This is a review and detailed measurements of the Lab.Gruppen E 4:2 "touring" pro amplifier. It was kindly sent to me by a member. The E42 costs US $899. If you don't know about the originally Swedish company they have been a fixture in pro amplification for many years. It has changed hands a few times and is now part of the same group as Behringer.
The E42 comes in a "1U" rackmount chassis:
There are no VU meters as we see in competitor's amps with larger footprint. There is useful indicators for current limit and protection however.
The rear shows the connections which while typical in pro world, are foreign to consumer electronics:
The phoenix connectors are used for both inputs and outputs. They are large and easy to terminate but obviously need custom cabling.
There is variable gain. I set it to max which produced a gain of 27 dB, approximating the nominal 29 dB which is common with consumer amps.
There is an odd Lo-z and 70 volt switch. It is common to have 70 volt mode (for long speaker runs) but not the way it is implemented here:
As you see, for 8 ohm you are supposed to use the 70 volt mode even though that label has nothing to do with such loading.
For 4 ohm, you have to use Lo-Z which is what I used for most of my testing. As you shall see, this proved to be quite problematic.
In general, I am not fond of a product that requires the owner to bend to its needs. I mean this is not a tube amp. WHy does it have a switch setting for the load impedance? Speakers don't have constant impedance anyway so in reality there is no good way to know what setting to use.
The 1U chassis mandates tiny fans which are almost always very noisy and that is the case here. While I have heard much louder, this is still something that is not acceptable in a standard home audio system unless you can place the amp in a different room.
The design here is Class-D amplification by the way and hence the ability to squeeze it all in this small enclosure.
Amplifier Audio Measurements
As usual, we feed the amp a 1 kHz tone and ask it to produce 5 watts into a 4 ohm load to represent low level music listening:
We see pretty high harmonic distortion at multiples of our 1 kHz tone (2, 3, 4, etc. kHz). SINAD which is a sum of distortion+noise then is dominated by high distortion giving the E42 an average rating amount nearly 100 amplifiers tested so far:
Signal to noise ratio is "OK at 5 watts:
But not that great at full power. Spec is a whopping 112 dB.
Frequency response shows some load dependency due to necessary output filter in class D amplifiers to attenuate switching noise:
I am using simple resistive load and still getting some peaking. A real speaker with its more complex impedance may cause other frequency response variations.
32-tone test signal resembling "music" shows the same distortion profile we have already seen:
So far the measurements aren't that bad and fit the level of performance pro amps usually target so you may be wondering why it got the headless panther rating. This is why:
I am only getting 85 watts with both channels driven versus 200! This is in Lo-z mode as instructed. The limiter kicks in and stops the amp from producing more power (reason the graph seems to go backward). Maybe the amp is designed to only allow for peak excursions? I tried running my tests to find that peak but could not because the limiter would keep kicking in, confusing the analyzer.
Switching to 70 volt input and 8 ohm gets us the specified power:
So seems like the amp does not like low impedance of 4 ohm even though it is well within its spec.
Testing frequency sensitivity we get a very complex set of graphs as we change that factor and run the above sweep:
Class-D amplifiers have very complex distortion profiles as the circuit is not a simple analog amplifier. So this is not unusual for the type.
One shining performance aspect was crosstalk:
This is near state of the art!
Finally, here is our very wide band spectrum analysis:
We see the switching frequency of around 370 KHz peaking to nearly -10 dB. I like to see at least 20 dB of attenuation here.
Conclusions
Lab Gruppen is a trusted brand in pro amplifier industry. As such, I am surprised by the results I achieved here. Company is proud of the limiting circuit in this amp for reasons that I don't understand from their writing. Whatever it is, it appears to be more designed to keep the amplifier from getting damaged (a real concern in live sound) than being performant. Combined with the fan noise and quite high price for such modest power level, it is really not a fit for home use.
Needless to say, I can't recommend the Lab.Gruppen E 4:2 amplifier.
-----------
As always, questions, comments, recommendations, etc. are welcome.
