Getting my amplification right....

Regis, when you say turning up the wick, are you giving it a lot more welly than you did the 140?

If not and the 140 was fine you may find there is something wrong with the 250.

"are you giving it a lot more welly than you did the 140:"

I really don't believe so, though I've learned to never, say never. The 250 sounds really very, very, good. There seems to be several other threads in the past that relate to 250 overheating problems. I kinda get the sense that the larger room size may be a challange compared to others.

The Neat importer has mentioned that the bigger space is really ideal for the 'Veets', giving them space to breathe. I should also mention that the 140 had 'upgraded' fuses. The system is also on 3 dedicated 10gauge lines.

Perhaps also the 140 would get too 'shouty'so I may not have allowed it to play loud, long. In any respect I only shut the 140 down 2 or 3 times in the 6 yrs. I've owned it, max. The 250 I shut down 3 times yesterday. I moved it around in the rack, even to the very top w/the volume @9:30, max.

TheFrampton cd is very well recorded w/lotz going on & it does really rock, but at similar levels, let say an Eva Cassidy cd, never gets the 250 overly hot. I believe I would find similar limits playing certain classical cds also, however I am reluctant to continually turn the 250 into a science experiment by attempting to overload it.
The protection circuitry seems to be working just fine as within 15mins or so it repowers with s subtle 'click', & proceeds as if all is well.

Regis

Regis,

IMHO your "problem" is the enormous amount of air volume in your listening room. FEW rooms have so much space, consequently most of your other listening/auditioning will be within smaller spaces where the amplifier under audition will be able to acoustically "load" the room. That is, the smaller space, the shorter reverberation time, the reflective nature of the walls, the smaller volume of the room, all quantitatively affect how loud the music will get. The new 250 is not able to push your speakers to push enough air to create the volume you want.

A couple of questions--what is the impedance of your speakers? A low impedance dip will put severe demands on any amplifier. It's not necessary that the impedance dip cover a wide range of frequencies, just perhaps enough that, when the going gets tough, the amplifier gets "winded". Second question--how efficient are your speakers? Less than 85 db? This figure would not be uncommon and in most rooms (say 12' x 15' or so...) the 250 would probably be able to play as loud as you need.

IMHO, if you really want to be able to play your music loud, you will need an amplifier with internal fans. Or some big beast of an amplifier with loads of watts and current. OR you may need to change your speakers to something that is more efficient. Your choice will depend upon
1. how highly you value the unique characteristics of the new 250
2. how much you want to be able to turn it up.
3. how much you value the capabilities of your speakers.
4. how much money you have to solve the problem.

You might enjoy reading my thread I posted last night about my new 135's.

Good luck and keep us posted.

Markus
========

It's possible that your new NAP250 is a bit premature in the 'off' stakes. Perhaps your dealer could advise?

Otherwise the NAP135 was introduced 20 years ago to deal with this issue in the then NAP250. In your case the NAP300 should fix the problem, the issue isn't the extra 10 Watts, it's the extra cooling capacity. If the 250 goes loud enough then 300 should go long enough (IYSWIM)...

Paul

Hi Markus, Those are very thoughful suggestions. In addition to my rooms size, we live at 8300' elevation, the air is thinner up here!;;-)

I've been told the Vitos r around 89db with a "reasonable" impedance. I do really like the new 250's sound, I know the Vitos have even more to offer. I am led to believe that they can 'punch well above their weight'. Bob from Neat had previously mentioned that his personal favorite on the Vitos was a pr. of 250's. These were the old style, him having not heard the new 250 when I had communicated w/him about such.

Hence my curiosity about the 145's vs a pr. of 250's. Or the 300. I do notice that both the 145's & the 300 have internal fans, the 250 does not. I understand that the 145's r newer, r they even available yet?

Can anyone comment as to how the 135's compared to a biamped 250 setup? Which was preferable?

Thanx....

Regis

"the issue isn't the extra 10 Watts, it's the extra cooling capacity"

When I first mentioned I'd shut the 250 down several times my dealer stated such about the necessity of fans. During the purchase phase the issue was never discussed.

?IYSWIM? Explain please.....

Has anybody heard the 145's?

Thanx....

