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Old 24th August 2010, 05:24 PM   #1191
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Thanks for confirmation. The chip is fine...tested it with the other psu board and the dc offset is at 79mv. and the other around 80mv
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Old 25th August 2010, 06:12 AM   #1192
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Default buzzz

when i connect my amp to the speaker, the speaker emits a buzzing sound. And when i connect the rca, the buzz became louder. why?? Is the chip too close to the power?
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Old 25th August 2010, 06:32 AM   #1193
Nis is offline Nis  Denmark
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I've just finished building the chassis for my gainclone. While putting in connectors I realized that the RCA connectors I've bought have the outer sleeve connected to the chassis. Is this bad? It seems like Peters connectors are isolated from the chassis.
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Old 25th August 2010, 08:47 AM   #1194
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In short: Yes, it IS bad. You have to buy RCA's which are fully isolated to avoid grounding problems. You will most certainly get a humming noise with the signal ground connected to the chassis via the RCA plugs.

Martin
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Old 25th August 2010, 09:51 AM   #1195
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dc after the diodes are 37.8v.
rail at 28.35v.
why is there a buzzing sound?
is the chip dead?
do i need to ground the pcb?

Last edited by pmchoong; 25th August 2010 at 09:53 AM.
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Old 25th August 2010, 10:03 AM   #1196
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pcb grounded but buzzing still exist. i think it is the rca. when connect to cable, the buzz becomes very loud
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Old 25th August 2010, 11:33 AM   #1197
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Quote:
Originally Posted by martinbls View Post
In short: Yes, it IS bad. You have to buy RCA's which are fully isolated to avoid grounding problems. You will most certainly get a humming noise with the signal ground connected to the chassis via the RCA plugs.

Martin
Thanks Martin. I'll see if I can get some isolated RCA's.
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Old 25th August 2010, 11:53 AM   #1198
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pmchoong, please make sure of these things:
1: As with the other gentleman your rcas should be insulated from the chassis. (its okay that they touch but it can cause ground loops which will buzz)
2: Do you have signal going to signal or do you have signal and ground switched around on your RCA plugs?
3: this buzzing can be caused by bad solder joints and if you made your own RCA cable there could be bad joints there or you could have bad joints in your input RCA jacks on your chassis.
4: solder joints could be bad at signal input to amp boards.

That covers bad solder joints I guess. Another thing to try is this:
With ground loop problems sometimes just touching signal wires, heatsinks, volume pots with our fingers can cause the hum to increase and then we know we have a grounding problem. With the amp on try this out. Wiggle the wires, touch the volume pot, touch the heatsink. Does the hum/buzz change when you do this?
Take some pictures. Lets see whats going on here.
The fact that it gets louder when you connect the RCAs makes me think that there is a bad solder joint that goes to ground. Check extra carefully for that and if you DIYed your own preamp check that on another piece of equipment to make sure its not part of the problem.
Uriah
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Old 25th August 2010, 11:54 AM   #1199
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Nis,
This might or might not be a problem. If you want to know before you spend the money then simply remove them from the chassis and plug them back together and see if you get the same problem.
Uriah
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Old 25th August 2010, 12:09 PM   #1200
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Quote:
Originally Posted by udailey View Post
Nis,
This might or might not be a problem. If you want to know before you spend the money then simply remove them from the chassis and plug them back together and see if you get the same problem.
Uriah
The only problem, yet, is that I need to drill some bigger holes in the chassis. I haven't actually done any soldering apart from putting the components on the board. I was just asking because Peter's connectors seems to be grounded and all connectors I could find around where I live were not isolated from the chassis.

I have ordered a pair of these: Pair Gold Plated RCA Phono Chassis / Panel Sockets on eBay (end time 25-Aug-10 19:41:50 BST)
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