High End Professional Amplifier for HiFi.

dnostereo

Active Member
Hi, I'm just wondering what peoples opinions might be for this.

I have a very high end touring amplifier, a Lab Gruppen FP6400. These are well over $5000 new and have massive power (2500wpc into 4Ohms). They are class TD (D) however their technology apparently produces AB sonic character/results.

Obviously it wouldn't be bad, but would it be quite good? If I was to sell it for $1500, would another more Hifi style amp be a better option?
 
Hi, I'm just wondering what peoples opinions might be for this.

I have a very high end touring amplifier, a Lab Gruppen FP6400. These are well over $5000 new and have massive power (2500wpc into 4Ohms). They are class TD (D) however their technology apparently produces AB sonic character/results.

Obviously it wouldn't be bad, but would it be quite good? If I was to sell it for $1500, would another more Hifi style amp be a better option?


If you have it, why would you not try it and say what you think of the sound?

I doubt many here have heard of the brand, let alone heard one in their system. Myself, I'm familar with the brand but never tried one in my systems...although I'd like to.
 
That's some really serious welding gear you have there! Why in the world would you want to swap it out? That is, what is the compelling reason to make a change? Are you going to something else that's more compelling or are you just wanting to try something else?

As you'll find in subsequent posts from others, a lot of it depends on the size of the room, the efficiency of the speakers you're using and how loud you play your music.

This isn't about the technology used in the amp - its about what you want to end up with.

Cheers,

David
 
That's some really serious welding gear you have there! Why in the world would you want to swap it out? That is, what is the compelling reason to make a change? Are you going to something else that's more compelling or are you just wanting to try something else?

As you'll find in subsequent posts from others, a lot of it depends on the size of the room, the efficiency of the speakers you're using and how loud you play your music.

This isn't about the technology used in the amp - its about what you want to end up with.

Cheers,

David
What David said. +1
 
So what your saying is that you have a killer German amp and you would like to sell it for a modern junk amp !

Cause that's what you are implying.....

That's probably one of the rarest amps here in the States !

If your not careful you might loose that before you know it and kick yourself for the rest of your life !

What you need is a preamp to plug a turntable into.....or whatever else you need plugged in....
 
Last edited:
What you need to go with that amp is about four of the most powerful JBL speakers you can find and a Technics SL-1200 turntable and invite your friends over to play some records. That amp is like almost indestructible.....

Make them bring the beer cause you got the tunes !
 
It's a pro amp, and on top of that it doesn't have a big transformer nor coke can caps. Plus it's a switching amp so it will sound like crap and fail prematurely. You won't able to fix it yourself with bailing wire and bubblegum. Oh, and did I mention lighweight? The power must be ILS rated. Pure rubbish. :rflmao:
 
Last edited:
First, try it and listen to it to see whether you like it or not. It is my opinion that equipment designed for specific purpose usually does not work well for other purpose. I don't know what is class TD, if it is like class D, I don't think it can compare with higher end hifi power amp. Highest quality amp still are class A or high bias class AB. That I don't think has change since way back.

Another thing is very high power amp usually does not sound very good at low volume like in stereo. Having 500W or whatever means nothing to the sound quality. In fact, it usually work the other way.

I don't want to get into why you want to do this or whatever, if you don't want it for the original purpose, if you can get $1500 selling it, you can get a very good used power amp for stereo that is designed for stereo. Names like Krell, Threshold, Bryston etc. You cannot tough the sound quality with any switching class D amps.

I would say the same thing if someone ask whether they can use a Krell to do PA or play guitar. hifi amp makes lousy guitar amp!!!
 
OP, whatever you buy, make sure that the company actually published service documentation before you make your purchase of a used piece. That pretty much rules out Krell, Threshold, and Bryston.
"Class D" (PCM) amplifiers sound terrible. Period. They're fine for subwoofer duty, but for serious listening through good speakers, they're harsh and lifeless.
 
If I could afford them, Lab Gruppen amps would be my choice for high power listening sessions. They are unreal how much power they put out. I think they make 20-25,000w amps also. They seem to be the standard for many band concerts these days for venues that can afford them
 
They are class TD, not D and sound VERY good. They also make Lake equipment

"The foundation of Lab Gruppen’s prowess in power amplification, Class TD is a breakthrough design that occupied Lab.gruppen’s co-founder Kenneth Andersson for nearly two years. Class TD combines the high efficiency of a digital Class D with the sonic purity of classic Class B designs.

The power supply rails precisely track the audio signal at all times, providing the required voltage plus additional headroom. This process is highly efficient, with only a tiny portion of the supplied voltage emitted as heat in the output stage. The audio path itself remains entirely in the analog domain. And because the audio path remains outside the switching portion of the circuit, the signal is free from any filtering ripple effects.

