[AKSA]

My apologies, Steve, Sparks,

I will introduce you to each other, so you can say, 'You're fine, how am I?'

Hugh

[stvnharr]

My apologies, Steve, Sparks,

I will introduce you to each other, so you can say, 'You're fine, how am I?'

Hugh

I wrote the reply on my brother's computer and didn't think to change the login.  That's how I became Sparks. 
However, I have made a few sparks while doing audio measuring and testing things.  Sparks usually mean bad things when the probes touch the wrong things at the wrong times.  I try to avoid that now, and as a result I am a bit better at doing the things I intend to do.

Steve

[AKSA]

Brad,

How are going with the diagnosis and repair?

Any progress?

Hugh

[Builder Brad]

HELP.

I never really resolved this "noise" issue, deciding to live with it for the time being, however yesterday I swapped the input caps on my AKSA100s that drive the woofers in my Orions. I now have fitted 40uf input caps per pair of AKSA100 modules and have noticed a definite improvement to the LF extension - but it has come at a cost!

The noise is back a with a vengence!

I have switched to the SS outputs for now as I am worried that the kick that occurs when I turn the gk1 on an off will damage the woofers. Whereas before the noise occured at a relatively lower level and for no more than 1 second, It is now lasting for 3-5 seconds on turn on and 5 seconds+ when I turn off.

This is really strange now as I am hearing the noise when I turn on my kettle in another part of the house as well.

I have not really tested this any further for fear of damaging the Voice coils in the drivers.

I will try to capture the outputs using my PC soundcard, to try to get an idea what is going on.

Brad

[AKSA]

Hi Brad,

The hot side of the GK1 output cap sits at around 48V, and this creates quite a charge up current into the input circuit of the amp when you switch on the preamp.  It's one of the reasons I use a small cap on the input to the AKSA;  it's a safety measure, but even so, there is a discernible thump at switch on.

Solution:  Turn on the amp AFTER you've turned on the preamp.

The noise you are hearing is a bit baffling, but could be LF noise coming off the tube, though I can't imagine why it's so noisy unless the bass input has been amplified.

What is the quality of this noise?  Low, rumbly, hiss, whatever?

Hugh

[andyr]

Hi Brad,

I keep my GK-1 on 24x7 (unless I go away for a few days).  Hence no noise! 
NB: Power amps and active XO are also on 24x7. 

It really doesn't consume much power ... and this means I don't have to go through a "warm-up" cycle to get it to sound its best!! 

Regards,

Andy

[Builder Brad]

Hi Hugh,

The noise sounds like the AC mains hum, with a bit of a "bounce"

Hi Andy,

I do normally leave all the kit on, but this is now too extreme, and i cannot risk the potential driver damage ect.

Brad

[Builder Brad]

Hugh,

I am wondering if this could be caused in part by the GK1R remote controller chip. This chip was replaced by the updated version that you kindly replaced a couple of years ago - unfortunately the chip was squashed in the post, but I managed to straighten the pins.

Recently I have been loosing some of the input selections and found that I could get them working again by pushing the chip into it socket. that chip was really smashed and I dont even think that all of the pins are in contact with the sockets.

Brad

[MikeC]

Hi Brad

I increased the input impedance into my Orion crossover and increased the GK1 output cap value some time ago, and received a similar surprise from the GK1. I just took it as a consequence of using valves and switch on my system with the Orion crossover subsonic cut engaged. I only switch to full range when I am about to listen, or at least 30 second after switch on. The same applies to switch-off, only in reverse.

Hugh is spot on with the question about bass amplification. There is so much gain at the extreme low end of the Orion crossover to equalise the dipole cancellation that any LF aberration is heavily amplified. I think the extreme low end emanating from the valve starting up is amplified through the crossover and overdriving the power amp input stage. This will not be apparent on "normal" speakers and is a consequence of the interaction of the designs. For reference, I modified my high pass filter so its roll-off is at just under 40Hz, so the generated noise is at a much lower frequency. I have no noise, once the valve has settled - I hear only a very low level hiss with my ear right up against the tweeter and some even lower level noise with my ear against the mid or my head right in the woofer cavity, both barely discernible. There is no apparent noise anywhere from 1 metre from the speakers.

Regards

Mike

[Builder Brad]

Cheers Mike,

That all makes sense.

I could work around this and may end up doing just that, although it could be tricky as the amps and ASP are not easily accessible.

I am concerned with the other effects, like the noise that occurs when I turn the kettle on - do you experience anything similar?

Hugh,

is there any way of altering the delay/relay muting on power up/down?

I am not even sure this is working for me because of the problems with the damaged controller chip.

Brad

[AKSA]

Hi Brad,

At the moment of switch on of the GK1, the tube filament is cold, and the voltage at the 'hot' end of the output coupling cap (the 1uF Auricap) is zero.  As the filament warms up over an 11 second span, the voltage starts to rise, though very slowly at first, then in the last second probably rises half the 48V.  I think it is this final ascent which causes the sharp thump on the ASP, which has vicious EQ to bring up the bass response of the open baffle design of the Orion.

The only way to prevent this would be to short out the input to the ASP for the first 15 seconds after switch on, and only then release the short, allowing signal to pass to the ASP.

As for the mutilated micro, maybe we should send you another?

Cheers,

Hugh

[Builder Brad]

cheers Hugh,

replacement of the controller chip could help as I really do not think all of the pins are making contact with the socket. PM sent.

do you have any idea what might be causing the noises when I turn of the kettle ect. they are the same type of mains buzz I hear when I turn on the amp, only lasting for a fraction of a second though.

Brad

[MikeC]

Hi Brad

I do sometimes get very small buzzes through the system, but it is very seldom and I can't put any pattern to it. Maybe there is intermittent contact from your controller chip affecting the pre-amp, so accept Hugh's offer.

Cheers

Mike

[Tinker]

I'd be interested to hear an update when the new chip is installed.  There may be some weird leakage from an ill-connected chip.

Noise-wise, though, the control portion of the GK-1 should be very quiet.  It was designed with a lot of paranoia about noise in mind. The relays switch both signal and ground on all contacts, the control currents are all DC, the chips runs at the way-inaudbile 4 MHz range, and it has the nice feature that the chip goes to sleep (shuts down all clocks) between button presses. 

T.

BTW Isometimes get buzzes in my Phoenix system when the washing machine switches between parts of the cycle. This cleared up with the installation of a power filter.

[Builder Brad]

Cheers Tinker + Mike,

Tinker,

I did not realise that the GK1 switched the grounds as well!

this explains why some of my inputs are noisy at times, almost as if I have not pushed a phono connector in properly.

Fingers crossed on the chip.

I am using Felicia balanced power conditioners on all my source and low current kit. Strangely enough the GK1R was the piece of kit that did not get the normally large benefits of the Felicia - I guess the design is already optimum, unlike most equipment. My symptoms are the same with or without power conditioning. 

Brad