Real opinions on Coldamp

[The golden mean]

Hi Ian,
I´m quite aware of the SMPS of my computer as I today took my new and forceful vacuum cleaner and removed some dust in it.

In my opinion it´s not only a question of constructing a supply that meets safety considerations but to make it in a way that doesn´t interfere with sensitive audio circuits. I´m not talking about PA systems now which in my opinion seldom have the qualities that pleases my ears; -pardon it may partly be due to some uneducated people handling them.

For Hifi you may very well have a low output MC pickup and the many times this signal has to be amplified makes the system very vulnerable.
There are some companies like Chapter Audio and Bladelius Group that has been up to the challenge to use SMPS in their amps and as a matter of fact the Bladelius amp Grendel ( a home cinema amp that quite a few people use for Hifi) with the SMPS has an option to upgrade it with a large complementary capacitor bank to make it better....

http://www.bladelius.com/

 

[iand]

Hi Ian,
I´m quite aware of the SMPS of my computer as I today took my new and forceful vacuum cleaner and removed some dust in it.

In my opinion it´s not only a question of constructing a supply that meets safety considerations but to make it in a way that doesn´t interfere with sensitive audio circuits. I´m not talking about PA systems now which in my opinion seldom have the qualities that pleases my ears; -pardon it may partly be due to some uneducated people handling them.

For Hifi you may very well have a low output MC pickup and the many times this signal has to be amplified makes the system very vulnerable.
There are some companies like Chapter Audio and Bladelius Group that has been up to the challenge to use SMPS in their amps and as a matter of fact the Bladelius amp Grendel ( a home cinema amp that quite a few people use for Hifi) with the SMPS has an option to upgrade it with a large complementary capacitor bank to make it better....

http://www.bladelius.com/

There's no magic about producing a SMPS with low enough noise and high enough quality for high-end audio, but it does need really good engineering by people who understand the noise issues associated with them (and noise shielding and isolation generally).

Unfortunately there are not many people who really do understand these issues, and almost none of them work for hi-fi manufacturers, partly because this is an "alien" area for them.

The SMPS shielding and isolation difficulties in audio -- even with low-level signals like MC cartridges -- are simple compared to those in radio transceivers like basestations, because most SMPS noise is above the audio band anyway.

The simple truth is that it takes considerable time, money and knowledge to develop such high-quality low-noise supplies (and often expensive non-audio test equipment). Manufacturers of equipment like basestations (or the SMPS suppliers for these) have all three of these.

Manufacturers of audio amplifiers are lucky if they have one

So in practice I guess you're right about SMPS in audio -- it's not that they can't be done properly, they just usually aren't...

Ian

 

[raintalk]

Right on the money

I want SMPS for pro applications for the same reasons I want class-d - to reduce weight and increase efficiency while keeping the quality of sound reproduction.

There are many companies making Class-D and just skipping the SMPS.

On the other hand, I now see companies that have class-ab, and class-h that are reducing their weight and increasing efficiency by just adding on an SMPS. (QSC for example)

I for one will be happy to see when/if Hypex ever comes out with their SMPS.

Come on class-d geniuses - more SMPS options!

 

[The golden mean]

Couldn´t Chord Electronics, Bladelius Design Group, Linn etc license their technology (SMPS) to PA-amp manufacturers?
These two branches seldom compete ?

 

[Eva]

I have some cool technology to offer so I may join the class-D and SMPS DIY module business in the future It certainly seems that there is some demand but I have to finish other projects first.

 

[ptwining]

I am curious...

Hi All,

I am curious. Has anyone reported an injury or failure regarding Coldamp power supplies?

Just to get it out of the way - they mis-used the forum and even they admit that this was a mistake. I actually emailed them to ask what was up.

I also wrote Coldamp about Eva's concerns. They acknowledged them and said that a plastic sheet between the SMPS frame and the chassis should be installed (now included with the kit) to prevent the situation Eva suggested.

Now, would they have thought of it before Eva made the remark? I don't now, but they seem to have responded in a responsible way.

I guess my point is this : maybe you are all right and Coldamp went to market too early - but - they went to market with something that worked and something that we wanted. Why aren't we, as a community, taking the attitude that we ought to help them to improve to better serve us instead of attacking them for not getting it right first shot?

They released a product that has worked perfectly for me and hasn't (as far as I know) killed anybody yet.

However, did I insulate that sucker seconds after Eva spoke - YES!

What? Do I look stupid?

Regards,
Tom

 

[iand]

Couldn´t Chord Electronics, Bladelius Design Group, Linn etc license their technology (SMPS) to PA-amp manufacturers?
These two branches seldom compete ?

Maybe they could, but I doubt that most of their designs could be successfully scaled up to the much higher power levels and power density demanded by pro audio, also with higher efficiency and preferably PFC.

