This demonstrates why we used to see ‘under powered’ rigs, driven hard into passive cabinets with cross overs, blow the HF. The amp distortion splashed the compression drivers. Excellent demo !
First v-dosc was with the LA48 (lab 4000). Later on they become the LA48A.(fp6400) Difference is they connect the switching powersupply negative side on the B-channel (10% extra power on the low frequencies)and some extra inputsensivity switches.
Cool, yeah we never owned LA48, did not even know about them. We bought V-dosc when it was Crest and Crown powered with XTA xovers. Went from crest to LA48a
Extraordinarily Great Video! Isolating the distortion components allows people to hear the impact of amp clipping rather than simply looking at specs or a graph. I assume the sine wave distortion is from the amplifier squaring off the signal. (It would be interesting to see the output on a scope, particularly with the sine wave input). It would also be interesting to see the frequency spectrum of the distortion (using an FFT analyzer looking at the difference signal). The sine wave signal should show you the distortion signal's relative levels of even-order (2x, 4x, 6x. . .) versus odd-order (3x, 5x, 7x. . . ) harmonics. In the HiFi world, it is assumed that the even-order harmonics (typically from a Tube or Class A amp) are better "Warm-sounding" and the predominately odd-order harmonics are worse "Harsh-sounding." In my experience, the way an amplifier performs when it clips, as measured with bursts signals (representing real-world wide-dynamic range program material like music with 20-30 dB peak to average ratios), is the difference that makes an amplifier sound good.
Dave and Sam, interesting test, it is what my ears told me in both pro audio and hi end home audio with good class a/b and class D amps. I prefer class a/b for above 200 hz and class D for bass .
it's a shame they don't make it anymore, my favourite amp... *crying great video! could you please show your test environment? ...i'm asking myself how do you listen to that stuff without run into the danger of blowing up your speakers..
So... this is what I went against all these years. Just the idea itself of beeing able to listen isolated amp distribution is revolutionary to my small world. And I'm looking right now at a left over QSC rmx5050 I never got to find a use for...
Maybe in the same realm as a singer repeating a word to emulate a delay and adjacent to adding reverb to sound like the instrument is in a reverberant room or recording multiple vocal overdubs to get a choir type sound or harmony. Artistic expression to achieve a desired results, all good.
@@DaveRat You are very generous. Having dealt with far too many small club djs, fighting a gain battle to try to preserve the speakers, I am somewhat less enthusiastic. That noise means work at a time of night that should be reserved for drinking. I place it in the same bin as a TV production that thought that SMPTE time code was a cool sound to put in a program. It's one of those things that, as a maintenance engineer, you should never hear outside of specific brief tests. I had 2 ideas for disco audio limiters, one was an Acme boxing glove on a spring, the other was a wage meter, it would start at the going rate for the night and every time the meters lit up red it would decrement.
Ha! Yes, ideally you would have limiters that prevent the speakers from ever being damaged. Then the DJs can just have at it and you are just an observer. But down the more fun side, a giant clip light facing the audience that lights red when the system is distorting with a sign above it that says: "Inexperienced DJ ruining the sound light"
No amount of protection will be enough for a pushy club owner flashing bottles of booze around on their favorite act night. One time I've been asked to operate a system I helped implement in a disco type club for that famous car pimpin' hip hop thing. I had to re-cone 6 out of the 8 subs before the next Friday night! Let's say I "exibited" some hearing discomfort for a while after that night
Oh my, well, doubling the number of subs and setting password locked limiters in the amps that only allow the max level of 1/2 the amount of subs would get ya pretty close
Why don't you show what's happening on the oscilloscope. It would be interesting for engineers like me to see these diagrams. Including FFT analysis if the oscilloscope has such an option.
I will do at some point but also I find that analyzing gear in ways that we don't actually use it can bias the tests and perceptions. If you or others are actually using a scope and fft to see waveforms on the inputs and outputs while mixing or setting up, then yes, that's a different story. I wanted to test based on the way people use the consoles rather than what the consoles can do when tested in ways that people don't actually use them This will become more clear when you get to future videos. Focusing on what is actually heard and the consoles visual interface of what it tells you you should hear, has kept me on track with finding stuff that the gear that makes pretty colored lines often distracts from or glosses over.
