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Class D Switching Power Amplifiers and Power D/A conversion

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Old 31st October 2012, 02:51 PM   #581
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To be honest it's hard for me to compare... I'm currently powering 2 subwoofers in 2 different setups with the L25D's... They're obviously very powerful but I haven't had the opportunity to listen to them in full-range, nor have I had the need to really push them. I'm having a house party in a couple weeks so that should be a good test .

Both of my systems are tri-amp'd and bi-amp'd so I've never had the opportunity to really listen to the amps in full-range... My next project will be some simple single, full-range driver speakers specifically for that purpose.
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Old 29th November 2012, 04:24 AM   #582
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I am running 2 l25d boards. They are ocp'ing long before I expect them to. Checking the board against the reference schematic shows that it has the same resistors defining the current limiting as does the amp7s. Checking the transistor specs show that they have almost the same voltage consumption, so even though the board has twice as much transistor, the overcurrent limiting seems to be set to the same value. Of course, I assume the 20d and the 25d use the same heat sink. Maybe the heat sink is the limiting factor for the power output on this board. Maybe with a larger heat sink, the overcurrent limits can be set higher.
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Old 13th December 2012, 05:03 PM   #583
redjr is offline redjr  United States
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I recently completed an amp build centered around the LJM L25D class D modules. Pictures can be found over here in the class D photo thread. For the short period that I have listening so far I can say it sounds very good. I'm presently using it to drive a couple of very inexpensive bookshelf speakers (Insignia NS-B2111), so please factor that in. While it no match up against my Pioneer SC-05 HT amp with ICEpower modules, it holds its own very nicely.

While I personally like a somewhat 'brighter' high-end, the amp delivers. In addition, I think the mid-range is spot-on, and the soundstage seems a tad fuller than my class AB amp. The base also seems slightly tighter - at least with the Insignia's. A sub-woofer added to the lineup would obviously provide much fuller bass. The Insignia's have a surprising range and sound good with a range of music. With some well recorded country music, the amp sounds full of life, with a slight 'edgy-ness' to the sound. The 'twang' comes through loud and clear. Country music is a good test for the dynamic range of an amp and speakers. Plus the LJM modules seem to be dead quiet as I can't hear any noise at with my ear up to the speaker, and definitely not from my listening distance.

Overall, I'm very happy with how the amp turned out and the sound it delivers for a rather inexpensive solution.

Rick
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Old 13th December 2012, 06:18 PM   #584
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Quote:
Originally Posted by redjr View Post
While it no match up against my Pioneer SC-05 HT amp with ICEpower modules, it holds its own very nicely.
How does something not match up at the same time that it holds its own?

Is that with the same speakers?

I'd expect the IRS2092's to sound every bit as good as the ICE amps.
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Old 13th December 2012, 07:46 PM   #585
redjr is offline redjr  United States
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Originally Posted by noah katz View Post
How does something not match up at the same time that it holds its own?

Is that with the same speakers?

I'd expect the IRS2092's to sound every bit as good as the ICE amps.
Hi noah, Yes, using the same speakers. I can't say for sure, but I suspect there's much more circuitry involved in the SC-05 - even in DIRECT mode that Pioneer engineered in to optimize the B&O ICE amps. After all, you can't expect a $45 set of amp modules to compete at the same level sonically with a $2000 receiver. Don't get wrong, the L25D sounds very good indeed, but doesn't have the silky smooth and effortless sound characteristics of the ICE amps. I continue to be amazed at the sound of the ICE amps in my HT.

Rick
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Old 13th December 2012, 08:03 PM   #586
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Hi Rick,

Just to be clear, you used the Pioneer's pre-outs feeding the L25's and compared the same source material and number of speakers?

Was your comparison sighted or blind?

Re the price, I wouldn't be surprised if Pioneer doesn't spend much more for ICE modules.

Anyway, I'll just have to see what I think when I get mine built, using Cristi's IRS2092-based CxD250's for L/C/R and CxD300's for surrounds.
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Old 13th December 2012, 08:20 PM   #587
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Default 2 questions (post box of ljm is sadly full)

I just have 2 questions to the community:
1) in one forum they change (reasonably) the first cheap input cap CP1 with 2 parallel 22uF Wima MKPs. I think the value could be too high because of limiting bass in signal. Can I take instead CP1 a MKT 6 uF ? I think it should work.

2) I have one 450 W torroidal with 2 x 42 VAC out and measured after power supply board about 61,5 VDC+. Is this eventually optimum because I read shortly ago that at higher supply voltages the L25D has some problems to handle 4 ohms speaker impedances.

Thanks

Quote:
Originally Posted by redjr View Post
While it no match up against my Pioneer SC-05 HT amp with ICEpower modules, it holds its own very nicely.
Woww ! Did'nt know that Pioneer produced an amp with ICE Power boards. Strictly I am a pure Stereo Fan but despite that 90 % of it's channels are useless are outside my purposes it seems to rock ! One critical point overal about the ICE Power amps is: it's sounds slightly clinical but maybe a listener's adjustment issue.
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Old 13th December 2012, 09:14 PM   #588
redjr is offline redjr  United States
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Quote:
Originally Posted by noah katz View Post
Hi Rick,

Just to be clear, you used the Pioneer's pre-outs feeding the L25's and compared the same source material and number of speakers?

Was your comparison sighted or blind?
No. I did not use the SC-05 pre-out, driving the LJM. That was not my intention. If anything, I would have used the SC-05 amp-in connection, to remove the SC-05 pre front-end circuitry. My testing was not that scientific. This has only been sighted casual listening. I just hooked up the speakers to both and listened - not extensively either - yet - I might add. I've been using my newly finished Doug Self's 2012 preamp to drive the LJM. Same source and same number of speakers.
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Old 13th December 2012, 10:34 PM   #589
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ok thanks
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Old 18th December 2012, 10:24 PM   #590
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Hi guys,

I run the fresh built amps for few hours now. What I don't like is the heat from the resistors, although I run tthe L25D's with 60V only. Is there a better way by replacing these guys? Did anybody have problems with burnt resistors?

Thanks,

Stammheim
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