Losses of 15-20% and poor power factor don't matter so much for hi-fi power levels; there's a big difference between designing a hi-fi SMPS with 85% efficiency at a few hundred watts and a pro audio SMPS with PFC and 95% efficiency at several kW.

This can be done nowadays using either ultra-fast-switching leading-edge devices (CoolMOS FETs, thinQ SiC diodes) in conventional hard-switched circuits (with 10ns or so switching times, which isn't quite so simple) or much more complex and difficult to design resonant-mode converters.

In both cases the design is a *lot* more difficult than a hi-fi type (or Coldamp SMPS.

Ian

 

[The golden mean]

Chord SPM 4000 2x750W into 4 ohms @ "only" 45 kg.
Chapter Audio was founded by a former Chord employee I was told. Time for someone to start a PA-amp company in the near future?

And as the first shot could be deadly some kind of certification may be a good idea? My opinion only. If I have to jeopardize with my life it will be under controlled circumstances such as mountaineering!

 

[iand]

Chord SPM 4000 2x750W into 4 ohms @ "only" 45 kg.
Chapter Audio was founded by a former Chord employee I was told. Time for someone to start a PA-amp company in the near future?

And as the first shot could be deadly some kind of certification may be a good idea? My opinion only. If I have to jeopardize with my life it will be under controlled circumstances such as mountaineering!

Powersoft K20 2x9000W/2ohms 1U 12kg 95% efficiency -- that's 1500W/kg as opposed to 33W/kg for the Chord

Ian

(yes I know it's not continuous sinewave rating, but not many people listen to continuous sinewaves -- output current of 108A rms tells you something though...)

 

[The golden mean]

So, it´s more of a financial issue than a technical problem? The solution; let´s start a company that makes SMPS kits for the demanding diy market!

An alternativ: build some portable horn speakers this way, then you don´t need more than 1000W :

http://www.soundsolutionsaudio.com/forum/index.php?showtopic=10834

Off topic: why use a SMPS in a phono amp? To anticipate regulations for more efficiency in all gear that is connected to the mains

http://www.aqvox.de/phono_de.html

Quote "Our designers created a completely new Low Noise power supply. Now the power output delivers with 10dB lower noise, cleaner energy and has a higher efficiency. Some better filters where added to ban the dirt also in lower frequencies. At the power supplies output resides a linear regulator. The result is audible. And the sound of the MKII is now better even under bad power conditions."

 

[iand]

So, it´s more of a financial issue than a technical problem? The solution; let´s start a company that makes SMPS kits for the demanding diy market!

An alternativ: build some portable horn speakers this way, then you don´t need more than 1000W :

If you want bass horns -- especially ones getting down to 30Hz or so, the bottom string on a 5-string bass -- you'd better have a *very* big truck to move them around in, because you'll also need multiple cabinets to get a flat response (typically 4 or more in a group, each about 500l volume -- search for "Labhorn").

Or you could use BMS18N850 drivers in 140l reflex boxes tuned to 32Hz, which are easily portable and handle 1200Wrms each down to the box cutoff -- 2 per side needs 2400W/4ohms. Put 4 smallish line array boxes over these (each 600W/16ohms) and you also need 2400W/4ohms for these. And you can fit all the above into an estate car rather than filling a van...

Apart from CAD Audio in Denmark (of which quite a lot has been said, none of it favourable) nobody's supplying either SMPS or class-D modules to the high power market, which is the one where they have the biggest advantage (weight/size/heat) over linear PSU and amplifiers.

I guess that's because everybody who has taken the time and effort to design such circuits would rather sell a finished amplifier for several times the price, which of course makes business sense...

Ian

 

[Eva]

Tapped horns produce the best low bass efficiency to volume ratio. Check the subwoofers forum. Their main drawback is limited upper bass bandwidth. Anyway, in order to get powerful bass, the important frequencies lie in the 50Hz to 250Hz range.

 

[SimonInd]

I built a 2 channel power amp based on 2 BP4078s and a SPS80 power supply last summer, before all of the controversy, and I'm delighted with it. Had I known about Pierre/ssanmor I may well have gone down the Hypex route but the posts by others that had heard both seemed to favour ColdAmp, plus as you have pointed out, they're cheaper.

Iand I'm in SW London so PM me if you want to come and take a look/listen to it.

Cheers
Simon

 

[Iyremenko]

I built a 2 channel power amp based on 2 BP4078s and a SPS80 power supply last summer, before all of the controversy, and I'm delighted with it. Had I known about Pierre/ssanmor I may well have gone down the Hypex route but the posts by others that had heard both seemed to favour ColdAmp, plus as you have pointed out, they're cheaper.