Dave, do you intend to compare the practical advantages and disadvantages of amp topology broadly speaking after these tests? I’ve always personally considered class-h to be the most optimal topology offering the best of balance in the real world/practical sense….
Modern amplifiers have moved past simple class-h designs. Instead, most use uniquely optimized digitally controlled power supplies that provide very high short-term output capabilities. Still, the length of non-clipped bursts and the recovery time between bursts varies significantly between designs. Additionally, most modern design's thermal condition can dramatically impact their performance. The dynamic variability makes it hard to compare amplifiers as their performance depends on the test signal or program material. For example, a design optimized for high frequencies versus one designed for subwoofer use would be very different.
@Dylan Dylan If I am correct the Lab FP and even PLM series are more similar to class G output stage. Main difference with other amps from that era is the SMPS.
@@stefsmits442 absolutely - I believe the dual stage voltage rails of class H and how they ramp oppose to switch in class G makes it a winner topology - in my mind offers the best efficiency vs audio quality vs weight. Class D offers high efficiency and weight benefits - but probably not considered a audible pleasing distortion Class AB offers superior audio quality but definitely not weight or efficiency Class G - the predecessor to H - switched dual voltage rails - offers efficiency and weight benefits Class H Ramps in the second rail, giving a more linear dynamic range, better distortion characteristics- but not as efficient and a little heavier then class D. That’s my understanding anyhow - i am probably wrong though ;) Of course the SMPS switching characteristics of each design from that period were talking about greatly alters efficiency, reliability and distortion property’s - especially in the HF band- that’s where a switching amp is let down IMO
Dave, a lot of people prefer old big heavy iron transformers in the power amps to provide "real" bass or better bass tone than the light weight switching amps, do you agree with this theory or not and do you think the high end price amps are much better for heavy work loads or are the cheap behringer or knockoff style amps just as good? Hope there is no such thing as a dumb question, your honesty is appreciated
Great question Steven. My gut says iron. But testing has shown me that it is not as much the age or amp type as the actual design of the specific amp. For example, old creat vs qsc vs crown with pulse tests has the creat as a winner. Newer amps lab gruppen was better than qsc and way better than the Peavey crest but then comparing a brand new powersoft to an old creat put the powersoft on top. What I did find is that the specs don't tell you how an amp wi perform with high level sub lows and low frequency bursts. You need to test and compare and there are old and new tech amps that perform well. I will try and do a vid on how to test amps for lows at some point
@@DaveRat at EAW in the day, we never had the time to do a deep dive, but the inductance of large voice coil subwoofers clearly impacted the performance of subwoofer amps. Testing amplifiers into dummy loads does not consider the impact of the reactive component of a loudspeaker load. Not to mention that the loudspeaker load characteristics significantly change as they get hotter.
@@DaveRat thanks for your honesty, a lot of us in the community are switching to amps like qsc 3402 / 3602 as they are made in USA, lighter, more efficient and reasonable on the secondary market. The heavy iron amps are becoming increasingly harder to get parts for it would be interesting to see how they fair against big ticket or cheap knockoffs, I am sure there would be much interest in this test or opinions
@@DaveRat If you really like to do amp power tests and want to get a very accurate and fast measurement, there's a product called the SMD Amp Dyno that seems to work pretty well. There's a couple of people on RUclips with them. One I know is a guy with a channel called Williston Audio Labs, he uses it on almost all of his videos. It's produced some very interesting results and conclusions. One interesting thing that I've learned is that Class AB amps typically have about 3db more peak power compared to it's rms while normal Class D amps might only have 0-1db extra peak power but higher end Class D amps will get more like 2db of peak power.
