[Matt]

Hi. It seems when I turn on my EMP, as the tubes wake up, so does this hum through the headphones. It seems directly connected to the light of the tubes. It does not increase as the volume pot is turned up, nor does it decrease when it's turned down and ultimately turned to it's lowest value. It is clearly audible and one need not strain to hear it.

Is this a normal thing?

- Matt

 

[Nick Dangerous]

Make sure you have clean power and tubes that aren't noisy.

 

[jeremymayf]

make sure your tubes are plugged in well. Mine came with one of the tubes leaning slightly--it was imperceptable if you looked at it---and there was some humming (in the left channel only) for the first few minutes of warm-up. After I checked the tubes and made sure they were plugged in well, the problem never recurred. jeremy

 

[Matt]

...I'm not sure how I'd do this. I am not even sure how to take them out.

Also, if I did take them out, could I switch the ones on the far left and right? (Just out of curiousity)

Best,
Matt

 

[joelongwood]

To take them out, just wiggle them very slightly while pulling up. Make sure you get the pins lined up when putting them back in. And, yes, you can switch the left and right tubes. It's actually a very simple operation. Just make sure everything is off and cool when you do this.

 

[Matt]

...but to no avail. Still has that "note." Is it just bad tubes? I notice that it corresponds not to the warming of the center tube (which goes first), but to the warming of the side tubes.

It's not loud by any measure, it's very "background," but it's still there. Arg...is this normal at all?


Best,
Matt

 

[Ross]

Matt,

I have the same problem with my EMP, and also with my other tube amp (the HD83), but only when I use it in one particular room. When I use it in another room, the hum disappears.

I think it is likely to be a powerline problem or something to which it is connected which is causing the hum.

Ross

 

[Dusty Chalk]

Could be a ground loop. What are you using as a source, and where do you have everything plugged in (headphone amp, source, transport if separate from DAC, etc.).

I just found a really screwy problem with my speaker setup: the two sides of my Monster HTS1000 cause a ground loop. 4 plugs each side, one side switched. Things needing plugged in:

- transport
- DAC
- amp
- sub
- tape deck (yes, I still listen to tapes -- don't eff with me)
- headphone amp

Current solution (not happy with) -- only plug the things in which are currently in use. Sucks to be me.

 

[joelongwood]

I have a very slight hum as well. I really have to listen for it.......it's more like a sense of a hum, it's so low. But it is totally inaudible once the music starts, so it's quickly forgotten.

 

[Matt]

That's very interesting about the room thing...I will try it in another location. That is weird, though, because I've never had an amp do that on me.

Yes, the hum is slight and seems to disappear once the music gets going, but still it's non-optimum and I do hear it during quieter passages, which to me is unacceptable, especially since SS amps I've heard don't have that "feature."

As far as "where everything is plugged in" goes, I have the EMP AC adapter plugged into a basic surge protector. The AC adapter of my Discman D-25S is also plugged in there (the big, fat, recommended RatShack one). I did this because the other female jack on that outlet is switched to control my lamp and I couldn't do both in one outlet.

As you can tell, I've got D-25S > AR "Y" minijack-to-RCA IC's > EMP > 1/4"-to-1/8" adapter > Sony flimsy headband earbuds.

(the last two are because I am STILL waiting on my F^*&!NG HD600s from Jan Meier. In three days (Wednesday), it will have been four weeks since I ordered! Geez!)

*huff...puff...huff...puff*

Anyhow, I'll take my baby on a tour of her new house (she hasn't seen anything but my bedroom so far) and see how she does.

Well, this is exciting. At least now there's a chance that it's not some f-up that I now have to send in for repairs and WAIT for...AARRRRGGGHHHH!

Thanks, guys. Oh yeah, and pray for my '600s.

- Matt

 

[chych]

Hmm crazy idea but try reversing the polarity of the power plug? It seems to remove the nasty hum in my MG Head... I take no responsibility for any damage though

 

[Rob N]

The hum your experiencing is almost certainly due to the output tubes.I've had the same problems when replacing the ECC88's on my Earmax,different sets of tubes even of the same make have different levels of hum.If your using high impedence headphones the hum problem should be greatly reduced.

The problem is caused because the Earmax uses AC heaters and not all tubes have perfect heater to cathode insulation thus allowing some of the AC to be amplified as well as the signal.DC heaters would have eliminated this,although some people say amps with AC heaters sound better.

 

[Tomcat]

chych,

I can attest to the fact that proper AC polarity is a major factor for fatigue-free sound with lots of low level and ambience information. Not only with the Earmax, but with anything that has a mains power supply. And it is the cheapest tweak of them all. But I have never had any hum problems with my Earmax Pro, at all.


Rob N,

that sounds like a reasonable technical explanation. The following is a bit off-topic, but I remember reading your posts at HeadWize. I am curious: any new results with your tube rolling experiments? Any new headphone amps you have tried? I remember that you had quite a lot of them: the EAR HP4, the Cary 300B, the Sugden Headmaster, X-Cans v1 and v2, and that, in the end, you preferred the Earmax Pro, because of its fatigue-free musicality. Since our criteria for choosing audio gear seem rather similar, I'd be interested in any new findings you might have had. Thanks!

 

[Rob N]

Tomcat, the only set up I've tried is the Stax SR404 headphones and SRM 006t amp which had a very spacious sound but I could not get use to the treble which sounded very bright and (at least to me) unatural.I also found the SR404 phones comfortable but they are a large awkward square shape.

In the Earmax i'm currently using stock JAN Philips 6922 and a Sylvania 6201 Gold Brand as input valve.I know alot of people think the Philips 6922 tubes are poor but I quite like the softer sound.For a brighter sound you could try 1960's Mullard ECC88 as output tubes.

For the input tube I've found a Mullard CV4004 late production military type / Mullard M8162 / Mullard CV4004 with gold pins (branded as Siemens ECC801S) also work well with very low noise.

Other tubes I've tried in the Earmax

12AT7WA Sylvania early 60's ? looks internally the same as the GB 6201 but no gold pins and has white lettering good smooth sound

6201 Sylvania early 60's ? grey wing shaped plates,extra support rods,white lettering good smooth sound

Siemens 6201 made in 1980's so probably not a genuine Siemens very microphonic

RFT ECC81 1980's? nothing special

Golden Dragon E81CC Chinese,gold pins nothing special

GEC A2900 (same as ECC81) military box 1968, internally looks completely different to any other ECC81,apparently only ever made by GEC bright sounding, more hum than normal, expensive

 

[Tomcat]

Rob,

thanks a lot for the update!

When the tubes in my Earmax Pro needed changing, I went with the JAN Philips 6922, once again, largely due to your favourable review at HeadWize. Come to think of it, it's a bit strange that you perceive them as rather warm and musical, while some are especially critical of their harsh treble. Steinmusic, the German store where I ordered the replacement tubes, strongly recommended them, as well.

And a JAN Philips 12ATWC. So I bought the 12ATWC as a replacement for the stock input tube. I think this has been quite an improvement. But if I had been able to get a Sylvania Gold Brand 6201 in Germany, I would have taken it. There has been nothing but praise for it, since markl posted his impressions of it with his Earmax Pro.

Concerning electrostatic headphones: I haven't heard a single one that I liked. Even the big Stax 007 combo (Omega II headphones with tube amp) left me cold. It has lightning fast treble but the sound just lacks body and heft from the mids on down. It was just too sterile and uninvolving for me.

Currently, my favourite headphones are closed ones: an Audio Technica ATH-W100 and a Beyerdynamic DT 770 Pro. I am still curious: Are there any headphones you are partial to?