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Lexicon DD8 Review (Multichannel Amplifier)

amirm

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This is a review and detailed measurements of the Lexicon, first generation DD8, 8-channel amplifier. It was purchased used by a member and drop shipped to me. The DD8 came from collaboration of Harman with TI (chip company) to produce very low weight, switching amplifiers for BMW car audio system. It was then later repurposed in this configuration for the Custom Integration (CI) industry. It is actually rebranded by a number of companies and sold under their label.

Note: our company, Madrona Digital, is a dealer for Harman products which includes Lexicon. So keep potential bias in mind as you read this review.

All 8 channels are provided in one compact, very cool running 1U rack mount chassis:

Lexicon DD8 Review Multichannel Amplifier.jpg


A stout on off switch manages power duties together with heftiest relay sound you have heard! The back will seem unusual for hi-fi market but is precisely what the custom integration channel needs:

Lexicon DD8 Review Multichannel Amplifier Custom Install.jpg


You can either feed the unit individually per channel or a "bus" input that feeds the same stereo input to all the channels. The latter is very handy for "whole house audio" where the same music plays in every room from ceiling speakers and such. A looped bus output is provided to cascade more of these units.

Output is provided through phoenix connectors which again is common and desired in CI channel as they are secure but small connectors. Individual gain controls are provided for every channel. You can also select mono vs stereo (again, useful in whole house audio where you usually want mono). And auto-sensing for channels not used. Trigger is also provided of course.

The available units are pulled out of existing installs so likely have many hours on them. And if the installer didn't know what he was doing, it may have been subjected to high temps. Indeed the first unit the owner bought did not work right, changing its gain with temperature. I traced it to the front-end of the unit. So know what you are getting if you buy them used.

Brand new, second generation DD8s cost US $3,500 (through dealer channels). This version listed for US $2,500. I see them listed for $1,300 right now on ebay but I believe the owner was able to get it much cheaper.

Lexicon DD8 Measurements
As usual, we start with our dashboard. I set the gain to max which nicely gave me 29 dB which is what I have standardized on:

Lexicon DD8 Measurements Multichannel Amplifier.png


This is above average performance with distortion kept below 100 dB;

Best multichannel custom amplifier review.png


Noise performance is good as well:
Lexicon DD8 Measurements Multichannel Amplifier dynamic range.png


Ideally we would get 16 bits at 5 watts but 15 is a good effort.

I was disappointed by the early cut off from the output filter:
Lexicon DD8 Measurements Multichannel Amplifier frequency response.png


This is due to rather low switching frequency of 250 kHz (common values are in 300 to 400 kHz), which made the filter harder to design:

Lexicon DD8 Measurements Multichannel Amplifier Switching Frequency.png


Crosstalk is fine:
Lexicon DD8 Measurements Multichannel Amplifier crosstalk.png


Power into 4 ohm is rather low:
Lexicon DD8 Measurements Multichannel Amplifier Power into 4 ohm.png


The protection circuit was aggressive which made getting max and peak power difficult. Still I managed to get some numbers:

Lexicon DD8 Measurements Multichannel Amplifier Max and Peak Burst Power.png


While we get more burst power courtesy of power supply designed for a lot more channels than two, max power with 1% THD+N still was rather low.

I then tested the amp using 8 ohm and surprisingly, it produces more power there:

Lexicon DD8 Measurements Multichannel Amplifier Power into 8 ohm.png


To see how the power scales, I measured max power using two and four channels. Both were the same using 8 ohm:
Lexicon DD8 Measurements Multichannel Amplifier Max Power 8 ohm.png


Most disappointing was varying the frequency and producing a power sweep:

Lexicon DD8 Measurements Multichannel Amplifier Power vs Frequency vs Distortion.png


As you see, there is huge penalty at higher frequencies. Furthermore, there are power related linearities.

Conclusions
In mid to low frequencies, the DD8 produces well above average performance. Above that frequency though, distortion increases substantially and other non-linearities surface. Output seems to have some load dependency while also rolling off early.

If you can get the unit for a few hundred dollars, then its compact enclosure and general performance may be a steal. You could almost push me to recommend it but I am not going to. I like to see better performance with respect to frequency response and high frequencies. I think for its intended custom install market, it is perfect (our company has installed a lot of these). For hi-fi use, you have to make that decision.

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amirm

amirm

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What is the MSRP of the unit?
It was at the bottom of the introduction. :) This version is no longer sold but when it was, it was $2,500.
 

MerlinGS

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If you can get the unit for a few hundred dollars, then its compact enclosure and general performance may be a steal. You could almost push me to recommend it but I am not going to. I like to see better performance with respect to frequency response and high frequencies.
Amir, you may not remember this, but a few yrs back you brought this amp up in a discussion at AVS. Fast forward a couple of yrs I was looking to purchase an 8 channel amp in a compact enclosure and I noticed Savant had decided to license the design (AMP 8125). I also noticed they were being sold cheaply on ebay ($200-$300). When I looked at the specs I noticed the issue with their frequency response (-1.5 dB at 20kHz); however, since my hearing is poor above 14 kHz I figured "why not". I purchased 2 for 200 and another 2 for 50 (PS problem). For what it is, it has served me well. I can't think of many 8 ch amps in this type of enclosure for a couple of hundred dollars.

