For $90, I purchased this amplifier from a private seller, and I only use it to play music and watch movies with a passive Paradigm dordle subwoofer. It would be difficult to find a better amp for the price I spent, and I am quite pleased with the amp's performance the way I have it set up!

For $90, I purchased this amplifier from a private seller, and I only use it to play music and watch movies with a passive Paradigm subwoofer. It would be difficult to find a better amp for the price I spent, and I am quite pleased with the amp's performance the way I have it set up!

Creates a wide expansive soundstage. Built like and as reliable as a brick but beautiful to look at. Huge VU meters. Abundance of clean power.

Meter lights burn out relatively fast. Power cord is a little light duty for power output and no balanced inputs... only RCA.

Great choice! The sound is very clean and not fatiguing, I would say a little more warm sound than my Denon POA-1500, which has a more neutral sound. | Hardscape Contractor

No control of the output.

One of the worst amplifiers I have ever owned the strengths good clean sound the weakness no power as advertised nothing impressive at all except the big green lighted needles and the size of the box. Everyone that saw it and heard it expected so much more for its size all show no go weak.

Big heavy box lighted green needles no real power very disappointed paid $500 dollars from JSG audio in Binghamton NY in 1998. He would buy and sell and barter so I traded it for a Yamaha receiver that blew the doors of the Onkyo its probably one of the best that Onkyo made it just told me don't buy Onkyo.

These vintage "M" series amps from Onkyo are unbelievable. When these were designed/built NO amps from Japan could get better than a "passing" grade regardless of the quality, innovation and sound. That was a mistake that "most" now will admit. If you honestly compare the build quality, sound and specs to ANY new amp you will find that to even "approach" these amplifiers you will need to pay about the same as the M-504 was new and "Adjust Accordingly for Inflation". Otherwise you will not be able to even come close to the sound and quality. And do the "New" amplifiers of the day sound better? Not necessarily! Some DO prefer the Onkyo's overall as do I. So lets HONESTLY compare the pricing to purchase a new "Solid State, Class A/B" amp with the same quality of sound, Innovation for it's time and actual power. Pass Labs "X-150.8"=$6,750. Krell "Duo75"=$6,500. McIntosh "MC-152"=$4,500. I chose those three as they are widely available and all have about the same amount of innovation, quality and actual power ratings as the M-504 did when released in it's day "1987"!. Other new and "cheaper" amps such as Marantz, Rotel and Parasound simply cannot compare any longer. Lastly, The fact that the flagship Onkyo "M" series amp, the M-510 at "300Wpc" and over 30 years old, now go for $6500+. While my pass Labs X-350 "350wpc" $13,000 new. And my McIntosh MC402 "400wpc" $7000 new. Which are both fairly new are both worth 1/3 LESS than the M-510 Speaks volumes! And according to "The Vintage Knob" was able to output 2x 1.2KW at 1 Ohm.....IN 1987!!!

In this year of 2018 moth m-504 amplifiers are getting a bit "long in the tooth" so they MUST be serviced to find any problems.

I love my Onkyo M -504. It has a lot of power and drives my speakers with authority and clean sound. It is heavy, overbuilt yet it looks very beautiful. The sound is very clean and not fatiguing, I would say a little more warm sound than my Denon POA-1500, which has a more neutral sound.

My only complain would be no control of the output like my Denon POA-1500.

Onkyo M-504 These are very solid clean amps. New versions today in 2017 are over 2000.00. A used clean 504 is selling for about 500.00. I bought mine for about 700.00 new in 1996. I see a three star review??? Noticed some guy who gave it 3 stars picked one up for 350 around 2006? I don't think he has one nor a clue. Maybe the BS ratings today might give kids wrong conceptions of power. Most class D amps today lack sufficient power supplies. They offer one great peak and then run flat; blending, distorting on their quest for energy as their capacitor banks drain under continuous loads. D amps today maybe okay for individual speakers or a sub that do not require sustained loads however, there is nothing like large quantities of raw current. Today Onkyo's flagship the m 5000a has a list price of 2499.00 and,,, the specs are,,, well,,, not as good as the m-504. Closer to the m-502. Are a few of the new tricks worth giving up power and cleanliness? NO. Actually I don't want those gimmicks nor would I have them. Looking for another 504 or a 508. The used market is tight, the 20 year old 508 selling for over 800.00. Wish I picked another one up new in 96.

I Bought apprx 20 years ago used the M-504 and the M-304 preamp and the Onkyo 6 disc cd player hooked up with my Cerwin Vega DX-9s and DX-5 Speakers the Onkyo system really cranks out the sound to all 4 Cerwin Vega's.All i can say is that they are all still going strong after 20 years or so sounding Crisp & Wall Shaking & HOT!!!

Well, a lot has been said about these amps over the years, and rightfully so. Here is an opinion from someone who has(and in some cases still does :)) own(ed) virtually every high powered amp made. Onkyo's Integra, and Grand Integra Metered amps(M504, 506, 508, 510, 588, 5090, 5099, etc.) are, and always have been top notch. Build quality, appearance, and musicality all in. I get tremendous laughs from all of the ridiculous posts from confused audiophile wannabees, and the endless pontificating from self described aficionados on what equipment to buy, and how to match and utilize it. Folks, here is the bottom line. First, figure out your budget. Second, buy the best equipment you can afford. Third, do the best acoustic engineering you can within the space you have available, and remember that speaker positioning is critical. Fourth, ENJOY THE MUSIC!. As for the Onkyo's being discussed, consider this. A new M-5000 retails for $15,000 !. An old, well preserved M will run you between $300, and $2000 depending on model. Compare that to an Accuphase, Hi end Mac, Threshold, Krell, etc. (You cant buy one of those for $300) Does the new M out perform the old ones? Probably not. Will it outlast them? Probably not. So, what do you think. For me, its a no brainer. I could afford a new M, but would I buy one over an older one at 5-10% the price. Not a chance. If you have never owned one of these amps, jump aboard and enjoy what you have been missing. If you already have one, then Im preaching to the choir. ENJOY!

Well here we go. The years are around 1987 to 1989 (need to find the receipt) and I was doing a DJ gig part time when the amp I was using said see ya and died on me. I don't remember exactly how I came to Onkyo but I found in Japanese it means "High sound" Thus the truth is in the listening. I am still to this day using my M 504 which is being pre-amped through a Pioneer SX850 from 1977. These two pieces are for me a perfect match in that I have the versatility of the 850 with the jaw dropping power of the 504 and I do mean power. I have sometimes while playing some classic rock albums intentionally tried to get the 504 to shut down and although I do not abuse my system I sure as heck am not afraid to "crank it up" They don't build products for consumer of this status now days. The richness of music can only be achieved when you're plugged in and can enjoy the analog/digital experience through clean uncluttered power that the 504 delivers year after year. My overall description for the 504 "BULLETPROOF"