[CButterworth]

What a saga I have had!!!!!

After deciding that the exchange rate of US to AU dollars were not good (for me), I forego the purchase of the inro-level GK-1 and ventured forth on building my own Aikido preamp (www.tubecad.com).  I bought the boards and had help with the PSU design.  The preamp uses four 6SN7 tubes.  Anyway, after a great deal of sweat, frustration, and tears, I can play music through the Aikido and AKSA.  Combined with my new(ish) Rega CD-player, the music sounds really amazing.

However.......one of my most frustrating battles was over 60Hz hum caused by a ground loop issue.  A recommendation was to lift the Aikido ground using a safe network of 20 ohm resistor, paralelled with a 0.1uF cap, and a diode bridge.  This, coupled with tweaking in the power supply has resulted in hum that is audible only close-up to the speakers.

So, I also thought about my AKSA55.  In this amp, I simply took a ground wire from the PSU star-earth and connected it to the chassis.  MY QUESTION IS:

Would a ground-loop lift installed in the AKSA, contribute in helping to diminish the hum???  Incidentally, the hum is still present when I play CD's from a battery operated CD-player, so I doubt that the Rega is causing problems (and if it is, I'll certainly be opening that puppy up, it cost too darned much).

I got the circuit for the ground-lift from http://sound.westhost.com/earthing.htm

Maybe the moral of the story is that I should have accepted the poor exchange rate and gone with preamp designed by Hugh around the AKSA (afterall I think his AKSA55, instructions, and support are second to none) - who knows????  But where's the challenge in that?

Charlie

[JoshK]

Charlie,  Have you ruled out the possibility that it is your tubes that are at fault?

[CButterworth]

Josh,

I haven't ruled out anything.  However, I am sure that at least the tubes are partly at fault.  The tubes that I originally bought were really, really cheap, unbranded Russian ones.  They are $4.95 new.  When I first got the Aikido running, they seemed incredibly microphonic.  Anyway, Bruce Anderson, which built an Aikido very early on gave me a pair of Magnavox and a pair of Westinghouse tubes.  The microphonics disappeared totally and it seemed that the hum was much less.

Anyway, one of those tubes gave up the ghost and I had to revert to using a pair of the Russian cheapies, in the output stage, I certainly get more hum than when I put them in the input stage.  I have read that the input tubes have a greater effect on the sonics of the amp than the output tubes, although I am running the output tubes hotter than the inputs.

I am considering buying a pair of RCA 6sn7GTW, or something similar.  Of course they aren't cheap.  What I do want is to try to achieve the "tube romance" that Hugh talks about.

Regards,
Charlie

[AKSA]

Hi Charlie,

Sorry to hear of your saga.

The AKSA has a lifted ground loop.

Try disconnecting the AKSA star earth from chassis - but be sure to connect chassis to IEC (power) earth.

Then connect the ground lifted AKIDO to the AKSA star earth.

This might do it - no guarantees, but worth a shot.

Cheers,

Hugh

[CButterworth]

Hugh,

So, I would run a ground wire from Aikido star-earth to AKSA star-earth?  Which side (AKSA or Aikido) would go to IEC earth - maybe both, or whichever works best?

As always, I greatly appreciate your advice.

We're busy saving for the LifeForce upgrade, although my wife and I are expecting our first baby in less than a month.  We are very excited, although it may delay our upgrade for a while.  We'll get to it in the end.

Regards,
Charlie

[AKSA]

Charlie,

Either/or;  whichever works best, but generally the power amp star earth should go to chassis earth.  Alternatively, you can in fact leave the star earth floating, it's quite safe due to the 4000V rating on the transformers, AS LONG AS CHASSIS IS CONNECTED TO IEC POWER EARTH.

Our little babies, born just a short time ago, are now 19 and 21!!  The younger one, Alessandra, decided she wanted to go overseas, so with her boyfriend arranged it all herself, including the money, and has just returned from a month in LA/NYC!!  She even hooked up with Paul Kaplan (aka Occam) and his family who showed her around NYC and showered her with hospitality!!

Just a tad more adventurous than her old man, I might add.....

My help is a pleasure, Charlie, hope it all goes smoothly from here on!!

Cheers,

Hugh

[LM]

We're busy saving for the LifeForce upgrade, although my wife and I are expecting our first baby in less than a month.

Sounds like you have already ordered your LifeForce upgrade.   Best wishes.

[CButterworth]

Hugh,  LM,

I hear you.  My main concerns for our baby was that I would be under 60 yrs when he/she graduates high school.  I'll just make it!

As for our music equipment, my wife Kara is very discerning (minored in music perfomance at Miami Univ. of Ohio) so she knows a thing or two about good sound.  Of course, I am pleased that she chose to major in Botany.  I keep teling her that we have a great system, as we need to make sure that Our Baby Got Bach    (well Kara does prefer Shostakovich).

I'll experiment with the star-earth configurations.  The first thing that I did with both of my projects was to ensure that the chassis was well earthed.  In fact, it'll give me a great opportunity to under the chassis earth on the AKSA and re-seat the star washers and nuts, etc.

I also have discovered that I need to find a tube cage.  One of our two dogs, Puck (a rather intense Pembroke Corgi) loves to shack the cr*p out of his soft-toys. On more than one occassion, vigorous shakes have resulted in teeth leaving contact with said toy and some fairly impressive trajectories by things such as sheep, cows, even an octopus.  It would really put Mozart out of his stride to be struck by a flying octopus!

Regards,
Charlie