GK-1 layout

RoyC · « **on:** 27 Feb 2003, 02:28 am »

I have had my GK-1 kit sitting on a shellf for a couple of months while I finished another project. I have just started working on the layout of the case. I use vibrapods under my current pre - a Bottlehead Foreplay. I would like to use them under the GK-1 also. I think that the Vibrapods work better if the weight is fairly evenly distributed (?). This is a problem with laying out the GK-1 since the two transformers are going to be much heavier than the circuit board (correct?). I was thinking of putting the transformers in a separate box. Aside from the extra work to build and wire this, does this seem like a good idea?

Malcolm Fear · « **Reply #1 on:** 27 Feb 2003, 03:07 am »

I used a standard 3RU rack mount case.
I mounted the circuit board to the front of the box, with the valves pointing skywards.
I mounted a transformer each side of the circuit board, about halfway between the front and the back.
I mounted the stage 2 board along the back, with a shaft extension coming to the front of the case, for input selection.
I use half inflated innertubes under a shelf of Corian, so I also require even weight distribution.
Works well.

AKSA · « **Reply #2 on:** 27 Feb 2003, 03:10 am »

Hi Roy,

Putting the GK-1 transformers in a separate box is just fine, and insulates you against possibility of hum intrusion. That way you can put the tranny box in the center of the large enclosure, thus optimizing weight distribution for the Vibrapods........

Enjoy the build - remember, it's the journey as well as the destination!

Cheers,

Hugh

RoyC · « **Reply #3 on:** 28 Feb 2003, 12:40 am »

Thanks Malcom and Hugh for the input. I am going with the external "tranny" box so I will need some additional wire for the secondary wiring. Should I get some more of the cat-5E cable supplied with the kit (and what is a good source?) or is there something even better (shielded?)?

AKSA · « **Reply #4 on:** 28 Feb 2003, 02:20 am »

Hi Roy,

My pleasure; hope it's helpful.

You could use some of the CAT5 with shielding; any electrical supplier will have it. The shield can be attached to mains earth; get three or four pair, it's quite suitable, but teflon is probably better because 150Vac is a high voltage, not strictly approved for CAT5. All other voltages are fine, of course.

Cheers,

Hugh

Pleb Plebian · « **Reply #5 on:** 28 Feb 2003, 10:40 pm »

Hi Roy;
I use 2mm^2 sheilded mains cable for the remote transformer links on my machines: as Hugh says, sheild to mains earth *seems* best to my ear (not much difference tho).
I just went down to my electrical wholsaler - plenty of options. They can also advise you on (through-panel) cable strain reliefs - very important for good life...

Note that I haven't remote-mounted the transformers in my GK yet - just those of my 4x 55's.
I'll get to the GK - but have an impending wedding occupying way too many of my waking moments!
Ah well - after the honeymoon, she'll be glad to banish me to the Dungeon (workshop/listening room) once more :-))
HTH
-D

Oz_Audio · « **Reply #6 on:** 28 Feb 2003, 11:35 pm »

I have all of my AKSA amps in wooden boxes with open bottoms and everything screwed to the top upside down.

The GK1 has the tranys in the same box 2" from the PCB with no metal shielding. I have no hum issues at all.

I did have a problem of the valves heating the timber and the top did dry out and split the wood between the valves. I have now fixed this by putting 1/4" feet on the bottom so air can flow through the box and out the valve holes. I can now put my hand on the timber between the valves, before it was too hot. I filled the splits with putty and you can hardly see the split.

I like wooden boxes as they are very easy to build in any size required and the finish can be stunning.

I will get new photos up soon of the finished GK1 with all switches now connected and the 55 as well.

Mark

RoyC · « **Reply #7 on:** 1 Mar 2003, 04:15 am »

Ok - Guess I'll take a trip down to Home Depot tomorrow and see what they have in the way of cable.

Another question (or three) - At this time I am not planning on going to stage 2 with the GK-1. However I know that I change my mind a lot so I would like to keep that option open as I design my case. I have read discussions about extension shafts for the input selector - I assume this means that the switch is mounted on the stage 2 pcb - correct? How much space is needed for this board?

Hugh has been helping me with incorporating my Placette Remote Volume Control into the GK-1 design (above and beyond the call I must say). In case this does not work out as planned, how much space will be required for the stage 3 board? Since the main pcb will be mounted close to the lid, could the stage 2 and 3 boards be attached to the base underneath if the case was say 3" high?

Any other things I would need to consider for possible expansion to stage 2 or 3?

AKSA · « **Reply #8 on:** 1 Mar 2003, 04:33 am »

Hi Roy,

Stage 2 Input/Switching pcb is 232mm (9 1/8" near enough) by 56mm (2 1/4"). The selector switch is indeed mounted on this pcb, and driven from a 250mm (10") extender shaft. The pcb is mounted at the rear panel, and carries all the RCA input/output sockets.

This is the only addition from Stage 1 to Stage 2.

Stage 3 is more complex, of course.

The rear input/switching pcb will be around the same size as for Stage 2, but will have relays on it rather than a selector switch.

The digital control pcb is 88mm (3 1/2") x 61mm (2 3/8" near enough), and the 5V 1A power supply is 5" x 4" and 1.8" tall. These should be mounted close together, far from the analog pcb or input/switching pcb at the rear panel.

Hope this defines the layout issues for you.

Cheers,

Hugh

RoyC · « **Reply #9 on:** 2 Mar 2003, 05:14 pm »

Hmm. That sounds kind of complex. I think I will just design the box for the stage 1 only and if I decide to go with the stage 2 or 3 later (kind of unlikely) then I will build a new box when I have the boards in hand to do the layout. I assume that the power supply that you mention for the stage 3 has a transformer. If so, I will at least build my external tranny box big enough to hold an extra xformer. Thanks again Hugh.