Just installed a C52

[eedork]

I picked it up yesterday afternoon, installed it in the rack last night, and have been listening to it all morning.

I upgraded from an MA6600/D100 which I was very happy with. My goal was to gain a little more flexibility, add a simple EQ, and pick up some of the new features that have been added to the C52. I'll be running it with a restored MC502 for the next week or so, and then with an MC7100 that I picked up on the auction site last night. I'll use the 7100 (which I've had and enjoyed in the past) until I have enough funds set aside to purchase a new, matching amp like the MC152 or maybe an MC302/MC452.

More thoughts to come later, but here is some initial feedback on the C52:

* It looks amazing and sounds great out of the box.

* The HR085 remote is a massive step up from the sticky plastic remote that came with the MA6600/D100. The HR085 looks like it belongs with a $7k preamp.

* I love the input naming flexibility of the C52. I really wish the MA6600/D100 had this feature.

* The EQ is great! I debated long and hard about the C52 vs. the C2600. Many people prefer the C2600, but I have a challenging room and have been itching to add a basic EQ to my system for a while just to cut a few peaks. I opted to go with the C52 for this reason (much second guessing here), and after some quick and dirty measurements and tweaks this morning, the 1kHz peak has been tamed and my in room response is much flatter now. A C2600 with the 8 band EQ would be the best of both worlds .. not sure why McIntosh does not build this.

Another big reason I upgraded was to add HT passthrough. I do not have an HT system now, but would like to experiment with 3.1 so that I can boost the vocals when watching movies. I have a MAC3 that I'm planning to use for this purpose and at some point I'll wire it all up and give it a try. The MA6600 did not have HT passthrough, which was a real bummer.

-Matt

 

[chuckworkb]

I picked it up yesterday afternoon, installed it in the rack last night, and have been listening to it all morning.



* It looks amazing and sounds great out of the box.


-Matt

Pictures please.

 

[motorstereo]

Congrats to you on landing a magnificent pre-amp........yes pictures please

 

[Mike Gibson]

Congratulations, you will surely enjoy the sound for a long, long time.

 

[Mamrak1]

After 3 McIntosh tube preamps I bought the C52. It is a state of the art preamp in my book. Enjoy!

 

[eedork]

I'll take some better shots at some point, but for now here are a few quick cellphone photos.

-Matt

 

[leftside]

Nice cabinet. And nice preamp where did you get that cabinet? Do the left and right sides open?

 

[eedork]

Nice cabinet. And nice preamp where did you get that cabinet? Do the left and right sides open?

Thanks!

It was dark in my living room when I took those pictures .. and I'm a terrible photographer, but yes, the doors do slide on the cabinet. It was purchased at Best Buy and is a Maria Yee design made of bamboo with six 'slots' in it (3 wide by 2 high). I've been very happy with it, but the shelves are fixed. So I'll have to get a new cabinet when I get the MC452 ..

-Matt

 

[kevzep]

I like that, "when I get the MC452"

 

[exhippy]

I highly recommend the 452. It's a great combo...


.

 

[twiiii]

A 7100 is a special little amp especially if driving low impedance loads. Sure the current amps have more signal to noise, which might work well with efficient speakers. But if your speakers are influenced by a very low source impedance finding a modern Mac amp with tight bass like a 7100 to 7200 might be a chore.

 

[eedork]

I received and installed the MC7100 a few days ago. Unfortunately it was damaged during shipping (one rear corner took a hit which resulted in a very slight bend in the cover). The good news is that the damage is only cosmetic and that the amp works and sounds great, just like I remember.

However, I have discovered one small issue. I have what appears to be a ground loop that is created when I use an 1/8" trigger cable (stereo) to remotely power the MC7100 from the C52. With the trigger cable plugged in there is a very low level hum. Remove the cable and turn the amp on, and there is zero hum. Very interesting. The trigger cable is stereo and is the same cable I've been using with other McIntosh components for years. I also tried a new 1/8" stereo cable and got hum with that one too. Note that the MC7100 is connected via balanced cables with XLRs to the C52.

Note that I traced it to the trigger cable after unplugging every other input, one at a time. I had a similar issue years ago with the coax coming into my house. That has been fixed, and disconnecting the cable from the cable box had no impact on the hum. The hum is definitely introduced by the trigger cable.

Has anyone else ever had a ground loop issue with McIntosh trigger cables? What was the solution?

-Matt

 

[Mamrak1]

I never had a trigger problem with my Mac equipment. Any chance you have another trigger cable to try?

 

[damacman]

well the C52 has a 3 prong cord with ground and the mc7100 a two prong polarized cord ... hmmm ....

you may want to call mcintosh on that one before trying random stuff like a 3/2 plug, etc.

