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Class D Switching Power Amplifiers and Power D/A conversion

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Old 28th September 2008, 07:58 AM   #91
dgm is offline dgm  Australia
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Join Date: May 2006
Berns,
I think you are not being as objective as you could be. Whilst some people might have issues in the way Coldamp have utilised the forums, I still have a lot of respect for them, what they are doing and their customer service. I was actually commenting that Coldamp modules have a lot of oomph - ie dynamics in the bass and punch in the midrange - and in fact slightly more than UCD. You have taken this as a criticism of Coldamp which it certainly isnt - its their strength in my opinion.
Sergio was commenting on performance at 40Hz because this is the frequency I stated I was using for testing my modules.


Sergio,
I am using a big finned heatsink now in a 3U case so there is NO question there is adequate cooling for the modules now. One of the modules I was using was one of the 2 that survived the drama in my previous 2U case and this might be on the way out.

In my mind it seems that for 4 channel applications a heatsink should be recommended for amateur builders for UCD and Coldamp. Companies with proper product development cycles may be able to develop simpler less robust systems (ie without heatsinks) that offer adequate cooling but amateurs cant afford the time and expense of learning by testing to failure.

I built the optocoupler protection circuit you sent using proto board but it didnt work reliably (I only received the circuit and parts list). I dont know why. I suspect my layout and connections could have had something to do with this. I also didnt understand the electrical limitations of optocouplers so wasnt comfortable with trying to troubleshoot it or modify it. Thus I moved to the Altronics protection kits which worked well though the HF protection side couldnt handle Coldamp or UCD.There is a big need for a small, very simple multi channel DC protection circuit kit (ie circuit board and parts) that switches the power supply to the module and has fuses bor both rails for each cahnnel so you can use a "crowbar" relay system (which many of the experts such as Rod Elliot say is essential) . Why not offer ready made matching 2 and 4 channel DC protection modules for the SPS80?

I have had a much longer and harder road getting to where I am now than I expected. Whilst I have learnt a lot, I would have preferred to have had a simpler challenge!

Whilst I have moved to the UCD side for modules, I am firmly on the Coldamp side for power supply. My next amp would be built with an SPS80. A power supply with a bit more capacity that was rated for a 4 channel system would also be good.

No doubt the BP4078 modules have improved at the next revision from mine, but the competition "just worked " right from minute 1 and this is something I like.

Derick
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Old 28th September 2008, 10:41 AM   #92
ssanmor is offline ssanmor  Spain
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Hello, Derick.
Thanks for your fair expression of your experience. And remember that, if you have any problem with your modules, they have a 2 year warranty. Even if you purchased them earlier, just contact us and we'll see how to solve the issues.
Regarding the DC protection, if you want we can give you the PCB layout design. By the moment it is not a product we are thinking in selling, and in fact no customer is asking for them, because output stage failures are very very rare.
Besides, we prefer to concentrate in the development of the new batch of products.
One of them is a low consumption amplifier that will solve all the heat issues in multichannel applications, by the way.
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Old 29th September 2008, 12:49 PM   #93
KeithC is offline KeithC  United Kingdom
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Hi Sergio,

one doesn't need output stage failure to get a large dc offset - I blew an EX3 drive unit by not switching off before introducing a valve line buffer at the input.

Hypex speaker dc protection is on their psus, so a combination of Hypex linear psu & BP4078 works just fine - in fact I find the BP4078 sounds better with a linear psu, and use my SPS80 to drive Ucd400s (on Quad L22s).

Regards,
Keith
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Old 29th September 2008, 01:06 PM   #94
ssanmor is offline ssanmor  Spain
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Thanks for your contribution, KeithC.
Yes, you don't need a broken output stage to get a large DC offset, but it is the most common cause (a problem in the input or drive stage could also cause this, but it is even more strange that this happens in solid state, from our experience).
Each customer seems to like a combination in particular, other ones like the sound of BP4078 with SPS80 more than with LPS30 linear PSU.
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Old 29th September 2008, 02:34 PM   #95
dgm is offline dgm  Australia
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Default Amplifier protection for SMPS

Keith,
What sort of protection are you using for your SPS80+UCD system?

Whilst the Altronics one that I am using is OK, I have disabled 50% of it - the HF protection and the AC sense shutdown. The circuit boards are big also.

I have seen others from Nordics projects (http://www.dxamp.com/construction/protection/) and rod elliots project 33 (http://sound.westhost.com/project33.htm), Velleman, Aussie amps, Jaycar, but these dont quite fit the bill.

DC protection is so simple, but all of the boards I have seen are far too complicated (eg those above) and none address switching between PSU and modules. I also dont feel like making my own circuit boards. I just want a board that fits a fuse for each module supply rail, and a relay for each module with DC protection. Ideally it should run from a 12V supply such as the SPS80 auxiliary supply.

Do you have any hints on where to get a PCB or a ready built unit?
Derick
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Old 29th September 2008, 07:48 PM   #96
KeithC is offline KeithC  United Kingdom
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Basically, no DC protection without Hypex PSU, just a vague hope that 85db/w units capable of handling 300w would be more likely to survive than 99db/w drivers with silver voice coils.

Overall I find the power level of class D kit ludicrous - never mind the quality, feel the watts. And I use them on speakers that I can drive from my headhone socket. Joke.

Mind you, with winter coming on I'll soon revert to 6wpc Decware Taboo, if only to heat my office.
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Old 1st March 2009, 07:20 PM   #97
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Default For what it's worth...

I've used a Coldamp SMPS for a pair of UCD 400's for a year or so now. It works fine.

I had the same UCD's on a 1KVA toroid and the Hypex supply before I used the Coldamp and I don't think there is any audible difference.

It hasn't killed me yet (crosses fingers) and it sounds pretty good. What's not to like? <grin>

Regards,
Tom
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