GK-1 just finished....burning in ! - SOLVED HUM

Felipe · « **Reply #20 on:** 5 Mar 2006, 09:52 am »

OK. I will not connect GK1 GND to chassis. It didnt do anything in the AKSA, so i believe it wont have any effect here either. I dont like the idea of having my GND output RCA connected to the chassis....

Just one question :

- Both channels will be having the same star earth around the volume pot body right ?

AKSA · « **Reply #21 on:** 5 Mar 2006, 11:40 am »

Felipe,

If the two pots are entirely independent (they are for the EL version) then you can have two star earths, one for each channel, thus keeping both earths apart at the preamp.

However, most CD/DVD players join the signal ground for both channels, so any imagined benefit from this independence is probably fatuous.......

Thus, you could join them to one Star Earth if you wish.

Cheers,

Hugh

Felipe · « **Reply #22 on:** 5 Mar 2006, 10:58 pm »

OK. I shielded 1 channel, created a star earth , isolated the transformers from chassis and disconnected the ES shield from Mains Earth.

Result is better noise ratio. I now have less HUM. But i suspect this was due solely to the transformers isolation. The Right channel still have all wires unshielded and has the same level of HUM as the Left channel.

I think i am happy with the result, not being able to eliminate hum completly but i now DO NOT HEAR IT from the listening position. I THINK....i am a litle tired today...ill do some real hearing tests tomorrow.

I sense another decrease in noise when touching the volume control body with my finger....but its of about 10% to 20% amount.

Do you think the noise may decrease when RIGHT channel is shielded and the STAR EARTHS are connected ?....Hmmm....at least i am not hearing it unless 30cm away. I dont feel like having all that shielding trouble again...maybe next weekend. And for sake of wire matching. I now have coax in LEFT channel and CAT5 twisted pair in RIGHT channel...

Thank you all for your help. I couldnt do it without YOU .

AKSA · « **Reply #23 on:** 5 Mar 2006, 11:05 pm »

HI Felipe,

Progress, I'm very pleased (and relieved!).

Quote

Do you think the noise may decrease when RIGHT channel is shielded and the STAR EARTHS are connected ?....Hmmm....at least i am not hearing it unless 30cm away. I dont feel like having all that shielding trouble again...maybe next weekend. And for sake of wire matching. I now have coax in LEFT channel and CAT5 twisted pair in RIGHT channel...

Yes, I do think it will make a difference. You could try connecting ES to mains IEC; that might further reduce hum when both transformers are isolated.

Cheers,

Hugh

Felipe · « **Reply #24 on:** 5 Mar 2006, 11:55 pm »

Just 1 more quick question , not regarding Hum now....

My new CD player has quite a high output. I control the volume with the remote control but i have to have the GK1 with about 5% or less at the control pot !!!

And if i want a low listening level the CD is at about 10% to 15%....i guess this is very odd.
Do you think the sound is of lesser quality with the volume at the GK1 at 3% to 5% ?

AKSA · « **Reply #25 on:** 6 Mar 2006, 01:35 am »

Felipe,

Yes, you might lose a little resolution. Put a voltage divider on the output from your CD player. I'd suggest two 10K resistors in series across the output; take the output to the GK1 from the junction of the two resistors. This will cut gain by 6dB (50%), permit you to use a higher setting on the volume control. If this is not adequate attenuation, you can further lower it with a 15K and 6K8 resistor in series across the output of the CD player. This will give you 31% of the signal.

Cheers,

Hugh

stvnharr · « **Reply #26 on:** 6 Mar 2006, 07:37 am »

Quote from: Felipe

Just 1 more quick question , not regarding Hum now....

My new CD player has quite a high output. I control the volume with the remote control but i have to have the GK1 with about 5% or less at the control pot !!!

And if i want a low listening level the CD is at about 10% to 15%....i guess this is very odd.
Do you think the sound is of lesser quality with the volume at the GK1 at 3% to 5% ?

Sorry to butt in here, but Felipe, is there not a fixed full signal output from your cd player?
I've never known a cd player to not have a fixed full signal output, even if there is a variable output as well.
Of course, I could be all absolutely mistaken in this instance.

Felipe · « **Reply #27 on:** 6 Mar 2006, 11:29 am »

Nope. No fixed output. Its a Marantz 63 KI.

But the output is at its maximum when i turn it on. I always have to turn down the volume to about 10%....

Even if i HAD a fixed volume output...it wouldnt do anything good because its just too HIGH....

I gotta cut the volume on the GK input...

Hugh,
These resistors (the series one at least) is going to be in the signal path. I guess its gotta be a Metal Oxide at least right.... The Shunt series resistor in a attenuator usualy uses a very high quality resistor because of this...

rabbitz · « **Reply #28 on:** 6 Mar 2006, 01:22 pm »

You could always add a good quality pot (10K linear?) after the CDP and set to a fixed level or get a pair of Rothwell in line attenuators.
http://www.rothwellaudioproducts.co.uk/html/attenuators.html

These CDP volume controls that return to maximum after turning off really suck.

