Yamaha M-4 vs MX-800. Which would you keep? (2024)

So I just acquired a broken MX-800 for a good price, although I have not taken delivery of it yet. I already have and quite like the M-4, which I completely went through, recapped, fuse resistors, 24 turn pots, etc, etc. I know the MX-800 is a bit more power, 170W vs 120W for the M-4. And the MX-800 is quite a bit more modern looking with large, imposing meters vs. the M-4's industrial design look and small output level meters. But how do they stack up in sound quality? In build quality? I must admit I am a big fan of the modular build of the M-4 i.e. a few connectors, a couple of screws and the whole channel, both drive and power boards, come out cleanly. I've been looking for a bigger, better amp than the M-4 and was very interested in an M-2 or M-80/85/1000 but then this MX-800 came along and the price was too good to pass up. So here I am. Of course I still have to repair the 800 first when it finally arrives. Just eager to get a jump on it. Oh, one other question. How similar is the MX-800 to the M-65, exactly the same except for cabinet and model number or are there significant differences?

Happy acquisition … keep both, it’s a no-brainer. If at gun point to make a decision, overpower the gunman, kick his errr … behind, and keep both.

How so? I was just glancing at the MX-800 service manual yesterday. Is it because like so many typical receivers, there are few connectors, most things are hard wired or wire wrapped and modules and boards are just a pain to remove? Or is it more the electrical design makes things harder to troubleshoot? I guess I'll find out when it finally arrives. I do have one other large power amp in the repair queue that may be in the final mix of my main system amplification, a Denon POA-1500- the one with the large, analog VU meters on the front. I used it for many years as original and then for another year after a recap, but one channel blew out quite catastrophically a while back. I have all of the parts to repair it, just need to get around to do it in between customer repairs.

I like matchy matchy, so I would choose the M-4 because I love my C-4. But, in your case the MX-800 is closer to the C-60 & T-80 from the ID standpoint. I would assume the MX-800 is a great amp, it's big brother the MX-1000 is held in high regard. So I agree with @Sparkplug you should keep both. You never know when a C-4 or CX-800 or CX-1000 will come your way. It would be a shame not to have a matching power amp ready to go...

I would keep the M-4. The M-60/65/80/85 were the end of the golden era IMO. I was able to repair the M series as a novice. I struggled a bit on the MX series though. After working on an MX-55 & two MX-600's I'm afraid to own amps above that tier. The MX's had a cooler front panel IMO.

I would keep the M-4. Easy to work on, no corrosive glue issues and almost no obsolete components (except the meters).

I would keep the M-4. I've owned this and an MX-800 and always found the sound of the MX-800 a bit flat and underwhelming.

Well the amp showed up today and I can now answer the question in the thread title. Keep the M-4! Oh man, this MX-800 is a real basket case! First of all, despite the shipper marking all sides of the box with "Fragile, Glass" signs (and the glass front is indeed intact and safe), all of the speaker posts were smashed inwards and were pulverized. Several chunks of plastic were in the bottom of the box and rattling around inside the unit. Further, the circuit board attached to the speaker posts is damaged as well. Not the end of the world, and one of the Speaker C posts was already broken off when I bought it. I would probably have replaced all of the posts anyway. But once I opened the cover to retrieve all of the broken plastic carnage for the pictures, that's when I noticed the myriad of further problems. I found a couple of medium sized caps bulged, one had already vented as the relief cutout was broken and open, found several toasted 1/4W resistors in both channels, the scorch marks from those resistors suggest some of the out put transistors are gone. I'm sure there are many more problems. Keep in mind, this is just a quick look. But here's the BEST, or at least most interesting problem. Apparently one channel had blown up before and rather than fixing it, someone elected to just cut all of the power wires to the channel and disable it. THEN, they went to the speaker output board, cut the blown channel's wires off and paralleled the remaining good channel speaker output to the bad speaker output. How's that for "stereo"?! I SHOULD return this for a full refund. But I know I can fix this. SMH, yes I know, I have a personal problem. I just sent the pictures of the damage to the seller and waiting to see what the response will be.

That is sad indeed … but if parts replacement is all it takes, you can do it and enjoy the amp even more despite the soldering-iron-waving imbeciles who damaged the unit. Do you have some pics to share of this tragedy?

Well the seller got back to me pretty quickly, apologized for the damage and offered a small portion of the purchase price back. In his defense, it was better packed than many items I buy and the shipping was free. I was hoping he would just automatically give me a full refund and tell me to keep it, which is usually what happens to me in these kind of cases (this has happened SOOOO many times I lost count). But that didn't happen this time. I told him I would like to try and fix it and get this amp going again and that I was hoping for maybe a half refund but I'd be willing to meet somewhere in between his offer and my hopeful request. I think it will work out in the end. It won't be free but I should be able to get it at a price I'm good with. Until I get a final disposition on it I'm not going to touch it. But to answer your questions, yes, I took lots of pictures. Once this is resolved I'll post some of the best ones. But in the end I wouldn't let my M-4 go! At least not for this piece.