How does the Ebtech hum-x work?
Lovguitar
when I hook up my tube reverb unit to my tube amp. Both have 3 prong
plugs. I didn't want to go with a plain old ground lift 3 to two
prong adaptor for safety reasons -- but it did work. The ebtech hum-
x also works fine, but I'd love to know how it does what it does. Any
techs out there willing to share?
thanks!!
Paul
Les Cargill
Lord Valve
No, it isn't.
You're as clueless about shit like this as you are
about Muslims. Shut the fuck up.
Lord Valve
Expert (please obsess)
Lord Valve
OK, kiddies - pull up a chair.
The $90 Hum-X works *really* well. So well,
in fact, that most people think some heavy mojo
must be involved...but inside that slick little adaptor
is a very primitive (but clever) little circuit. In a
standard AC receptacle, you have three contacts -
hot, neutral, and ground. The hot and neutral lines
pass straight through the adaptor, although there's
a tap from the hot line (with a resistor) to power the
LED. The mojo is in the ground line, which has
a pair of 6A/1kV diodes between the wall ground
connection and the adaptor's output socket ground.
These diodes are connected in parallel, with
the anode on one diode connected to the cathode
on the other. (And vice versa, obviously.) The
pair of diodes has a 1K 1/2-W rsistor in parallel
with it; as far as I can see, this resistor serves
to produce a "correct" indication when an outlet
tester is plugged into the adaptor, since without
it, the outlet tester will give an "open ground"
indication.
In use, the adaptor is placed between the wall
outlet (or socket strip outlet) and the line cord
of the device you're powering. It breaks ground
loops, and does it well, without putting any screwy-
sounding isolation transformers in the audio
signal path. My key rig was buzzing like a beehive
before I put three of these between my keyboards
and the socket strip. They worked so well I was
intrigued, and decided to sacrifice one of the
devices to find out what was in it. The guts are
heavily potted, and it was difficult to reverse-
engineer; I had to carve the potting compound
away from the components with several different
types of knives - an X-acto, a utility knife, several
scalpels, a file or two, etc. It took quite awhile!
Once I found out what was in there, I built a
custom AC box with a set of diodes between a
12G ground buss and each AC outlet. I used
a Bud-box and some square snap-in AC receptacles,
with a nice fat 12G line cord for the AC input. I also
included three heavy-duty MOVs, connected line-to-
ground, neutral-to-ground, and line-to-neutral. I had
hoped to modify one of those "line conditioner" rackmount,
units, but all the ones I had in stock - four different brands,
in fact - used duplex-style outlets which self-grounded
to the chassis. Snap-in outlets, on the other hand,
are available with no "automatic" ground connection,
and can be isolated from the chassis and from each
other, having solder connections for all three contacts
at the rear. My key rig now plugs into a slick-looking
block with seven outlets on it - three on each side, one
on the face opposite the line cord entry point.
This is an ingenious device; it rates the title because
the people who came up with it were geniuses - they
figured out how to sell $2.00 worth of parts for $90.
My hat is off to them. ;-)
Lord Valve
Expert (please obsess)
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boardjunkie
I've seen that diode/resistor/cap trick used in some amps as a way of
quieting the ground circuit in the front end. Seems like it was used
in some PV and Fender models IIRC.
Lovguitar
WOW!!! Thanks for your response. Glad you took the time to reverse
engineer the thing and to answer my question.
Thanks again!
Les Cargill
> Les Cargill wrote:
>
>> Lovguitar wrote:
>>> I picked up an ebtech hum x because I've been getting a bad ground hum
>>> when I hook up my tube reverb unit to my tube amp. Both have 3 prong
>>> plugs. I didn't want to go with a plain old ground lift 3 to two
>>> prong adaptor for safety reasons -- but it did work. The ebtech hum-
>>> x also works fine, but I'd love to know how it does what it does. Any
>>> techs out there willing to share?
>>>
>>> thanks!!
>>>
>>> Paul
>>
>> It's an isolation transformer.
>> http://en.wikipedia.org/wiki/Isolation_transformer
>>
>> --
>> Les Cargill
>
> No, it isn't.
>
You're absolutely right - the Hum-X is not the Hum Eliminator,
which *is* an iso xformer.
> You're as clueless about shit like this as you are
> about Muslims. Shut the fuck up.
>
Ah, no. No, I don't think so.
> Lord Valve
> Expert (please obsess)
>
>
--
Les Cargill
tommyh...@gmail.com
Lord Valve
Lord Valve
Expert (fuck you)
dcd_g...@hotmail.com
;-) Gaston
Lord Valve
> Wow.. what is the reason you are do aggressive? I'm just asking out of curiosity.. your reply is very informative and useful, though.
> ;-) Gaston
and certain asswipes who posted here. Some of them are still
here, and I still delight in pissing upon the clueless fucks.
Lord Valve, ThD
Expert (FUCK YOU!)
Got guns? *WE* do.
leeli...@gmail.com
> a pair of 6A/1kV diodes between the wall ground
> connection and the adaptor's output socket ground.
> These diodes are connected in parallel, with
> the anode on one diode connected to the cathode
> on the other. (And vice versa, obviously.) The
> with it;
The Hum X can handle 6 amps. But I want to build one that can handle 20 amps for a Quested AP-800.
So instead of 6A/1kV diodes I'd have to use a pair of 20A/1kV diodes.
But in the proposed 20A version, what should the value of the resistor be?
Lee
B