McIntosh amp help

[deepinton]

Given that a vald abx test requires exact level matching and instant switching, you'll be hard pressed to pull it off properly. Genuine audible differences (if there are any) are usually due to differences in output impedances of the different amps under test.

Either way, you have some nice toys to play with. The hypex based Buckeye amps are pretty much SOTA, and those MC 501s are hoss amps. Both seem appropriate for the impedance dips and phase angles of your speakers, which are notoriously difficult loads.

Agreed, proper abx testing is difficult to set up and needs help which is not always forthcoming. I did one recently to compare Qobuz with Spotify. Kept everything identical except the streaming service and had my kid switch for me. I picked Qobuz for 8 of the 10 track segments where Qobuz offered a hires stream. That kinda settled it for me, although some folks claim that Qobuz uses algorithmic equalization to make stuff sound better.

 

[PENG]

Agreed, proper abx testing is difficult to set up and needs help which is not always forthcoming. I did one recently to compare Qobuz with Spotify. Kept everything identical except the streaming service and had my kid switch for me. I picked Qobuz for 8 of the 10 track segments where Qobuz offered a hires stream. That kinda settled it for me, although some folks claim that Qobuz uses algorithmic equalization to make stuff sound better.

If you could pull it off and do it double blinded, and you still manage to score better than 5/10 consistently then you have very discerning capability, even then, you can't be sure you heard the difference unless you score much higher than that, it would simply mean the difference is so small that it may not be worth the extra effort and/or cost. I have tried it on the buckeye Hypex amp, a VTV Purifi amp, Bryston 4B SST, Parasound Halo A21, and a few other amps, never could hear a difference and my tests were not even truly DB, but just volume matched single blind though I did not try to know which devices I was listening to. FR measurements also showed they should sound the sound, based on FR and THD.

I would still buy a McIntosh amp but it will be just for the build quality and look, and that I always wanted one when I was a teenager many years ago, and it is very affordable, comparing them to other jewelry like amps such as D"agostino's. Other more expensive amps such as Boulder's look almost ugly to me lol... I wouldn't buy used though, but a dealer's demo may be okay for me if there are in brand new like condition.

 

[deepinton]

All true. I just want to hear the difference (or lack of it) for myself and move on. I do not put too much weight on cosmetics, preferring to listen in the dark. I only picked the used Macintosh because an opportunity came by and they hold their value. They do have amazing build quality, and while that does help longevity, I am not sure if that adds anything to the sound. I got both the units cleaned up so just need to hook everything up, hope nothing is wrong with the amps and get back to listening.

 

[deepinton]

Ok, got both units cleaned, all switches, connectors and contacts deoxit'ed, meter lights calibrated and everything put back together. There were a couple of loose connector clips and I also found a loose case clip ( that has no apparent function) laying around. Hooked everything up and I am very pleased to say all is well! The sound is pristine. I do have to set the marantz about 10 points higher than the Hypex, but still have tons of spare capacity. I have not yet started the abx testing but happy that the 501's are working as they (probably) should. Many thanks to folks here, and especially Peng for persevering with the argument that the mode switch was not a hard switch.

 

[PENG]

Ok, got both units cleaned, all switches, connectors and contacts deoxit'ed, meter lights calibrated and everything put back together. There were a couple of loose connector clips and I also found a loose case clip ( that has no apparent function) laying around. Hooked everything up and I am very pleased to say all is well! The sound is pristine. I do have to set the marantz about 10 points higher than the Hypex, but still have tons of spare capacity. I have not yet started the abx testing but happy that the 501's are working as they (probably) should. Many thanks to folks here, and especially Peng for persevering with the argument that the mode switch was not a hard switch.

Happy to know you got everything cleaned up and working well, those are beautiful and high performance power amps that should last a very long time if you use them.

To be clear about those switches, I did not mean to say they are not physical switches, as they could be (even if they may or may not be in this case).

My point was mainly that they are not used to switch off one or the other of the inputs and the schematics confirm that they don't "switch off" the XLR input signal at all, but it does not connect the RCA input so if you use the unbalanced inputs, you would have to select that position otherwise you won't get any output from the amp. I don't know if you have tried to use the RCA inputs yet, so I thought I mention mention this so you won't be surprise if and when you need to use the unbalanced inputs.

By the way, those amps are so heavy, so I wonder if you have them shipped to you or you picked them up locally (lucky you in that case)?

Regarding the volume need to be higher, it is simply because the Mc501 has lower gain than the Classe, so nothing to be concerned about unless you need to listen at very high level. In that case, I would suggest you consider trading in the AV8802A to something like the AV20, or AV8805 if you prefer to go with a used model.

 

[deepinton]

I don't know if you have tried to use the RCA inputs yet, so I thought I mention mention this so you won't be surprise if and when you need to use the unbalanced inputs.

No, haven't tried RCA, but nothing in my chain today needs RCA. And yes, I do understand the function of the switch now. That service manual schematic was very helpful.

Regarding weight, these are heavy on per watt basis. It does help that they are mono blocks so the weight is distributed over 2 units. My Classe is a bit heavier (98 lbs) but it does 5x180 watts. I had to drive about 3 hrs each way to pick these up.

As far as volume is concerned, I couldn't go beyond 70 on the 8802a without getting the family riled up ( I have a sound controlled room but the bass still finds a way out, even though I don't use my subwoofers for 2 chanel listening), so I am in no hurry to upgrade the pre-pro.