NX150 listening impressions - diyAudio
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Old 11th September 2006, 05:19 AM   #1
rabbitz is offline rabbitz  Australia
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Default NX150 listening impressions

Before I bought the NX150, I searched around to find some reviews and listening impressions and came up with virtually nil as it's only new, so I thought it would be a good idea to start a thread for NX150 builders to pass on their thoughts.

I noticed destroyerX has some listening impressions and like Carlos I'm a huge fan of AKSA and the 55N+ has remained my reference for a few years and will continue to do so as it suits my listening. Also like Carlos I like to build and try different amps but I've only built about 0.01% of what he has.

The NX150 was tested in a system which uses a Sony CDP990, AudioSector NOS DAC, AKSA GK-1 SS section (no tubes), floor standing speakers using Scan Speak 18W/8531G00 & S2905/970000 drivers.

The first impression is one of overall smoothness without a hint of harshness. Female vocals do not have any edginess and remain controlled at all times as do other instruments in the Midís. Top end has a nice quality but misses that last amount of shimmer.... only a very small amount but noticeable.

The stereo image is very good and there is depth appearing in the sound stage . The vocals or instruments are well defined.

The bass has good tonal quality and is very powerful and maybe too much so for my system, but I did extend the speaker ports as an experiment and the bass became neutral and tonally balanced so it is just a matter of retuning the speaker to suit.

Overall, I'd say the sound is very accurate but I miss that extra charm, induced by H2 harmonics. The NX150 would kick a lot of commercial amps out of the way easily such as a Rotel I recently had.

I could easily live with the NX150, it is a Fine Amplifier.

The instructions are adequate for an experienced builder but maybe might need a few extra bits that we take for granted for the non experienced, such as heat sink mounting with Mica washers, checking for shorts onto the heat sink etc.

I'm looking at this amp in a very critical view considering the equipment that is out there and has to compete with plus I've had over 35 years in this game and have my own listening idiosyncrasies.

Anthony Holton was very swift to supply support and help during construction and has added this review to his web site plus some pics for those who are interested.
http://www.aussieamplifiers.com/nx150.htm

I'm not affiliated with Aussie Amps but I've added this thread as it's good for those interested in a DIY amp to get an idea of the sound. There are several other amps on this forum where I have also added listening and other comments from my experiences.
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Old 11th September 2006, 05:36 AM   #2
rabbitz is offline rabbitz  Australia
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Default NX150 inside and tweak

I thought I'd be smart and try a couple of tweaks by changing the input caps to Mundorf MKP's and C6 & C7 to Elna Cerafines. As usual with my limited amp design knowledge I bombed and the amp sounded best with the original components as supplied. If any builder does find some worthwhile enhancements, they can be posted so others can benefit.

I've add a pic of the inside and this 3U size case is an Altronics H5039 (Australia) which gave me plenty of room. It was mostly chosen as it has vent holes top and bottom where the heatsink is located plus has an easy internal mounting system so the amp can be worked on with the top and bottom covers removed. The pic has the tweak components shown before it was returned to original. This amp uses the PSU-Two power supply that is also supplied from Aussie Amps.
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Old 11th September 2006, 06:07 AM   #3
AKSA is offline AKSA  Australia
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Peter,

Nice review, and beautifully made amp!

Anthony has discussed his amp with me and he feels it's a corker - your experience bears this out. My congratulations to Anthony for his new product!

You may be right about the H2, but there's enough anecdotal evidence around to suggest that tuning an amp for best sound goes beyond the H2 and extends to the entire distortion spectrum. It's complicated!!

Your speaker skills were invaluable - nice trick with retuning!

Cheers,

Hugh
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Old 11th September 2006, 08:22 AM   #4
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Hi Everyone

I did some Distortion tests on the NX150 and my up and coming NX400 amp today.

Into a 8 Ohm load @ 1khz it was down in the noise floor 0.005%
It only rose to just below 0.01% @ 10khz
Which is not far of the Max resolution of my HP Meter.

This would give you some idea of the Precision of this design.
and hopefully the quality of its sound quality.
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Old 11th September 2006, 08:46 AM   #5
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Default The amplifier continues to work here, and it is very pleasant to listen to

A very clear and nice sonics.... a precise amplifier.

regards,

Carlos
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Old 11th September 2006, 08:51 AM   #6
rabbitz is offline rabbitz  Australia
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Thanks Hugh.

I bet tuning an amp for the best sonics is complicated and gives me a head ache just thinking about it.... best left to guys like yourself and Anthony. I'm only an amp builder and my amp tweaking ability sux.

Tuning speakers to an amp or other components is important and it would be easy to dismiss a fine amp if not done. I've designed and built plenty of speakers and are tweaked to suit a particluar amp, system or application and when used with another amp, can have quite different sonics. There is however, one amp that has handled them all.... you know the one.

The NX150 handled the workshop and the main system with ease but I didn't have my speakers from hell here that normally sorts out amp low impedance capabilities..... only one amp has handled those and no prizes for guessing which amp.
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Old 11th September 2006, 11:51 AM   #7
SamL is offline SamL  New Zealand
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Hi rabbitz,

Interesting review. I notice that Carlos is running his NX150 around 55Watt. How much are you running yours at?

TIA,
Sam
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Old 11th September 2006, 11:53 AM   #8
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Default Tune the speakers plays a good goal in the sound quality direction

Not only adjusting the speakers, using passive filter, trying to reach the most possible flat response.

This match would create some problems to the amplifier, as it do not like those RLC there....this will create a need of the amplifier matching with the whole system.... speaker plus passive crossover network.

The result of the match is great, reason why i think that we must buy amplifiers and speakers from the same factory...as they are matched and will sound the best possible.

I feel very good to see that others could perceive this, and use to do this matching.

regards,

Carlos
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Old 11th September 2006, 12:01 PM   #9
rabbitz is offline rabbitz  Australia
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Quote:
Originally posted by SamL
Hi rabbitz,

Interesting review. I notice that Carlos is running his NX150 around 55Watt. How much are you running yours at?

TIA,
Sam
Mine's running 59V rails without a load so would do a tad better than the 56V rail 146W into 8R and 230W into 4R. I think if I remember correctly, Carlos is going to do a full power version as well.
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Old 11th September 2006, 04:11 PM   #10
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Default I am giving up related to construct the full power version.

The speakers i have are already hitting the bottom of the excursion with my lowered power version..... i can imagine problems with the full power version.

At least, i will have to buy more speakers and disturb my neighboors (more!)...as i live in a building.

The small power version sounds good enougth.... also i will have 2 pairs free to check more schematics...as i am maniac to construct and listen....a maniac!

regards,

Carlos
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