PS I'm actually a little surprised at some of its good measurements, I did not expect this all things considered
PPS For those considering purchasing, my units have been very reliable, but please notice I also was able to purchase units with PS issues, so I cannot confirm how reliable these units may or may not be.
 
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amirm

amirm

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Amir, you may not remember this, but a few yrs back you brought this amp up in a discussion at AVS.
I don't remember that. But I do know I was impressed by it then and was thinking about using it for surround channels in my theater. You have far better memory than I do on this. :)

I purchased 2 for 200 and another 2 for 50 (PS problem).
That's killer pricing!
 

LTig

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I'd like to disagree with the statement distortion being below -100 dB. With up to 6 higher order HD components scratching the -100 dB line the sum (THD) clearly is higher.
 

wwenze

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I'd like to disagree with the statement distortion being below -100 dB. With up to 6 higher order HD components scratching the -100 dB line the sum (THD) clearly is higher.

When you measure noise (RMS) you will also always get a higher value than the noise floor seen in the FFT chart... same logic
 

jhaider

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It was at the bottom of the introduction. :) This version is no longer sold but when it was, it was $2,500.

A variant of that version is still available from Crown, CT8150.

https://www.crownaudio.com/en/products/ct-8150

Major differences are better inputs (balanced, Phoenix connector), annoying ground closure standby (as opposed to 12V trigger), faceplate with non-removable rack ears.

I picked up the 4 channel version (CT4150) for Auro/Atmos heights. It’s fine. It would be nice if it had a normal home audio trigger, but it’s connected to a Panamax box that has triggered outlet banks.
 
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Helicopter

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Thanks Amir. I agree this will do the job if the price is right. It is no Hypex amp, so not worth $2500 or whatever 8 channels of Buckeye costs.

I prefer to note the potential Madrona/Harman bias and move on, rather than to keep it in mind the whole time I read the review. ;) i do like the straightforward disclosure. So far I have not inferred any bias in your reviews of Harman products despite the potential for it.
 

restorer-john

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Interesting review @amirm. :)

For the purpose you described (running whole house ceiling/wall speakers) in a large home for background muzak, parties, or get-togethers, it would be fine in a large rack of other similar gear. Amazing what you can squeeze into 44mm of height.

Here's another switching amp with disappointing HF distortion at low-med levels and only falls as the power goes up and the harmonics start falling off the end of the 45kHz analyzer setting bandwidth. Although the 15kHz one is strange. Much would also be the function of the rapidly falling HF response hiding some sins.
 

Helicopter

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Interesting review @amirm. :)

For the purpose you described (running whole house ceiling/wall speakers) in a large home for background muzak, parties, or get-togethers, it would be fine in a large rack of other similar gear. Amazing what you can squeeze into 44mm of height.

Here's another switching amp with disappointing HF distortion at low-med levels and only falls as the power goes up and the harmonics start falling off the end of the 45kHz analyzer setting bandwidth. Although the 15kHz one is strange. Much would also be the function of the rapidly falling HF response hiding some sins.
I am sure it is better than the Russound SDB-4.1 transformer based speaker selector I am using to run 4 pairs of built in speakers with a Harmon Kardon HK 3770.
 
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amirm

amirm

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Here's another switching amp with disappointing HF distortion at low-med levels and only falls as the power goes up and the harmonics start falling off the end of the 45kHz analyzer setting bandwidth.
Speaking of this, I am thinking of eliminating the 20 kHz test. It screws up the visual display if one doesn't take the bandwidth into account. If there are no objections, I will do that in the next review.
 

restorer-john

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Speaking of this, I am thinking of eliminating the 20 kHz test. It screws up the visual display if one doesn't take the bandwidth into account. If there are no objections, I will do that in the next review.

I'm not sure people take into account the test bandwidth and the fact that a decreasing HF THD is not good, but merely the harmonics falling off the plot. How much time does it save you to scrap one 20kHz THDvsLevel?
 
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amirm

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I'm not sure people take into account the test bandwidth and the fact that a decreasing HF THD is not good, but merely the harmonics falling off the plot. How much time does it save you to scrap one 20kHz THDvsLevel?
The test is automated so doesn't take any effort. I just think it is confusing when it always shows less distortion at 20 khz than 15 kHz.
 

restorer-john

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The test is automated so doesn't take any effort. I just think it is confusing when it always shows less distortion at 20 khz than 15 kHz.

I agree, but it also sets a precedent of not testing THD at the limit of the generally accepted range of human hearing.

Amplifiers be they Class D or other classes could have skyrocketing THD which will get missed or minimized if you stop at 15kHz. There's plenty of Class AB amplifiers with poor HF THD too.

Are you going to apply the same rules to all classes/topologies?

Personally, I'd leave it in, but I don't know how many times you have to explain the bandwidth/harmonics issue to people.
 
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