Regis

Hmmmmm some interesting comments....

had a street party last night and used my second system for sounds - 62/Hi Cap/140s driving Kabers. Bearing in mind that the speakers where outside there was no possibility of them acoustically loading the universe; the stuff was on from abour 5 pm until about 1.30 a.m. at levels up to 10-11 oclock and although the amp got warm there was no cut out.

To me, it sounds like there is a problem with the 250.

Speak to NANA, or maybe Richard has a view from Music HQ?

Regards

Mike

On the Yellow Brick Road and happy

Mike, a 250 makes about twice as much power as a 140, and given its regulated power supplies is rather less efficient while doing so. If there's an amp in the range that's going to shut down then it's the 250.

It would still be worth checking that the heat sensor is within tolerance, I presume the dealer could do this. Perhaps NANA or someone who really knows what they are talking about should advise?

Paul

quote:

---

Originally posted by Regis:
Approx. 8 weeks ago I installed the new 250 into my system replacing a 140. (cd5/72/HiCap/new 250/Neat Vitos) About a month in, right on schedule the amp developed all the texture/finess/ & punch I anticipated. All was well and I moved to audition the new 282, wishing to upgrade my pre.

Our main listening environment is the living room of our log home in Colorado, measuring 25'x 26' w/16' vaulted cielings; so a pretty large space with very nice acoustic potential. Occasionally we like to 'wick to volume' a bit & seem to have rather quickly hit the upper registers of the 250's ability to drive the Vitos. Not on all material but some, such as the new Frampton cd 'Now', the 250 continues to overload & shut down b4 the cover of 'While my guitar gently weeps', track 9 I believe, w/the amp at only 9:30 max.can finish playing.

I've moved the amp around but nothing seems to help. (Short of mounting the small fans suggested elsewhere.) Trouble is, when the spirit moves, I want to be able to at least fill the room w/an 'excitable' level of volume. So....

What to do? Has anybody heard the 145's? If so how do they compare to the 250? I read that they have internal fans, would they outperform the single 250?

Would a pr. of 250's in a biamp configuration be better than the 145's? Would it allieviate the overheating by allowing each 250 to put its resources to only the top or bottom drivers? Does a pr. of 250 offer anything the pr. of 145 would not?

Would I run up against the same issues if I owned say a 300, since it only appears to put out an additional 10wpc?

I want to add that the 250 pushing the Vitos is a wonderful match offering 'gobsmacks' of musical pleasure. The 'Veets' r an isobarik spkr. but I don't believe that they have any 'unreasonable' impedance curve. The 140 did a very resonable job driving 'em.

I had hoped to be making the decision btw. 282/252 but feel I need to get my amplification correct. Any input or suggestions is appreciated. Thanx...

Regis

---

Why dont you try to trade the new 250 for a 4B-SST Bryston amp. It will handle the job. People use Bryston and Naim together with great success. At least give Bryston a try you may like it and it will save you lot of money.

The room size clearly isn't the issue if shut-down occurs with the volume control at only 9:30. IRC, all Naim power amps are gain matched so that a more powerful amp (say the 250 over the 140) will stand the volume control being taken higher before it starts to complain. Methinks the protection circuitry is a bit trigger-happy in this case, or should I say box.



Regards,

Steve.

Hi Folks,

Strange that we're discussing this issue again with the new range. I thought Naim had addressed this issue in the new 250? Shame to have bring out the old noisy fan to remedy this with such a new amp.

Jens

Component quality issue?

I think we're on to something here and the amp needs to be tested by the experts. I just find it amazing to think that it will shut down in protest so soon unless as Mark R above has suggested that a sensor is set too low. Perhaps the "trip" is either set too low or maybe it's just broken.

A bummer to have to sent it out for eval tho'. Perhaps your dealer can provide some kind of loaner for a few weeks.

BTW, regarding the Bryston recommendation. Way back in the early to mid '90's when I used to read the abso!ute sound and stereophile (and hi-fi world, positive feedback, the audiophile voice and audiophile, and every other hifi magazine I ever saw) the Bryston amps were universally respected and highly thought of.

markus
--------

The best way of lessening the tendence of a 250 to go into thermal shutdown is to maximize its ability to dissipate heat. Thinking back to trusty O-level physics you have

1. Conduction.
2. Convection.
3. Radiation.

Each of these can be maximized with a little bit of attention.

