mark,What about these heated wire cutters,That was mentioned in the TW build guide.Are they expensive? Thanx Mike

[M Fowler]

Well to be able to afford to buy more wire and amp parts I use my cheap hardware store strippers, unheated.

For teflon I would imagine that would be a good way to go Mike, but I hate teflon wire.

Mark