F5 hum

preiter · 8th September 2009, 08:04 PM

One channel my my F5 clone (Peter Daniel's boards) is humming badly. The other channel is silent.

The hum happens only when I have a signal connected (whether or not signal ground is connected). I even get hum when I connect the signal in to star ground.

I measured the resistance between board ground and star ground at .2 ohms. There is only one ground connection between the board and star ground.

Any clues about how to go about diagnosing this?

Nelson Pass · 8th September 2009, 10:15 PM

Try evaluating the noise with shorted inputs (hot to ground)
with the input grounds not externally connected to each other.

preiter · 8th September 2009, 11:41 PM

The hum happens when there is no external connection and the right signal input is shorted to star ground.

Nelson Pass · 8th September 2009, 11:51 PM

Then I would look for oscillation, if you have a scope.

preiter · 10th September 2009, 02:44 AM

Quote:

Originally Posted by Nelson Pass

Then I would look for oscillation, if you have a scope.

No such luck

Would oscillation be at 60 hz? I thought that was usually a high frequency thing.

Nelson Pass · 10th September 2009, 04:36 PM

Yes, it's a high frequency thing. The hum or buzz is just
the part you get to hear.

preiter · 10th September 2009, 06:47 PM

I think I found it. It's just a poor ground connection. The crimp-on ring connectors I used to connect all of the wires to star ground aren't making a very good electrical connection.

To find it, I connected a wire to the working channel's signal input and probed around with the other end to find out what wires hummed and what didn't. In the absence of a scope you have to get creative.

Charly1 · 3rd June 2012, 12:49 PM

Even my problem is similar. U use cilvier F5 board and Jims 2 power boards for each channel. When there is no input its great no noise at all ver clean. As soon as connect CD player or preamp it start humm. Any practical experience on this and solution?

Melon Head · 3rd June 2012, 12:58 PM

Are the rca jacks isolated from the chassis?
A picture would help though

Charly1 · 3rd June 2012, 01:07 PM

Melon. U refresh my brain. I made two amplifiers one raw allumium RCA ground was touching the ground it does not make the noise. Seems you give a vauluble point m second amplifiers I use proper box from Modushop. I think that RCA is not touchning the chasis. tmrw I will check that point. Highy appriciate ur feedback.

8th September 2009, 08:04 PM	#1
preiter diyAudio Member Join Date: May 2006	F5 hum One channel my my F5 clone (Peter Daniel's boards) is humming badly. The other channel is silent. The hum happens only when I have a signal connected (whether or not signal ground is connected). I even get hum when I connect the signal in to star ground. I measured the resistance between board ground and star ground at .2 ohms. There is only one ground connection between the board and star ground. Any clues about how to go about diagnosing this?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th September 2009, 10:15 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Try evaluating the noise with shorted inputs (hot to ground) with the input grounds not externally connected to each other.

8th September 2009, 11:41 PM	#3
preiter diyAudio Member Join Date: May 2006	The hum happens when there is no external connection and the right signal input is shorted to star ground.

8th September 2009, 11:51 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	Then I would look for oscillation, if you have a scope.

10th September 2009, 04:36 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	Yes, it's a high frequency thing. The hum or buzz is just the part you get to hear.

10th September 2009, 06:47 PM	#7
preiter diyAudio Member Join Date: May 2006	I think I found it. It's just a poor ground connection. The crimp-on ring connectors I used to connect all of the wires to star ground aren't making a very good electrical connection. To find it, I connected a wire to the working channel's signal input and probed around with the other end to find out what wires hummed and what didn't. In the absence of a scope you have to get creative.

3rd June 2012, 12:49 PM	#8
Charly1 diyAudio Member Join Date: Apr 2012	Even my problem is similar. U use cilvier F5 board and Jims 2 power boards for each channel. When there is no input its great no noise at all ver clean. As soon as connect CD player or preamp it start humm. Any practical experience on this and solution?

3rd June 2012, 12:58 PM	#9
Melon Head Banned Join Date: Nov 2006	Are the rca jacks isolated from the chassis? A picture would help though

3rd June 2012, 01:07 PM	#10
Charly1 diyAudio Member Join Date: Apr 2012	Melon. U refresh my brain. I made two amplifiers one raw allumium RCA ground was touching the ground it does not make the noise. Seems you give a vauluble point m second amplifiers I use proper box from Modushop. I think that RCA is not touchning the chasis. tmrw I will check that point. Highy appriciate ur feedback.