Quad 909 amplifier buz problem

[steevo]

I recently bought a Qaud 909 power amp and have discovered that it has
what i think is an internal ground loop problem. When I connect bothe channels
to my audiolab preamp there is a slight buz from both speaker, you have to put your ear close to the speaker to hear it but its there. If connect each channel indvidually then the right channels appers to be ok, the left how ever has a very low level of buzz noise. when both channels are pluged in the buz appears in both channels. This is obviously destroying the signal to noise ratio and distortion performance of the amplifier. Needless to say I am very dissapointed.
Has anyone bought Quad 909 amp recently and had the same problem.

As a side note, quad have done away with earth connection on the mains power supply, the amp is now a class II appliance. This might have something to do with the problem.

Has audioholics ever tested the quad 909 power amp, does anyone know.

Steevo

 

[walter duque]

First thing I would try would be a cheater plug.

 

[highfigh]

First thing I would try would be a cheater plug.

"As a side note, quad have done away with earth connection on the mains power supply," was the start of the second paragraph.

 

[highfigh]

I recently bought a Qaud 909 power amp and have discovered that it has
what i think is an internal ground loop problem. When I connect bothe channels
to my audiolab preamp there is a slight buz from both speaker, you have to put your ear close to the speaker to hear it but its there. If connect each channel indvidually then the right channels appers to be ok, the left how ever has a very low level of buzz noise. when both channels are pluged in the buz appears in both channels. This is obviously destroying the signal to noise ratio and distortion performance of the amplifier. Needless to say I am very dissapointed.
Has anyone bought Quad 909 amp recently and had the same problem.

As a side note, quad have done away with earth connection on the mains power supply, the amp is now a class II appliance. This might have something to do with the problem.

Has audioholics ever tested the quad 909 power amp, does anyone know.

Steevo

Take a piece of any kind of wire and connect it to the preamp and the power amp. You can touch it to the RCA shields or the case on both pieces, if you want. If the noise goes away, find a way to make it a permanent connection or try another set of interconnects.

 

[walter duque]

"As a side note, quad have done away with earth connection on the mains power supply," was the start of the second paragraph.

I guess missed that one. Maybe it's something causing it that' plugged into the same circuit.

 

[TLS Guy]

I recently bought a Qaud 909 power amp and have discovered that it has
what i think is an internal ground loop problem. When I connect bothe channels
to my audiolab preamp there is a slight buz from both speaker, you have to put your ear close to the speaker to hear it but its there. If connect each channel indvidually then the right channels appers to be ok, the left how ever has a very low level of buzz noise. when both channels are pluged in the buz appears in both channels. This is obviously destroying the signal to noise ratio and distortion performance of the amplifier. Needless to say I am very dissapointed.
Has anyone bought Quad 909 amp recently and had the same problem.

As a side note, quad have done away with earth connection on the mains power supply, the amp is now a class II appliance. This might have something to do with the problem.

Has audioholics ever tested the quad 909 power amp, does anyone know.

Steevo

I own three 909s and all of them are dead quiet.

The mains lead should NOT have a connected ground. My amps have cables that look like three pin but they are not. There is no connection in the ground.

Does the map hum when not connected to anything? If not the amp is OK.

A system should have one ground. I find the biggest problems especially with computer hook ups is resistance between cable grounds, phone grounds etc.

Stopping your kinds of problems, means a good house ground. That is three 7' copper rods, tied together. Phone, cable and satellite grounding blocks, need tying to the house ground wit 4 gauge copper.

Once you get this sorted out you will be vary happy with your 909, quite the best domestic amp you can get.

 

[takayama]

Hi TLS Guy

"The mains lead should NOT have a connected ground. My amps have cables that look like three pin but they are not. There is no connection in the ground."

What do you mean by "The mains should NOT.......? The power cable that came with my amp sure looks like a 3 prong = hot+neutral+ground???
My 909, which I just got used, has a hum/buzz when connected. It gets quiet when the pre-amp is turned off. My old NAD amp never gave the hum/buzz like this Quad (everything else remains the same set-up). The salesman told me because the 909 amp is very revealing...
I'm using Quad ESL-63 speakers.
As you said I disconnected signal input, then the amp does not make any noise through the speakers. Still not sure why NAD never did but this 909 is doing, louder through the right speaker.
I've read the big transformer that is in the unit is throwing EMF and being picked up by the amp boards. One reason new Quad QSP has metals shields attached to the amp boards?
Also this amp gets really hot...

Thanks
Daniel

 

[TLS Guy]

Hi TLS Guy

"The mains lead should NOT have a connected ground. My amps have cables that look like three pin but they are not. There is no connection in the ground."

What do you mean by "The mains should NOT.......? The power cable that came with my amp sure looks like a 3 prong = hot+neutral+ground???
My 909, which I just got used, has a hum/buzz when connected. It gets quiet when the pre-amp is turned off. My old NAD amp never gave the hum/buzz like this Quad (everything else remains the same set-up). The salesman told me because the 909 amp is very revealing...
I'm using Quad ESL-63 speakers.
As you said I disconnected signal input, then the amp does not make any noise through the speakers. Still not sure why NAD never did but this 909 is doing, louder through the right speaker.
I've read the big transformer that is in the unit is throwing EMF and being picked up by the amp boards. One reason new Quad QSP has metals shields attached to the amp boards?
Also this amp gets really hot...

Thanks
Daniel

The mains lead that comes with the 909 looks like a three pin lead but it is not. Use and ohm meter and see if there is a connection between the earth pins either end. If there is, it is the wrong cord. You can make it the correct one by using a ground break.

The fact that the buzz goes away when the preamp, is off means there is nothing wrong with your 909. What you have is a ground loop. In your system, only the preamp should be grounded, and NOTHING else.

 

[takayama]

Thank you TLS guy.
Your method worked.
Daniel

 

[TLS Guy]

Thank you TLS guy.
Your method worked.
Daniel

Thank you for the feedback. I'm glad your problem is solved. That salesman does not know his craft. He should of immediately given you the correct advice on how to solve your ground loop problem and not shot his mouth off about "revealing" amps! Take his advice with a grain of salt from now on.

 

[slipperybidness]

Thank you for the feedback. I'm glad your problem is solved. That salesman does not know his craft. He should of immediately given you the correct advice on how to solve your ground loop problem and not shot his mouth off about "revealing" amps! Take his advice with a grain of salt from now on.

Good advice.

Salesman obviously didn't have a clue so just spitting out nonsense to try to act like that is the nature of the amp.