Lexicon DD8 Review (Multichannel Amplifier)

[Rebelhifi]

Ro808,

I have the CT8150 on the back 4 channels and 4 atmos channels. The NC400 monoblock on on the main 3 channels. I have not done a comparison of the two types of amplifiers on the same speakers. An ear to the speaker tweeter test - the NC400 is quieter but I need to put my ear against the speaker for both amplifiers. So, the CT8150 which has balance inputs has a pretty low noise floor. For the surround and height channels, I am very pleased with the CT8150. (much better than the Crown XLS150 units I had). For sound quality, I had guests at the house for a party and put in Led Zeppelin 2007 Concert Bluray on the projector/home theater (played in Dolby Atmos). The guests were amazed with the music and how dynamic the system was. Led Zepellin's last concert came into the room. Now, they all want to have a concert night once per month. Sorry, I don't have any further comparison from a sound quality standpoint - direct / head to head. Overall, the NC400 monoblock (It was the DIY kit from Hypex) and CT8150 give me a dead quiet room with my JVC projector (low lamp). The channel separation is awesome. So, the dynamics come from a black background and discrete from all over the room. Fortunately, my best set-up to date.

 

[jhaider]

Ro808,

I have the CT8150 on the back 4 channels and 4 atmos channels. The NC400 monoblock on on the main 3 channels. I have not done a comparison of the two types of amplifiers on the same speakers. An ear to the speaker tweeter test - the NC400 is quieter but I need to put my ear against the speaker for both amplifiers. So, the CT8150 which has balance inputs has a pretty low noise floor.

One other benefit of these amps is attenuators on every channel. That can help preserve digital headroom in a multichannel system and lower noise floor from upstream components.

 

[Ro808]

After I saw people using CT amps to actively power their DIY horn systems (with TAD drivers a.o.), the CT 8150 seemed a suitable option for my own DSP-managed horn system.

In short, decent performance, balanced inputs for about the price of a single ALLO VOLT+D (including power brick) isn't bad.

These amps may not be optimal partners for larger, low efficient (multi-way), high-end loudspeakers that require lots of power to move the lossy multiple 8 or 10" woofers, like the 80 dB Magicos that were reviewed in the same issue of Stereoplay.
They most likely won't appreciate impedance drops close to, or below 3 Ohm either.

Over the past 20-30 years, the loudspeaker industry's focus has shifted to 'everything flat'.
Few people seem to be aware of the drawbacks inherent in this approach regarding efficiency, (off)load and phase versus replication of the input signal's wave shape.
In this thread some clues are touched.

 

[dlaloum]

I also agree. But one has to be careful allowing a downward trend of "frequency creep" or "lowering the ceiling" simply to appease a technology that plays by different rules. The same attention to detail and minutiae which @amirm has applied to D/A converters, has clearly paid off in spades with products being supplied for reviews improving at an exponential rate. It would be a shame to lose that momentum.

It's a tough one for sure, but my position is harmonics or intermodulation artifacts should be retained, up to and including the top end of the agreed human limits of hearing, regardless of any noises from the vested interests, or their associated fanboi peanut galleries.

Absolutely agree with IMD as more illuminating in many respects, but again, the old tests which used mains frequency (60 or 50 for us) and 7-8kHz at 4:1 were phenomenally useful, but less so now in the world of HF SMPS supplies. 19/20kHz with nothing above and only focusing on the audible range shows us nothing about potential interactions or instability outside the audible band. Is Class D these days as well behaved up there as Class AB wasn't?

Some of the measurements get difficult with bandwidth constrained designs... if a component has a brick wall filter at say 22kHz - it is hard to measure the THD when some of the harmonics would be above and beyond that filter.
(and would they be meaningful?)

