[fajimr]

finally getting around to building my GK-1

I went through the instructions this weekend in preparation and noticed that Hugh suggests that the PCB be mounted to the case lid... I imagine so that lining up the tube holes would be easier.  Seems that the final power and input/output wiring (I'll be rigging up my own selector switch as I've got an EL model)  might be a bit tricky once the PCB is mounted on the lid and the wires might be longer than if it was  mounted to the case.  I'd like to try to keep the wiring as simple as possible here.

What have been the experiences of other builders out there?  I've noticed that many have mounted theirs in the case itself..

thanks in advance- looking forward to the next step in AKSA sound 

jim

[PSP]

Hi Jim,
The GK-1 sounds fantastic, but it can be a bit of a bear to work on.  I suspended my analog PCB on two rails (with L-shaped cross section) just under the top cover.  http://www.audiocircle.com/index.php?action=gallery;area=browse;album=490&pos=1

It took very careful measurement and even more careful drilling.  I also used a Greenlee punch (I think that's the brand and I'm writing from work) to cut the final holes for the tube sockets.  Cutting that large a hole with a Unibit in thin metal is trouble (although if you had trouble with the Unibit you probably could place the warped section between two pieces of wood and beat it reasonably flat with a hammer).

Good luck,
Peter

[Jens]

Hi Jim,

I put my PCB upright, power connections at the bottom. This does indeed mean that the tubes are lying down - but you avoid cutting holes in the cover of your inclosure for them, and the tubes do not seem to care

[Seano]

My tube PCB is currently mounted on the base rather than the lid.  It is sitting on red masonry wall plugs to keep the thing high enough to have the tubes poke out the top.  But it won't stay this way.  The next case will have the PCB mounted much like Jens - valves tucked away.

[jules]

I'm going floor-mounted, blue masonry plugs, internal tubes with windows in the front of the box and vents on top. The transformers will be in a separate, shielded, stainless U channel of their own [at the back] and switching [source and volume] will be by courtesy of a pair of splendid Elmas. This will all go inside a CAD designed stainless steel case with countless holes in it for everything. I'll post a pic if it's useful  [haven't got a camera at the moment].

jules

[andyr]

I went through the instructions this weekend in preparation and noticed that Hugh suggests that the PCB be mounted to the case lid... I imagine so that lining up the tube holes would be easier.

thanks in advance- looking forward to the next step in AKSA sound 

jim

Hi Jim,

I know you will like the improvement which the GK-1 will give you! 

Now, you seem to want to make your GK-1 sound the best it can so I just wanted to make a couple of suggestions:

1.  Don't mount the PCB too close to the front panel (whether you attach it to the floor or the lid of the case).  I suggest you should give yourself the option of easily replacing the stock GK-1 volume pot with a TKD stepoped attenuator later on ... and these are big mothers - they need about 2" depth clearance, behind them.

2.  Make sure you mount the PCB so that the tubes are oriented magnetic E-W, when the case sits on your rack/benchtop.  Otherwise, the influence of the earth's magnetic field will screw up your imaging.   

Good luck,

Andy

PS: Drilling the holes in the lid for the tubes to poke through is no big deal if you have a hole-saw The hole can be,say, 5mm wider than the tubes without looking ridiculous.  I like seeing the glow!!   

[AKSA]

Lovely humor, Andy, you clearly are holding your mouth correctly.....

Jim, Seano's suggestion of mounting the pcb on 2" masonry inserts, made of tough plastic, is a good one.

This is how I mount the pcb effectively on the base in the Swift.  It does, as you say, minimise power wire lengths, and incidentally affords some damping with the base.

Not long now!   

Cheers,

Hugh

[fajimr]

thanks everyone.... what a great community, I ask about a couple of options I was considering and I get even more to ponder 

so maybe I should refine my question:   

I know that hum seems to be an issue more in building this preamp than the amp and that is my main design concern-  Should I try to design the layout to 1) keep the wires  to the selector switch (which will be in the rear close to the rca's) short, 2) the power wires short, 3) to keep the PCB as far away from the transformers as possible (they will be in the opposite rear corner from the rca's).  If yes to all, is there a priority list?

I like the idea of the tubes sticking out the top (and luckily my kids are old enough not to want to touch them now) so I will stay with the vertical and geo-magnetical orientation.

cheers
jim

[edited for grammatical accuracy]

[andyr]

so maybe I should refine my question:   

I know that hum seems to be an issue more in building this preamp than the amp and that is my main design concern-  Should I try to design the layout to 1) keep the wires  to the selector switch (which will be in the rear close to the rca's) short, 2) the power wires short, 3) to keep the PCB as far away from the transformers as possible (they will be in the opposite rear corner from the rca's).  If yes to all, is there a priority list?

cheers
jim

I suggest - seriously, this time!  - that you should put a steel divider between the transformers and the PCB(s).  That way you are definitely minimising the possibility of hum.  And put the IEC/power switch/fuse at the back of case, near the transformers, to keep mains wires short.

IMO, the DC power wires can be as long as is convenient, providing you:
a) braid the +v/-v/0v wires of each run, and
b) route them so they are not close to the PCB.

You may still end up with some hum when you first switch it on but I assure you, it is possible to remove this.     My GK-1 is dead silent.