One of my pink panthers is getting frustrated with the state of the country and wants to run for a political office!!! Naturally he is looking to me to provide seed capital for his campaign. Heaven knows what little money I have won't be used to plaster signs on people's laws and power poles! But maybe you can make his desires come through by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The E42 comes in a "1U" rackmount chassis:
There are no VU meters as we see in competitor's amps with larger footprint. There is useful indicators for current limit and protection however.
The rear shows the connections which while typical in pro world, are foreign to consumer electronics:
The phoenix connectors are used for both inputs and outputs. They are large and easy to terminate but obviously need custom cabling.
There is variable gain. I set it to max which produced a gain of 27 dB, approximating the nominal 29 dB which is common with consumer amps.
There is an odd Lo-z and 70 volt switch. It is common to have 70 volt mode (for long speaker runs) but not the way it is implemented here:
As you see, for 8 ohm you are supposed to use the 70 volt mode even though that label has nothing to do with such loading.
For 4 ohm, you have to use Lo-Z which is what I used for most of my testing. As you shall see, this proved to be quite problematic.
In general, I am not fond of a product that requires the owner to bend to its needs. I mean this is not a tube amp. WHy does it have a switch setting for the load impedance? Speakers don't have constant impedance anyway so in reality there is no good way to know what setting to use.
The 1U chassis mandates tiny fans which are almost always very noisy and that is the case here. While I have heard much louder, this is still something that is not acceptable in a standard home audio system unless you can place the amp in a different room.
The design here is Class-D amplification by the way and hence the ability to squeeze it all in this small enclosure.
Amplifier Audio Measurements
As usual, we feed the amp a 1 kHz tone and ask it to produce 5 watts into a 4 ohm load to represent low level music listening:
We see pretty high harmonic distortion at multiples of our 1 kHz tone (2, 3, 4, etc. kHz). SINAD which is a sum of distortion+noise then is dominated by high distortion giving the E42 an average rating amount nearly 100 amplifiers tested so far:
Signal to noise ratio is "OK at 5 watts:
But not that great at full power. Spec is a whopping 112 dB.
Frequency response shows some load dependency due to necessary output filter in class D amplifiers to attenuate switching noise:
I am using simple resistive load and still getting some peaking. A real speaker with its more complex impedance may cause other frequency response variations.
32-tone test signal resembling "music" shows the same distortion profile we have already seen:
So far the measurements aren't that bad and fit the level of performance pro amps usually target so you may be wondering why it got the headless panther rating. This is why:
I am only getting 85 watts with both channels driven versus 200! This is in Lo-z mode as instructed. The limiter kicks in and stops the amp from producing more power (reason the graph seems to go backward). Maybe the amp is designed to only allow for peak excursions? I tried running my tests to find that peak but could not because the limiter would keep kicking in, confusing the analyzer.
Switching to 70 volt input and 8 ohm gets us the specified power:
So seems like the amp does not like low impedance of 4 ohm even though it is well within its spec.
Testing frequency sensitivity we get a very complex set of graphs as we change that factor and run the above sweep:
Class-D amplifiers have very complex distortion profiles as the circuit is not a simple analog amplifier. So this is not unusual for the type.
One shining performance aspect was crosstalk:
This is near state of the art!
Finally, here is our very wide band spectrum analysis:
We see the switching frequency of around 370 KHz peaking to nearly -10 dB. I like to see at least 20 dB of attenuation here.
Conclusions
Lab Gruppen is a trusted brand in pro amplifier industry. As such, I am surprised by the results I achieved here. Company is proud of the limiting circuit in this amp for reasons that I don't understand from their writing. Whatever it is, it appears to be more designed to keep the amplifier from getting damaged (a real concern in live sound) than being performant. Combined with the fan noise and quite high price for such modest power level, it is really not a fit for home use.
Needless to say, I can't recommend the Lab.Gruppen E 4:2 amplifier.
-----------
As always, questions, comments, recommendations, etc. are welcome.
One of my pink panthers is getting frustrated with the state of the country and wants to run for a political office!!! Naturally he is looking to me to provide seed capital for his campaign. Heaven knows what little money I have won't be used to plaster signs on people's laws and power poles! But maybe you can make his desires come through by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
