Koss EQ50 3-Band Stereo Equalizer

This equalizer is extremely useful if you are trying to listen to -- say -- tapes of old time radio, shortwave broadcasts, or noisy AM signals. You can reduce harshness, improve bass response, and reduce noise effects.

However, it does have some limitations, related to its low price. At $20 retail price, such a helpful and flexible gadget will not have perfect audio performance, and it doesn't. There is a SLIGHT hiss audible at all times, apparently intrinsic in the audio chip used for the headphone amp. The hiss is introduced after the volume control; it's there all the time. Depending on the input voltage of the device to which it's connected, the hiss can be as loud as -30 dB, or as soft as -50 dB or lower; and it is predominantly a very bright hissing. So extremely efficient, bright headphones may exaggerate it. I hope Koss improves this device in a future model; but for low fidelity source material, and with phones that are not extremely bright, the hiss introduced by this device is MUCH, much lower than the hiss intrinsic in a tape, radio broadcast, or old recording and will quickly be ignored. If, however, you are hooking this to a CD player to listen with excellent phones to wideband digital recordings, you'll notice the hiss -- and be annoyed, depending on your sensibilities.

I am glad I purchased one. My intended use was to listen to cassettes of old time radio shows. Many of the commercial tapes are not well corrected and sound extremely harsh and thin; this equalizer fixes that quite nicely. The bands are well chosen to have an aural effect where poor recordings have flaws.

For background: I am a retired audio engineer with three decades in broadcasting and recording, and an enthusiast of OTR and recordings of old classic performances of music from the fifties back to the twenties, many of which NEED help that this equalizer can provide.


Couldn't do my job without it.   March 24, 2006
Michelle L. Gilbert (Cleveland Heights, OH)
9 out of 10 found this review helpful

First off... note: I don't use this for my MP3 player. I'm a medical transcriptionist who spends her day immersed in technical dictation by doctors with heavy accents, surrounded by background noise, often speaking nearly inaudibly. This thing has saved the day for me. The EQ on the unit helps allay the inconsistency in sound quality from one dictator's environment to the next. The volume control has made even the quietest dictations perfectly audible.

My accuracy and production have increased measurably in the four or so years I've used this thing, with not a single problem with the unit itself, though I do, of course, go through a lot of batteries.

So the short story is... if you are looking for some fancy high performance gadget for your Ipod, this probably isn't what you want. If you don't need packaging glamour, or if you're looking for something to help you decode quiet spoken word recordings, this is probably what you want.


Agreed: horrible product DO NOT BUY!!   December 25, 2002
7 out of 9 found this review helpful

Unfortunately, I disregarded the pervious reviewer and purchased this product anyway. It is very noisy (heavy hissing)--totally unacceptable. I'm highly disappointed in Koss.


horrible product DO NOT BUY!!   September 25, 2002
5 out of 7 found this review helpful

This e-band stereo equalizer is horrible. There is a heavy hissing sound whenever you try to listen to music through it. For example, you can use it to enhance the bass on an mp3 player, but all you get is a loud hissing which totally ruines its purpose. Don't waste your money! It's just not worth it.


Cellphone Interference!   October 3, 2005
Tom Rix (Masterton, New Zealand)
5 out of 5 found this review helpful

There is a little story before this:

I bought a pair of Sony MDR-XD100's (they are full cup headphones) because I lost the earbuds which came with my mp3 player (Sony HD5). I took them out of the package and found that, even at full volume on the player, it cannot drive the headphones sufficently. I went to a few electronics stores then found the KOSS EQ50.

On with the review:

Yes, there is a slight hiss, but I find it alright. The biggest gripe I have is that whenever someone within about 2-3 ft (IE, on a bus or subway) uses a cellphone, this devices picks it up. You can get the same effect by using a cellphone next to an unshielded pair or speakers. I do most of my listening at home so this won't bo too much of an issue.

It also does a great job of amplifying the signal, it works very well, I can now listen to my XD100's properly (and they are very good!). I haven't used the EQ much but what I can say is that it is very, very sensitive. Raising the bass slider a third above normal makes a massive difference. At a half, my headphones start to distort.

If your looking for a nice little EQ and/or preamp this is the product for you. It has its drawbacks though, mainly the problem with cellphone interference and of course, the hiss but it isn't too loud & I can live with it.

I reccomend this product if your looking for a budget portable equalizer or headphone amplifer.