Monoblock vs two channel

[Vaughan Odendaa]

Just wanted to know, I've heard that monoblocks have zero crosstalk and is one of the apparent advantages over stereo amps/multichannel but how important is crosstalk in stereo amps/receivers and is it an audible phenomenon in consumer electronics?

 

[ImcLoud]

I have used a lot of modern multichannel amps and NEVER heard any cross talk... I usually do like mono blocks for stereo music listening, but I ended up getting an xpa2 for my 2.2 system because after demoing multiple mono blocks, {outlaw, carver, emo, ect} I like the xpa2's sound the best..

Its all up to the end user on what sounds good...

Out of curiosity I unplugged one input on my 2 ch amp and then plugged a speaker into the side with no input and no speaker to the other side that had an input plugged into it, then turned it up all the way.... No sound came out of the side with no input plugged in... Obviously not the best way to test for cross talk, but made me feel good.

 

[Irvrobinson]

In most cases of well-designed electronics crosstalk is inaudible, especially in separate two channel amps.

 

[Irvrobinson]

Out of curiosity I unplugged one input on my 2 ch amp and then plugged a speaker into the side with no input and no speaker to the other side that had an input plugged into it, then turned it up all the way.... No sound came out of the side with no input plugged in... Obviously not the best way to test for cross talk, but made me feel good.

And dangerous too, if you used the XPA-2. All it would have taken was one pop or transient coming through that speaker and it might have blown a driver or two, and you might have been deaf.

 

[Vaughan Odendaa]

So there are audibility thresholds for crosstalk distortion? If so, what are they and are they well known and documentated? Or is crosstalk one of those variables that is a bit of a grey area?

 

[Steve81]

So there are audibility thresholds for crosstalk distortion? If so, what are they and are they well known and documentated? Or is crosstalk one of those variables that is a bit of a grey area?

Basic Amplifier Measurement Techniques — Reviews and News from Audioholics

Crosstalk - measures channel to channel isolation. We take it one step further and do All-to-One crosstalk measurements where all channels but the channel under test act as a noise source. This measures stereo separation. We test this at 1 watt and full rated power to ensure issues such as magnetic coupling or power transformer saturation don't adversely affect performance. We like to see a number of at least 60dB @ 1kHz for channel to channel crosstalk and about 50db when its a seven channel amp doing All-to-One crosstalk measurements.

I'm unaware of crosstalk being a serious problem on even relatively inexpensive 2ch receivers. For example:
http://www.audioholics.com/reviews/receivers/hk-3490/hk-3490-measurements

Running a full range frequency sweep from the preamp all the way through the power amp at full rated power (120wpc @ 8-ohms), I measured channel to channel crosstalk where the channel under test was at idle while the adjacent channel was running and vice versa. The Audio Precision plotted crosstalk for each channel under these circumstances and showed that the worst channel exhibited around 90dB at 20 kHz which is a phenomenal result. Anything greater than 60dB at 20kHz is considered inaudible by even the most critical ears. There is no doubt that the stereo separation in this receiver is superb.

 

[ImcLoud]

And dangerous too, if you used the XPA-2. All it would have taken was one pop or transient coming through that speaker and it might have blown a driver or two, and you might have been deaf.

Yeah, could have definitely blown a few speakers {thats what warranties are for lol}, but probably no hearing damage...
A while back, I was sighting in the scope on my brand new Dakota D97 {chambered in .375 H&H}, and I dont know if it was from the excitement of getting on the paper with the first 3 shots, or that all of the first 3 shots were touching each other!!! But I took my muffs off, while I cleaned the barrel and got ready for the next 3 shots, when I was done I picked the rifle back up and settled in to take another few more shots, I pulled the trigger and instantly thought the world shutoff!!!

To make it worse the rifle had a brake machined into the barrel, Luckily the rifle was on the bipod and a pair of sand rests, because I would have dropped my $5K rifle on the ground... All I could hear was Ringing in both ears and multiple sharp pains in my right, it lasted about 3 days, I went to the emergency room when the ringing didn't stop {the pain only lasted 5 minutes or so}. They did an examine and sent me to an ear nose throat guy who said the ringing should only last a week and gave me some drops and antibiotics!!! He said the hairs in my inner ear probably broke off causing tinnitus, and it takes a few days for them to grow back...

I have since shot the rifle with the db meter {my meter goes up to 170 and it says OL when I tried to meter it, I had to set the meter up about 12 feet away and it measured 159db!!! I would say its 175+ at the muzzle... My ears hurt just thinking about it, good thing I was outside, if I was ever shooting from the indoor range, I would be deaf...

 

[Steve81]

I pulled the trigger and instantly thought the world shutoff!!!...I have since shot the rifle with the db meter {my meter goes up to 170 and it says OL when I tried to meter it, I had to set the meter up about 12 feet away and it measured 159db!!! I would say its 175+ at the muzzle... My ears hurt just thinking about it, good thing I was outside, if I was ever shooting from the indoor range, I would be deaf...

Ouch! Funny how it's never like that in the movies/TV. One of the few times I've pulled the trigger without hearing protection, I was in between a couple of sheet metal barns which really boosted effect. It didn't feel good, and that was just a piddly 38 revolver.

 

[jinjuku]

So there are audibility thresholds for crosstalk distortion? If so, what are they and are they well known and documentated? Or is crosstalk one of those variables that is a bit of a grey area?

Are you talking crosstalk or push/pull transistor crossover distortion?

Channel crosstalk isn't distortion. It's one channel of the amp attenuating to the signal in the other channel.

