[Tabascosauce]

Today I completed the case work and wiring of my GK-1M.

Both the analog and switching PCB's passed all the tests in Hugh's instructions.

On wiring up the mute switch and volume pot, and connecting the two PCB's, I fired it up.

Both channels play music with very low volume levels (way below any acceptable levels).  The hum level was quite loud (but this may be a separate fault, as I need to tidy up the wiring).  The music signal did seem to have a reasonable quality to it (but it was hard to tell with the hum).

Obviously, I need to carefully check my work.

However, has anybody else had a similar problem, or can anyone suggest what I should check first?

[rabbitz]

Pot wired correctly and tubes pushed all the way in?

[Tabascosauce]

This is so strange.  I tried it twice this morning, with problems.

I put it down for a few hours, and just wired it up again.  No hum, volume at perfect levels, and it is sounding very sweet 

I've done nothing to it, other than touching the tubes to make sure they were in their sockets.  Either the tubes needed a jiggle, or I have a case of voodoo electronics

[PSP]

If it's loose tubes, you might need some contact enhancer (Caig DeOxit, or similar), but be cautious wiggling the tubes when you are powered up.

I blew a woofer (GR-Research Paradox 1) in my bedroom system.  I had my TLP on the workbench and was thus using an old Bottlehead Foreplay as my preamp.  By accident, while adjusting the volume, I bumped one of the Foreplay's tubes, got a mighty thwack out of the speaker, and thereby killed a woofer (it had sprung way past Xmax and would not go back to normal, reversible displacement).

My GK-1R seems much more gentile than the Foreplay, but I still would be very careful moving the tubes with power applied.

Peter

[AKSA]

Hi Paul,

If it's a self-correcting fault, then you have a poltergeist cruising around the pcb tracks.......

I would suggest resoldering all the connections around the volume control and the tube socket, and checking that wires connecting to the pcb are well attached.  This does sound like a poor connection.

Peter's advice is good too;  tube pins get very hot, and are subject to oxidation.  This builds and eventually threatens electrical contact - very common on large tubes like the Russian 6C33C.  Good idea to remove the tube every month or so and clean the pins, or even to simply pull it out and put it back in.  The Caig stuff is very good - but carries a high price tag in Oz.

If it happens again, measure the plate current on the tube, it might be down, indicating precisely this problem.  Over a year or so, the thermal cycling of the pcb tube socket can slowly vaporise all the flux in the attaching joints, and thus turn it into a 'dry' joint.  Dry joints are very unstable, but at the beginning always show as a thermal fault, coming and going with heat.

Hope this helps,

Cheers,

Hugh

[Tabascosauce]

Thanks Hugh and Peter.

I had a short listen to this last night, without any burn in.

It is a significant step up from my MAS Charisma preamp.

Sound stage is better, there is much more detail and clarity between instruments is improved.  And yes, emotional engagement is significantly better.

I played a very good Japanese vinyl pressing of Bill Evans, and it was the best piano sound I've yet heard.  The dynamics were very life-like.

Hugh, I'm very glad I took my second leap of faith!

I'll post some more impressions and photos soon.

[Rocket]

Hi Paul,

Glad to hear that you have finished your aksa gk1 preamp.  It should be a significant step up from your old preamp.  I'd like to come around for a listen some time and i thought i could bring along a new phonostage which i've bought.  I still have the cornet phonostage but i'm looking to sell it as there was too much hum in my system.  I suspect the problem probably is because i have not wired the lundahl step ups properly.

Regards

Rod

[Tabascosauce]

Rod, no problem.  Give me a couple of weeks to properly finish it off.

[AKSA]

Paul,

This is great news!!  Thank you for reporting 'first review'!

I remember debating my products with Darl Singh of NZ, the man who built the first GK1 to my design.  He said to me then that he felt the GK1 was my best product, with extraordinary natural sound and incredible sound stage.  I'm not sure, the LF and GH are pretty good, but the GK1 is an absolutely unique piece of topology no one else to my knowledge has yet tried....

It gets better still with burn in, just about all audio components seem to improve as the caps bed down.

I am really pleased that your 'leap of faith' has worked out - and again, my apologies over the transformer delivery difficulties we had!

Cheers,

Hugh