Cool cool and interesting. I try and do my tests with inexpensive readily available gear or using almost no test gear at all whenever possible so people can replicate and test their own stuff. I am more about teaching people how and why to test than the actual tests themselves
I found your speaker cable audibility test to be fascinating, but IMHO this test is flawed. What you're hearing is not purely the distortion; instead, you're hearing the part of the sine wave not being reproduced + the distortion. THD analyzers take the signal to be tested and remove the fundamental with a band-reject or notch filter. What's left is distortion + noise, and at clipping, noise will not be an issue. That would be what you want to hear. I assure you, it's a way nastier sound that what you heard from this test. And that sort of test would answer the question of the sound of a clipping tube amp vs. the sound of clipping SS amp. Note, of course, not all SS amps clip the same, nor do all tube amps. I've seen vintage Marantz receivers from the mid-70's that could be pushed (with music) to a fair amount of clipping on an oscilloscope, but you could barely notice it in the music. I still don't know why this is, but I've seen and heard it in person.
Hmmm, this low tech comparitive really just allows us to hear potential differences but does not really put those differences into a perspective of audibility. As far as older and tube amps natural ability to offer compression and/or distortion that is not undesirable, and therefore sound perceptively louder for a given wattage, yes, that also occurs when dealing with analog vs digital wherein analog distortion can be more forgiving and listenable than digital distortions. Compression is non linear and can be viewed as a form of distortion but not necessarily an undesirable form.
@Dave Rat In most cases, tube amplifiers (and particularly Class A Tube and solid-state amplifiers) produce much lower odd-order relative to even-order harmonics resulting in a "smoother" or "warmer" sound than class A/B (and class H) amplifies. This is generally thought to be a by-product of switching distortion between plus and minus signals (audio, not power supply).
Ok so power amps today are pushing 5k per channel but the amps of yesteryear pushed mabey around 1000rms at the most. But today it’s all class D back then it was AB before that it was A from what I’ve seen A seemed louder than AB but AB seems quieter than D. Concerts haven’t really gotten much louder than they were in the 90’s but we have 3-4 times the power. I find it hard to believe that’s all headroom. Is there some equation I’m not aware of do these amps process power in a way that makes a class A amp louder than a class D amp. Their should be some equation that proves the spl of 50 watts class A or AB is the same as the SPL of 50 watts class D. Where’s all those extra class D watts going? Anyway thanks for the video. I wish there were more information online about the super sub ive searched all over the internet for info about it. But it’s simply not out there. I e seen all of yours but in total I’ve seen about 30 minutes of footage about this sub and haven’t heard anyone talk about actually using them except your 10 min video at Coachella. I’ve been waiting years to hear someone talk about actually using them on tour it thanks again for the video
@Jam Band The difference is that the bass cabinets of 30 years ago or more were usually horn-loaded, while today they're usually direct radiators that need 4-10 times as much power. Like acoustic suspension speakers in 1960's home stereos, the speaker industry has taken advantage of rising available power to make the speakers smaller.
Yes, the amount of watts delivered to sound systems has grown significanlty. Yes, modern loudspeakers are less efficient, smaller, lower distortion and offer much better coverage than older systems. When designing and building sound systems there are 6 factors that I see as the fundemenals: Size Weight Max volume Sound quality Cost and Aeethetics/ergonomics Each of these impacts the others. So as sound systems get smaller, and sound better, they get heavier and require more power and more expensive. The fidelity of a modern high end concert is truly astounding and amazing compared to what was considered state of the are 20 years ago. And it takes a lot more watts to get there
This demonstrates why we used to see ‘under powered’ rigs, driven hard into passive cabinets with cross overs, blow the HF. The amp distortion splashed the compression drivers. Excellent demo !
👍👍
I never blow a speaker with one of my lab amps
this is awesome! learning alot! wish this was a course when i was in school! cant wit for the next video!
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First v-dosc was with the LA48 (lab 4000). Later on they become the LA48A.(fp6400) Difference is they connect the switching powersupply negative side on the B-channel (10% extra power on the low frequencies)and some extra inputsensivity switches.
Cool, yeah we never owned LA48, did not even know about them. We bought V-dosc when it was Crest and Crown powered with XTA xovers.
Went from crest to LA48a
Just got my first Rat sound hoodie delivered. Wow.. what a thing.. quality piece of kit Dave.
Awesome! And thank you!!
This was a really interesting video Dave!
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Extraordinarily Great Video!
Isolating the distortion components allows people to hear the impact of amp clipping rather than simply looking at specs or a graph.
I assume the sine wave distortion is from the amplifier squaring off the signal. (It would be interesting to see the output on a scope, particularly with the sine wave input).
