I added two 755 amps to my setup and am now using the Yammy as a pre/pro. I shared my thoughts of the combination at audioholics. Here is a copy of my review:

Hello,

Where should I start? I wanted to buy an amp to power all the channels in my home theater room. I have the Yamaha RX-V2500 receiver to use as a pre/pro. My speakers consist of Klipsch across the front (two RF-25 Reference floor-standing speakers for the front channels, two RB-25 bookshelf speakers for the presence channels located above and outside the fronts, and a KT-LCR Classic speaker for the center channel), four Definitive Technology BP2X speakers for surround and surround back speakers, and two SVS 20-39CS+ subwoofers. I run an InFocus Screenplay 4805 projector on a 16 X 9 Da-lite 92’ screen. For sources I have a Denon DCM-380 5-disc CD player, Denon DVM-1815 5-disc DVD player, a Pioneer DV-C503 5-disc player, and a Pioneer DVL-909 Laserdisc/DVD player. I also use Monster HTS-5000 and Panamax MAX-5100 line conditioners. I was using the Yamaha to power all the speakers but the subs. For the subs, I had a Carver AV-705x 5-channel X 125 watt amp powering them.

All 3’ component video cables are Acoustic Research PR190 cables and the 25’ run to the projector is an Acoustic Research PR193. All audio interconnects are Acoustic Research PR130 cables. These are decent cables and can be found very cheap from time to time at Amazon.com. My home theater room is about 18’ long and 12.5’ wide with a ~7’ ceiling. The primary listening position is centered about 12’ back from the front of the room.

I decided to go with the outlaw amps as I have heard very good things about them and the new pricing makes them a real bargain. I was debating on getting the 770 or the 755 and decided on a pair of 755s to give me 10 channels. I took the 755 over the 770, because the channel modules were space further apart and thought this would give me better channel separation and would run cooler than the 770. I do not know for sure if the 755 and 770 use the same size transformers, but from the pictures and spec sheet for the amps, they look the same and I thought the 5 channels of the 755 would have more raw power to pull than the 7 channels of the 770.

Getting the Outlaw 755 amps downstairs was a real task. The boxes are quite large and ~90 pounds each. Each amp is double boxed and shipped via FedEx and fared very well during shipping. I had to open the top of each outer box and then tip it over 180 degrees and, then, was able to remove the inner box. I had to get the amp out of the inner box using the same method. Once the amps were out of their boxes they were front heavy but much more manageable and presented no problems getting them into the rack (a homemade shelving structure constructed with vertical 2 X 4s and 3/4” plywood for the shelves). I left about 3.5” of clearance on the top of the amps and the rack has no sides. These amps are rugged and the RCA and speaker terminals on the back are of excellent quality (much beefier than those on the Carver I have. The amps come with a mono 3.5mm cable for the 12-volt trigger on the back of the amp. I ran one of the 3.5mm mono cables from the receiver to each line conditioner and set the high-current outlets for switched operation. The 6’ power cord is quite large, fit very tightly both in the amps, and in the 20 amp dedicated circuits I ran for each line conditioner / amp.

The front of the amp is somewhat plain, with only the Outlaw logo and the power button. I have heard many complain about the bright green glow of the power button, but must say by default (not using settings to tone down any lights) it is the dimmest light on any of my equipment. It is more of a pale yellow than bright green and was not a distraction to me at any time throughout my viewing. After hooking everything up (all the speakers except the back surround as only have 10 amp channels and can not run them and the presence channels with the Yamaha at the same time anyway) and turning the amps on for the first time, I was amazed at how quiet the amp and Yamaha RX-V2500 were. There was no audible noise when right up to the amps and speakers whatsoever.

I started by recalibrating my speaker levels using my Radio Shack SPL meter. Then, I fired up Attack of the Clones chapter 40 and was amazed at the difference in sound. I had to make one more adjustment as the bass was a little too strong. With the Carver powering the SVS subs I had to use the tone control of the 2500 to increase the base from 125Hz and down by 4.5 dB. I set it back to 0dB and again adjusted the channel levels…Now were in business. Bass with the 755 was very strong and very controlled. In the midrange and high frequencies I stared hearing things in movies and CDs I have never heard before. I was worried about the highs being to harsh with the Klipsch speakers, but was quickly put at ease when the amps opened up the sound field but at the same time produced very nice airy highs with no harshness. I also noticed dialogue with movies became crystal clear while producing theater level effects. Before it always seemed that in order to get great loud explosions and so forth the actors voices were too throaty and slightly distorted. Imaging was much better than that of my previous set up especially across the front but also front to back. It was probably more noticeable in front due to the Def Techs being bi-polar speakers and dispersion being in their nature.

I also popped Toy Story 2, U-571, and Pearl Harbor in the Denon. The beginning of Toy Story 2 has some of the lowest bass you will find and a variety of surround effects. I have easily watched and demoed this scene more than 100 times and was constantly noticing background noises and details I had not heard before or were not as clear as they are now. With U-571 chapter 15 (depth charges) the explosions had more in your face pop and great bass. I was afraid my wife would yell at me because things were staring to move around upstairs. When the charges are dropped into the water it used to always sound like some of them were being dropped behind you when you saw it sinking in front of you on the screen; this was much more accurate with the Outlaws. The attack in Pearl Harbor was incredible. The planes entering the harbor had much more authority and bullets had me ducking for cover. I was thoroughly impressed with the 755 amps performance on movies.

