Hum issues

[lotus340r]

Hi guys,

I have a hum with my act2.2/350, even when the pre is in standby mode.

Is there a way to get rid of this without using so called 'cheater' plugs.

I don't think i'd be happy about not having everything earthed at the mains.

[joeinid]

I am not sure there's any way around the cheaters. I hope I'm wrong.

[rthomeint]

Every CJ amp I have owned with a three prong plug has required a cheater. You could try a cheater with a wire attached to the third prong ground to say a water pipe or the electrical box.

[GaryProtein]

Originally Posted by rthomeint

Every CJ amp I have owned with a three prong plug has required a cheater. You could try a cheater with a wire attached to the third prong ground to say a water pipe or the electrical box.

Doesn't using a wire attached to the third prong when using a cheater plug defeat the purpose of the cheater plug??

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(1) I would try grounding the preamp and power amp to the same outlet to avoid a ground loop between different circuits. (2) You could also use a wire to ground the chassis of the amplifier to the chassis of the preamplifier so they share the same ground. (3) You could use the cheater plug and not have it grounded, which isn't a big deal, and trust me, you'll get over it.

I have used all three of these options at different times with different systems, and depending on the individual case, they all work.

[lotus340r]

Originally Posted by GaryProtein

(1) I would try grounding the preamp and power amp to the same outlet to avoid a ground loop between different circuits.

Thanks, how would this work ?

They both go into a purepower 2000. Would both plugs have to share the same outlet socket ? Or would I wire both mains leads into a single shared plug ?

[lotus340r]

Originally Posted by GaryProtein

(2) You could also use a wire to ground the chassis of the amplifier to the chassis of the preamplifier so they share the same ground.

Hi, sorry but on this option, do i just leave the two mains leads as is ?

[Rayooo]

if all preamp input cables are all disconnected, with preamp in standby as described, does it still hum? .. that is, the only signal cables connected at all are going from preamp output to pwr amp input.

[rthomeint]

[QUOTE=GaryProtein;315071]Doesn't using a wire attached to the third prong when using a cheater plug defeat the purpose of the cheater plug??

This is a way to connect a 3 prong power cord to a 2 prong outlet. Some cheater plugs were made with a short peace of wire leading out were the thrid prong would be and this is used to ground at a screw used to attach the outlet cover plate, which would use the electrical box as a ground. This way to ground a three prong plug to a 2 wire electrical system which is the way alot of homes built before the 70s were wired.

[lotus340r]

Originally Posted by Rayooo

if all preamp input cables are all disconnected, with preamp in standby as described, does it still hum? .. that is, the only signal cables connected at all are going from preamp output to pwr amp input.

Thanks, yes, it still hums with no inputs connected.

Also, if i just plug in one RCA lead and then short each channel the hum still persists.

Also, if i swap in a different preamp it still hums.

I tried plugging the power amp into a differemt wall socket the other side of the room but no change.

The most odd is that I opened up the plug on the power amp mains lead and disconnected the ground wire but it still hummed.

[lotus340r]

Very weird. I have everything plugged into a Purepower2000 which has its own back up battery. I put it into battery mode and literally disconnected the purepowet from the mains at the wall and it sill hummed. I also disconnected every other piece of equipment apart from the pre and power.