Nexo amps
Printed From: Speakerplans.com
Category: General
Forum Name: Amp Forum
Forum Description: The 'Stopping Jake Fielder moaning constantly' forum description...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=60498
Printed Date: 23 April 2024 at 10:46am
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com
Topic: Nexo amps
Posted By: Lex
Subject: Nexo amps
Date Posted: 14 December 2011 at 12:37am
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Hi, Anyone had any experience with the Nexo NX amps? I've got a ps10 r2 setup running off powersoft amps and TD controller, but can you get more out of the NX amps i.e. using the presets in the setup to get optimal performace? Thinking of repacing my powersofts with a 4x1 or 4x4. Like to hear peoples experiences rather than marketing hype. Just FYI: K8 running a PS10 per side D4002 running an LS600 (going to get another sub soon hopefully) I do mobile DJ'ing and private parties, looking for max efficiency and sound quality. Thanks in advance!  |
Replies:
Posted By: DjLeco
Date Posted: 14 December 2011 at 11:00am
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Inside are YAMAHA amps autooscilant TD class.
Very small smps trafo, very weak storage capacitors (too less uFarads, just 1640uF per rail)
http://postimage.org/image/62zu6pzi9/" rel="nofollow">
 http://postimage.org/image/aii9bzbwh/" rel="nofollow">
 ------------- I'm A Stupid SMART Romanian... |
Posted By: jonminns
Date Posted: 14 December 2011 at 12:02pm
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K8 on PS10s?? That's totally excessive!! ------------- 4 ohms is for wimps |
Posted By: ceharden
Date Posted: 14 December 2011 at 12:14pm
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I've mixed in a venue a few times which uses a single NX amp to drive two twin 18's and four PS15 R2's. No complaints about the amp at all, no headroom issues etc. Wasn't a small room either. Talking about secondary capacitors. The Chevin A series amps only have about 15uF of Polyester caps per rail on the secondary side and no-one complains about them. In fact having tested them on the bench, I couldn't detect any evidence that a lack of capacitance there was a problem. |
Posted By: DjLeco
Date Posted: 14 December 2011 at 1:25pm
So, why Crown, Labgruppen, Powersoft, uses alot of 1000uF/200 Volts capacitors parralel per rail (between 10000 and 20000uF total capacitance per rail, 20000-40000uF total capacitance)?
They are stupid?
Uf , mondial crysis, amplifier will become, empty inside...
http://www.youtube.com/watch?v=Gh0Aw9iHaSI" rel="nofollow - http://www.youtube.com/watch?v=Gh0Aw9iHaSI ------------- I'm A Stupid SMART Romanian... |
ceharden wrote:Posted By: dunc
Date Posted: 14 December 2011 at 1:28pm
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Running a big gig at the minute at Doncaster Racecourse with 3 NX4x4 Amps (Totally Overkill) Amp 1 runs 2 RS18 Subs and 6 boxes og GEOS12 Amp 2 runs 4 PS15s Amp 3 runs 4 PS10s. Im running out of speaker power, rather than amp headroom, however they are all intelligent enough to limit to the appropriate levels (and with my FOH engineer, we need it) |
Posted By: teslaman
Date Posted: 14 December 2011 at 2:16pm
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Whether you put your bulk reservoir storage on the primary side or secondary side (or both) of your PSU design is entirely up to you, one is not necessarily better than the other. In terms of getting small ripple voltage on the output DC rails VERY small capacitors can be used on an SMPS but only if the bulk storage is on the primary side. Vice versa is also possible and allows clever techniques like PFC to be included without needing additional stages in the primary circuitry... Big secondary side caps do not in themselves say if an amplifier will have good performance or not. I'm not familiar with the Chevin amps but I can absolutely believe ceharden's comments if the PSU switching frequency is high enough. Also amplifiers whose secondary side voltages track the audio signal will have to have small caps otherwise they could not have the required slew rate...
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Posted By: DjLeco
Date Posted: 15 December 2011 at 12:48am
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What's the association between secondary, or primary capacitor(s) and slew rate? Ha ha ha...
So, let's put just 1uF capacitor per rail, is enough, huh?
For increasing slew rate...
Bullshit.
Slew rate is alot dependant of internal compensation of that amp and Ft of output devices, at every amplifier based on AB Class, Class H, H2 , H3, or H4 step, G class amplifier, TD class is Tracking Class D amplifier, wich after downconverter is a classical AB class amplifier.
Bigger capacitor(s) storage, is better for heavier transient responses, and longer term sustained power, instead burst power, also lower ESR ,very important for noise ripple on SMPS output, especially on non regulated ones (like all Yamaha SMPS amps) we don;t talk about PFC here, Yamaha maybe never heard about active PFC....