 

[eedork]

Thanks guys! I have tried a second trigger cable - no luck - still have hum with that one as well. I'll have to do some additional testing tomorrow.

Maybe Ron-C can chime in with some thoughts?

And yes, the MC7100 is two prong whereas the C52 is three prong.

-Matt

 

[eedork]

I just tried a few different things, and now I'm even more puzzled. I sacrificed one of my 12V trigger cables and cut the sleeve - now there is no "ground" connection between the two ends - just a tip and ring connection. I thought this would sever the ground loop, but it does not. Weird.

Next I tried another set of balanced cables, still hum. Then I tried a set of unbalanced cables, still hum.

The final thing I tried was to disconnect the signal cables from the amp and leave just the 12V trigger cable connected. When I powered up the C52, I was expecting the amp to turn on, but it does not. As soon as I connect one of the signal cables, the amp turns on.

I do have everything plugged in to an APC G5BLK power strip, but I don't think that has anything to do with this.

-Matt

 

[damacman]

Ground has to be shared between the units in order for the trigger signal to turn on the amp. When you cut the shield of this cable, that path can still be completed
by the ground pin of the XLR cables or the shield of the RCA cables.

I tend to think the source of the noise is the earth ground via the ground prong on the C52's power cord. Ideally, earth ground (green) and neutral (white) have the same potential to ground within the panel in your home as they share the same ground buss. In reality, this isn't always the case at the outlet itself as there can be any number of ressons - daisy chained outlets with a poor connection, etc. The resulting ground loop
is simply the audible side effect of current flowing between grounds of different potential.

You may temporarily move the C52 and MC7100 to an outlet on a different circuit - preferably closer to electrical panel of the home. If you still lose the hum, suspect the circuit. If you still have the hum, you likely have a component compatibility issue. While lifting the earth ground of the C52 with a 3/2 cheater plug may solve the problem entirely, it may mask the real problem - which could prove to be a safety issue if
not fixed correctly.

 

[eedork]

Hi damacman -

Excellent info, thank you for posting!

This is a very interesting issue. I've got a few more data points to share. Earlier today I moved the 7100 to the game room above my garage and connected it to a MAC3 pre/pro (I left the C52 in the living room system). I had the same results with the MAC3 - hum when the trigger cable is connected and lovely silence when it is not. This room is on the other side of my house in a relatively new structure with (presumably) good, new wiring. This proves that there is no issue with the C52, which was my biggest concern. Other than that, I'm not sure what these results tell me since I've now seen the ground loop / hum with two different preamps on two different circuits within in my house. The MAC3 is also from the same generation as the MC7100, so I don't think it is a component compatibility issue.

One possibility is that there is an issue of some kind with the 7100. Suspecting this, I popped the cover and took a look around. I noticed one loose connector on a pair of wires that run from the trigger port PCB up to the front panel - when I saw that I said "yes!" thinking that the loose cable must be the issue, but unfortunately it wasn't. Taking a closer look at the trigger port PCB I noticed that the only the tip of the 1/8" jack is connected. The sleeve is not carried off the PCB, which explains why cutting the shield on my trigger cable had no impact.

Now I'm baffled. I can't figure out how applying a DC voltage to the trigger port on the MC7100 could cause a ground loop - that cable supplies only a DC voltage, no ground, yet when it is connected a ground loop is introduced.

I tried a cheater plug on the pre and still had hum. For now I've removed the trigger and am just powering the 7100 on/off manually.

My head hurts!

-Matt

 

[ron-c]

Did you try a Mono trigger cable? The only real solution is to buy a new amp that matches the C52 ......

You can test the power conditioner by plugging the MC7100 and C52 into a AC terminal strip and bypassing the conditioner.

Thanks,
Ron-C

 

[eedork]

Did you try a Mono trigger cable? The only real solution is to buy a new amp that matches the C52 ......

You can test the power conditioner by plugging the MC7100 and C52 into a AC terminal strip and bypassing the conditioner.

Thanks,
Ron-C

Hi Ron -

Thank you for the response. Yes, I've tried both a stereo and mono trigger cable. Both result in hum. It looks like only the tip of the trigger cable is actually connected to anything inside the MC7100. The ring and sleeve (within the MC7100) are not connected, so it shouldn't matter if a mono or stereo cable is used.

I have another question. Would you expect the MC7100 to have issues like this using a MAC3 as a pre? I am seeing the same hum issue with the MAC3 as well.

A new amp is likely at some point. I need to sell a few items first!

Thanks!
-Matt