[Jens]

Hi,

I have just placed an order for a GK-1R with Hugh, and it is on its way to me as I am writing this.

Obviously, I have read all posts I could find about the GK-1, including the whole Valhalla thread. I may implement a few of the goodies mentioned at some point.

I was wondering, though, whether there were any considerations about layout and enclosure that any of you wanted to comment about. Is the GK-1 prone to hum or other problems related to the placement of the various sections in relation to one another? Also, any considerations about vibrations that I should take into account?

In my AKSA 55 N I use and sandwich bottom consisting of a 2.5 mm aluminum sheet (the bottom of the enclosure, actually), a piece of 3 mm bituminous felt underneath, and a piece of 22 mm MDF underneath that. This is as dead as it gets! Oh, and the 55 N now weighs in at around 14 kgs (dual trannies)!

Any thoughts?

Cheers,

[PSP]

Hi Jens,
My GK-1R is still in its shipping carton, awaiting the completion of several other audio projects.

I did open the box, however, and Hugh includes a suggested chassis layout that should minimize noise.  If you expect the mail any day now, you can wait.  If you need it quickly, I could fax or send you a scanned image of the suggested layout.

I've had enough microphonics with my Foreplay preamp (bedroom system) that I will definitely include vibration isolation in my GK-1 build just to be on the safe side.  I will probably use something like your approach.

Take care,
Peter

[Jens]

Hi Peter,

Thank you for your post. No need to fax any of the things that come from Hugh - I'll see those when I get the package. But thank you for offering your help.

What I was thinking about was things that people might have experienced - also with the other GK-1s.

Anyone?

Cheers,

[Malcolm Fear]

Hi Jens
I ended up using a 3RU case for my GK-1. The height of the Auricaps (underneath) and the height of the valves (on top) is higher than a 2RU case. I didn't want the valve through the top (I don't have the gear to drill accurate large holes in the top of the case.
I used to live 50km south of where I am now. In the old place, the transformers were quiet. Where I am now, they vibrate.
I paid no attention to transformer placement. They didn't introduce hum, wherever I located them.

Hope that helps.

[dayneger]

Hi Jens,

My kit just arrived, too, and I'm currently working on various chassis layouts.  Unfortunately I can't give you wise advice about what works, but if you'd like I can email a digital image of what I decide on (I'll be doing the layout in 3D CAD, so I can take a screen shot).

From the looks of the parts there should be several good configurations.  In general it should be easier mounting things to the back, top and front while leaving the bottom easily removable for access to everything.

Not much but I hope it helps!

Dayne

[Jens]

Hi Jens
I ended up using a 3RU case for my GK-1. The height of the Auricaps (underneath) and the height of the valves (on top) is higher than a 2RU case. I didn't want the valve through the top (I don't have the gear to drill accurate large holes in the top of the case.
I used to live 50km south of where I am now. In the old place, the transformers were quiet. Where I am now, they vibrate.
I paid no attention to transformer placement. They didn't introduce hum, wherever I located them.

Hope that helps.

Hi Malcolm,

Hm - I was thinking of having the tubes horizontal instead of vertical to avoid the enclosure getting too high. Otherwise I will cut holes in the top. The tops of the my other enclosures are perforated all over, so it's probably not that difficult.

If you are having problems with your trannies vibrating you might consider a DC trap. Very easy to make - worked a treat with some of my toroids.

Thank you so much for your input!

Cheers,

[Malcolm Fear]

Hi Jens
I tried the circuit board on its side. It still won't fit in a 2RU case.

BTW, I have found one of the hard things is removing stuff, to replace it with upgrade stuff (Riken Ohms, Black Gates etc).
I would work out all of your requirements first up. Some of the pcb holes will not fit Auricaps etc.

Also be aware that some tubes are taller than others (if you start tube rolling).
I also mounted the transformers as close to the sides, and in the middle as possible. I am an "innertube support guy", so I wanted an even balance point.

Do you have a circuit for a DC trap. I think Hugh sent me a design for something or other to stop the vibration, but I forgrt if he gave it a name.

[AKSA]

Hi Mal, Jens,

Wow, up early today!

Here's that circuit (if I can put it in somehow!) which kills transformer vibration.  It is originally Russian, and works by blocking DC to a level of +/-1.3V.  It is the DC on the lines - varies from grid to grid - which discombobulates transformers (particularly toroids) and makes them hum.




Diode bridge is 1A UF4007 for GK-1/TLP, caps are 10,000uF rated to 16VW.

Hope it comes through......

