removed volume pots GainClone

Digidoo · 9th April 2006, 06:46 PM

Hi,

A few months ago I finished my first Audio DIY project; a GainClone. It's a quite simple design, two monoblocks and one powersupply. At first I wanted to use a couple of potmeters for the volume, but I used quite low quality ones.

Now I've got a nice DIY pre-amp and I removed the volume pots from my GainClone. The result is an enormous ground problem. Below you can find some pic's of the amp as it is now. Please remember that this is my first project and it isn't very pretty, although it did sound pretty.

The Powersupply, which works fine:

Left:

Right:

How it is in practise:

Thanks for the trouble everyone!

Nordic · 9th April 2006, 07:29 PM

I would make sure the RCA plugs are isolated from the case for a start, can't see them clearly on the pictures. Also I would put a -10 -56k resistor between the ground and hot points on the input RCA.

Edit again..

Hah I see Baz also saw that... post

Bazukaz · 9th April 2006, 07:30 PM

Hi,
Ground loops usually uccur due to incorrect wiring.
The output ground must be connected directly to PSU ground.The same for trafo's mid point.
ICs must also go throgh separate ground wires to the same common gound.
It is also important to add ceramic caps close to ICs(100nF or so).
A ~10K resistor across input/Ground helps , when inputs are left floating.

LM3886 must be totally quet if everything is made correctly.
I use gainclone without volume pots too.

neutron7 · 9th April 2006, 08:22 PM

is there any hum when theres nothing connected?

are both amps are sharing the same supply? if so they are not really monoblocks. the ground could be forming a loop from the interconnects sheilds, your preamp and the shared power ground. you could try lifting the ground on one of the preamp outputs.

bremen nacht · 9th April 2006, 08:42 PM

isn't 1000uF a bit on the low side for reservoir caps?

9th April 2006, 06:46 PM	#1
Digidoo diyAudio Member Join Date: Dec 2005 Location: Hopefully in the Black Madonna	removed volume pots GainClone Hi, A few months ago I finished my first Audio DIY project; a GainClone. It's a quite simple design, two monoblocks and one powersupply. At first I wanted to use a couple of potmeters for the volume, but I used quite low quality ones. Now I've got a nice DIY pre-amp and I removed the volume pots from my GainClone. The result is an enormous ground problem. Below you can find some pic's of the amp as it is now. Please remember that this is my first project and it isn't very pretty, although it did sound pretty. The Powersupply, which works fine: Left: Right: How it is in practise: Thanks for the trouble everyone! __________________ “Of course the music is a great difficulty. You see, if one plays good music, people don't listen, and if one plays bad music people don't talk.”

9th April 2006, 08:42 PM	#5
bremen nacht diyAudio Member Join Date: Feb 2004 Location: england	isn't 1000uF a bit on the low side for reservoir caps? __________________ All this radio needs is a fuse

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9th April 2006, 07:29 PM	#2
Nordic diyAudio Member Join Date: Sep 2005	I would make sure the RCA plugs are isolated from the case for a start, can't see them clearly on the pictures. Also I would put a -10 -56k resistor between the ground and hot points on the input RCA. Edit again.. Hah I see Baz also saw that... post

9th April 2006, 07:30 PM	#3
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	Hi, Ground loops usually uccur due to incorrect wiring. The output ground must be connected directly to PSU ground.The same for trafo's mid point. ICs must also go throgh separate ground wires to the same common gound. It is also important to add ceramic caps close to ICs(100nF or so). A ~10K resistor across input/Ground helps , when inputs are left floating. LM3886 must be totally quet if everything is made correctly. I use gainclone without volume pots too.

9th April 2006, 08:22 PM	#4
neutron7 diyAudio Member Join Date: Dec 2003 Location: Toronto Canada	is there any hum when theres nothing connected? are both amps are sharing the same supply? if so they are not really monoblocks. the ground could be forming a loop from the interconnects sheilds, your preamp and the shared power ground. you could try lifting the ground on one of the preamp outputs.

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