Regards,

Andy

[fajimr]

ahhhhh, something my 8 yr old son could understand.  thanks andy! 

[Jens]

I agree entirely with Andy - make sure to shield the PCB from the trannies and the mains.

I've got steel dividers both in front and back, as I have the PCB in the middle. The trannies are in the rear left corner, and since mine is a GK-1R, the PSU for the digital circuits and relays is in the front left corner.

All wiring from the trannies to the PCB run outside the steel dividers and merely goes through grommets in the dividers at exactly the places they enter the PCB. Please note that all wires coming from the trannies are AC, as all rectification takes place on the PCB.

Good luck with the building! 

[rabbitz]

I ended up with the both transformers on one side on the lid of the case so AC ran on this side only and the PCB was shielded by the lid. The GK-1 was extremely quiet and had to stick the ear up to the speaker to hear any hum.

[fajimr]

thanks again jens and rabbitz...

seems that everyone is concerned with the placement and isolation with the trannies- I understand that. 

Any issues with the wiring of a selector switch?  I will place the switch as close to the RCAs as possible and have some cotton sleeved silver wiring to try.

time to get that iron out!!!  but first I want to make sure I've got a good idea of where everything will go...

jim

[RonR]

Just to add some grist to the mill........

My GK-1 has the Analogue board split into 2 halves, in order to keep the high voltages at one end, and the low voltages at the other. No hum at all.

Cheers,

Ron.

[davew]

Hi, 
       You may want to consider mounting as much as you can on the roof of the enclosure.  Except the front buttons and rear RCA's or course.  This way you can route all the wires much more easily.  Everything would be upside down in the finished product but removing the bottom gives instant access to everything.  If you dont want nuts and bolts sticking out of the top, mount everything to a shelf near the top and put on a nice smooth false top.
        I've read comparisons for shielding materials for the transformers ie steel vs aluminium etc but cant remember the results,  so if anyone has that info I would appreciate hearing it again.  Good luck with the build...Dave.

[fajimr]

dave

actually the closer I get to mounting, the easier mounting to the lid looks  .  My reason for mounting on the case floor was mainly aesthetic but I think if I find some nice black hex head screws, mounting on the lid might not be that bad.  making all the necessary tranny, wiper, input/output connections when the PCB was mounted on the floor might prove more difficult with my failing eyesight and large hands...  Peter's suspension mount might indeed be a good compromise.

I've got a separate thread in the lab on shielding
http://www.audiocircle.com/index.php?topic=41476.0

cheers
jim

[kyrill]

thanks again jens and rabbitz...

seems that everyone is concerned with the placement and isolation with the trannies- I understand that. 

Any issues with the wiring of a selector switch?  I will place the switch as close to the RCAs as possible and have some cotton sleeved silver wiring to try.

time to get that iron out!!!  but first I want to make sure I've got a good idea of where everything will go...

jim

hi
hi

Ah,,what is more important, convenience, looks over sound quality or the reverse? Especially when you build it yourself.
I will always choose whatever it takes ( within reason and cost) for every approach to enhance the sound quality

Sound out of the speakers is made ( modulated) out of wall socket current. That is my first basic assumption.
When that "raw material" reaches my amp it must be as pure as hell,ehh  heaven.
So i start with a balanced transformer, (mothertransformer) into a series of filters( i use 2 relative cheap but good filters from  http://www.bluecircle.com/index.php?menu_id=1755last see how they clean up video signals )  and from there on ALL my current wires to amps or devices are shielded or twisted within themselves

The amps I made myself ( Aksa's and now building GK-1) have there power supplies outside the main box, in a stand alone box 30 cm away from the pcb of the amps. All the boxes are made of wood internally shielded for RFI
hum and hiss are still hearable very very softly with my ears 2-3 mm from the tweeter or speaker.
5 cm away from it,  i can actually not hear it anymore. I give every box the tiniest led i can find red for the pws, blue for the preamp yellowgold for the amp and prefer to listen in the dark..
Before I had the balanced mother transformer i noticed thad at night my setup had this "magic" but very seldom during the day. With the balanced transformer  i have this magic 24 hrs a day..

[fajimr]

Ah,,what is more important, convenience, looks over sound quality or the reverse? Especially when you build it yourself.
I will always choose whatever it takes ( within reason and cost) for every approach to enhance the sound quality

hi kyrill

As far as I understand it, the question of sound quality doesn't come into play.  In fact mounting on the base might allow for shorter runs which might provide less chance of hum from the power connections.  I'm mainly looking for the most elegant design/construction solution with a nod to aesthetics.

cheers
jim

[kyrill]

Fajimr

How is it going?

[fajimr]

hi kyrill

the board is built.. a slight delay waiting for the platinum upgrades but easy going (relatively) thanks to hugh's excellent instructions and my budding soldering skills and some great photos from Jens of his upgrade...

now I am pausing as I have to build in my own selector switch (I got the EL).. Luckily Peter (PSP) has given me some great advice and photos to help me conceptualize the layout. 

I like to work in short bursts as it keeps me both focused and fresh... so next is the switch wiring and then I'll come back to wire up the trannys and do some testing... 

thanks for asking 
I'll let everyone know when I am finished.... 

jim