Iand I'm in SW London so PM me if you want to come and take a look/listen to it.

Cheers
Simon

Hi Simon, which users were those? Was it this one?

http://www.diyaudio.com/forums/showthread.php?postid=1251533#post1251533

Does it still whistle?

 

[SimonInd]

No, it was an English guy (KeithC) who ran the amp with Lowther loadspeakers - mentioned in this thread
http://www.diyaudio.com/forums/showthread.php?s=&postid=962785&highlight=lowther#post962785

The fact that only one user (Pierre) was posting about Coldamp did lead me to find a second opinion before purchasing.

Now it's earthed properly it doesn't whistle at all, in fact the TAG McLaren Power Amp, that I still use for centre and rears, generates more noise with it's transformers than the SPS80/BP4078 combination does hooked up to speakers.

I think the modules and service are good but they could improve quality control, however they've clearly shot themselves in the foot with their antics on this forum. It's a shame really because it's a good amp IMO.

Simon

 

[iand]

Tapped horns produce the best low bass efficiency to volume ratio. Check the subwoofers forum. Their main drawback is limited upper bass bandwidth. Anyway, in order to get powerful bass, the important frequencies lie in the 50Hz to 250Hz range.

I know, I've been following Tom Danley's work for at many years -- I actually came up with the tapped horn idea before he published anything about it, but at the time couldn't find any dependable way of designing and optimising it. It was me who got David McBean to put the ability to add the radiation from the other side of the driver into Hornresp, though at the time this couldn't be inside the horn mouth -- of course now it can and so modelling tapped horns is much easier than it was.

Tapped horns do indeed have the best efficiency to volume ratio, but it's difficult to make a small high-output one that goes down to bottom C (which our bass player uses regularly, and we *do* notice the difference with PA which can't cope with this) -- the cone unloads rapidly below the horn cutoff so you can't use bass boost to restore this without running out of cone travel.

If you draw a line on the size-efficiency treadeoff graph then for a low-ripple system response they're smaller and less efficient than a non-tapped horn, larger and more efficient than a reflex. They also have unusual driver requirements (Fs about 1.5x horn cutoff) which are not easy to find, most long-throw pro drivers have Fs much too low (the Ciare 12.00SW is one of the few exceptions), some car drivers would work well but are vastly overpriced. Another issue is the big resonant peaks/notches just above the passband which are difficult to get rid of, so the main speakers have to go below 100Hz so they have to be bigger...

Our existing sub is a collapsible reflex box (16ft3 unpacked, 6ft3 packed -- think Russian dolls) using a Seismic Systems 8196 driver (modified version of the Aura 1808) which goes down to 25Hz (because our bass player used to have a custom bass which went down to low G). However it runs out of headroom sometimes in big halls, high-power amps are cheaper than they used to be (or should be), and he doesn't use that bass any more.

The advantage of the BMS18N850 in reflex boxes is that the line array tops (which are a weird shape due to CD horn used) can pack neatly inside them for transport -- the inside of a tapped horn is chock-full of partitions for obvious reasons...

Ian

P.S. If you can find the right drivers (not easy!) and don't want to reuse the space inside for other things like I do, the tapped horn is the best solution, as you say.

 

[Eva]

The JBL 4520 "super scooper" from 1950s can be considered in many aspects a tapped horn. It works much in the same way as tapped: The mouth of the horn interacts with the driver resulting in increased LF output and flatter frequency response with no LF ripple. Two cabintes with four 15" drivers play down to 35Hz with efficiency in the 110dB/w range, and they play up to 800Hz or so due to direct cone radiation (this depends on driver choice). There are only two narrow notches at 135Hz and 270Hz, but no peaks.

In fact, The further the driver is placed from the mouth and into the horn the worse the frequency response becomes and the narrower the bandwidth. The way to get reasonable bandwidth and the least notches and peaks is to put the driver just at the mouth (they had already figured out in 1950 ). 15" drivers were a precious resource back then, so they found out how to make good use of them. The tapped fashion is not that innovative.

In fact, Tom Danley's TH115 seem to measure much in the same way as the good old JBL super scoopers, except that they no longer produce clean midrange.

http://srforums.prosoundweb.com/index.php/fa/5006/0/

 

[iand]

I never did get a satisfactory reply from Tom about what the real difference was between a tapped horn with the driver at the mouth (which many of his have have) and an old-style scoop horn, of which there were a vast number in "the old days"

Ian

P.S. Though few of them could have been correctly designed, except by pure good luck or trial-and-error...

 

[EnvisionAudio]

I have some cool technology to offer

You mean $$$$ technology, right?

 

[ackcheng]

I am using their SPS80 and SPS80HV to drive my Hypex amp. It has been running for more than a year and if going well.