It would also be interesting to see the frequency spectrum of the distortion (using an FFT analyzer looking at the difference signal). The sine wave signal should show you the distortion signal's relative levels of even-order (2x, 4x, 6x. . .) versus odd-order (3x, 5x, 7x. . . ) harmonics.
In the HiFi world, it is assumed that the even-order harmonics (typically from a Tube or Class A amp) are better "Warm-sounding" and the predominately odd-order harmonics are worse "Harsh-sounding."
In my experience, the way an amplifier performs when it clips, as measured with bursts signals (representing real-world wide-dynamic range program material like music with 20-30 dB peak to average ratios), is the difference that makes an amplifier sound good.
👍
Dave and Sam, interesting test, it is what my ears told me in both pro audio and hi end home audio with good class a/b and class D amps. I prefer class a/b for above 200 hz and class D for bass .
🤙👍🤙 interesting, I actually prefer a/b for sound and D for cost, weight, size, output power per rack space, and minimal power draw
You are both so cool. 😊
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it's a shame they don't make it anymore, my favourite amp... *crying
great video!
could you please show your test environment?
...i'm asking myself how do you listen to that stuff without run into the danger of blowing up your speakers..
The setup is disassembled now
Another great example of why blinking red lights are usually a bad thing in the audio world we live in. Just my two cents. Cheers - E
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So... this is what I went against all these years. Just the idea itself of beeing able to listen isolated amp distribution is revolutionary to my small world. And I'm looking right now at a left over QSC rmx5050 I never got to find a use for...
The next vid with the powersoft X4 will be interesting as well
Sorry for writing distribution instead of distortion.
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Touted as "the coolest amp on the planet"
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Have You ever heard about the Nexo NxAmp 4x4? would love to hear it overdriven. These videos are so interesting! Thank You!!
I've heard of it but not tested it or used it. Thank you!
Fun!
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@8:30 wonder if the smell was the enamel melting? Hopefully no voice coil died during the making of this video.
I fried the resistor load!
What do we think of dance tracks that deliberately use a clipped sound to make it seem like they are exceeding the sound system capabilities?
Maybe in the same realm as a singer repeating a word to emulate a delay and adjacent to adding reverb to sound like the instrument is in a reverberant room or recording multiple vocal overdubs to get a choir type sound or harmony.
Artistic expression to achieve a desired results, all good.
@@DaveRat You are very generous. Having dealt with far too many small club djs, fighting a gain battle to try to preserve the speakers, I am somewhat less enthusiastic.
That noise means work at a time of night that should be reserved for drinking. I place it in the same bin as a TV production that thought that SMPTE time code was a cool sound to put in a program. It's one of those things that, as a maintenance engineer, you should never hear outside of specific brief tests.
I had 2 ideas for disco audio limiters, one was an Acme boxing glove on a spring, the other was a wage meter, it would start at the going rate for the night and every time the meters lit up red it would decrement.
Ha! Yes, ideally you would have limiters that prevent the speakers from ever being damaged. Then the DJs can just have at it and you are just an observer.
But down the more fun side, a giant clip light facing the audience that lights red when the system is distorting with a sign above it that says:
"Inexperienced DJ ruining the sound light"
No amount of protection will be enough for a pushy club owner flashing bottles of booze around on their favorite act night. One time I've been asked to operate a system I helped implement in a disco type club for that famous car pimpin' hip hop thing. I had to re-cone 6 out of the 8 subs before the next Friday night! Let's say I "exibited" some hearing discomfort for a while after that night
Oh my, well, doubling the number of subs and setting password locked limiters in the amps that only allow the max level of 1/2 the amount of subs would get ya pretty close
Why don't you show what's happening on the oscilloscope. It would be interesting for engineers like me to see these diagrams. Including FFT analysis if the oscilloscope has such an option.
I will do at some point but also I find that analyzing gear in ways that we don't actually use it can bias the tests and perceptions.
If you or others are actually using a scope and fft to see waveforms on the inputs and outputs while mixing or setting up, then yes, that's a different story.
I wanted to test based on the way people use the consoles rather than what the consoles can do when tested in ways that people don't actually use them
This will become more clear when you get to future videos.