Conduction: It has been known for people to place a bowl of ice on top of the 250s case during times of need. This virtually guarantees that thermal shut down will not occur, but is somewhat messy and relatively short term. But it WORKS. I imagine having a billet of brass stuck away in the freezer for such occasions would also work and be less of a water-damage hazard.

Convection: This is having cooler air drawn across (or into) the chassis. This can be achieved by having a low power/low noise fan strategically positioned. Or even placing the 250 on the floor directly over one of the air-conditioning registers. Which would not work at all when the air is turned off, or used to heat. I have my gear in a walk in closet. I had the builders put an a/c vent into the closet-this certainly helped lessen the effect of having 13 powerered black boxes in a small room. Again, it doesnt work in winter, when I have to close the register.

Radiation: Remember the entire case is the 250s heat sink. Putting it on a carpet effectively reduces its radiating area by almost 50%. Stacking equipment also greatly reduces the abilty to radiate heat. You will find that having a 250 on its side (as in vertical) will allow its undersurface to radiate just as effectively as the top. This of course does not lend itself to audio-grade equipment racks. If you do have it on a rack, increasing the distance between the bottom of the case and the rack will also help. This can be done by putting a few cones/spikes under the chassis and allowing a bit more airflow. That opens the Pandoras box of how cones etc affect the sound of the gear. In my experience, very minimal when used under a power amp, and the benefits of additional cooling outweighs any potential decline is sound quality.

There is also increased radiation when the ambient temperature is lower. Turn down the thermostat or place the gear next to a window.

Ron
Dum spiro audio
Dum audio vivo

All of the excellent feedback has sent my mind a spinning. Trying to recollect all or any additional changes I may have introduced into the system w/the addition of the 250 vs the 140 I came up w/the following.

My local Naim dlr., Rick @Audio Alternative in Ft. Collins brought my white naca5 up to spec for the Vitos by soldering an additional pr. of bananas onto the end for both sets of binding post. B4, they had been jumpered w/the naca5 going to the top post.

The Vitos r a ported spkr. w/the top port being about 3" from the top in the rear. They r supplied w/two prefabed foam inserts for 'deadening' the port. Prior to the addition of the 250 I could not easily notice any difference w/the foam inserts installed or w/out. With the 250 I found that there was a certain upper midrange sharpness w/the foam inserts in place that I enjoyed. Could the addition of the inserts place additional strain on the amp?

Well yes, kinda. This a.m. I ran the 'routine' once again, this time w/the foam inserts removed.
The results were that the 250 indeed made it through the playing of the entire cd! So I put on the new Dandy Warhols, 'Welcome to the Monkey House' to continue the 'torture. Unfortunetly, about a song into it, the 250 cut out again, apparently taking slightly longer to reach its thermal limits.

I've put the 140 back in the loop, playing at the same volume levels, letz see what happens now.....

Regis

Good newz! I 'killed the 140' also. ;-(

Must be something to do w/not wanting to work hard on labor day....

Really the 140 was kinda shouty & I was about to turn it down when it cut out.

Maybe I'll see if I can borrow a loaner 250 & try the bi amp route.

In the meantime I'll 'cool it on the wick'.

Must remember it's only 80wpc....

Anybody else pushing Neat Vitos out there?

Thanx again for all the input, seems I have a few items to check out going forward.

Regis

Biamping almost certainly will not help-at least not in terms of preventing thermal cut-off. Relieving the 250 of maybe the 2-3 watts the tweeters will require does not significantly reduce the load imposed by the mid/bass drivers. What bi-amping may do is give you a clearer more tuneful sound as the tweeter which produce the most important portion of the bandwidth will be driven by an amp that is nowhere close to gasping for current. You may however find that allowing one 250 to drive each side in the pseudo-monoblock configuration (the so-called NAP125 cofiguration) will make things far easier as no amp will then be burdened with having to drive L+R bass, which is what is causing them to heat up in the first place-although this configuration makes 2/4 of the available channels redundant, it halves the current (and heat) that each amp needs.

