2. amps-preamps
  3. 1332600947

Hum from both speakers...This is New Please read.

Hi All, I would like to say I am new to channel after a long recovery from mid-fi! I am building a system in my home office. It consists of; Jolida 302crc (new tubes tried ), Jolida glass FX Dac, Jolida jd9, Rotel 2500 turntable..., pioneer elite pd65. Monitor Audio Silver RX2, Epos M Sub.
AQ rocket 88 speaker cable, AQ IC's.

So, the Jolida 302 is new. Since the first setup there has been a hum from both speakers. For the last month, I have been going insane throwing time and money at the problem. I have read, I think, every post on audiogon bout hum and the related links connected to other sites.

So, this AM, I am chasing the problem again, and I noticed that when I disconnect the negative speaker connection on the right speaker it goes away. Dead silent. Plug it back in and It returns. If I do this on the left speaker, it does not go away. Thes are biwired speakers and the hum only goes away on the right speaker, negative, low Freq posts. If I switch speaker sides, hum is still there but removing the right negative does nothing.

So,

Is it the negative speaker post on the amp?
Is it the negative speaker post on the speaker?
Is it the cable?

Could the ground in the amp or the speaker be loose on the right neg. post?

I know this subject has been beaten to death, but I think I am going to need counseling if I don't solve this.

Thanks in advance,

Troy
plosive
wolf_garcia
6,631 posts
 
Ground "floating" often fixes this sort of thing...I use my REL sub "floated" (it has a switch for this)...works fine and the whole system is hum free. I also use a PS Audio Humbuster to keep DC crap out of the main amp (currently a Jolida 502P).
atmasphere's avatar
atmasphere
11,633 posts
 
That does sound like it could be a ground loop problem, but if so it has something to do with the subwoofer. If you unplug the subwoofer from the wall that should manage the hum.

If not, then my 2nd theory is that there is a wiring bug in the output section of the amplifier.
plosive OP
16 posts
 
First off, thanks for all the responses! I tested so many different things yesterday, my head was numb by about 11pm PST. So to know avail, I could not make it go away. Even with cheater plugs on everything and nothing!!!!! Different plugs around the house.... My neighbors house!

So as I sit now, the AMP is now making it's way to the very kind and awesome tech's at Jolida. While it is there having it's hum chased down and killed, I am having the rest of the upgrades done and will be going to KT88 tubes when it gets back.

So for now, I have plugged my 1976 Pioneer SX 850 receiver again and I stand with my mouth agape at how great it really does sound!!!! Clean, smooth, rich, warm and vintage!

I may have to consider keeping it as the preamp and see how that works out.

Thanks again all and I will update when the traveling AMP returns home.

Troy
minorl
1,015 posts
 
I'm not sure you have tried things in the right sequence.
1. Plug CD player into DAC into pre-amp
2. Plug pre-amp into amp
3. plug amp speaker out to speakers.

Turn everything on. Noise? no. Then plug another component in such until noise comes and you have found the problem. if yes, there is noise from 1-3, then turn everything off and then unplug the DAC from the pre-amp. Turn equipment back on. Noise? no. then it is either the DAC, the CD player or the cables between the DAC and the pre-amp or the cables from the CD to the DAC. turn components off, then unplug each cable one at a time and turn equipment on to see if noise is still there or gone.

The best and easiest way to isolate a bad piece of equipment or a ground loop is to start simple. one source to pre-amp to power amp to speakers and if noise is there, turn off, unplug cd first, then DAC then pre-amp then etc.

once you have found the component, and remember to do this is sequence so that only that component could be the problem, then isolate and repair the component or replace it. lots of times it is a ground loop. I have gotten rid of many ground loops by doing the following. 1). Plug all low level signal electronics (CD, DAC, pre-amp, tuner, TT, etc.) into a power conditioner/source and then plug that into a separate independent outlet. 2) plug the amp into their own separate independent outlets.

I have found that a minimum of three separate outlet runs to the circuit breaker panel is required. All low level electronics plugged into a power conditioner/device, amps plugged into their own separate power outlets.
plosive OP
16 posts
 
Minori,

Thanks for the detailed plan. I like the very structured approach and as soon as the AMP returns, I am going to try your methods.

As far as the outlets, my problem is the distance from the source. Should I purchase long PC's (~12 feet to the next outlets)? What is better, Longer power cords or IC's?

I have some freedom in the room as far as placement and I have been considering a rack on the side wall and running longer speaker cables and/or a mix of components on the front wall. This would be helpful as space is an issue up front.

The System is in my home office. If you look at my system, you can see that everything is sitting on a credenza. I am not happy with this placement.

Some components can go in the cabinet, but I would like to have the Jolida, Pioneer and the VPI Scout (Being delivered Saturday 3/30/12) visible for looks and ease of use. I also have the Jolida Phono Stage, Jolida DAC and a Pioneer Elite CD player. Behind the cabinet are all the cables and a monster HT2500 power center. Any Ideas on optimum placement would be much appreciated.

Thank you for your time already. Any help on the above from you are anyone else that would like to support a newbie, would be great!
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