Tube Preamps and hum

polkatese

Folks,

I am curious if it is expected that tube preamp is "noisier" than SS preamp. I noticed that, with my new Dodd MLP, I get slight hum and white noise. It's not the case with my SS setup. I have MLP, Krell 400xi (in power amp mode), and LSi15 setup. I also plugged the MLP through PS Audio Ultimate Outlet brick. While it helps a bit, I still can hear the white noise. Is it due to higher-gain amplification?

As far as sound, the MLP sounds great, improvement in bass quality is very obvious, mid and high are cleaner and detailed. I would characterize its sound as "weighty."

Any advice on what I can do to eliminate the noise? thanks..

ND13

I get the slight hum with my ELP, also. I've been told thru some PMs that it shouldn't ,but I'm very pleased with the sound so far. I don't have the white noise issue, though.

shack

http://www.polkaudio.com/forums/showthread.php?t=29885

reeltrouble1

Yes you will get a slight bit of hum with tubes that is normal.
What is slight? Well with my MLP Dodd I have to be within 1 meter to notice it and put my ear to the SRS-SDA speaker to really hear it, it is slight. If you notice it lessens as the tubes warm up or it starts to become more noticeable you may very well have a bad tube, Gary Dodd burns everything for 100 hours to check for probems etc, but a tube can be damaged in shipping.

RT1

dragon1952

I get a slight hum from my ELP also. You have to put your ear up to the speaker to hear it however. I just assumed this was normal.

ND13

dragon1952 wrote:

I get a slight hum from my ELP also. You have to put your ear up to the speaker to hear it however. I just assumed this was normal.

Yes, same here. You have to be very close to the speaker and it is only when the standby/mute switch is engaged. I let mine warm up for at least 15 minutes, is that long enough?

polkatese

ok, gents. thanks for the quick response. That is what I heard within a feet or so from the speaker, so, I assume it is normal, then.

shack

I'm not sure it is "normal"...just common. When I emailed Gary on several occasions he stated that in a couple of systems he had my ELP hooked up to it was dead quiet. He was finally able to connect it to a friends system that produced the symptoms and allowed him to do some additional power supply filtering which improved the problem significantly. I think it may be a system/synergy issue. Hum in some...not in others...

ND13

I haven't unhooked/moved/adjusted any part of my system(save for the tubes) since the initial set-up so i might try that to see if anything changes. I didn't notice any difference in the hum with the different tubes, so I don't think they have anything to do with it in my rig.

polkatese

shack wrote:

I'm not sure it is "normal"...just common. When I emailed Gary on several occasions he stated that in a couple of systems he had my ELP hooked up to it was dead quiet. He was finally able to connect it to a friends system that produced the symptoms and allowed him to do some additional power supply filtering which improved the problem significantly. I think it may be a system/synergy issue. Hum in some...not in others...

Shack,

So, did your ELP finally "knows" the words? I am still trying to find a way to "silent" my MLP. Any suggestions? Thanks...

faster100

Seems to be a dodd pre thing, My audio experience pre didn't hum.. nor have any of my ss pre's... Not saying its a problem, But its evident its common with the elp and mlp on this forum anyways...

dorokusai

I've owned in-house, Anthem, Cary Audio, Consonance, Dodd Audio and Sonic Frontiers, and they all exhibited "hiss" in one way shape or form....it's a tube artifact. It will also vary with different tubes and is as much a part of it's "signature" as the actual audio spectrum reproduction.

I've never heard a noticeable "hum" in ANY of them. If you have it, you have a problem.

beardog03

My Rotels humm with my ELP..
Not so much with the Parasound....(very vague)

may be it`s a grounding issue...
or the amp your using..?

just a thought....

jcaut

I get a little hum from my ELP. Actually the Sunfire amp that it's connected to has a very slight hum with nothing connected to it- It's not dead quiet anyway. When the ELP is switched on, the hum increases a little bit. I still have to be right against the speaker to hear it. When the pre is switched into the system (mute off) the hum and hiss increase about threefold. It's still not what I would call objectionable. I figured it was normal. If the room is very quiet, I can hear it from a few feet back from the speakers, though. It's about the same with all the tubes I've tried.