 

[dlaloum]

Ro808,

I have the CT8150 on the back 4 channels and 4 atmos channels. The NC400 monoblock on on the main 3 channels. I have not done a comparison of the two types of amplifiers on the same speakers. An ear to the speaker tweeter test - the NC400 is quieter but I need to put my ear against the speaker for both amplifiers. So, the CT8150 which has balance inputs has a pretty low noise floor. For the surround and height channels, I am very pleased with the CT8150. (much better than the Crown XLS150 units I had). For sound quality, I had guests at the house for a party and put in Led Zeppelin 2007 Concert Bluray on the projector/home theater (played in Dolby Atmos). The guests were amazed with the music and how dynamic the system was. Led Zepellin's last concert came into the room. Now, they all want to have a concert night once per month. Sorry, I don't have any further comparison from a sound quality standpoint - direct / head to head. Overall, the NC400 monoblock (It was the DIY kit from Hypex) and CT8150 give me a dead quiet room with my JVC projector (low lamp). The channel separation is awesome. So, the dynamics come from a black background and discrete from all over the room. Fortunately, my best set-up to date.

I would (and have) argue(d), that in most cases, noise/hiss from amps is related to issues with gain and signal levels in the interface between pre and power - typically related too low an input V, resulting in excess gain needed at the power amp, amplifying noise from the entire chain (and not specifically or particularly from the power amp itself).

 

[patoulol]

Je suis passé du Purifi 1ET400A aux CT8150 et 4150 car j'avais des problèmes de boucle de masse impossibles à résoudre.

Et des problèmes pour gérer les gains. A l'écoute aucune différence.

Translated by moderator. English only please.


I upgraded from the Purifi 1ET400A to the CT8150 and 4150 because I was having ground loop issues that couldn't be fixed.

And problems managing winnings. Listening no difference.

 

[Rebelhifi]

I had no issues matching levels for my Dolby Atmos system (mix of 3 NC400 for the front channels and CT8150 - side, rear, and height). I used Audyssey MultiEQ with all XLR connections from Marantz AV processor.

 

[patoulol]

I had no issues matching levels for my Dolby Atmos system (mix of 3 NC400 for the front channels and CT8150 - side, rear, and height). I used Audyssey MultiEQ with all XLR connections from Marantz AV processor.

Sorry for the translation error @moderator:, I wanted to write in English

Yes, my Purifi had ground loops. Not the CT8150

What do you think of the difference between the CT8150 and the Nc400?

Does your CT8150 make a small whistling sound when it's turned off?

 

[Rebelhifi]

Sorry for the translation error @moderator:, I wanted to write in English

Yes, my Purifi had ground loops. Not the CT8150

What do you think of the difference between the CT8150 and the Nc400?

Does your CT8150 make a small whistling sound when it's turned off?

The CT8150 is several feet behind the screen in an enclosure. I do not hear anything on or off (sorry). I don’t remember any issue when installing (everything was quiet). The setup is great. My friends and I do concert nights in my bar / home theater (when the wives have book club). The system is dead quiet when nothing is playing and plays at concert levels without issue.

 

[patoulol]

ok

What do you think of the difference between the CT8150 and the Nc400 ?

 

[Rebelhifi]

ok

What do you think of the difference between the CT8150 and the Nc400 ?

I am not in the camp of different sounding amps. I do hear the signal to noise ratio difference (background hiss) of lower quality amps on my Klipsch horns. Both the NC400 and CT8150 are very quiet (have to put my ear to the horn to hear hiss on the Klipsch). NC400 is more powerful (significantly) at 4 ohms and 2 ohms. But, the CT8150 has not run out of power for surround duty at concert sound pressure levels.

 

[patoulol]

I am not in the camp of different sounding amps. I do hear the signal to noise ratio difference (background hiss) of lower quality amps on my Klipsch horns. Both the NC400 and CT8150 are very quiet (have to put my ear to the horn to hear hiss on the Klipsch). NC400 is more powerful (significantly) at 4 ohms and 2 ohms. But, the CT8150 has not run out of power for surround duty at concert sound pressure levels.

