just in general, all gear has a difference in grounding potential. once you start hooking them all up, it is collective. we just have to combat the physics with technology.
the more gear you have just multiplies the problem, but the more gear you have makes for more character in your recordings...WHAT A PARADOX!!!

Ah I see.

I definitely like having different preamps for different tones etc and wouldn't want to sacrifice this!

I am wondering if a different headphone amp like the Samson S-Phone or ART HeadAmp 6 might not suffer from this hum with my other gear?

Would this be likely??

well, look at it this way, what happens when you stack noisy gear? by itself the noise is bearablr, but the more times you do it, it increases your noise floor and soon, the mix becomes fairly unclear. same with collective hum. if you get 3 pieces with noticeable hum inline with one another, it'll make for an unpleasant listening experience. if you already have a headphone amp, just try the ground lift adapter and see if that helps.

btw, i just tried a ground lift on my behringer headphone amp and it dropped the noise a few db. while not entirely gone, did help it out from where it was. my headphone amp is located in the tracking room and in another room from the CR. each room has 2 dedicated circuits and all go back to a secondary panel i setup just for the studio.

don't you have places like Wal-mart, it don't have to be made by mogami

If I bought a ground lift box, where should I put it in the signal path?

Should I put it between the outputs of my audio interface and HA4700 or should I plug it between the output of my GAP PRE73 and HA4700?

Do NOT life electrical grounds.
lift the signal grounds when you have to.

the aux inputs are unbalanced so you cant lift their ground. are you sure you are running the correct signal into them?
Lift the signal ground on the main input.

Ok I've just bought a Behringer MICROHD HD400 Hum Distroyer and I have to say the hum has completely gone!!

I first tried it by putting it between one set of outputs of my Layla 3G and the main inputs of the HA4700 and there was no change, hum was still there!!!

I then placed the HD400 between the second output of the PRE73 and the aux input on the HA4700 and hey presto the hum has gone!

The HA4700 is now working nice and quiet!

I am still confused as to why I would need to do this because it would appear that no matter which preamp I've tried this with and with balanced or unbalanced leads I always get an hum on the auxillary inputs of the HA4700.

I can't help but think that this is a problem with the HA4700 or dodgy wiring inside????

it is probably due to the fact that the GAP uses a wall wart transformer and has no dedicated earth ground.

FWIW: This is to me the best HP amp I ever used/owned. APHEX Systems 454 HeadPod(tm) Headphone Amplifier
Not the cheapest but simply the best. I´ve used several others before and they always lacked in gain and suffered from distortion problems. "Loudness heavy clients" complained before..but not anymore!

Whilst this may be the case for the PRE73 this wasn't the case for some of the other preamps I've tried?

Of the units you asked about.....I had a Presonus HP4 for about a year.

In that year it worked as advertised....nothing spectacular....but it worked.

After about a year, it developed scratchy pots. Do a google search and you will see this appears to be common with this unit.

It went in the trash, and I have yet to replace it.


For the price / performance, the Behringer seems like a good option.

Best of luck.

My Behringer 4700 died on me after a while, I had bought it new.

I had about 2 ok channels left, the other 2 channels did strange things. I tried to repair it.. *Note to everyone.. Behringer's are not made to be repaired. Glue all over everything, and other issues.* Then it seems like there were probably some faulty parts that would need to be ordered, replaced, and re-sautered into the board, and I'm not a tech wizard, so into the garbage it went. I understand Art gear is made to be fixed, not thrown away, so I like them for that.

Anyway, I like all of the features on the Behringer, but if there was a better brand that made the same thing with better quality for twice the price, I'd buy that.

Six months back, I searched and searched, and never did find the right item that would replace it. I bought an old Mackie headphone distribution amp thing instead, and it's nice, but doesn't have the features I want. As much as I don't want to, I've been tempted to buy another Behringer (and feel stupid for it), but I'm holding off, as I really don't want another one, I think they are ok (as in mediocre) for a while, but before long, garbage.

I have the same problem and it is exclusive to my GAP Pre. My other pres run quietly for the most part. The power in my house is pretty noisy and every outlet is ungrounded. I'm thinking of picking up the Hum Destroyer now to place in the path between the GAP Pre output and Audiofire 8 input. Would the Hum Destroyer affect the signal quality of the recorded source? Or would it just remove the hum and leave everything else intact? Does anyone know?

Try plugging the power brick of the AudioFire in if it's running on FireWire power.

My problem is definitely the Behringer HA4700. I've tried doing this with 6 different preamps (Focusrite ISA One, SPL Goldmike, ART MPA Gold, Focusrite Trakmaster Pro, GAP PRE73 and Studio Projects VTB1) and still have the same problem!!

I don't get any of this noise when I plug the PRE73 into either my Saffire Pro 24DSP and Echo Layla 3G preamps. In fact it is one of the quietest preamps I've tried!

I only use my Behringer HA4700 when someone needs to hear themselves REALLY loud! I use the Behringer Micro HD400 Hum Destroyer between my interface and HA4700 for getting rid of the noise when I use it!

I power my audiofire8 with a standard AC power cord, the kind that detaches from the back of a computer. I bought the audiofire used, without the original accessories, and this is the sort of cord that the guy at Echo recommended. I've never powered it solely through my computer's firewire port; didn't even know I could. The hum is only noticeable (aggravating) with the GAP pre.

Also, I'd say it is definitely a ground loop issue with my GAP pre, since the hum is loudest at 60hz, and then gets quieter at intervals of 120...240...etc.

I used to sell Samson at wholesale. The S-Phone was a really reliable unit, and hasn't been redesigned since it was introduced. They were made to be fixed, if necessary.
The B-word company tends to source end-of-run parts because they're cheap, but finding them for repairs is a pain.

Our church installed the Samson and it's been a great unit: running 5 pairs of in-ears...

Absolutely. I have power conditioners from Furman and Monster and everything goes into them. if the rack gear has a front panel switch, I use it. For those that don't, I use the power conditioner to switch their power, then do the front panel switched items one at a time.

I'm trying to decide between one of the Furman headphone mixers/distributors and the Presonus HP-60. You can get the Presonus cheaper but I like the Furman design that puts the breakout box in the studio so the musician can do his/her own tweaks on volume and more-me.

Thought I'd post a quick update!

I'm still in the market for a new headphone amp.

I picked up a secondhand HC-6 last week and found I had some issues with this! It looks as though it may be faulty and have to go back for a refund!

I was seriously considering getting the ART Headamp 6 Pro but have read a few worrying user experiences of channels popping and blowing headphones !!!
I did notice that all these defective units were bought from the same store and were bought within a month or so of each other so could be a dodgy batch!! Still worrying though that 4 of them blew headphones with exactly the same fault! Some of my headphones cost over £200 and don't want to be replacing those!!!!

The SM Pro Audio HP6e looks like a good option but can't find many user experiences of this one!?? One person likes it and another doesn't and that's about it!!!

It's been a while since I posted this thread and I'm wondering how peoples headphone amps are holding up?? Anyone discover any faults/issues with any??

Just picked up an HA4700. Once I plumb it in i'll let you know how it is.

Gotta say though that according to the specs it's different to the HA8000 and it looks like the amps in the HA4700 are much more beefy. I'd rather have 2 HA4700 over one HA8000.

HA4700 has great features but the hum is ridiculous.

Anyone know of a good alternative?

Maybe faulty power supply. Try ground loop cut.