McIntosh distortion


Platinum Member
Username: Nuck

Post Number: 13684
Registered: Dec-04
It has been mentioned many times, usually fom JV that 'Mac is Mac' and the sand and tube amps are going to give you as linear sound as Mac can do, with which I agree by experience.

But as my ears have cleared after a 3 week head cold, I listened last night at higher levels and wondered how the MA6900 amp is at distortion at max.

Would the sand amp be as forgiving as, say, a 275 tube amp in distortion? The tubes bend so gracefully that sometimes the distortion seems like music, at least to me

So just now, I put on a well known recording (Mellencamp...Uh Huh) and tried to blow up my amp.
The Power Guards begin to flash at around 200w on the meters, then glow steady as the meters touch well beyond the 200w peak.

This is where it gets interesting. there is one notch above solid guard where the amp REALLY steps up, like a TON!
I detected very little, if any distortion either inside the small house, and not from outside with a window open.
The outside test is usually easier to pick up bad sound to me,for some reason.

The Mac6900 has more power than expected(!)
and it drives very nicely.
Keep in mind that the Gallo's are a very easy load and 86db.

I have to say that this amp distorts with no sharp edges, no surprise SS clips and no harshness.

You can imagine how loud this was.

Gold Member
Username: Mike3

Wylie, Tx USA

Post Number: 2158
Registered: May-06
Nuck, your Power Guards will not allow the amp to clip.

From Roger Russell's site:

Power Guard was a circuit patented by Sidney Corderman and Ron Evans. Patent number 4,048,573 was awarded on September 13, 1977 and titled Amplifier Improvements For Limiting Clipping. It prevented the amplifier from generating distortion or "clipping".


Power guard is now described as a waveform comparison circuit that continuously monitors the output signal and compares it with the input signal. If distortion occurs at the output, the Power Guard circuit reduces the input signal level until the distortion is reduced below clipping. The amplifier gain is then restored.

The whole process of the Power Guard circuits takes only a fraction of a second. Although this action is not audible, the resulting sound at maximum power levels always stays "clean".

Not only was this a very important improvement for the amplifier, but also for loudspeakers. Many amplifiers, including McIntosh, could be inadvertently driven into clipping. Not only was the resulting sound harsh and distorted but also the energy generated from the harmonic distortion products was sometimes enough to burn out the mid-range and/or tweeters in some speaker systems. All new amplifier designs continued to feature Power Guard.

Imagine how loud it might have been...

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 14061
Registered: May-04

Yep, your amplifier cannot clip the signal. Though standing outside your house to prove this while trying to blow up your amp is not advisable under any circumstances. Even Andre doesn't try to do that!

Nuck, you really need to buy some Peavy crap for this outside stuff.


Gold Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 3132
Registered: Feb-07
It's a testament to McIntosh that even Nuck can't blow it up, although maybe Andre could.

A "Mac is a Mac" may be try, but I can't help but think that my entry level 6300 is nowhere on the same level as even Nucks 6900.

Silver Member
Username: Hawkbilly

Nova Scotia Canada

Post Number: 696
Registered: Jul-07
Sorry to hear you couldn't blow your amp up Nuck. Better luck next time. Maybe crack that bad boy open and take the governors out.

Gold Member
Username: Mike3

Wylie, Tx USA

Post Number: 2160
Registered: May-06
"I can't help but think that my entry level 6300 is nowhere on the same level as even Nucks 6900."

Not sure I would agree, just my opinion as I have not heard either straight up much less side by side.

Not counting any Mac gear heard in audio shops, only what I have played in my media room, I have to say that there is a common thread among their products. I hear a bigger difference between their tubes and solid state than I did between solid state models. The 7300 having had more power generated more space and drive than the MA-6200 JV had on loan to me but they carried the same signature. The 7300 was a generation or two newer.

I would think that with both the 6300 and the 6900 being currently sold models that they would sound more alike than the 7300 and 6200 did for me. Since they are newer with newer electronics some gains should be heard there as well. I would think Nuck would have a lower noise floor due to the high output power supplies, which also would get his running a bit louder (based on like speaker efficiencies) than your 6300, but not much else would be noticeably different.

JV might have more to say on this.

Gold Member
Username: Soundgame

Toronto, Ontario Canada

Post Number: 1030
Registered: Jun-08
Nuck - you're still up to the tricks. I haven't done the listening outside the house one since I was a teen.

Gold Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 3136
Registered: Feb-07
That makes sense Mike. I guess I have a little bit of McIntosh envy since mine is just the entry level integrated. Not that I'm not happy with it, quite the contrary. Might even compliment it someday with a Mac tube amp.

Platinum Member
Username: Artk

Albany, Oregon USA

Post Number: 10850
Registered: Feb-05
Things that make you go hmm.

Platinum Member
Username: Nuck

Post Number: 13687
Registered: Dec-04
It was simply a test of the amp and how it reacts to abuse. The amp never got past warm, ater 2 mins of the loud stuff and 3 hrs at 10 watts or so.

I did the outside thing with windows open to remove the immediate infuence of the room, and the sound is very accurate when standing between 2 open windows.

It was the extra notch that impressed me most, where I got a noticeable increase in volume (3db)?
and the meters bent closer to wide open, under guard, yet gave more.

This shows, if nothing else, that Mac6900 IA has a lot of great guts, and the Gallo's are a very easy speaker to drive.

The Mac would have done that for about 1/10th of a second on the Mani 2's.
Choose speakers wisely, as usual.

Gold Member
Username: Exerciseguy

Fort Hamilton, NY United States

Post Number: 2978
Registered: Oct-04
How are we to trust your hearing after such abuse?

How far away does your closest neighbor live?

Being rather easy to drive, how did the Gallos handle all that juice, any lasting repercussions?

Platinum Member
Username: Nuck

Post Number: 13693
Registered: Dec-04

Very close, but they ignore me, I am not around much, and it was early.

CM, these speakers will take as much HIGH QUALITY power as I can throw at them.

I have used the Classe ca300 amp with another pair.
Mike used the overachiving MC7300 300 wpc at them.

They are not timid in the least.

Yet, they play so well at 1W that it is always shocking.
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