B&K AVR-202i DIY repair possible? Relays buzzing (I think) - otherwise normal? - Page 9

ZepOfLed · 4th August 2009, 11:24 AM

Thanks Iain,

I'll have a look around the forum and post some pictures tonight, though you may not like the looks of it

. It's far from most of the neat and orderly amp wirings I've seen on this forum, but then I don't have a PCB for the RCAs/pots. It's "ghetto" if you'll excuse my terminology. Back later.

ZepOfLed · 5th August 2009, 12:50 AM

Iain, I have sent some pictures of my wiring to your email address. The ones labeled '(edit)' have annotations. Quite a mess it is

! If you need any clarification or, more pictures, I'll be happy to oblige.

The main star point has a bolt with loops connected to the end of each GND wire. I could only salvage one of these connections from the preamp section, so I made a "pre-star-point star point" for the RCA and pot GNDs and connected it to the main star point via the last loop. I don't know if this is a problem or not.

Like I said, with my mp3 player as an input, there is no buzz or hum.

The hum happens when I have inputs from another mains connected component, but I guess that is generally the case

.

Iain McNeill · 6th August 2009, 04:31 PM

Logic says that it's the leakage current in the input grounds thats putting a hum on the pot grounds due to that son-of-star ground scheme of yours

My gut says it's the huge loops formed around the pots with your wiring.

I'd try shielded cable from input to pot. Shielded cable from pot to amp PCB. tie both shields at the pot. tie the shield at the PCB board. don't tie the shield at the RCA jack. Tie both the RCA ground and the amp input ground to the REAL star point.

ZepOfLed · 8th August 2009, 04:12 AM

Ok, this is strange. I was just messing around, using my friend's HK as a preamp for my B&K 202 power amp, when I found an interesting development.

This whole time that I had been using the HK, I was routing video signal from the PS3, through the HK and out to the TV via RCA cable. This is when I mentioned the apparent ground loop buzz.

However, when I disconnected the video cable from the TV, the buzz disappeared almost completely. I'm now using HDMI from my PS3 straight to my projector and there is only an almost inaudible hiss (I had to put my ear right up to the speaker to even dream of hearing it). So, it looks like that was the source of my buzzing troubles.

It seems strange to me though that a video RCA, making no interaction with the amp directly, would affect the signal so much. (It went from the monitor out on the HK to the video in on the TV.) Must have caused some adverse ground issues somehow. Oh well!

In any case, I have the amp working the way I like and can finally enjoy it again. Now I can really think about improvements and the future of my amp making/modding hobby

Thanks again to you who gave such helpful advice!

NOTE: MTAtech, whenever you are ready, let me know where you want to start on your 307 and I'll let you know whatever I can.

Iain McNeill · 8th August 2009, 04:46 AM

The hiss is noise from the digital streams. Even digital signals need a ground return and all grounds have resistance. Making electrons follow a path is like herding cats

Keep us posted on your mods!

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4th August 2009, 11:24 AM	#81
ZepOfLed diyAudio Member Join Date: Jun 2009 Location: State College, PA	Thanks Iain, I'll have a look around the forum and post some pictures tonight, though you may not like the looks of it . It's far from most of the neat and orderly amp wirings I've seen on this forum, but then I don't have a PCB for the RCAs/pots. It's "ghetto" if you'll excuse my terminology. Back later.

5th August 2009, 12:50 AM	#82
ZepOfLed diyAudio Member Join Date: Jun 2009 Location: State College, PA	Iain, I have sent some pictures of my wiring to your email address. The ones labeled '(edit)' have annotations. Quite a mess it is ! If you need any clarification or, more pictures, I'll be happy to oblige. The main star point has a bolt with loops connected to the end of each GND wire. I could only salvage one of these connections from the preamp section, so I made a "pre-star-point star point" for the RCA and pot GNDs and connected it to the main star point via the last loop. I don't know if this is a problem or not. Like I said, with my mp3 player as an input, there is no buzz or hum. The hum happens when I have inputs from another mains connected component, but I guess that is generally the case .

6th August 2009, 04:31 PM	#83
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	Logic says that it's the leakage current in the input grounds thats putting a hum on the pot grounds due to that son-of-star ground scheme of yours My gut says it's the huge loops formed around the pots with your wiring. I'd try shielded cable from input to pot. Shielded cable from pot to amp PCB. tie both shields at the pot. tie the shield at the PCB board. don't tie the shield at the RCA jack. Tie both the RCA ground and the amp input ground to the REAL star point.

8th August 2009, 04:12 AM	#84
ZepOfLed diyAudio Member Join Date: Jun 2009 Location: State College, PA	Ok, this is strange. I was just messing around, using my friend's HK as a preamp for my B&K 202 power amp, when I found an interesting development. This whole time that I had been using the HK, I was routing video signal from the PS3, through the HK and out to the TV via RCA cable. This is when I mentioned the apparent ground loop buzz. However, when I disconnected the video cable from the TV, the buzz disappeared almost completely. I'm now using HDMI from my PS3 straight to my projector and there is only an almost inaudible hiss (I had to put my ear right up to the speaker to even dream of hearing it). So, it looks like that was the source of my buzzing troubles. It seems strange to me though that a video RCA, making no interaction with the amp directly, would affect the signal so much. (It went from the monitor out on the HK to the video in on the TV.) Must have caused some adverse ground issues somehow. Oh well! In any case, I have the amp working the way I like and can finally enjoy it again. Now I can really think about improvements and the future of my amp making/modding hobby Thanks again to you who gave such helpful advice! NOTE: MTAtech, whenever you are ready, let me know where you want to start on your 307 and I'll let you know whatever I can.

8th August 2009, 04:46 AM	#85
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	The hiss is noise from the digital streams. Even digital signals need a ground return and all grounds have resistance. Making electrons follow a path is like herding cats Keep us posted on your mods!

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