GC noise and heat issues

fishski13 · 7th July 2009, 09:33 PM

i built a GC based on Peter Daniel's schematic, but without input R1: http://www.diyaudio.com/forums/attac...amp=1210693738

when connected to my pre-amp (CK2III) i have no issues - sounds wonderful without noise or overheating. but when the pre-out is muted on the pre-amp, i get a buzz that starts out very faint in both channels, but increases in volume with time. the temp of the chassis increases too - gets pretty hot.

what's going on here? is this oscillation?

[IMG]

[/IMG]

Shenda · 7th July 2009, 10:50 PM

Yep!

fishski13 · 7th July 2009, 11:06 PM

thanks!

so a Zobel network of 2.7uF cap in series with a 10R resistor between speaker (+) and (-) will work?

for clarification, when the pre-amp outs are un-muted and the amp is idle, i get no buzzing and the GC is thermally stable - it's only when the output is muted that the buzzing occurs and the amp becomes hot.

leadbelly · 7th July 2009, 11:13 PM

Quote:

Originally posted by fishski13
so a Zobel network of 2.7uF cap in series with a 10R resistor between speaker (+) and (-) will work?

Probably not. Since changing the input configuration affects things, it sounds like your problem is there. Are you sure R2 is connected properly?

fishski13 · 7th July 2009, 11:16 PM

well here's a pic - the twisted wire is ground:

[IMG]

[/IMG]

leadbelly · 7th July 2009, 11:20 PM

Sorry, I can't see any of your pics. I don't know if it's the firewall at work or bad links. Maybe somebody else can help.

fishski13 · 7th July 2009, 11:24 PM

http://i23.photobucket.com/albums/b3...esHi-Fi001.jpg

or

http://i23.photobucket.com/albums/b3...esHi-Fi001.jpg

leadbelly · 7th July 2009, 11:32 PM

OK, it's my work firewall, can't see your pictures.

Also, I looked at the "preamp" you linked, there's no mute circuit in the schematic, so what does your "mute" do?

Thzar · 7th July 2009, 11:39 PM

I see all the pictures

If the R2 is not connected + no input pot is used you will get the whole Vcc on the speaker output. = toasted speakers.

But it sounds like the preamp is the failing link.
The mute function is not mute, litterally speaking.

Tried different source,? like mp3 player
or shorted the inputs and just wait and see whats happened, if its silent silent and cool ?

Salas · 7th July 2009, 11:51 PM

Also make sure that the filter capacitors are not in touch with the sinking plate. Are they getting somewhat hot? Can you angle them a bit?

7th July 2009, 09:33 PM	#1
fishski13 diyAudio Member Join Date: Sep 2008 Location: Minneapolis, MN	GC noise and heat issues i built a GC based on Peter Daniel's schematic, but without input R1: http://www.diyaudio.com/forums/attac...amp=1210693738 when connected to my pre-amp (CK2III) i have no issues - sounds wonderful without noise or overheating. but when the pre-out is muted on the pre-amp, i get a buzz that starts out very faint in both channels, but increases in volume with time. the temp of the chassis increases too - gets pretty hot. what's going on here? is this oscillation? [IMG][/IMG]

7th July 2009, 11:16 PM	#5
fishski13 diyAudio Member Join Date: Sep 2008 Location: Minneapolis, MN	well here's a pic - the twisted wire is ground: [IMG][/IMG]

7th July 2009, 11:20 PM	#6
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Sorry, I can't see any of your pics. I don't know if it's the firewall at work or bad links. Maybe somebody else can help. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

7th July 2009, 11:32 PM	#8
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	OK, it's my work firewall, can't see your pictures. Also, I looked at the "preamp" you linked, there's no mute circuit in the schematic, so what does your "mute" do? __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

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7th July 2009, 10:50 PM	#2
Shenda diyAudio Member Join Date: Sep 2007 Location: Bihac	Yep!

7th July 2009, 11:06 PM	#3
fishski13 diyAudio Member Join Date: Sep 2008 Location: Minneapolis, MN	thanks! so a Zobel network of 2.7uF cap in series with a 10R resistor between speaker (+) and (-) will work? for clarification, when the pre-amp outs are un-muted and the amp is idle, i get no buzzing and the GC is thermally stable - it's only when the output is muted that the buzzing occurs and the amp becomes hot.

7th July 2009, 11:24 PM	#7
fishski13 diyAudio Member Join Date: Sep 2008 Location: Minneapolis, MN	http://i23.photobucket.com/albums/b3...esHi-Fi001.jpg or http://i23.photobucket.com/albums/b3...esHi-Fi001.jpg

7th July 2009, 11:39 PM	#9
Thzar diyAudio Member Join Date: Jun 2008	I see all the pictures If the R2 is not connected + no input pot is used you will get the whole Vcc on the speaker output. = toasted speakers. But it sounds like the preamp is the failing link. The mute function is not mute, litterally speaking. Tried different source,? like mp3 player or shorted the inputs and just wait and see whats happened, if its silent silent and cool ?

7th July 2009, 11:51 PM	#10
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Also make sure that the filter capacitors are not in touch with the sinking plate. Are they getting somewhat hot? Can you angle them a bit?

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