 

[Vaughan Odendaa]

[quote="jinjuku]Are you talking crosstalk or push/pull transistor crossover distortion?[/quote]

Crosstalk .. sorry, I just thought of crosstalk as a type of distortion. Thanks for correcting me.

 

[Vaughan Odendaa]

I read the Audioholics article. I don't doubt the source, but is there any evidence to corrobrate it? Have studies been done to confirm the lack of audibility beyond a certain point or is 60 dB the golden number?

 

[ImcLoud]

Ouch! Funny how it's never like that in the movies/TV.

Yah, you see clint shooting a 44mag with no ear protection, that gun easily reaches 160db, and then if you ever did it in a small room or a car forget it, it shuts your brain off, lol...

Another great thing about movies is when a shot blows someone through a window lol, its physically impossible, for something to generate that much force without originating from a greater force is against everything science has taught us. In other words, if you weigh 200lbs and shoot a guy who weighs 200lbs and the shot makes him fly 6 feet through the air, you will have to also move 6+ feet in the opposite direction because you are holding the gun... I watched a guy get shot in his vest with a 12g 3 1/2 mag shell, he didnt move 3 inches... I mean I shoot a soda can full of sand {so the bullet doenst just shred through} with a .308 round, and it only flys about 3 feet, that weighs about a pound, so a 200lb person hardly moves...

 

[jinjuku]

I read the Audioholics article. I don't doubt the source, but is there any evidence to corrobrate it? Have studies been done to confirm the lack of audibility beyond a certain point or is 60 dB the golden number?

In these circles it's common knowledge like water is wet...

 

[Vaughan Odendaa]

I know what you are saying, but again, is there any hard data to corroborate the claim? It's not that I doubt the claim, in fact I agree but I don't know why I'm agreeing. ; ) Like THD, most consumer amps produce absurdly low levels of THD, beyond a certain number it's all academic and I assume there are studies that support that claim.

I just thought there might be a study or something to support the claim that crosstalk is largely immaterial in most semi-decent consumer gear.

 

[jinjuku]

I know what you are saying, but again, is there any hard data to corroborate the claim? It's not that I doubt the claim, in fact I agree but I don't know why I'm agreeing. ; ) Like THD, most consumer amps produce absurdly low levels of THD, beyond a certain number it's all academic and I assume there are studies that support that claim.

I just thought there might be a study or something to support the claim that crosstalk is largely immaterial in most semi-decent consumer gear.

Google it....

 

[Steve81]

I know what you are saying, but again, is there any hard data to corroborate the claim? It's not that I doubt the claim, in fact I agree but I don't know why I'm agreeing. ; ) Like THD, most consumer amps produce absurdly low levels of THD, beyond a certain number it's all academic. I just thought there would be a study or something to support the claim that crosstalk is largely immaterial in most semi-decent consumer gear.

I'm unaware of any studies specifically targeting the audibility of crosstalk. OTOH, various blind tests performed over the years tend to indicate that the threshold of audibility has been met by even entry level receivers.

 

[Steve81]

Yah, you see clint shooting a 44mag with no ear protection, that gun easily reaches 160db, and then if you ever did it in a small room or a car forget it, it shuts your brain off, lol...

Another great thing about movies is when a shot blows someone through a window lol, its physically impossible, for something to generate that much force without originating from a greater force is against everything science has taught us.

With respect to movies/TV, I think this is probably the funniest tidbit of them all:

The Gun Zone -- FBI Handgun Wounding Factors and Effectiveness

Further, it appears that many people are predisposed to fall down when shot. This phenomenon is independent of caliber, bullet, or hit location, and is beyond the control of the shooter. It can only be proven in the act, not predicted. It requires only two factors to be effected: a shot and cognition of being shot by the target. Lacking either one, people are not at all predisposed to fall down and don't. Given this predisposition, the choice of caliber and bullet is essentially irrelevant. People largely fall down when shot, and the apparent predisposition to do so exists with equal force among the good guys as among the bad. The causative factors are most likely psychological in origin. Thousands of books, movies and television shows have educated the general population that when shot, one is supposed to fall down.

 

[Irvrobinson]

Channel crosstalk isn't distortion. It's one channel of the amp attenuating to the signal in the other channel.

In the broadest definition you're correct. It's just mixing. But crosstalk generally isn't consistent across all octaves; it is often greater at high frequencies than at low frequencies, and sometimes by 20db or more, so it could affect the overall system frequency response as perceived by the listener - if it were significant, but it isn't in electronics. Only phonograph cartridges and magnetic tape heads have significant levels of crosstalk.

 

[AcuDefTechGuy]

I read the Audioholics article. I don't doubt the source, but is there any evidence to corrobrate it? Have studies been done to confirm the lack of audibility beyond a certain point or is 60 dB the golden number?

I think a XTalk of 60dB from 20Hz-20kHz seems to be the magic number. Of course, higher is better as far as spec. The high-end boasts XTalk of 100dB 20-20kHz.

Most AVRs have a XTalk of 70-80dB @ 1kHz, which means 50-60dB from 20Hz-20kHz.

I wouldn't worry about, though.

 

[j_garcia]

I've used monoblocks for all three mains previously and I am now using an XPA-3. I really don't see crosstalk as being an issue with modern amps. The reason you want monoblocks IMHO, is to allow each speaker to have an independent power supply so that during peaks each speaker gets as much power as it needs as opposed to a multichannel amp that would share the total power among all channels. If you have an amp that is sufficient for your demands, that really isn't an issue though.