MC152 and a few other questions

[mg16listener]

Spoke with McIntosh this AM and they will be sending a new one down. They seem to feel it is either a bad connection or a meter failure but it did pass inspection at the factory before it left. They also said to go ahead and use it till the new one gets here. I suppose I could always pop the top and trace down the connection and re-seat it just in case the issue is simply a connection.

Very disappointing but at least it looks like it will be taken care of by a full replacement. I like c_dk's thoughts on SASP. Most of dealers just do not do this type of thing. Some of them did back in the hey day of audio systems but now so much.

 

[techguy0192]

I ordered my MC152 from Audio Classics. It was shipped in all the correct packaging/cartons. I connected power and hit the switch. Nothing. I opened the top cover to find a thin ribbon cable that crossed the autoformer area to a the front control PCB was disconnected. This was a very thin/delicate cable with a very small connection area; it would have benefited from a locking connector. Once you get the top off it's very easy to see around the meters. You're right, these are heavy and I didn't want to full with return shipping. My background is in electronics and computer science with a day job in systems engineering, so it was nothing to me to pop the cover off and look inside. But yes, you shouldn't have to deal with this. The good thing is Mac is making it right.

 

[mg16listener]

Thanks for the advice. I will pop the top and take a look and see if it is an obvious fix.

 

[c_dk]

My installers, bless their hearts, could burn up a half a day of no longer billable time when ever they were a hour away from the shop......I often wish I could have packed their lunches to keep them on the job site, let alone a hiccup with a problem product.

I am sure Twii has his own stories.......

 

[twiiii]

I'm glad you have plenty of head room with your 152, it makes all the difference in the world in real world long term performance. If you were pushing your amp most of the time so that the power guard was barely flashing I guarantee choosing the correct transformer connection would be most necessary. Like you, my woofers have a very low impedance dip, but it doesn't seem to effect my MC 207 amps in the slightest.

 

[mg16listener]

Dealer sent out new replacement MC152 today. Everything works as expected. So far so good. My initial impressions is the system has more low end than before and the amp has better control over the speakers. However, I can see the presence of signal the speakers may not be able to reproduce because it is below their range.

Question:
My speakers are 4 ohms and this is the taps I am using. Some recommend using another tap like 8 ohms instead. What would be the effect of trying this out.

Thanks for all the advice. Looking toward a nice weekend of tunes in the updated system.

 

[zebra03]

 

[c_dk]

Overheating the amp is possible when using the 8 tap for 4 ohm speakers.....

I believe some have found better control of their speakers by going a tap lower, most likely because the speaker marketing people chose to find a way to rate their 4 ohm speakers as a 6 or 8 ohm speakers.

 

[Anthem]

Question:
I picked up a mc152 on July 4. I like to listen to my Anthem Statement d2v preamp via the balanced inputs and my Primaluna Prologue preamp via the unbalanced inputs. When both are hooked up together, when i slide the switch to unbal to listen to the Primaluna i get 50% reduction in volume. Full volume comes back only when the balanced IC's are removed. Is it not possible to have both balanced and unbalanced IC's connected at the same time?

 

[damacman]

Question:
I picked up a mc152 on July 4. I like to listen to my Anthem Statement d2v preamp via the balanced inputs and my Primaluna Prologue preamp via the unbalanced inputs. When both are hooked up together, when i slide the switch to unbal to listen to the Primaluna i get 50% reduction in volume. Full volume comes back only when the balanced IC's are removed. Is it not possible to have both balanced and unbalanced IC's connected at the same time?

Do not do this!!!! Only one connection at a time. You're lucky that you haven't damaged something.

 

[techguy0192]

Question:
I picked up a mc152 on July 4. I like to listen to my Anthem Statement d2v preamp via the balanced inputs and my Primaluna Prologue preamp via the unbalanced inputs. When both are hooked up together, when i slide the switch to unbal to listen to the Primaluna i get 50% reduction in volume. Full volume comes back only when the balanced IC's are removed. Is it not possible to have both balanced and unbalanced IC's connected at the same time?

Yikes! Don't do that. Also, the two connection options (RCA & XLR) have different gain, so there's no way to compare. If you are comparing preamps, it is import to level match to ensure the accuracy of the comparison.

 

[ddude003]

My owners manual shows...
Input Impedance 22,000 ohms Balanced and 22,000 ohms Unbalanced... I do not think this is a typo... Block diagram shows common between Balanced and Unbalanced where the switch does not show switching one leg off and the other on... The amp is designed as fully balanced thru and thru... This amp is designed to only have one input from a single preamp... As others have said... "Don't do that"... And if there is any confusion please do call McIntosh and ask for yourself... That is why they have a support group...

 

[Anthem]

Thanks guys. You are correct in your thinking.

Here is Chuck Hinton response from McIntosh.

The RCA input is connected to ½ of the balanced input, with 2 preamps connected, even with one off, the 2 legs of the balanced input will see 2 different loads and the amp will not run correctly.

In addition, preamp that is on will still be sending voltage to the OFF preamps output, this may cause damage.

If both the preamps are accidentally on, there will be a war and one will lose, damage is VERY likely.


Only one of the inputs on the amp should be connected at a time.

 

[quartersaw]

Overheating the amp is possible when using the 8 tap for 4 ohm speakers.....

I believe some have found better control of their speakers by going a tap lower, most likely because the speaker marketing people chose to find a way to rate their 4 ohm speakers as a 6 or 8 ohm speakers.

My Mc452 runs very, very warm when using the 8 ohm tap with my allegedly 6 ohm Cerwin Vega XLS-215's. Interestingly, the amp runs almost cold when using the 2 ohm taps, and 'comfortably' warm w/the 4 ohm taps.
The amps seems to sound best using the 8 ohm taps, unfortunately.

 

[ddude003]

Your MC452 has "McIntosh Sentry Monitor and Thermal Protection power output stage protection circuits ensure the MC452 will have a long and trouble free operating life. Built-in Thermal Protection Circuits guard against overheating."

Has it ever gone into protection mode when running, as you say, "very warm"... If not then I would not worry about it... Or you could call McIntosh Support and ask about what may be going on... Your Cerwin Vega XLS-215's are pretty efficient if one can believe their published 95.3 dB (@ 8 ohms @ 1 meter full) Impedance: 6 ohms... And I wonder if they really run down into the 4 ohms and below range...