What does the ALH1 Audio Hum Eliminator do?

The ALH1 Audio Hum Eliminator eliminates hum in Stereo and Home Theater Systems. Components in different locations are most susceptible. Hum results from slightly different ground potentials at the power plugs. Long audio cables exasperate the problem. The ALH1 Hum Eliminator will cancel hum up to 2.5 volts- plenty of capability to handle common ground related hum up to several hundred feet in length in a building (typically up to 20mv). The ALH1 Hum Eliminator cannot correct for defective audio cables or defective AC power wiring or connectors. Also, performance is only assured with modern 3-prong grounded receptacle wiring.

How does the ALH1 Audio Hum Eliminator work?

The ALH1 is an active electronic circuit which cancels hum by processing only the difference between the signal and the shield ground, effectively cancelling hum on the shield ground by injecting an opposite polarity hum signal. The signal remains true and unmodified, and has the same output level as the input. Independent controls are provided for tuning the circuit to the individual type and length of cable. The ALH1 Hum Eliminator is unlike an isolation transformer, which has insertion loss (drop in signal level), poorer frequency response, and greater distortion across the frequency band. Transformers can provide massive quantities of Common Mode Rejection at higher voltages, but that is rarely what is needed in a home audio system. Also, a quality transformer needs complicated winding and is therefore expensive. The ALH1 delivers highest performance audio quality.

What components can be used with the ALH1 Audio Hum Eliminator?

You can use the ALH1 to connect TV Line outputs, Cable Box Line outputs, Computer Sound Card outputs, CD Players, Tape Players, Stereo or Home Theater Line outputs, and other sources to the Line Input of Stereos or Home Theaters or other amplifiers. The interconnect cables can be up to several hundred feet long.

How do you adjust the ALH1 Audio Hum Eliminator?

Because all electrical wiring and audio installations are different, the DCI Specialty ALH1 Adjustable Audio Hum Eliminator has an adjustment for each channel to tune it to your specific installation.

Simply turn the adjustment control for minimum hum.

How does the ALH1 Audio Hum Eliminator compare with other products?

A comparison of other types. Data from their web sites as of 10/18/04:

Model: DCI Specialty ALH1 Jenson CI-2RR Radio Shack 270-0054
Type: Stereo Electronic Circuit Stereo Isolation
Stereo Isolation
Adjustable: Yes-
Independant Channels
No No
DC to 100khz +/-0.2db 20 to 20khz -0.03db/-0.7db
0.25 to 50khz -3db
300-4,000hz +/-3db
Distortion: <0.01% DC to 100khz 0.04% @ 20hz
<0.001% @1khz
Not Stated
0db @ 1khz 0.82db @ 1khz Not Stated
40db 95db @ 60hz
85db @ 3khz
Not Stated
Price: $65.00 $177.95 $16.99

Comparison Summary:

The DCI Specialty ALH1 has significantly better flat frequency response across the entire audio band. It also has lower distortion, and higher output than both.

The Jenson unit exceeds the ALH1 only in CMR. However, the ALH1 does suppress hum 40db (1/100'th of its original level), which is WAY down there.

The Radio Shack unit has frequency response that is barely better than speech quality, and being a consumer grade transformer circuit, distortion and insertion loss are predicatively high.

The DCI Specialty ALH1 provides professional grade audio performance at a reasonable price.

ALHI Testimonials

Over the years, we've received some very entertaining emails from customers. These emails were unsolicitated.

I received my ALH1 Monday, 10/5/15 (6 days transit to Massachusetts).

Package was crushed and wet, paperwork inside damp, and the two bubble packs were flat...but the unit, the power supply, and the connecting cable appeared undamaged and OK.

At a first test, it appears to eliminate 95%+ of the hum. I hear a small amount of a different, underlying, hum with the ALH1 adjusted, zero input signal and volume control all the way up, but I don't listen with that much volume. This is audible on either of two different sound systems. I hear a noticeable snap or pop from the speakers at one point of pot rotation when adjusting either pot. I think it works very well.