Watch here Crown SMPS of Macrotech I series power supply, output storage is almost 12000uF per rail (24000uF total storage capacitors), loaded on dummy load 4 ohms each channel, how many volts dropping between IDLE, and MAX load on 4 ohms each ch:
http://www.youtube.com/watch?v=Mq6RvGba7qc" rel="nofollow - http://www.youtube.com/watch?v=Mq6RvGba7qc
Official is +/- 162,5 Vcc in idle, and drops till around 2x 161Vcc on max load, till limiting.
That means a very good SMPS , in mine opinion.
Proof:
http://postimage.org/image/phjda3pop/" rel="nofollow">
 ------------- I'm A Stupid SMART Romanian... |
Posted By: Muckerbarnes1
Date Posted: 15 December 2011 at 1:03am
Totally agree on switching frequency and storage, but not that small. I'm with Claudiu there. Big enough is OK, but bigger is better to a point. I just don't see the slew rate relationship as above. Can you explain. ------------- Billy Dawg. |
Posted By: teslaman
Date Posted: 15 December 2011 at 10:08am
Yes I probably didn't explain that too well, happens when your brain goes off on a tangent! Thanks for asking nicely tho rather than unleashing the dogs!, I wish DjLeco could do the same! I was referring to a very specific type system where the output of the power supply tracks the instantaneous voltage of the audio signal (with some DC superimposed) and is then followed by a BTL class-AB output stage, a.k.a. BASH amplifiers. The slew rate I was referring to was that of the modulated DC rail NOT the output signal. The principle is the same with tracking down-converter amplifiers like Lab Gruppen except they have standard DC rails followed by a non-isolating step-down converter (I believe). In either case the capacitor on the output of the power supply or down-converter needs to follow the audio signal whilst minimising ripple from the PSU switching frequency. It is thus a compromise on value as if it's too big it will not be possible for it to track the audio signal quick enough, hence limiting the slew rate of the DC rails and affecting efficiency and/or performance. Regarding small caps on SMPSU outputs, what value do you think is an acceptable minimum? If we take the example of a non-regulated supply with the bulk capacitance on the primary side. The power supply would typically use a 95% duty cycle or thereabouts. After full-wave rectification at the transformer output we have a signal that is spending 95% of its time at the required DC voltage anyway, the 5% dead time it will not be supplying current hence the output cap will be supplying the load. So lets assume 100kHz switching frequency (low by modern standards) and work out the duration of the dead time, answer = 0.25us. Lets assume the load on the DC rail is 20A peak for this particular amplifier (fair estimate for 500W-1kW amplifier) and now work out the ripple for a 15uF capacitor: dv/dt = i/C = 1.33V/us and hence approximate ripple with 0.25us dead time is 0.33V peak-peak! I know there are various assumptions in this calculation but it's in the ball-park and 0.33V ripple at 200kHz (it's double because of full-wave rectification) is pretty good. You likely just as much due the ESR of electrolytics if you used a few parallel 'big' caps? The situation can be worse if the supply is PWM regulated as the "dead-time" is increased but at the same time an inductor would be included between the rectifiers and the cap in this case which gets you back to the same ball-park. Same goes for the step-down converter used in Lab Gruppen etc. which will have an inductor by necessity. Hence, assuming my maths and assumptions are OK then I return to my previous comment that I can perfectly beleive that nice quality low-ESR 15uF cap is OK for a power supply output |
Posted By: DjLeco
Date Posted: 15 December 2011 at 12:51pm
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I will make a test, soon, with a capacitor Polypropylene of 25 uF/250 Vdc per rail, and after with a multiple capacitors parraleled (electrolytics) , and I will put scope probe on output DC of SMPS to observe the noise ripple, in 2 examples.
Freq will be exactly 100Khz, unregulated SMPS.
