250 into NBL's does not go!

LP12 with 3-o-clock...? Is that not a little bit too loud? If the sound gets distorted the amp is overloaded, thus the heat.

- Jun

Can you give some ideas how loud was the music? For example, the music was loud to the point that you have to scream to maintain a conversation. Volume setting at 3 o'clock? My normal listening is at 9-10 position with a 87 Db/m speakers at a distance around 3 m from the speakers. I remember that not to long ago some members on this forum were made to believe that they only need a Nait for the job...

[This message was edited by Tuan on WEDNESDAY 16 July 2003 at 23:53.]

Finally, the irrefutable evidence of actual experience !

It really irks me to see poor old Matt Worlock being told that the best way forward for him from his 82/180/NBL system is to add a supercap to the 82. Source first is all very well but I would rather spend an evening with your mum than a dead supermodel (and if you disagree you are on the wrong forum - you need www.necrosupermodels.com). The fact is that (within reason), NBL's need power and control first, THEN you add the finesse.

Congratulations on your new rosewood beauties... would you share some photo-images of this exotic finish with us?

Looks like you need a 500.

Good listening; the music's groovin' frightfully more.

Regards

Philip

naimniac for life

Wait a minute sire.
You mean you have driven your brand new NBLs at very loud volume? Do you want to kill them?
Volume at 9 o'clock max (from CD level source , for vinly it depends on the gear) for at least 100 hours, after and only after that, you can push the throttle.
It is quite normal your 250 ran hot: new speakers are much more demanding for the amp. The drivers surrounds are still stiff, they need more power to move air. And the NBLs are 4 ohms, they need current.
I have already said here, IMO, bare minimum for NBL 3*olive 250 or 1 new 250, but they start to shine with 2*135 or 300 passive (i've not tried yet 3* new 250 and 2*145). And active should be in the upgrade path when source and preamp are maximized.

Emmanuel

All opinions are my own, and reflect those of the organisation i work for, even if not stipulated.

[This message was edited by Manu on THURSDAY 17 July 2003 at 05:11.]

Hi Blythe,

quote:

---

my old faithful 250 (well, one of them) is driving the NBL's.

---

Why only one? Why not both? Double the transformer VA, double the peak current, double the heatsinking capability. Should work fine with one channel of each, ask Naim or your dealer to modify the interconnects to give you "125s". Even so, 3 o'clock on vinyl is fan-full-on-time for Floyd and 135's or 500...

NBLs are very efficient - can you put them closer to the wall and/or remove damping form the room and put in hard, reflective objects instead?

I remember when the ex Swedish importer used a pair of DBL driven by a poor 250. He had a bowl with melting ice on top of the amp to keep it cool!

JohanR

Johan,

I think Julian once suggested putting the 250 on its edge and directing a room fan at it.

Jeremy

You're all barking up the wrong tree.

Go check out the latest MF amp. It's called the Kilowatt. No clues as to it's power handling capabilities.
Yes it might be dull beyond belief, but as the man says "better to be with your mum, than a dead supermodel", like it.

quote:

---

Originally posted by Jun Keller:
LP12 with 3-o-clock...? Is that not a little bit too loud? If the sound gets distorted the amp is overloaded, thus the heat.
- Jun

---

There was no distortion, it was just very loud. I was alone so have no idea if I could have managed a conversation.
With my old Active SBL's, I have, on occasion, listened to Vinyl on full volume (on a quieter recording) again without apparent distortion - the room was shaking but sometimes I like to really feel the music :-)
I was obviously expecting too much from the set-up yesterday with the NBL's.

Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

quote:

---

Originally posted by Tuan:
Can you give some ideas how loud was the music? For example, the music was loud to the point that you have to scream to maintain a conversation. Volume setting at 3 o'clock? My normal listening is at 9-10 position with a 87 Db/m speakers at a distance around 3 m from the speakers. I remember that not to long ago some members on this forum were made to believe that they only need a Nait for the job...

---

It was loud - the floor was shaking, the bass punched me in the chest, it was approaching orgasmic! That guitar solo sent shivers down my spine. It was loud but no way painful. Just how can I describe "loud"?

Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

quote:

---

Originally posted by Manu:
Wait a minute sire.
You mean you have driven your brand new NBLs at very loud volume? Do you want to kill them?

---

Actually, I should have mentioned that they are 2nd hand, previously loved NBL's, so the precautions you quite rightly mention, do not really apply here.
Never try it at home with a new pair guys!

Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

[This message was edited by blythe on THURSDAY 17 July 2003 at 09:34.]

quote:

---

Originally posted by JeremyB:
Hi Blythe,

quote:

---

my old faithful 250 (well, one of them) is driving the NBL's.