Felipe · « **Reply #29 on:** 6 Mar 2006, 04:43 pm »

Great product.
I like the idea of not having to reduce the gain inside the GK1, this way if i change the source, i'll have no problems what so ever....

Thanks!

AKSA · « **Reply #30 on:** 6 Mar 2006, 09:10 pm »

Felipe,

Yes, 1% metal films, Beyschlag/Vishay/Dale/Roederstein are just fine.

The upper resistor, connected to the 'hot' output, is critical for sonics; the lower resistor, connected to ground, is in shunt and nothing like as significant sonically.

Man, that Marantz has a high output!!

Cheers,

Hugh

rabbitz · « **Reply #31 on:** 7 Mar 2006, 04:46 am »

Felipe, if you need a different value just contact Andrew Rothwell but 10dB should be ample. If you get a pair, try it between the CDP and the GK-1 and also try it between the GK-1 and power amp.... it can make a difference.

hifryer · « **Reply #32 on:** 7 Mar 2006, 04:01 pm »

I didnt see any mention of this in quickly scanning this thread, so apologies if it is already dealt with.

If you still have hum, the first thing to determine is if it is 50Hz or 100Hz ( 60 / 120) .

If 50Hz it is coming from the transformer. You put in copper shields leading me to suspect your transformers are close to the electronics.

Copper shields are for electric fields such as rf interference and have no effect on magnetic fields. You found they make no difference.

If 50Hz hum, try mild steel or iron shields. These reduce magnetic fields.

Dont forget the filament transformer and make sure you tightly twist the heater wiring and keep well way from board where you can. Make it short not pretty.

cheers

Felipe · « **Reply #33 on:** 8 Mar 2006, 03:41 pm »

Quote from: hifryer

Dont forget the filament transformer and make sure you tightly twist the heater wiring and keep well way from board where you can. Make it short not pretty.

Thanks hifryer,

Just didnt understood what you meant with "filament transformer" and "twist the heater wiring" ???

Regards,

hifryer · « **Reply #34 on:** 8 Mar 2006, 04:20 pm »

well the GK1 tubes are AC heated. I think there is a separate transformer for this. It could induce magntic hum depending on where you locate it. Keep it way from the signal path.

If you twist the wires from it to the tube sockets it helps contain any stray AC fields from these getting into the signal path as hum. Keep these well way from the solid state amplifier sections.

You have previously asked Hugh and he would be on top of this if a problem.

I make it as a general observation of a possible noise source.

GK1's built to the instructions are generally very quiet. Anything with a tube in it can have a small amount of noise. You can hear this if your speakers are VERY sensitive.

cheers

hifryer · « **Reply #35 on:** 8 Mar 2006, 04:24 pm »

sorry long time since i looked at a GK1!!

heaters are probably wired by board tracks so no issue!!

does it have two transformers or one with a separate heater winding??

anyway whatever wires from transformers should be twisted and kept away for low level input circuitry.

if you built to a given interconnection layout this will have been taken care of by Hugh.

Felipe · « **Reply #36 on:** 8 Mar 2006, 07:47 pm »

2 transformers, 1 for each channel. all AC wires are twisted and kept away from the signal input/output.

I am thinking of covering the inside of the copper plates with MUMETAL.
This will probably erase the remaining hum...

Thanks

AKSA · « **Reply #37 on:** 8 Mar 2006, 09:03 pm »

Felipe,

Just how much hum remains? From what distance from the drivers can you hear this noise?

Try isolating the transformers from the chassis electrically.

Rom in Italy tells me this really worked for him and I can see it's a good option.

Cheers,

Hugh

Rom · « **Reply #38 on:** 9 Mar 2006, 08:10 am »

Hi Felipe,

My cure on my TLP hum problem was basically getting rid of the metal case all together, and swap it with Flexiglass (lexan as known in other places) by doing so, I completely isolated electrically (or magnetically)the transformer and the TLP board, I did the same thing on my GK1 prior to this and since I did not have any hum issue on the GK1 might as well do the same on the TLP and it works. I have even replaced the coaxial and have a CAT5 cable now and still it's hum free.

I have the CD player on pause and have the TLP on full volume and no Hum or any noise coming out on the speakers on top of this I have about 3 meter of coaxial lead from the TLP to the amp.

Good luck and have fun.

Cheers
Rom

Felipe · « **Reply #39 on:** 9 Mar 2006, 09:16 am »

Hi guys,

The remaining HUM can be heared clearly till about 50cm away from speaker.
From the listening position, in absolute silence (night time) , i can hear a very faint HUM. Its almost imperceptible....but its there.
Its still very audible next to the speakers so i WILL try to remove it.

Rom,
My case is all wood. No electrical contact except on copper plates around the transformers. I did isolate the trans from the copper plates and i believe this was the thing that turned the BIG hum into the SMALL hum.

Coax and CAT5 seems to have same effect on this because i have LEFT channel on coax and RIGHT channel on CAT5. Same hum on both speakers....
This is why i will try to shield the copper plates with an aditional MUMETAL.
Its this or take the trans out of the box...and place them in a separate. But that's so odd....

I will try to measure the hum frequency next weekend. maybe this will help to determine if this is really from the trans..
Cheers