I get it, thank you. If I didn't have my ground loop problem with the purifi, I would have kept it. Maybe I'll take the risk of testing Nc400

 

[patoulol]

Quick question @dlaloum: here is the curve of my LR speakers We can see that they go down to 2.5 ohms at 100Hz! so my CT8150 will be limited for this part? @dlaloum

Fig.1 Paradigm reference, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

 

[Ro808]

Quick question @dlaloum: here is the curve of my LR speakers We can see that they go down to 2.5 ohms at 100Hz! so my CT8150 will be limited for this part? @dlaloum

Fig.1 Paradigm reference, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

Quite remarkable that you've "upgraded from the Purifi 1ET400A to the CT8150 and 4150"

While not exactly ideal, the impedance drop at 100 Hz should't cause problems in normal use (i.e. not THX Reference Level).

 

[patoulol]

Quite remarkable that you've "upgraded from the Purifi 1ET400A to the CT8150 and 4150"

While not exactly ideal, the impedance drop at 100 Hz should't cause problems in normal use (i.e. not THX Reference Level).

could this difficulty at 100hz explain why there is a lack of speed in the bass at high volume?

 

[Ro808]

Technically, it's the lack of current the amplifier is able to maintain (load regulation).

As Atkinson states: "The speaker's impedance plot (fig.1) reveals it still to be quite a demanding load, however, with a magnitude that drops to 2.5 ohms at 104Hz".


Here's a more in depth explanation.

 

[patoulol]

Technically, it's the lack of current the amplifier is able to maintain (load regulation).

As Atkinson states: "The speaker's impedance plot (fig.1) reveals it still to be quite a demanding load, however, with a magnitude that drops to 2.5 ohms at 104Hz".


Here's a more in depth explanation.

THANKS according to this graph at 2ohms there are 70watts available with the CT 8150

 

[dlaloum]

Quick question @dlaloum: here is the curve of my LR speakers We can see that they go down to 2.5 ohms at 100Hz! so my CT8150 will be limited for this part? @dlaloum

Fig.1 Paradigm reference, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

The link to the graph is broken... won't come up

The good thing though is the amp specs specifically state that it is stable for loads from 2ohm to 16ohm...

The bad thing is, that this is the only mention of 2 ohm (for the beefier XLS series, they are fully specified at 2 ohm... )

You can expect that the max power available at the 2.5ohm minimum could be substantially lower.... (as an example my Quad 606 amps provide 130W@8ohm but only 90W@2ohm.... and 90W@2ohm equates to roughly 22W@8ohm).

Having said that - in real life usage.... it should be just fine!

 

[dlaloum]

THANKS according to this graph at 2ohms there are 70watts available with the CT 8150

Yep - so that equates (very roughly) to 17W@8ohm

In my setup with inefficient 86db/wm speakers, I average around 3.4W to 4W and peaks never get to 16W

Also depending on your setup in terms of subs and crossovers - that minimum around 100hz may not be a big issue as the heavy lifting at that point may already be on the sub.

In my setup, I could hear no difference between the 440W XLS2500 (1200W@2ohm) and the 130W Quad606 (90W@2ohm) - as long as you have "enough" power for your SPL's, and the amps are stable into the load - you should be OK.

 

[Ro808]

THANKS according to this graph at 2ohms there are 70watts available with the CT 8150

Indeed, which likely contributes to the perceived 'slow/sloppy' bass at higher output levels.

The woofers in my bigger 2 way system are 102 dB and don't drop below 5 ohm, so the CT 8150 is basically overkill > due to the high efficiency/easy load.


This might improve performance (slightly):

Passive Bi-Amping:
You'll need 4 channels for 1 pair of speakers. Remove the speakers jumpers. Use outputs 1 and 3 to connect respectively the LF and HF of the left speaker, according to the +/- signs. Do the same with outputs 2 and 4 for the right speaker (depending on your input wiring of course).

From the Crown Manual:

It's recommended to consult the respective manuals to ensure correct jumper settings etc.