---

Why only one? Why not both? Double the transformer VA, double the peak current, double the heatsinking capability. Should work fine with one channel of each, ask Naim or your dealer to modify the interconnects to give you "125s". Even so, 3 o'clock on vinyl is fan-full-on-time for Floyd and 135's or 500...

NBLs are very efficient - can you put them closer to the wall and/or remove damping form the room and put in hard, reflective objects instead?

---

The 250 is only until I can give the active 3x250'S a listen and compare them to the 300. I'd rather not mess around with my existing gear until I can demo the Active 250's and a 300.
Regarding positioning, I can't remove soft furnishings as I need something to sit on and something to draw across the windows on dark nights :-)
The NBL's are back against the wall with no reasonable way of re-positioning them, without ruining the asthetics of the room. See later posts for pics.
The floors are inch think solid Oak boards with large rug in middle of room and a couple of runners either side, behind the settees. Some areas of wood are exposed etc. The curtains are swagged and tailed - good old fashioned style, so accoustically, I'd say pretty neutral. Not totally dull, not too bright. My dealer always comments how good kit sounds in my room - and I agree with him.
At 3-o-clock, the fan was on with the 300 that I used a few months ago.......

Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

quote:

---

Originally posted by Philip Pang:
Congratulations on your new rosewood beauties... would you share some photo-images of this exotic finish with us?
Looks like you need a 500.
Regards
Philip

---

Yes I do need a 500 but don't have that kind of money for an amp at the moment!
Here are some pics for you:






Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

quote:

---

Originally posted by PR:
blythe

This may be the answer.

If you are listening at 3 o’clock with vinyl, I assume you may be listening to CD at 1 o’clock due to its higher output? If the 250 doesn't cut out with CD, maybe you should invest in a phono stage like the Tom Evans, which will push the vinyl output higher than your CD player, allowing you to probably listen at 12 o’clock. It will also massively improve your Linn sound leaving your CDS2/XPS2 a distance behind.

---

Actually, with CD, it seems to be nearer the 12-o-clock postition for maga loud listening, though usually, I don't go over 11 - o-clock.
10 o-clock is more typical for me listening to CD.
If I go the route of a different input stage for phono, does it mean I'll love it so much I'll have to re-buy my entire CD collection on Vinyl??!!

Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

Dear Bythe,

Please let me know how you get on with the 3* 250 active dem, I"ll be interested to know as I'm thinking of going that way myself.

As far as your apparent excessive volume goes my thinking is that the 250 has overheated because your vinyl source has very little gain & is basically attemting to amplify a very quiet/small signal, this it is having to do massively for you to hear any kind of healthy listening volume. Surely when your using your cd player anything (dependent on recorded volume of album) over 12 0' clock would be pushing it! I tend to go up to around 10.30-11 as a max when using my CDX/XPS with some cd's sounding very loud at about 9 0' clock.

I would hate to think you were abusing those lovely rosewood nbls ................ ...love them ........cherish them !



Hey Minky pal...I could well go 135's passive then active with the buggers, but I'm still interested to hear what 3* 250 active can do

I,m feeling particulary good natured today....And want to wish everyone well

Mad Boy Matt

I think that the problem here is down to vinyl itself. Basically the signal taken straight from an LP has little or no bass, hence the need to massively boost lower frequencies with equalisation at the phono stage. The problem is that while the bass frequencies are boosted so too are low level vinyl nasties. Often makers attempt to limit this by filtering out the lowest frequencies (IEC standard equalisation has a sloped low frequency filter). We do not do this with our phono stages as you lose the lowest bass frequencies of the music as a result.

Obviously the amplifier then has a much harder job to do in amplifying vinyl subsonics and at very high levels may run warmer than normal and may even trigger the thermal protection circuitry on early or Olive fascia amps.

Really clean bass frequencies and absence of low level nasties on CD are perhaps one reason why the problem is not cropping up when replaying CDs at similar high volumes.

Richard

Blythe,

You could still biamp with your 2nd 250. No modifications would be require to your cables. Simply plug the second amp into the next output on your supercap and drive left-right high frequency units,m or possibly drive just the bass units from the added amp. You already have all the cables to do this, just a matter of plugging in.

Regards,
Frank.
All opinions are my own and do not reflect the opinion of any organisations I work for, except where this is stated explicitly.

It's nothing to do with gain. Poor turntable installation may be relevant, if you're experiencing some sort of subsonic feedback. I would have thought the sound would be obviously wobbly though.

But the basic issue is that the NAP250 is being driven beyond its limit. It gets hot, it switches off. The original Naim solution was the NAP135 which is only half a NAP250 yet has extra cooling. Using two NAP250 as mono amps, going active with three, or moving to NAP300plus are all possible solutions. But first maybe improving the ventilation of the amp installation will help?

There is a sub-cult of people who have caused NAP250s to shut down, welcome to the club!

Paul

Blythe,

As you know I had the NBL's on the end of my 252/300 for a few days.