Ron
Dum spiro audio
Dum audio vivo

Regis,

I think Naim should really come to your rescue and check out whether your amp's cutout is coming in at the right temperature. Mind you-you can do this as well. How hot is the case at shutdown? Should be getting pretty warm.

If it is the case that the new 250 is still prone to thermal cutout then I think that Naim has been really, really slack in their R&D. After all this single issue was probably the one thing this amp was consistently criticized for. Everyone likes the tunes it plays, but no-one likes the shutdown that comes with letting this amp do its stuff. This phenomenon has been reported with many different speakers (used to happen with my Epos 22s as well), so it is a real issue. What is the point of introducing a new range that doesn't even address the major shortcoming of the old? The cynic in me suggests that Naim were unwilling to fan cool the 250 in order not to pinch sales from the old 135, and now the new 145 or 300! In the words of a terrible Aussie shock jock (Darryn Hinch): Shame Naim, Shame Naim.

Jens

quote:

---

Originally posted by Regis:
Good newz! I 'killed the 140' also. ;-(

Must be something to do w/not wanting to work hard on labor day....

Really the 140 was kinda shouty & I was about to turn it down when it cut out.

Maybe I'll see if I can borrow a loaner 250 & try the bi amp route.

In the meantime I'll 'cool it on the wick'.

Must remember it's only 80wpc....

Anybody else pushing Neat Vitos out there?

Thanx again for all the input, seems I have a few items to check out going forward.

Regis

---

Well you clearly need a more powerful amplification. If you want to use naim amp you may have to get something with active cooling inside like a pair of 135s ot the new NAP300. Bryston is always a good choice but it is no Naim (so what?)

I found that LINN played REAL LOUD! compared to my NAIM but hey it just don't sound as good. So I am looking for a linn for Saturday morning rock sessions then I will use NAIM the rest of the time. LINN seems pretty cheap on the used market.

Ken

If loudness alone is desired there are many economical alternatives to Naim on the market. On the used market, Hafler, Threshold, Krell, Crown all come to mind.

I've found that, given the acoustics of the places where I DJ for dances, quantity is more important than the absolute quality of watts. Speaker quality for PA systems is also very different than that of home hi-fi, with many compromises made.

Markus
---

quote:

---

Originally posted by Jens:
If it is the case that the new 250 is still prone to thermal cutout then I think that Naim has been really, really slack in their R&D. After all this single issue was probably the one thing this amp was consistently criticized for.

---

Jens,

JV stated on the original forum that there was no space within the 250 to implement fan cooling, as this required quite sizeable heatsinks.

Part of the reason that the 135 is single channel, is that the space freed by the boards for the other channel can now be dedicated to heatsinking instead.

Maybe 145s are the answer here, if they are fan cooled, as they are cheaper than 2x250 and only 70% of the price of a NAP300 (at least here in the UK).

One word of caution, I believe that custom XLR cables may be required, as they are supplied in a mono-only config for AV?

cheers, Martin

P.S. I wonder how much thinner the air is at 8300'. Could make a lot of difference to the cooling, whilst also making the speakers less efficient.

P.P.S. having the port unblocked will make the speakers slightly more efficient in the bass, and this may be why the amp lasted a little longer.

E-mail:- MartinPayne at Dial.Pipex.com

Ok. Now for the truely humbleing part of this 'hobby'. Subtitled, 'confessions of an audio dolt',or 'how my misses showed me I had 'cement btw. my ears'.

First I'd again like to thank any & all who contemplated my dilemma & offered perspective & possible remedy. Within the last 24hrs that has grown to include Rick Duplisea of the Audio Alternative in Ft.Collins, CO., Mike Pranka, the U.S. Neat, Rega, & Dynavector importer/rep, & Bob Surgeoner of Neat who zereoed in on the 'issue' this a.m. (from afar no less!)

We have been extra busy w/home & work issues this summer, spending long days doing things other than 'listening', & were eager to prepare for the months ahead by doing additional system upgrades. We had auditioned the 200/250 over the July 4th wknd., selecting the 250, & pretty much returned to our routine until recently making time to audition the 282 pre & maybe the CDXII.

Anybody who has 'borrowed' a piece of kit has went through the scramble of disassembly & reassembly of installing into the existing system. Several times I've secretly wondered why I put myself through such a process. After all, one can work so hard to get everything optimized 'just so', cable dressing, getting the spkr. cables up off the floor, all the little details. And then we go & rip it all apart for a 3 day loaner....

