Layout critique?

[composition4]

Hi all,

My first tube amp build and just wondering if you have any suggestions on the layout of components? I made a fairly big (but skinny) chassis to fit the head, it's about 28 inches long.

Please let me know what isn't very good about this layout and if you have any suggestions!

[img::]http://s12.postimage.org/juilldjkr/layout3.jpg[/img]

Thanks
Jonathan

[sliberty]

A chassis that narrow must have been meant for a combo, with tubes mounted on the edge. I am a little worried about how close the big glass will be to your OT.

With that many pieces of iron, I would wait until firing up the amp to permanently mount them to the chassis, just in case you need turn one or more on different axis to eliminate induced hum.

[composition4]

Thanks for replying... Do you think it would be better if I put the power tubes in front of the preamp PCB instead? I could fit them in there..

[martin manning]

You've got a lot of distance between your PT's and your OT, so I wouldn't think there will be any induced hum problem. I don't know how likely it is that the OT and power tubes would couple in some unwanted fashion, but you could move the right-most power tube socket over to the other end of the line to make the pairs equidistant from the transformer's centerline. That way you would get common-mode rejection.

[Structo]

That will be a cramped chassis due to it's width.

Are you stuck with that design or can you make one wider?

Also, won't the reverb tank pickup noise from the preamp board if it is directly above?

[composition4]

Unfortunately I'm stuck with that width... it's probably wider than it might look, it's only 1 inch less wide than a standard 100W Marshall chassis.

So it looks like I (potentially) have two issues:

1. Is the short distance between the OT and the power tubes (I measure 1 inch of space between them) going to be a problem?

and

2. Will the reverb tank (which I'll ground the tank chassis of course) pick up any noise from bring mounted above the preamp tubes?

Any further input is appreciated!

Thanks
Jonathan

[Reeltarded]

Actually, I looked a second time and I just believe you will have a snug fit of board backspaced to pots depending on depth.

[Structo]

That is sort of what I was wondering.
I have built in cramped chassis and it is a challenge to wire them.

If the board is pushed up against the pots it makes it even more difficult.

I think at this point your only choice is to build it then sort out any problems after it is operating.

This started as a Hammond organ amp.
I shortened the chassis (too much!) and first built a Deluxe type circuit then a Plexi then a Rocket type which is where it sits now.
3 x 12ax7, 2 x 6V6GT, 5U4GB
The voltage was too high so I added a stud mount Zener diode to drop that a bit.

[composition4]

Oh I probably should mention that the pots are being mounted to a separate panel that sits an inch in front of the chassis, so that won't be a problem...

Might sound strange but I have my reasons for doing it that way!

Anyone got an answer the the 2 potential problems I mentioned earlier?

[desu boi]

1. Is the short distance between the OT and the power tubes (I measure 1 inch of space between them) going to be a problem?

and

2. Will the reverb tank (which I'll ground the tank chassis of course) pick up any noise from bring mounted above the preamp tubes?

1. is absolutely no problem. The power tubes aren't really sensitive, they work in common mode, and they have anodes that cover and shield the sensitive parts.

2. How will you mount the reverb tank? If it is bolted directly to the chassis it will interfere with the preamp tubes? Will it be bolted to the "roof" inside of the headshell? It should be okay, the preamp will not radiate bad stuff. The biggest problem will be the wiring to and from and the recovery circuit, but these problems you will have whichever way you do it.

[composition4]

Thanks for the reply, yes the reverb tank will be mounted to the roof above the preamp board...

Thanks
Jonathan

[composition4]

One other thing, is it likely to be a problem that the connection between the OT and the speaker jacks will cross back over past the power tubes?

[desu boi]

Not if you use insulated wire.