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Old 17th October 2012, 02:46 PM   #561
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Quote:
Originally Posted by Cristi View Post
The boards from the pictures I've posted were purchased by a customer of mine from the same "authorized" source. In fact he bought several modules, he's building multi-channel amps for public announcement and he had to try them. They failed the tests, 3 of them being damaged in less than 5 minutes. later on he bought few boards from my site and after successfully testing them, now I'm making a custom version for his multi-channel application. I asked him to send me two of these boards, I've been curious why they failed. If you notice, reading some older posts in this thread, I also had a good opinion about them till I got them in my hand.
I'll make some time next week and make some THD tests for the boards after (if I can) repair them and post the results. since I don't have an AP unit yet, only a Kenwood VA2230, accurate enough but no PC interface to save the graphs, it will take some time, and not sure is worth the effort while dealing with rigid attitudes.
Next I expect to be accused that I try to advertise my own boards, but before writing this, ask yourself's why I haven't opened a single thread at class D section trying to promote something. Even at Connexelectronic section (which I pay for) is quite silence and I'm also not inpatient to make more waves. Eventually everyone can do what he wants with his money and spend them more or less wisely. But keep in mind that while consciously purchase low-quality or substandard parts boards, you do nothing than to escalate the phenomenon.
Nobody is accusing you of anything , and allot of things can go wrong assembling a board , you should know ! so there is no case here .
I assume you're an experienced electronic guy , so if you want to make a honest opinion , just order some LJM's from an "Authorised source" put them together and then make your judgement .

Cheers ,

Rens
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Old 17th October 2012, 04:50 PM   #562
redjr is offline redjr  United States
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Quote:
Originally Posted by Cristi View Post
The boards from the pictures I've posted were purchased by a customer of mine from the same "authorized" source. In fact he bought several modules, he's building multi-channel amps for public announcement and he had to try them. They failed the tests, 3 of them being damaged in less than 5 minutes. later on he bought few boards from my site and after successfully testing them, now I'm making a custom version for his multi-channel application. I asked him to send me two of these boards, I've been curious why they failed. If you notice, reading some older posts in this thread, I also had a good opinion about them till I got them in my hand.
I'll make some time next week and make some THD tests for the boards after (if I can) repair them and post the results. since I don't have an AP unit yet, only a Kenwood VA2230, accurate enough but no PC interface to save the graphs, it will take some time, and not sure is worth the effort while dealing with rigid attitudes.
Next I expect to be accused that I try to advertise my own boards, but before writing this, ask yourself's why I haven't opened a single thread at class D section trying to promote something. Even at Connexelectronic section (which I pay for) is quite silence and I'm also not inpatient to make more waves. Eventually everyone can do what he wants with his money and spend them more or less wisely. But keep in mind that while consciously purchase low-quality or substandard parts boards, you do nothing than to escalate the phenomenon.
I too would like to understand the failure of the ljm amps in question. It may or may not be related to sub-standard parts. Maybe a direct short. Maybe driven to clipping and beyond. I appreciate your willingness to do this. My point was not to accuse anyone of anything, but in the interest of full-disclosure the next time you should probably mention that you sell a competing product.

I have purchased 2 SMPS from Connexelectronic and I'm very pleased with the quality and performance of the units. I too, believe there's alway room for improvement in the level and quality of amps I build. I will very much consider looking at what you have to offer for a future project.

Rick
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Old 17th October 2012, 09:55 PM   #563
skood is offline skood  Australia
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Quote:
I too would like to understand the failure of the ljm amps in question.
I've been using my ljm 15d units in an active setup driving a midbass unit at full output at times and there's been no issues. Using them for about a year now, seem pretty solid units to me..
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Old 18th October 2012, 05:58 AM   #564
Cristi is offline Cristi  Europe
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I understand that there must be a price threshold, below that, the quality of the parts doesn't matter at all or is seen as "fine for the price" or even excellent. Then once we cross that threshold the expectations for parts quality rise exponentially. Or simply my expectations and quality standard are far too high? I'm just curious what's that quality threshold. If is not that low, I guess I can substantially increase my revenue by just decreasing the quality level for my boards while keeping the price, or keep the quality and rise the price. Eventually the price/quality would be the same as I discover now that the market ask for.
All the so called allegations are based on objective observations, and can be verified following this thread and pictures from the post mentioned above, as well as by those who have purchased similar boards as the ones I got my hands on. Or there is a reason for them to keep quiet.
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Old 18th October 2012, 10:46 AM   #565
zog666 is offline zog666  Australia
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Quote:
Originally Posted by skood View Post
I've been using my ljm 15d units in an active setup driving a midbass unit at full output at times and there's been no issues. Using them for about a year now, seem pretty solid units to me..
Same here, pair of L20D driving Econowave passive crossover speakers - driven by a Connex PSU.