Jason

RuSsMaN

It has to do with the input impedance and design of solid state amps. It doesn't have anything to do with the Dodd (or any other) design. Tube preamps are meant to mate with tube amplifiers. Gary isn't lying when he says the ELP (and up) are DEAD quiet. They are, hooked up to his 120w tube monoblocks.

You can get lucky, and find a good 'match' with no hiss mating tube and solid state, but it's really a crap shoot. That being said, the benefits of the tube/ss combo outweigh the negative (hiss) substantially.

My SRS 2's have some hiss, but I'm not changing anything. Melos SHA-1 Tube line amp, and Conrad Johnson Sonographe 120 Solid State amplifier. Two very highly regarded peices of gear - but not a 'perfect' match on the noise floor. As stated above, the plus greatly outshines the negative.

You want your tube preamp dead quiet, ditch the solid state amp.

Final note, hum and hiss are two different animals. 60 cycle hum is not the same as an impendance mis-match, or harmonic hiss.

Cheers,
Russ

jcaut

Makes sense to me. I probably won't be ditching that Sunfire anytime soon however. I'll just live with the slight noise.

I generally listen to my stereo with music playing anyway.

Jason

jcaut

Just saw your edit, Russ. Mine does sound a lot like 60Hz hum. I've looked at all the usual stuff to eliminate it, without any luck. I've only got the pre, amp, and a CD player connected (actually it's a DVD player, but no video, or any connection to the TV) and they're all plugged into the same surge strip connected to a dedicated 10ga. / 20amp circuit.

I did discover, a while back that the Sunfire amp, despite having a three prong power cord (not removable on this model) does NOT have the ground connected to the chassis or anything. It's just clipped off inside the case. I figure they had some reason for doing this, but I've wondered what would happen if I connect the ground to the chassis.. The DVD player has the stock two prong cord, and the ELP has the removable IEC cord. I presume the ELP chassis is connected to the ground prong.

Jason

beardog03

[QUOTE=
I generally listen to my stereo with music playing anyway.

Jason[/QUOTE]


now that`s almost quote worthy...

dorokusai

I'll add to what Russman mentioned, as the "hiss", if you even hear that shite, should go away with the media involved. If you can't hear the music, the you have a problem.

unc2701

With my ELP, I get slight hum w/ the Adcom, none with the brystons... The bryston has pretty good ground loop rejection, so that's probably what it is w/ my system.

dorokusai

There are a few tangible reasons that this condition, "hum", could be created

Outlet
Interconnect
Component

I will presume that said individual has tried to eliminate the above variables....???

I recently found that I had a bad F Type Cable IC(MAIN), when I went thru a Component Video upgrade. The F cable worked perfectly up until then, which was strange. The cable ended up having a short, that was not present prior to the upgrade. It had me angry for a couple hours, then I just shot myself in the head.

All is well.

polkatese

Thanks guys! I supposed it's a matter of getting used to tubes' characteristics for me. I stacked my gears, and sit next to CRT TV, so I was curious if it might contribute to the increased noise floor. I have checked the outlet and interconnect. Component is the one that I am working on right now.

Update: As it turns out, G-loop problem! I doin't mind hiss, but G-loop is annoying. So, on to the cure...

organ

Like Russ said. Tube pre and SS amp combo can be noisy depending on the input imp of the amp. I get more noise with that kind of set up. When I have tubes all the way, I have to place my ear right up against the driver/tweeter to hear any noise. It's a little more noisy if I use a ss amp. I could hear it hum from maybe 1ft away and the hiss from several inches away.

Maurice

W WALDECKER

my Anthem pre 1L does not hum at all. it does exhibit a very slight hiss when i am near the speakers with no music playing. it sounds so good when the music is playing that i can forgive the slight hiss when it is not. i think it is a small price to pay for the warm musical quality that tubes provide...WCW III

madmax

With my Audible illusions I get zero hum, zero white noise with either solid state amps or tube amps. (although my tube amp has the slightest hum of its own coming from the transformer, not the speakers).