Stephen B.

I am not usually a skeptic but when I first hooked up the ALH1 it did not eliminate the ground hum. After about 15 minutes, I was getting a little frustrated. My Technical Pro amp has a fixed/ground switch so I switched it to ground, since I was eliminating a ground hum. I had grounded the amp to the outlet in an earlier attempt to rid of the hum. No luck. I checked all the leads on all my components the Creative Labs X-Fi HD external soundcard, the ALH1, the Amp and my Behringer B2031P monitors. I then adjusted the ALH1 and the hum disappeared. Like Magic! I had listened to THAT hum for at least six months and IT was GONE. This may be the best $47.50 I ever spent on any audio component in over forty years. I believe. Thank you for a simplistically unique invaluable product.

Mike B.

Received the unit today and installed it. Had to use a transformer with our voltage (240vac) but giving the same output as the one you sent. The unit works really well and has fixed my problem. Thanks a lot.

Regards, John D.

Just following up….I’m very happy with the ALHI. Here’s a testimonial in case you’re looking for any…

I had a significant hum problem after hooking up the TV in my bedroom to a cable box in another part of the house. I tried the Radio Shack isolator with no success (it didn’t remove the hum and made the sound worse). The ALHI, on the other hand, eliminated the hum while preserving the audio quality. Highly recommended!

Scott T.

Hi I work for Al.........

Al liked the first one. it has more of a crisp sound than using an iso max isolation trans. because u have a 100khz bandwidth!!!!!!!


Just received it and I hooked it up. Very easy hookup and to adjustment! It works!!!! Thanks a lot. Great product. I will tell all my friends and also my son who is a computer tech who couldn't figure out the hum. Ground loop must be a very common problem with AC circuits. A very reasonable fix.

Again thanks, Steve L.

Hi, I received the ALH1 today and it solved my ‘buzz’ that existed between my Denon 3803 and Samson S1000 sub amp. I thought you might be interested in my thread on the Home Theater forum.

Home Theatre Forum

Thanks for offering a wonderful product and for the quick shipping. If I ever encounter someone with the ‘buzz’ I will send them your way.

Kind regards, John W.

Hello....just a big thank you for a superb product that really works!!! I have been having nothing but problems with a low frequency hum that I tried everything to get rid of with no success until your hum eliminator solved it! I have a very expensive high end home entertainment stereo system with a computer hooked up for playing my extensive list of albums or even online radio (anything from the net)....but had this pervasive low frequency hum that was present whether the volume was on a very low setting or on high....and with a quick adjustment of the dials on your unit, the hum was completely gone.

Thanks again for a superb product!

A very happy customer!!!!

Bob F.

Thank you for your product; it effectively eliminated the hum with little or no adjustment. I’m very satisfied and have told others about it.

Tom F.

Hi, I recently purchased an ALH1 for evaluation in my home system and so far I love it. I am also evaluating the Radio Shack 270-0054, and, based on my results so far, I think your stated specifications for the Radio Shack unit should be rechecked. You state it's response as 300-4,000hz ±3db. Using Stereophile's Test CD octave/decade test tones, I'm getting much wider bandwith than that, more closely resembling the full audio spectrum, e.g. 20-20khz (no specified ± db range). I think Radio Shack used to make a couple of isolators, and perhaps it's the other one that has the limited bandwith.

Just FYI...thanks...Dave

Note: Followup from Dave after reviewing Radio Shack's specifications-

Can't argue with their own specifications! Shows what can happen with a subjective (my listening results) versus objective evaluation.


And one from someone that the ALH1 did NOT work for:


Hi, Got the new one, Still the same issue. It must be some kind of capability thing with my gear. I will send both back I greatly appreciate your time and great service. It is nice to see when someone stands behind their product with action and not just words.

Thanks, Don