------------- I'm A Stupid SMART Romanian... |
Posted By: Tapeworm
Date Posted: 15 December 2011 at 1:55pm
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Heres a nexo amp rack (3x 4x4s and 2x 4x1s) we are using at work for a theatre show we are doing in the colston hall bristol. running 4x rs15 subs, 2 hangs of geo s12, 2 hangs of geo s8, 4 ps8 front fills, and a load of ps10 monitors. this will be used in conjunction with their in house centeral hang of s12s also ran of nexo 4x4. the nx amps sound noticably better than our qsc powerlights with tds!   ------------- http://www.nslproductions.com/" rel="nofollow - NSLproductions.com http://www.neverlution.co.uk/" rel="nofollow - neverlution.co.uk |
Posted By: Lex
Date Posted: 15 December 2011 at 4:49pm
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Thanks for the replies guys! Looks like an NX amp is the way forward - got some saving to do! Interesting discussion to! Yeah the K8 is overkill but was an impulse buy on ebay and i can add another two ps10's with headroom. Cheers all. |
Posted By: Muckerbarnes1
Date Posted: 15 December 2011 at 4:54pm
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David I understand what you are trying to say with cap size for smps, switching, commutating etc. It's just the cross wires between this and 'other' amp configurations. Calculations are fine. Yes we can do this. Ears are a wonderful thing on the right head. Personally class AB only. H etc, yes ok. The rest can get lost. I hate the idea of messing with the audio chain, hence some amps really do sound crap, fuzzy and broadcast HF. @ Claudiu are you going to do this test on a class AB? Or can you state what amp config? ------------- Billy Dawg. |
Posted By: teslaman
Date Posted: 15 December 2011 at 5:30pm
Absolutely agreed that the ears are the final judges, no question. When I buy an amp I don't care what's inside, what topology, what PSU etc. as long as it sounds good and delivers the power I need. We all suffer a bit form generalisations like "class-AB or H amps with big toroidal transformers and big reservoir caps are best for bass" but some of us have limited exposure to different amps and believe it just because we read it here. As an engineer I like to believe I try to be a bit more objective and if I come across something that is really good I like to try and find out why that might be. I think the reason I posted on this thread is because I don't agree with comments like "It only has x uF of caps so it's gonna be crap", it's just too much of a generalisation. There are many ways to engineer a solution to a design problem and unless your intimate with the designers thoughts then you can't really comment on the design. To go back to your point, use your ears to judge, not your eyes! PS: If I were designing an amp with a conventional SMPS my gut feel would be to put the bulk storage caps on both primary and secondary sides but I would need to justify the reasoning to myself first. A gut feel is just a starting point, not a justification for an approach! I wouldn't rule out using a tiny value cap for my secondary if it worked and sounded better than the other ways
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Posted By: audiomik
Date Posted: 15 December 2011 at 5:53pm
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Malc Re: "Personally class AB only. H etc, yes ok. The rest can get lost." Come on now! A decent Class A Amp at this time of year keeps things warm as well as providing drive for the 'speakers  Mik ------------- Warning! May contain Nuts plus springs, washers, screws, etc, etc. |
Posted By: teslaman
Date Posted: 15 December 2011 at 6:06pm
How about "class-AD" (??) class-A output with tracking switch-mode pre-regulator; bet that would upset the audiophiles  Not a bad idea though
 On second thoughts... |
Posted By: audiomik
Date Posted: 15 December 2011 at 6:24pm
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Well, was thinking of a high quality Class A design with Regulated Linear Power supplies..... weather forecast is for snow tonight! Then again a 'Class-BC' design might be of interest to those of us with a passing interest in History perhaps??? Mik ------------- Warning! May contain Nuts plus springs, washers, screws, etc, etc. |
Posted By: Muckerbarnes1
Date Posted: 15 December 2011 at 7:25pm
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Sorry Mik, I should of pointed out the obvious. I remember me Rodgers class A. I remember as a young lout fixing many of them, along with Sugdens. Many using Germanium o/p too (AD149) Then of course our beloved valve amps which we understand.  BC ( before computers) Hmm sounds naff. He hee O/P tracking.....  NO!!! ------------- Billy Dawg. |
Posted By: teslaman
Date Posted: 15 December 2011 at 9:42pm
lol  Shunt regulators at that with light bulbs for dropper resistors, then you get your heating and lighting for free
Maybe that would increase the WAGs acceptance factor too?? |
Posted By: DjLeco
Date Posted: 16 December 2011 at 12:58am
Yess, I will do on AB class amplifier (mine modules) at +/- 100Vcc, but also I will put some dummy load , directly on +/- rails, around 16 ohms, and 8 ohms too.
Scope will be double, one analog to amp output, and digital to smps out (x100 probe), directly on DC and after to smps trafo out, to see waveform.
But, I think I will do this tomorrow, or couple days after, I'm at work, it keept's me very busy couple days, till we finish recordings for christmas period.
Keep close. ------------- I'm A Stupid SMART Romanian... |
Posted By: Nachural
Date Posted: 16 December 2011 at 9:31am
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That simple question sparked off a very interesting debate and showed the depth of knowledge that exists on this forum! ------------- it's all just cardboard and magnets really |
Posted By: audiomik
Date Posted: 16 December 2011 at 11:56am
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Claudiu given the number of threads on here regarding 'Burst' output comparisons between different Amplifiers; a test using say a 4 cycle sinewave burst at maximum peak voltage output below clipping of the Amplifier output for the first 2 half cycles - to best demonstrate any differences in output for the rail capacitor values? Would also be interested to see Spectrum analysys of Amplifier Outputs with the different capacitor values as I suspect that they may show some PSRR related differences? Mik ------------- Warning! May contain Nuts plus springs, washers, screws, etc, etc. |
Posted By: audiomik
Date Posted: 16 December 2011 at 3:08pm
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Claudiu will also be good if you can post 'scope/analyser screen images with test conditions please, for those of us who don't use Facebook! thanks Mik ------------- Warning! May contain Nuts plus springs, washers, screws, etc, etc. |
Posted By: DjLeco
Date Posted: 16 December 2011 at 5:02pm
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Aidiomik, presuming, the amp will must to amplify, to 0 db output ,a bass guitar, one passage of couple seconds of constant 35-40 Hz sound, or a synthetsizer wich gives 3-5-10 seconds of 30 Hz sound, how do you think the burst power amps, will act?