Focusing on what is actually heard and the consoles visual interface of what it tells you you should hear, has kept me on track with finding stuff that the gear that makes pretty colored lines often distracts from or glosses over.
Dave, do you intend to compare the practical advantages and disadvantages of amp topology broadly speaking after these tests?
I’ve always personally considered class-h to be the most optimal topology offering the best of balance in the real world/practical sense….
Modern amplifiers have moved past simple class-h designs. Instead, most use uniquely optimized digitally controlled power supplies that provide very high short-term output capabilities. Still, the length of non-clipped bursts and the recovery time between bursts varies significantly between designs. Additionally, most modern design's thermal condition can dramatically impact their performance. The dynamic variability makes it hard to compare amplifiers as their performance depends on the test signal or program material. For example, a design optimized for high frequencies versus one designed for subwoofer use would be very different.
Agreed, I will release a vid in testing a powersoft X4 next
@Dylan Dylan If I am correct the Lab FP and even PLM series are more similar to class G output stage. Main difference with other amps from that era is the SMPS.
👍
@@stefsmits442 absolutely - I believe the dual stage voltage rails of class H and how they ramp oppose to switch in class G makes it a winner topology - in my mind offers the best efficiency vs audio quality vs weight.
Class D offers high efficiency and weight benefits - but probably not considered a audible pleasing distortion
Class AB offers superior audio quality but definitely not weight or efficiency
Class G - the predecessor to H - switched dual voltage rails - offers efficiency and weight benefits
Class H Ramps in the second rail, giving a more linear dynamic range, better distortion characteristics- but not as efficient and a little heavier then class D.
That’s my understanding anyhow - i am probably wrong though ;)
Of course the SMPS switching characteristics of each design from that period were talking about greatly alters efficiency, reliability and distortion property’s - especially in the HF band- that’s where a switching amp is let down IMO
Dave, a lot of people prefer old big heavy iron transformers in the power amps to provide "real" bass or better bass tone than the light weight switching amps, do you agree with this theory or not and do you think the high end price amps are much better for heavy work loads or are the cheap behringer or knockoff style amps just as good? Hope there is no such thing as a dumb question, your honesty is appreciated
Great question Steven. My gut says iron. But testing has shown me that it is not as much the age or amp type as the actual design of the specific amp.
For example, old creat vs qsc vs crown with pulse tests has the creat as a winner.
Newer amps lab gruppen was better than qsc and way better than the Peavey crest but then comparing a brand new powersoft to an old creat put the powersoft on top.
What I did find is that the specs don't tell you how an amp wi perform with high level sub lows and low frequency bursts.
You need to test and compare and there are old and new tech amps that perform well.
I will try and do a vid on how to test amps for lows at some point
@@DaveRat at EAW in the day, we never had the time to do a deep dive, but the inductance of large voice coil subwoofers clearly impacted the performance of subwoofer amps. Testing amplifiers into dummy loads does not consider the impact of the reactive component of a loudspeaker load. Not to mention that the loudspeaker load characteristics significantly change as they get hotter.
@@DaveRat thanks for your honesty, a lot of us in the community are switching to amps like qsc 3402 / 3602 as they are made in USA, lighter, more efficient and reasonable on the secondary market. The heavy iron amps are becoming increasingly harder to get parts for it would be interesting to see how they fair against big ticket or cheap knockoffs, I am sure there would be much interest in this test or opinions
I will try and look at cheap vs expensive new amps
Hi
Very interesting.
Have you tried the distortion test with an old school tube amp?
Not yet but that would be fun to do
@@DaveRat If you really like to do amp power tests and want to get a very accurate and fast measurement, there's a product called the SMD Amp Dyno that seems to work pretty well.
There's a couple of people on RUclips with them. One I know is a guy with a channel called Williston Audio Labs, he uses it on almost all of his videos. It's produced some very interesting results and conclusions.
One interesting thing that I've learned is that Class AB amps typically have about 3db more peak power compared to it's rms while normal Class D amps might only have 0-1db extra peak power but higher end Class D amps will get more like 2db of peak power.
Cool cool and interesting.
I try and do my tests with inexpensive readily available gear or using almost no test gear at all whenever possible so people can replicate and test their own stuff.