Listening to the NBL's I felt they needed a bit more control. I had a lot of advice stating the NBL's only really work on the end of a 500!

Regards

NB

quote:

---

Originally posted by Richard Dane:
I think that the problem here is down to vinyl itself. (edited by Blythe) Obviously the amplifier then has a much harder job to do in amplifying vinyl subsonics and at very high levels may run warmer than normal and may even trigger the thermal protection circuitry on early or Olive fascia amps.
Richard

---

That's pretty well what my dealer told me: (I phoned him in a bit of a panic!) the amp, when playing Vinyl has to work harder than when playing CD's in part due to also amplifying all the background crap etc. and due to the level of bass information there.
This morning, I've been playing CD's pretty loud without any problem and the amp was only getting warm, certainly not HOT like last night!
In all my time with Naim equipment (around 14 years) I have NEVER had an amp trip out before!
I realise that I was pushing it very hard but it still came as a surprise when it stopped working, thankfully, litterally at the end of the track - I went to play the next LP and there was no sound :-(
This morning everything sounds great, so thank goodness for thermal protection!
Oh, also, it was about 30 degrees here last night before the storms!

Computers are supposed to work on 1's and 0's - in other words "Yes" or "No" - why does mine frequently say "Maybe"?......

quote:

---

There is a sub-cult of people who have caused NAP250s to shut down, welcome to the club!

---

I belong to that cult... when listening at 'realistic' levels to a friends system (2x250, Snaxo, Linn Tukan speakers) the amps shut off in mid-tune. Never had a 250 trip its output protection before when actively driving a speaker as the load is far easier to drive (no pesky inductor coils etc), moreso such a small speaker. Having said that I have not yet had one of the 135s shut down with the active DBLs, although I have on several occasions had the tweeters melt down due to raw excess volume. I much rather the amps would have shut down- which would never have happened as the tweets need as little as 10 watts to turn them from bread to toast; only a flea-powered single triode amp would fail at these power outputs.

Ron
Dum spiro audio
Dum audio vivo

"So I wonder what we did before CD. I wonder how quality clubs (disco techs) managed to play the sound so loud without closing down early due to amp stress."

...was provided by Richard in his original post in this thread.

Subsonic Filters in the phono preamp that are missing from the Naim design.

I had several preamps in my youth that had a "subsonic filter" button on them so you could switch the filter in and out.

BTW, what is the TT sitting on? Could better supports sort out the TT? With NBLs in house, the TT has mucho more feedback to deal with esp when the volume is cranked!

- GregB

Insert Witty Signature Line Here

This is probably peculiar to the original long lived NAP250. Of all the Naim power amps it is the one that has the least margin for cooling. When it gets too hot it turns off, you wait, everything cools, normal service is resumed. This is rare enough not to be a big deal.

An amp destined for 'club' usage would be specced to deal with its environment. If Blythe is going to drive his NBLs that hard from vinyl then he needs a suitable amp, and that isn't a NAP250.

Paul

PR,

getting decent bass extension onto (and off) vinyl has always been a major problem. It's one of the reasons why when cutting a record often the bass has had to be mixed down to mono &/or rolled off in order to make a successful cut. You then have the problems inherent with equalisation both at the cutting stage and at the phono pre-amp stage...

Don't get me wrong, as many here will already know, vinyl makes up the lions share of my music collection, but even I will admit that accurate bass extension has never been it's strength and definitely an area where digital performs much better.

Apart from the actual music recorded into the vinyl grooves, the vinyl itself contributes a lot of very low frequency subsonic rubbish to the overall mix. If you have a system which can retrieve a lot of bass information off an LP and if you've ever taken the grilles off your speakers, some LPs can cause an alarming amount of bass driver movement even though the stylus may be just tracking a "silent" groove. Even though what you're hearing is effectively silence, your amplifier is working very hard indeed. This is one reason why the European IEC equalisation standard became so popular. By effectively filtering and rolling-off the very lowest frequencies life was made much easier for both amp and speakers.


I have not heard a Microgroove but expect it to be very good performer based on long experience of a Lithos updated ISO HR (I believe the Microgroove is a simplified version of the Lithos ISO HR). I concur that the ISO did bring many "CD" like qualities to vinyl replay. Unfortunately I also found that I was getting more and more critical of vinyl's faults when listening to it and felt disconnected from the musical performance. I still contend it's an excellent phono stage but maybe just not to my taste. Having said that, it provided no magic cure for the aforementioned bass problems.

With regard to our own phono stages, yes their essential design goes back even further than you suppose to the 70's. We have made small evolutionary changes over the years but the basic circuitry remains the same. Many would contend "why fix what isn't broken" but I think the Prefix did bring some new and very worthwhile ideas to the table. I think our phono stages work well because they play to vinyl's strengths. But then that's another thread entirely...

Richard