Cheers,

Hugh[/img]

[dayneger]

Jens,

The main PCB measures about 267 x 80mm.  The tubes are not in the middle of the 80mm--about 19.5mm in from the side and 70.5 or so center-center (symmetrical on the 267mm length).

The relay board is 233 x 67mm, the keyboard pcb is 128 x 70 and the DCpcb is 56 x 88.  The prebuilt dc powersupply has about a 108 x 83mm footprint (and tends to get in the way of the layout  )

If you want to do a asymmetrical layout and are planning to isolate on innertubes, you can usually add mass to the chassis to even things out later. . .

Dayne

[Oz_Audio]

I have photos of the layout of my GK1 in the gallery section, no hum.
http://www.audiocircle.com/circles/modules.php?set_albumName=album84&op=modload&name=gallery&file=index&include=view_album.php

Mark

[Jens]

Hi Mal, Dayne, Hugh, Mark,

Thanks for all your good comments. I'm jutting down notes as fast as I can!

Mal, I am aware that if  I want to tweak it will be practical to do it right away. I may add some tweaks initially, but will try to put things together in such a manner that it won't be too difficult to swap components.

Hugh, thanks for posting the DC trap diagram - it saved me the trouble of doing it. I am using a DC trap on my CD, the 55 N, the power amp for the bass section (ICEpower module), and my current preamp. Especially, the CD and the ICEpower toroids used to be somewhat noisy at times. Now they are dead silent.

Dayne, thanks for the details about the PCB sizes - and Mark, thanks for the link to the photos of your beautiful wooden enclosures.

I think I will go for my usual 2RU enclosure and let the tubes "go through the roof". It will not necessarily a symmetrical layout, as balancing is not a major issue. However, I will not purchase the enclosure until I have all the parts so I can set up a mock layout.

Cheers,

[PSP]

Hugh and others,
Is there any reason why I couldn't build Hugh's DC blocking circuit into my DIY AC line fiter and surge protectors (Jon Risch design)?  

http://www.geocities.com/jonrisch/surge.htm

If I interposed the DC blocking circuit between the line fiter/surge protector elements and the mains outputs (and used a 20 amp bridge, for example) I could block DC from all of the components plugged into the system (I have two filter boxes... one for digital, the other for analog).

Mains --> J Risch line filter / surge protector --> DC block --> filtered mains

Any problem with this thought?

Many thanks,
Peter

[Jens]

Hi Peter,

You shouldn't have a problem using the same DC trap for several pieces of equipment. I don't think there is such a thing as "DC crosstalk", as the various pieces of equipment hardly produce any DC, if any at all.

As long as the diodes are large enough, I think you should be fine.

Cheers,

[AKSA]

Peter,

Should work fine just as you describe.  My impression is that there is a lot of residual DC on the mains both in Australia and the US, and the slowdiode.gif circuit I posted scotches any and all of it up to +/-1.3V.

Jens,

Thanks for the reply!

Cheers,

Hugh

[andyr]

Hail, fellow AKSA-philes,

As I understand it, Hugh posted a diagram of a "DC block" circuit because some AKSA/GK-1 users were complaining that their power transformers were humming ... and this would appear to be bcoz a small amount of DC is coming in thru da mains?

I happen to have:
* a 1KVA mains isolating transformer (240v in:240v out), and
* a phono stage (NOT my still-to-be-completed GK-1!!) whose toroid hums.

So I decided to see what would happen when I plugged the phono stage into the isolating transformer.  Lo and behold ... the humming disappeared.

So it would seem that a mains isolation transformer is an alternative to Hughs "DC blocker" circuit, if you have a problem with humming mains transformers on your source components.

I say "source components" because I think these constant-current devices will not be "mains-currrent-limited" by plugging them into a mains isolation transformer (the effect of which, I am told results in the sound being "closed in").  However, as I understand it, the heavy current draws (for a milli-second or two) of power amps do not like being "resisted" by a mains isolating transformer - so they are not a good thing for AKSA power amps.

If any Melbourne AKSA-philes are interested in making a test, I'd be happy to bring my isolation transformer round for a listen.  Can't post it, though, bcoz it weighs a ton!!

Regards,

Andy

[Jens]

I am now in receipt of the GK-1R kit and ready to start assembly. Have been reading through all of the documentation - quite a piece of work, as always very thorough. Goodonya, Hugh!

Anything I should be especially careful about (apart from the error on the analogue PCB already mentioned in the documentation)?

Will probably start slow assembly tonight - can't wait!

Cheers,