Regardless, I simply concluded that the 282 would really require me to upgrade my power supply from the single, old style, hicap I currently own. That would provid the 'audio spectacle' my ears desired. Additionally the 'source first mantra' echoed in the back of my mind. After all, the cd5, fantastic though it is, is only Naims entry level 'playa', & my P3, well you get it....

So I'm thinking if I get the pre, no way I'm happy unless I also get a 'supercap' for it also, which if you did it all at once, kinda slaps you to look into the 52. A veritable hop from the 82/scap. But.....my sources 'need some juice' to do such a system justice, right? Such is the 'old tea' swilling around in my head recently.

This was my mindset when I first shut down the 250. I was in the process of earning my 'doctor of ignorance' degree.

Well on Tuesday, the wife & I made the 100 mile drive from Pine to Ft.Collins to hear the cdxii which had arrived. It would also give me an opportunity to discuss the overheating 250 issue. I was pretty certain I needed: a)another 250, b)a pr. of the unheard 145's, or c)a 300 to properly drive my Vitos.

Within minuetes my better half/'the one w/the pristine ears' made mention as to how the demoed system sounded better than our home sys.

Ouch!

It was a 202/200/espeks match & she was right. But why?

So yesterday I hauled the Vitos all the way back up to Ft.Collins for a proper comparison.

One of the issues I come up against is that not many people here in the states are that familiar w/the Neat product line. I know that Mike is working hard to change this, but I'm pretty sure that I may have the only pr. within a couple of states. So we hook 'em up & side by side & crimminy, they sound like crap!

About a second later Rick states that I've gotten not one, but two blown tweeters!

I immediately feel like an idiot....

This morning, Bob from Neat emailed me asking the condition of such 'tweets'. Stating "if the tweeters have been overdriven it could cause them to change impedance"

What a jackass I am. Somewhere, sometime during all of this 'smaltz' I had blown out my first set of tweeters! And... having cement for ears didn't even know my system was seriously 'pucked up'! The 250 didn't like such conditions & I had been perhaps uncounciously attempting to compensate for loss of detail & indormation by cranking it up. My own 'perfect storm'. I feel like Gilligan, who marooned w/Ginger & MaryAnn, was on a perpetual search for the Professors lost 'coconut radio'.

An 'ear humbling' experience.....

As to how. or when the tweets went bleep I have no idea. New units r on the way & I fully expect that any & all issues regarding the 250/vito overheating issue will be resolved w/each showing to be the excellent & premium product they truely r.

Once again, all pain & confusion have been truely & solely, self inflicted.

Thanx all.

Regis

quote:

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Regis - don't feel too bad - the same thing happened to me several years ago - it is amazing how good speakers can actually sound with blown tweeters!

---

Especially with 7 phases of Mana under the blown tweeters ;-) (phase envy going on here.. I only have 2).

Years ago when us poor students pooled our hifi to assemble the best possible combination were were using a pair of KEF Concordes with a Nytech. One side sounded terrible compared to the other (or so we thought). That speaker was returned to the dealer (Robert Richie) who then blew up an A60 amp when passing square waves through the speaker- which passed every test and was given a clean bill of health. It turns out that the 'better' sounding speaker had a blown tweeter and was thus smoother and less spiky....and the intact speaker was the one initially deemed to be faulty. Doh.

Ron
Dum spiro audio
Dum audio vivo

quote:

---

Ha Ha - that is more or less what happened with me too! I was at St Andrews Uni too, and using a Nytech at the time into some Tangent TM1s.

---

Which years were you there between? maybe our paths crossed, although I just knew 2 other people using Nytech... who lived across the hallway from each other in C-block Andrew Melville... neither used TM1's though- one had active ARC101 and the other the very treacly sounding KEF104AB. I was in StA from 1977-1981.

My first speakers were Tangent RS4s....they survived all of the upgrades to the point of LP12/Ittok/Karma/42/Hicap/135s and were sold only when I moved to the US. Had the bastards wired up internally with NACA4 too I did.

Ron
Dum spiro audio
Dum audio vivo