hissing sound, is that a ground loop?

stump4545 · « **on:** 15 Feb 2010, 09:42 pm »

when i power up my new system i notice a slight hissing sound coming from the speakers when there is no music playing?

i have a tubed pre amp, solid state amp, dac, and a mac mni.

is that the dreaded ground loop or something else?

Wayner · « **Reply #1 on:** 15 Feb 2010, 10:00 pm »

No. A ground loop will produce a 60hz (really low) frequency hum. What you may be experiencing is some unusual gain issues.

Wayner

mjosef · « **Reply #2 on:** 15 Feb 2010, 10:59 pm »

Quote

a slight hissing sound coming from the speakers when there is no music playing

Perfectly normal if your ear is within a feet (or two) of the speaker. The level of the hiss would vary with the sensitivity of the system.

stump4545 · « **Reply #3 on:** 15 Feb 2010, 11:05 pm »

yes i only hear it when i'm a 1-2 feet away from the speaker. it doesn't really bother me just wanted to make sure nothing was wrong

jriggy · « **Reply #4 on:** 16 Feb 2010, 04:00 am »

I recently added a Conrad Johnson PV14ls2 tube pre to my system and now get an audible hiss @ the listening position... BTW, my speakers are 87db sensitivity.
Could someone explain what an "unusual gain issue" is???

ltr317 · « **Reply #5 on:** 16 Feb 2010, 04:11 am »

Does the hiss come from both channels?

lcrim · « **Reply #6 on:** 16 Feb 2010, 05:49 am »

It could be tube rush or it may be that your system gain is such that you are hearing the power supply in your preamp.

JakeJ · « **Reply #7 on:** 16 Feb 2010, 07:38 am »

I'll bet my nickel on noisy tubes. In stump4545's case hearing tube "rush" that close to the speaker is fairly normal. In jriggy's case hearing it at the listenig position is unacceptable and he need to find quieter tubes.

NOS (New Old Stock) tubes are probably not necessary but if your system is resolving enough it could solve the problem and improve sound quality. The PV14LS only has two tubes in it andif both channels are affected then replace both. Probably not too expensive and if you source them from CJ they will likely be tested and matched. If you decide to use a vendor othere than CJ just be sure of the vendor's rep for quality. You can find a long list of tube vendors that members have had experience with and give recommendations for in this thread.

Hope this helps.

JakeJ

gerald porzio · « **Reply #8 on:** 16 Feb 2010, 11:25 am »

You're hearing the thermal noise generated by your tubes.

jriggy · « **Reply #9 on:** 16 Feb 2010, 08:57 pm »

Quote from: gerald porzio on 16 Feb 2010, 11:25 am

You're hearing the thermal noise generated by your tubes.

Will changing the tubes (as others suggested) elevate this?

I will switch out to one of the spare pairs that came along with the unit and see if it diminishes...

gerald porzio · « **Reply #10 on:** 16 Feb 2010, 09:54 pm »

Changing tubes might help it, but there are no guarantees. If you like the preamp, it's certainly worth a shot.

drphoto · « **Reply #11 on:** 17 Feb 2010, 04:37 am »

I personally wouldn't source the tubes from CJ. They'll likely be Sovteks and overpriced. I'm not knocking, CJ, btw. I like their gear and the fact they support their legacy equipment, I just think you can get better tubes for the money elsewhere.

(I still wish I had my CJ MV-45 amp)

Noseyears · « **Reply #12 on:** 17 Feb 2010, 04:39 pm »

Another cause is the cables, If they are not shielded you might be picking up some interference or radio signals.

gerald porzio · « **Reply #13 on:** 17 Feb 2010, 08:47 pm »

If it was a cable issue the OP would hear hum not hiss.

Ronm1 · « **Reply #14 on:** 20 Feb 2010, 01:35 pm »

As others have said its the h/w more than laikely the/a tube. Should be easy enough to t/s.

jriggy · « **Reply #15 on:** 20 Feb 2010, 10:10 pm »

Quote from: Ronm1 on 20 Feb 2010, 01:35 pm

As others have said its the h/w more than laikely the/a tube.

Huh?

Ronm1,

you may be responding to the OP but, could you translate your response for me? Sorry for not getting your short hand... I want to assume that "h/w" = hardware but...

thanks

avahifi · « **Reply #16 on:** 20 Feb 2010, 11:01 pm »

Is the hiss coming from one channel or both channels?

Important question.

Frank Van Alstine

JakeJ · « **Reply #17 on:** 20 Feb 2010, 11:35 pm »

Quote from: avahifi on 20 Feb 2010, 11:01 pm

Is the hiss coming from one channel or both channels?

Important question.

Frank Van Alstine

Rereading the OP he used the term "speakers" so I assumed it meant both channels. I could be wrong but that's how I came to the conclusion it might be excessive tube rush.

Quote from: jriggy on 16 Feb 2010, 08:57 pm

Will changing the tubes (as others suggested) elevate this?

I will switch out to one of the spare pairs that came along with the unit and see if it diminishes...

Did you get a chance to swap out tubes and if so what were the results?

Quote from: Wayner on 15 Feb 2010, 10:00 pm

No. A ground loop will produce a 60hz (really low) frequency hum. What you may be experiencing is some unusual gain issues.

Wayner

What (I believe) Wayner is referring to is that your preamp has too much gain for your amp (or vice versa). How far do you turn the volume knob before it's too loud. Typically if you get to the three o'clock position then its about right but if your at the "too loud" level at say ten o'clock then you may have too much gain from the amp (or preamp) resulting in hearing excessive tube rush or the limit of the preamp's noise floor better known as signal to noise ratio given in dB. An example might be DAC XYZ boasts a signal to noise ratio of 105 dB (good) and DAC ABC has a signal to noise ratio of 78 dB (not so good).

If the above is true it is too much gain. If not it's likely noisy tubes and getting better one should solve the problem. Frank's offering to help is very valuable and he has more tube and electronics knowledge in his pinky finger than I do in my whole body. Listen and learn

Is that about as clear as mud?

Jake

jriggy · « **Reply #18 on:** 21 Feb 2010, 06:26 pm »

JakeJ,

Thanks so much for the details... I have not gotten a chance to change the tubes yet (leaving town shortly for the week)... I believe I have a good amount of vol 'knob' movement. The C-J pre (PV14ls2) has buttons for up and down vol. but I use anywhere from "10" to "30" or sometimes "35" for displayed level numbers... That seems like good 'knob movement' to me... It may still be gain with the high gain C-J pre going into a hi current amp (Halo A51), with relatively low efficiency speakers (87db). Am I right to think that?

The extra tubes I have to switch to are the same as what is in there BTW

Ill, try the other tubes when I get back, and maybe even try another brand, then look into excessive gain after that... Excuse my lack of tech knowledge here, but what numbers do I look at for the pre and amp when checking this out???

Thanks so much

Jason

gerald porzio · « **Reply #19 on:** 21 Feb 2010, 06:33 pm »

It's not a matter of #s, but whether the hiss gets reduced thru any changes in tubes you substitute. Why put the cart ahead of the horse? You haven't done anything yet.