Class TD is bridgeable, highly reliable, and maintains a flat response with complex loads as low as 2 ohms nominal. Also, it does not interfere with RF equipment such as wireless (radio) microphones. Though treated separately here, R.SMPS and Class TD were conceived and engineered as an integral design within the amplifier platform. Working together, this new generation of proprietary circuits produces more power from a smaller package while at the same time maintaining Lab Gruppen’s peerless reputation for sonic excellence. The highs stay crisp and transparent. The mids are defined, warm and natural. And the tight low end delivers breathtaking visceral impact"
 
A 120 volt, 15 amp circuit can only deliver 1800 watts. Even at 100% efficiency, you can only get 1800 total watts out. This can be briefly exceeded on peaks due to slow trip nature of circuit breakers, plus the stored energy in the power supply capacitors.
20 Kilowatt amps would have to run on 3 phase power.
 
They are class TD, not D and sound VERY good. They also make Lake equipment

"The foundation of Lab Gruppen’s prowess in power amplification, Class TD is a breakthrough design that occupied Lab.gruppen’s co-founder Kenneth Andersson for nearly two years. Class TD combines the high efficiency of a digital Class D with the sonic purity of classic Class B designs.

The power supply rails precisely track the audio signal at all times, providing the required voltage plus additional headroom. This process is highly efficient, with only a tiny portion of the supplied voltage emitted as heat in the output stage. The audio path itself remains entirely in the analog domain. And because the audio path remains outside the switching portion of the circuit, the signal is free from any filtering ripple effects.

Class TD is bridgeable, highly reliable, and maintains a flat response with complex loads as low as 2 ohms nominal. Also, it does not interfere with RF equipment such as wireless (radio) microphones. Though treated separately here, R.SMPS and Class TD were conceived and engineered as an integral design within the amplifier platform. Working together, this new generation of proprietary circuits produces more power from a smaller package while at the same time maintaining Lab Gruppen’s peerless reputation for sonic excellence. The highs stay crisp and transparent. The mids are defined, warm and natural. And the tight low end delivers breathtaking visceral impact"

OK, so it's not a PCM amplifier. It sounds like a class AB amp with sliding bias and a switchmode power supply similar to what Bob Carver has been building and selling for nearly 40 years.
Hopefully, they're a lot more reliable.
 
A 120 volt, 15 amp circuit can only deliver 1800 watts. Even at 100% efficiency, you can only get 1800 total watts out. This can be briefly exceeded on peaks due to slow trip nature of circuit breakers, plus the stored energy in the power supply capacitors.
20 Kilowatt amps would have to run on 3 phase power.

It can be exceeded on peaks for quite a while, musicially speaking, due to breaker trip curves (as you mentioned).

Even with 2500W continuous test bench power. Typical average power on the verge of clipping is going to be only ~1/8 of that.

I use Crown CE4000 in bridged mode (rated 2800w into 4 ohms) on 120Vcircuits. No problem to occasionally tickle the clipping indicators without tripping the breaker.
 
Last edited:
20 Kilowatt amps would have to run on 3 phase power.

I wondered how they did that, thanks for the info. I believe Mohegan Sun runs Lab Gruppen amps and I can tell you, I have never heard a concert venue that sounds better then Mohegan Sun, they have these arrays on either side with the JBL cannons for the bass. SPAC in Saratoga is the best outdoor venue soundwise followed closely by Red Rocks, not sure what they run for amps there now since I have not been there since the late 80s
 
I am not claiming I am an expert, this is just my opinion:

I heard about modulating the rail according to the input signal so you have low voltage across the output stage all the time. I think it was Sun Fire or something. It is not for free, because of the early voltage of the output transistor, changing the collector voltage changing the characteristic of the transistor and creates distortion. So it is not free lunch. I don't know how much it will affect the sound, but it is NOT simple class AB by any stretch and I do not believe you can get the performance of a true class AB.

There are many attempts to keep the amp in class A region using variable bias, many patents had be written including one by Nelson Pass in the 70s, I simulate a lot of them, none of them work, they create more distortion than people expect. that's the reason they never get into the main stream. When you talk about higher end amp, everything matters. As a guitar amp designer before and currently designing a hifi power amp, you never use equipment for different purpose.

As I said before, since OP has the amp, try it, talk is cheap. If he like it, keep it. But if not, and if he can sell it for $1500, you can get into a used class A amp that is going to be in a different league.

Lastly, why do you want 2000W for hifi equipment? You hardly go beyond 5 or 10W with transient seldom reach 100W. You waste power, operating the amp away from optimal region. I just get the feeling some people think more is good, much more is better. I don't think that's how it works. You have the sweetest amp that is single ended tube amp that are under 10W.

I don't claim to be expert, but I do have a large collection of schematics of high end hifi amps, never seen one with funny scheme, that says a lot what the true experts think.

From my experience, there is an optimal loudness, if you crank below that, the system( amp included) does not open up, too loud, it get distorted. You try to keep the system operating in the optimal......that is to know what is your listening level and buy accordingly. You get a 2000W amp, you never run it in optimal level.