It was time to move on to 2-channel testing. I listen to mostly 80’s rock and classical / jazz. I put Def Leppard’s Hysteria, XYZ’s Hungry, and Duke Ellington / Johnny Hodges’ Side by Side in the Denon CD player and I started my listening in stereo. The Hysteria album was reproduced by the Yammy / 755s combo very well. The image was centered nicely and vocals came across very clear and bass was strong and accurate. I was recently at a Def Leppard / Bryan Adams concert here in K.C. and was able to reproduce bass similar to what I heard and felt at the concert when I measured this with the SPL meter it was between 105dB and 110dB. I did not listen very long at this level as I do value my hearing, but was impressed I could hit this level with no distortion and with the amps not even breaking a sweat (the Yamaha’s internal amps could do nowhere near this level cleanly). XYZ has some great bass and tons of tear ‘em up guitar riffs. Again the bass here was well pronounced and midrange was powerful and tight. Terry Ilous' vocals can get a little high and screechy with the wrong amp, but the Outlaws did very well.

After rocking out for a while, I moved on to the Side by Side album which is a must have if you like a good alto sax and catchy swing music. Johnny Hodges and his sax are the real stars here and the sax sounded very nice with the Outlaws. The track “You Need to Rock” is one of my favorites and sounded really well. The recording is dated and can be pretty harsh at louder levels and the Outlaw did succumb to some of this at almost uncomfortable levels. The piano, bass, sax, and drums / cymbals all sounded rather convincing, but the background if the recording is less than perfect with a certain amount of static and noise. Basically, if the recording is quite rough to begin with, the 755 will amplify the roughness as any other amp would. The other albums I used are by no means reference recordings and did much better. I switch over to 7-channel stereo and was again impressed with the results.

The outlaws easily filled my room with very clean, robust sound. At no time during listening to music or movies did the amps get hot, only slightly warm to the touch. If you cannot tell from above, I am very happy with my purchase and would recommend Outlaws amps to anyone. These babies really pack a punch and are a great bargain. I was debating between the Outlaw 755s and the Emotiva MPS-1 and have not heard the Emotiva, but have no regret in my decision. For about $300 more than the Emotiva, I got an additional 3 channels of amplification. If Yamaha actually puts out a receiver or processor that will allow you to run 9.2 besides the Z9 I will pick up an M-200 monoblock from Outlaw to give me the last channel (number 11) I need. As you can see from the pictures, I still have some cable management to take care of and now all my equipment no longer fits in my rack. I have several components in the closet the rack is located in and need to find a way to get them out in the open. I am sure my wife will appreciate another hole in the wall somewhere.

Doug, I doubt if you are still checking this thread 3 months after posting it, but if you are, I would appreciate hearing more of your (or anyone else's) thoughts on the Yamaha RX-V2500. They are now discontinued, but still widely available with low prices. I have read several reviews saying they have very good quiet preamp stages when used with an external amplifier.

I went to Tweeter to audition the 2500 and the Denon 3805, both as receivers using their internal amps. I selected CD or DVD in 2 channel mode with no disc playing, and cranked the volume all the way up. The Yamaha produced a hiss that was plainly audible 10 feet away. It was slightly quieter in "Pure Direct" mode but not much. The Denon was virtually silent with my ear pressed against the speaker grill. I repeated this test at a different Tweeter store and the results were the same.

So here are my questions.

1. Is this a meaningful test with any real-world listening relevance? The hiss only became noticeable from the Yamaha when the volume was close to maximum. At typical listening levels, there was little or no audible hiss with either product.

2. Is it possible that the Yamaha's preamp stage is in fact very quiet, and all of the noise came from the unit's amplifier? I have not personally heard either receiver as a preamp, but I was impressed by your report that the Yamaha was very quiet paired with the Outlaw amp.

Based on my experiment, I could not talk myself into buying the Yamaha despite the nice features and low price. Assuming all the hiss comes from the internal amplifier, I would not even want to use it for movie surround channels.

1. Okay, I just went downstairs to test this. When I get to +5 I start hearing a hiss. It gets louder as I proceed to +16.5 on the reciever's display. I normally listen to the unit at -20 if I am going for pretty darn loud. My wife will make me lower this if she is watching as well. If I am rocking to music, and I mean really rocking (concert levels) I have gotten to -10. I can't stand this level for too long myself, and wouldn't try to as it could definately cause ear damage. Until I reach +0 (with no source on) the setup of the 2500 and Outlaws is dead quiet.

2. As I still get the hiss at insane levels with the amps, it would have to be inherent in the 2500's preouts. Let me stress though, that I would be in pain and agony from the loudness, long before I ever got to the point where any hiss would be heard.

The unit's internal amps aren't bad (I lived with them for a while and was fairly happy), but with the Outlaws, I heard many things and details that were not apparent with the internal amps. The bass is also extremely clean and tight now. I would not hesitate to recommend the combo to anyone. The only caveat I could see would be if your speakers were really inefficient and you had to totally crank the volume to get to loud levels. For the price, the 2500 is simply unbeatable.

Thank you for the followup. It appears that baseline hiss can be heard either with the 2500's internal amp or with an external amp, although in either case it is not noticeable until 0 dB or higher on the volume.

I should have also told you that when I calibrate my system I go to -20dB on the Yammy and then set each channel equal to 80dB. I throw this out because most people set their unit to be at 75dB when a reciever/pre-pro is turned to 0dB. So, hopefully you can see this hiss would have absolutely no bearing in real listening as I will never get within 5dB of the 0dB setting on the unit.