Preamp hum problem somehow related to inputs

arjscott · 21st October 2006, 12:20 AM

Hi all,

I recent bought a preassembled Twisted Pear Kookaburra preamp from a friend and have just finished putting it in an enclosure.

It sounds fantastic and puts my current consumer hi-fi integrated amplifier to shame, even with the problem I've encountered.

I have to say I have very little knowledge of electronics, but you have to start somewhere, right?

Anyway, the problem is, at high volume a rather loud hum appears to be generated and can be heard from the speakers.

I found if I wave my fingers near the input RCA or cable it affects the sound of the hum significantly. And, if I place my finger over the end of the RCA, the hum stops.

Does anyone know what the problem is, and if so, how can I solve it?

Thanks in advance.

Andrew.

v-bro · 21st October 2006, 12:36 AM

Seems like there's a ground problem, how does it sound with the input unplugged?

Leolabs · 21st October 2006, 01:07 AM

Maybe bad contact regarding ground wire.

Minion · 21st October 2006, 02:15 AM

Yes, It sounds like the Ground (Maybe the ground on the RCA inputs/Outputs) as loose or not connected....

Try tieing the ground wire from the RCA to Ground....

arjscott · 21st October 2006, 07:06 AM

Thanks for the replies. Quite right - it seems one of the inputs was not gounded properly.

It seems so simple now :-)

Andrew.

21st October 2006, 12:20 AM	#1
arjscott diyAudio Member Join Date: Apr 2006 Location: NZ	Preamp hum problem somehow related to inputs Hi all, I recent bought a preassembled Twisted Pear Kookaburra preamp from a friend and have just finished putting it in an enclosure. It sounds fantastic and puts my current consumer hi-fi integrated amplifier to shame, even with the problem I've encountered. I have to say I have very little knowledge of electronics, but you have to start somewhere, right? Anyway, the problem is, at high volume a rather loud hum appears to be generated and can be heard from the speakers. I found if I wave my fingers near the input RCA or cable it affects the sound of the hum significantly. And, if I place my finger over the end of the RCA, the hum stops. Does anyone know what the problem is, and if so, how can I solve it? Thanks in advance. Andrew.

21st October 2006, 12:36 AM	#2
v-bro diyAudio Member Join Date: May 2006	Seems like there's a ground problem, how does it sound with the input unplugged? __________________ Max. cone displacement can be several foot on any speaker!Too bad it can be done only once......

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21st October 2006, 01:07 AM	#3
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Maybe bad contact regarding ground wire.

21st October 2006, 02:15 AM	#4
Minion diyAudio Member Join Date: May 2006	Yes, It sounds like the Ground (Maybe the ground on the RCA inputs/Outputs) as loose or not connected.... Try tieing the ground wire from the RCA to Ground....

21st October 2006, 07:06 AM	#5
arjscott diyAudio Member Join Date: Apr 2006 Location: NZ	Thanks for the replies. Quite right - it seems one of the inputs was not gounded properly. It seems so simple now :-) Andrew.