I previously wrote a very positive review on this product concerning noise issues on various channels on this unit. I have as promised in my first review to report any negative reviews that I might find later during my testing of the unit, and I'm doing so at this point in time. The first tests I did were done in the first half an hour of starting the unit up, and at levels a recording engineer would listen at. The levels are between 80 and 90 DBs. Wlile listening at these levels during the first half of an hour from start up, there was no noise on any channel. However during the next few hours, the noise level on the channels closest to the transformer, became noticeable, but was not excessive. For those of you who choose to listen or monitor at greater levels, it might become more noticeable. Looking at the design as a whole, I decided to try something. I removed the top cover,and run the test again. With the cover off the unit, which allows the heat from the transformer to escape, the unit is as quiet as a mouse, with only a couple of DBs gain in noise, as you go to the very highest channels 6,7,8, even at extended volume settings. If you look at the unit, you'll notice that ther are no vent holes, and no way for the heat from the tranformer to escape. In my opinion, this is a design flaw. As heat builds up, resistance increases, causing the channels closest to the tranformer to have an increased noise level. Leaving the cover off, reduces the noise level by a bunch. Suggestions to the manufacturer. Move the transformer outside the unit itself, or provide the unit with vents to get rid of the heat. You've produced a very fine product, that has a design flaw, but other than that, I'de rate this product at the top of my list. Fix it, and help those of us who have in good faith purchased your product, continue, to give it a positive review.

Having just received this pruduct, I'm not going to make too many statements at this point, however, there is one issue I'de like to address. Noise level on various channels. I don't think so at this point. I hooked the unit up with the purpose of exposing this excessive noise level. As a matter of fact, I almost, put it on the don't buy list, because of the negative reviews I saw posted. In other words, I checked it out from the word go, because I didn't intend to keep it if the negative feedback were true. So far, I've checked it out, at any listening level that,one who respects their own hearing would use, I don't notice any noise issues. The input cables were as about as cheap as you can find, and still no noise issues. Sonic quality at this point, is as advertised. You can bet if I do have any issues with this product, I'll be as quick to write a negative review as anyone else. Long term, who knows what I might find, but short term, I'm not seeing noise on any channel as an issue. I hope this helps those who may have considered this product, but avoided buying the product, due to noise issues posted. So far, if this product continues to work like it has in my initial tests,it's a great buy at the price I gave at musicians friend. If not, I also purchased a 24 month New ADH Warranty Replacement Plan, which should help if I'm disappointed, in the pruduct later. If I'm disappointed in either one I'll let you know.

For the price you really cant beat it. but its really hard to ignore all the static and extra noise that comes through his headphone amp. Its so noisey. If your looking for a clear and quiet headphone amp this is not what you want.

I read a lot about this product and the hum issue and decided to buy it anyway. The HUM is definitely present on channels 6-8 in increasing severity as the channels get closer to the power supply switch. Channel 6 puts noise only on the right side whereas channel 7 on the left side of the headphone. On channel 8, you have equal hum on both sides. It is a 60 cycle hum most electric guitarist experience when they touch the tip of the guitar cable plugged into an amp -- except this hum is less than 5% of the total signal and it is easily masked by the music.

The self induced hum cannot be improved by better cables, but could only keep it from getting any worse when carrying audio signals. I am using a high quality balanced snake cables to this product. Also it is not related to the power source it is plugged into. If the cabling or the power source was really the issue, then it would affect all channels equally, not just 6-8 and the noise should subside when the signal cable is unplugged.

As for channels 1-5 they sound really good and quiet. For studio work, if you can live with first 5-6 channels, it is a good value. Then you can use the noisy channels in live situation, as they are not really intolerable -- these noisy channels still have very good signal to noise ratio.

Feature wise they are pretty good, If I designed it, I would turn the rear headphone out jacks to direct out, so that you can feed the audio signal into this headphone amp and another audio equipment (bypass mode). Right now the front and rear output jacks are connected together -- instead the rear jacks should be connected to the direct input, so that it will work sort of like a patch bay! Also the direct input jacks override the main inputs -- would have been nice to blend the main input and the direct input if the direct input is plugged in half way (Sort of like the half-normalled TRS jacks on some equipment.)

The noise can be cleaned up, if they designed it with an external DC supply (brick) or better shielding of the signal and the internal power supply.

Overall it is still a good value for the first 5 pristine channels and highly tolerable and useful 2-3 last channels. I would continue using it and not pay any extra for the other products in its class, as the first 5-channels are as good or better than comparable product in this range.

for the people experiencing a hum, check all powered sources that the amp may be linked to, i had a hum but it was just the stage light dimmer switch creating a disturbance with the fluctuation of voltage use. this unit is a great buy