Will act like here:
http://postimage.org/image/dz5pi2dd7/" rel="nofollow">
 Extracted from here:
http://www.diy.poweraudio.ro/albums/userpics/10001/BENCH_COMPARISON_TEST.pdf" rel="nofollow - http://www.diy.poweraudio.ro/albums/userpics/10001/BENCH_COMPARISON_TEST.pdf
Making a test like mine (the one I will present down) , with those amplifiers, how do you will think they act?
Look here, just one small test, of mine first attempt of TD class amplifier with mine classical AB module amplifier, equipped with autooscilant downconverter, how it perform supplied at 330Vdc (+/- 165Vcc), where after showing second clipping, the SMPS shuts down of protection acting (3300Watts protection turns down SMPS).
It sustain power , 110Vrms on 4 ohms dummy load, or not sustain?
I have tested more than 30 seconds continuous, no limits.
I see no limmiting of skinny storage capacitors, or final output stage limmiting, like burst power amps does!
http://www.youtube.com/watch?v=guoLw9e4Seg" rel="nofollow - http://www.youtube.com/watch?v=guoLw9e4Seg
http://postimage.org/image/2zheuyvj8/" rel="nofollow">
 http://postimage.org/image/2zhjtkx0k/" rel="nofollow">
 And please compare it with Crown, on same dummy load, wich limmits itself (no touching volume knob), as you see in next clip, wich concludes with printscreen above:
http://www.youtube.com/watch?v=vL1a2efPUMg&feature=player_embedded" rel="nofollow - http://www.youtube.com/watch?v=vL1a2efPUMg&feature=player_embedded #!
So, if we watch the acting of Powersoft K10, it gives a burst of 100mSecs of 7,5 Kw, then limmit instantly to 6Kw in next 900 mSecs, then after 200mSecs limmits to 2500 watts, finally offering 1300 watts ...
So, wich amp will be ok, by example for dubstep music, bass exclusive?
One old school amp, or one with a good one SMPS, with good storage and regulation, or those liar amplifiers?
------------- I'm A Stupid SMART Romanian... |
Posted By: audiomik
Date Posted: 16 December 2011 at 6:07pm
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Think you've missed the point, am interested to see the burst measurement as described in my earlier post when using different values of rail capacitors... Suggest test frequency of 10kHz so as to reduce loading effects from lower frequencies. Can't really comment on the other things as I don't have access to youtube here. Please see post before your last one? Mik ------------- Warning! May contain Nuts plus springs, washers, screws, etc, etc. |
Posted By: MarjanM
Date Posted: 16 December 2011 at 6:51pm
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Not 100% sure but i think the new Matrix amps are SMPS AB class. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
Posted By: andyamp
Date Posted: 16 December 2011 at 9:28pm
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Not 100% sure but i think the new Matrix amps are SMPS AB class. and G and D ------------- a wise man changes his mind a fool does not. http://www.matrixamplification.com/ - http://www.matrixamplification.com/ |
Posted By: Muckerbarnes1
Date Posted: 17 December 2011 at 1:32am
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Bring on the D. Matrix class D. Wunnnerful! ------------- Billy Dawg. |
Posted By: Milli Watt
Date Posted: 18 December 2011 at 3:09am
OOOOOH! that does sound interesting in more ways than one  Milli |
Posted By: Earplug
Date Posted: 04 January 2012 at 4:15pm
To get back to the original post maybe Lex should just go for the Yamaha and forget Nexo - anything with the Nexo badge on it means a 1000% markup!  These are pretty good and cheap (and have to be better than powersoft ):http://www.thomann.de/es/yamaha_p7000s_endstufe.htm - http://www.thomann.de/es/yamaha_p7000s_endstufe.htm |
Posted By: jplevene
Date Posted: 04 October 2013 at 11:20am
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We hold NXAmps (details of ours http://www.hirehop.co.uk/rent-item/Amplifier-Nexo-NXamp-4X1-with-integrated-Controller/1085. - http://www.hirehop.co.uk/rent-item/Amplifier-Nexo-NXamp-4X1-with-integrated-Controller/1085.html) and I have to say WOW !!!!! The amp is incredible, you can do so much and the sound is on a different level. We employ loads of sound engineers, most use d&b, everyone of them has been blown away with the amps and the sound quality.
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