I am designing my first amp, but I have been EE for a long time and designed guitar amps before. I did a lot of study and I end up designing an amp that is only 60W into 8ohm and 120W into 4 ohm. I am more concentrating on having the amp running in clase A for the first 16W with 8ohm or 8W in 4ohm load, that's where my sweet spot. You got for bigger the better, there will be a lot of sacrifice in the design, believe me, I know that, been pulling hair for a while.
 
Last edited:
Wow thank you all for such amazing feedback and information. I think everything said is completely valid and useful to know.

I have tried it on my main speakers using my Luxman R-1070 as the pre. I really love the sound this receiver makes with my speakers (large 4 way with Vitavox woofer). I think the Lab added just a tad more clarity and authority on the bass; so much so I had to turn the bass down on the pre, also really don't want to blow those woofers as they're virtually unobtainable.

I have some very large speakers that came from Imax cinemas that run 4 x 12" 500watt woofers each side. I'm considering the Lab may be good to hook up to them should be able to power all 8. I do like to play it pretty loud also. I'm in Australia so we have 250v power.

Swapping it out for a Krell, Classe or similar could definitely be a consideration as I'm assuming these would run hifi perhaps a bit better although as mentioned, Lab Gruppen (and the model that I have) are up there with the best when it comes to professional touring and very reliable.
 
First, try it and listen to it to see whether you like it or not. It is my opinion that equipment designed for specific purpose usually does not work well for other purpose. I don't know what is class TD, if it is like class D, I don't think it can compare with higher end hifi power amp. Highest quality amp still are class A or high bias class AB. That I don't think has change since way back.

Another thing is very high power amp usually does not sound very good at low volume like in stereo. Having 500W or whatever means nothing to the sound quality. In fact, it usually work the other way.

I don't want to get into why you want to do this or whatever, if you don't want it for the original purpose, if you can get $1500 selling it, you can get a very good used power amp for stereo that is designed for stereo. Names like Krell, Threshold, Bryston etc. You cannot tough the sound quality with any switching class D amps.

I would say the same thing if someone ask whether they can use a Krell to do PA or play guitar. hifi amp makes lousy guitar amp!!!

I am not claiming I am an expert, this is just my opinion:

I heard about modulating the rail according to the input signal so you have low voltage across the output stage all the time. I think it was Sun Fire or something. It is not for free, because of the early voltage of the output transistor, changing the collector voltage changing the characteristic of the transistor and creates distortion. So it is not free lunch. I don't know how much it will affect the sound, but it is NOT simple class AB by any stretch and I do not believe you can get the performance of a true class AB.

There are many attempts to keep the amp in class A region using variable bias, many patents had be written including one by Nelson Pass in the 70s, I simulate a lot of them, none of them work, they create more distortion than people expect. that's the reason they never get into the main stream. When you talk about higher end amp, everything matters. As a guitar amp designer before and currently designing a hifi power amp, you never use equipment for different purpose.

As I said before, since OP has the amp, try it, talk is cheap. If he like it, keep it. But if not, and if he can sell it for $1500, you can get into a used class A amp that is going to be in a different league.

Lastly, why do you want 2000W for hifi equipment? You hardly go beyond 5 or 10W with transient seldom reach 100W. You waste power, operating the amp away from optimal region. I just get the feeling some people think more is good, much more is better. I don't think that's how it works. You have the sweetest amp that is single ended tube amp that are under 10W.

I don't claim to be expert, but I do have a large collection of schematics of high end hifi amps, never seen one with funny scheme, that says a lot what the true experts think.

From my experience, there is an optimal loudness, if you crank below that, the system( amp included) does not open up, too loud, it get distorted. You try to keep the system operating in the optimal......that is to know what is your listening level and buy accordingly. You get a 2000W amp, you never run it in optimal level.

I am designing my first amp, but I have been EE for a long time and designed guitar amps before. I did a lot of study and I end up designing an amp that is only 60W into 8ohm and 120W into 4 ohm. I am more concentrating on having the amp running in clase A for the first 16W with 8ohm or 8W in 4ohm load, that's where my sweet spot. You got for bigger the better, there will be a lot of sacrifice in the design, believe me, I know that, been pulling hair for a while.

Where to start, where to start..

I'll point out that one of the manufacturers you note as being truly high-end, Krell, uses techniques to "keep the amp in class A", which you complain about. (See iBias.) I would also argue that companies like Bel Canto and Classe also qualify as "high end" despite the fact they make extensive use of switching amps. Indeed, Bel Canto has gone from being a company that builds only tube amps to building only switching amps. There might be a reason for that. I'm also not sure why you're bringing up guitar amps since they're a completely different animal specifically designed to not be "high fidelity".

Switching amps have come a long way and are not to be dismissed so quickly.
 
Back
Top Bottom