I am more about teaching people how and why to test than the actual tests themselves
The gain 32db o 41db is for 2300 whats 4 homs
I found your speaker cable audibility test to be fascinating, but IMHO this test is flawed. What you're hearing is not purely the distortion; instead, you're hearing the part of the sine wave not being reproduced + the distortion.
THD analyzers take the signal to be tested and remove the fundamental with a band-reject or notch filter. What's left is distortion + noise, and at clipping, noise will not be an issue. That would be what you want to hear. I assure you, it's a way nastier sound that what you heard from this test. And that sort of test would answer the question of the sound of a clipping tube amp vs. the sound of clipping SS amp. Note, of course, not all SS amps clip the same, nor do all tube amps.
I've seen vintage Marantz receivers from the mid-70's that could be pushed (with music) to a fair amount of clipping on an oscilloscope, but you could barely notice it in the music. I still don't know why this is, but I've seen and heard it in person.
Hmmm, this low tech comparitive really just allows us to hear potential differences but does not really put those differences into a perspective of audibility.
As far as older and tube amps natural ability to offer compression and/or distortion that is not undesirable, and therefore sound perceptively louder for a given wattage, yes, that also occurs when dealing with analog vs digital wherein analog distortion can be more forgiving and listenable than digital distortions.
Compression is non linear and can be viewed as a form of distortion but not necessarily an undesirable form.
@Dave Rat In most cases, tube amplifiers (and particularly Class A Tube and solid-state amplifiers) produce much lower odd-order relative to even-order harmonics resulting in a "smoother" or "warmer" sound than class A/B (and class H) amplifies. This is generally thought to be a by-product of switching distortion between plus and minus signals (audio, not power supply).
Cool cool thank you Ken, I will try and test a class A amp at some point
LA48 is lab 4000 and la48a is lab 6400 😊
Interesting I didn't even know there was an LA 48
@@DaveRat i learn just that too when i buy 48a but the seller say 48 but iam happy now, 200w more on 4ohm
Very cool and thank you
@@DaveRat Thanks you from Sweden just on hour from lab gruppen conpany start 😀10/10 for all the video you do!
what’s your option of the crown xls drivecore amps? thanks
Not familiar with them
Thanks for your reply.
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Ok so power amps today are pushing 5k per channel but the amps of yesteryear pushed mabey around 1000rms at the most. But today it’s all class D back then it was AB before that it was A from what I’ve seen A seemed louder than AB but AB seems quieter than D. Concerts haven’t really gotten much louder than they were in the 90’s but we have 3-4 times the power. I find it hard to believe that’s all headroom. Is there some equation I’m not aware of do these amps process power in a way that makes a class A amp louder than a class D amp. Their should be some equation that proves the spl of 50 watts class A or AB is the same as the SPL of 50 watts class D. Where’s all those extra class D watts going? Anyway thanks for the video. I wish there were more information online about the super sub ive searched all over the internet for info about it. But it’s simply not out there. I e seen all of yours but in total I’ve seen about 30 minutes of footage about this sub and haven’t heard anyone talk about actually using them except your 10 min video at Coachella. I’ve been waiting years to hear someone talk about actually using them on tour it thanks again for the video
@Jam Band The difference is that the bass cabinets of 30 years ago or more were usually horn-loaded, while today they're usually direct radiators that need 4-10 times as much power. Like acoustic suspension speakers in 1960's home stereos, the speaker industry has taken advantage of rising available power to make the speakers smaller.
Yes, the amount of watts delivered to sound systems has grown significanlty. Yes, modern loudspeakers are less efficient, smaller, lower distortion and offer much better coverage than older systems.
When designing and building sound systems there are 6 factors that I see as the fundemenals:
Size
Weight
Max volume
Sound quality
Cost and
Aeethetics/ergonomics
Each of these impacts the others. So as sound systems get smaller, and sound better, they get heavier and require more power and more expensive.
The fidelity of a modern high end concert is truly astounding and amazing compared to what was considered state of the are 20 years ago. And it takes a lot more watts to get there
6dB clipping isn't even a lot of gain.
Oh man switch mode amps do horrid stuff.
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