I did apply the recommended tweaks mentioned at the start of this thread... applying the missing heat sink paste, low ESR filter caps. I have never run them near their full capability, I just like having the headroom there.
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Old 18th October 2012, 12:42 PM   #566
redjr is offline redjr  United States
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Quote:
Originally Posted by Cristi View Post
I understand that there must be a price threshold, below that, the quality of the parts doesn't matter at all or is seen as "fine for the price" or even excellent. Then once we cross that threshold the expectations for parts quality rise exponentially. Or simply my expectations and quality standard are far too high? I'm just curious what's that quality threshold. If is not that low, I guess I can substantially increase my revenue by just decreasing the quality level for my boards while keeping the price, or keep the quality and rise the price. Eventually the price/quality would be the same as I discover now that the market ask for.
All the so called allegations are based on objective observations, and can be verified following this thread and pictures from the post mentioned above, as well as by those who have purchased similar boards as the ones I got my hands on. Or there is a reason for them to keep quiet.
We can argue about the diminishing returns of the quality of the parts used in any amp. But, you also stated in post #557 that the design and layout of the L-series amps pcb is not just sub-par, but terrible for class D. Is this just a difference of approaches of design implementation between two 'engineers' (ljm and Cristi), or do the items you mention in your post affect the overall, noticeable, audible and sonic characteristics of the amp? Operative word being noticeable. Apparently, the sound must be 'good enough' based on testimonials in this forum.
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Old 19th October 2012, 04:18 PM   #567
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Default Extra capacitors only for bass L15D-PRO?

A quick question to those who know much more than I do

I am now building my 3 channel L15D-Pro based amp with the Connecs smps500R at +/- 50V.

My idea is to "insulate" the high and mid boards from the bass board by putting 2 capacitors in the bass board power-supply lines. Hope this will flatten power fluctuations in the higher frequencies and improve sound stability (image etc.)

Heavy power off pops are not desired.

I can choose between 4700uF-80V or 10.000uf-63V or nothing at all of course.

Thank you in advance
Peter

Last edited by peterhenk; 19th October 2012 at 04:19 PM. Reason: typo
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Old 19th October 2012, 05:08 PM   #568
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by peterhenk View Post
A quick question to those who know much more than I do

I am now building my 3 channel L15D-Pro based amp with the Connecs smps500R at +/- 50V.

My idea is to "insulate" the high and mid boards from the bass board by putting 2 capacitors in the bass board power-supply lines. Hope this will flatten power fluctuations in the higher frequencies and improve sound stability (image etc.)

Heavy power off pops are not desired.

I can choose between 4700uF-80V or 10.000uf-63V or nothing at all of course.

Thank you in advance
Peter
I can't remember exactly, but I think it was Cristi who suggested adding around that amount of capacitance on the output of his SMPS was always a good thing. I'm using 2 L15D's with one of his 300R's and 6800uF/80V on each power rail. I can't say I did an A/B of with and without, I just built it that way the first time. (and no power pop offs)
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Old 22nd October 2012, 06:17 PM   #569
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Another happy user of Ljm's boards.
Have 2 L20d on a Connexelectronic SMPS driving two Markaudio speakers.
I'm actually getting better results (with my specific setup) than previously with a TK2050.
The boards (stock ones from one of the two recommended sellers) are well built, components are good for the price range, I've added an extra speaker protection driven from a different PSU.

The only serious tests I've seen are the distortion tests made by Trevmar here, the alegations made in this thread are for me just hearsay without any value until things are proven.
I'm sure Cristi can show us more detailled infos and tests (I know he is a skilled engineer, offering some great products) to help the debate here.

Until then, I continue very happy with ljm's L20d.
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Old 23rd October 2012, 12:39 PM   #570
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Can anyone tell me if I'm voltage limited with the L15d Pro @ +/-42v? I'm hoping to get 300w into 4R

Thx
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