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Old 16th August 2011, 02:47 PM   #31
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Join Date: Feb 2010
Location: Powell River, BC Canada
I have been very close to buying several T4s for our Klipsch home theater consisting of Klipschorns, LaScala clone center and Heresy sides. We will have this in an active crossover arrangement. These speakers are all very efficient and highly revealing. Any idea how the L20D might compare to the T4 in sound quality?

Thanks,
Rod
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Old 17th August 2011, 04:06 AM   #32
ljm_ljm is offline ljm_ljm  China
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Join Date: Sep 2006
Very happy to see a friend of L20D can have a good opinion.

About 4 R speaker drivers.

L20D can be good work.

L20D voltage recommended value for work 60 +-+ 80 V to between V.

This voltage can let amplifier output 250 W of power in the load (+ 8 R 75 V)

And the inter-class D CLASS of voltage amplifier is a requirement, not with the recommended voltage difference is too big.

So L20D in four European of time also is can output the 250 W power above, (+ 75 V)

Because of the IRFI4020H IC OUT restricted in 9 A or so.

So L20D even work in the next four and the output power and can't more than 9 * 9 * 4 = 324 W.

But in fact, we don't use the 300 W power so much. Can be at ease use.

This and common simulation power amplifier is the same.
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Old 17th August 2011, 05:35 AM   #33
Bernie7 is offline Bernie7  Singapore
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Join Date: Dec 2008
Quote:
Originally Posted by ljm_ljm View Post
Very happy to see a friend of L20D can have a good opinion.

About 4 R speaker drivers.

L20D can be good work.

L20D voltage recommended value for work 60 +-+ 80 V to between V.

This voltage can let amplifier output 250 W of power in the load (+ 8 R 75 V)

And the inter-class D CLASS of voltage amplifier is a requirement, not with the recommended voltage difference is too big.

So L20D in four European of time also is can output the 250 W power above, (+ 75 V)

Because of the IRFI4020H IC OUT restricted in 9 A or so.

So L20D even work in the next four and the output power and can't more than 9 * 9 * 4 = 324 W.

But in fact, we don't use the 300 W power so much. Can be at ease use.

This and common simulation power amplifier is the same.
Ok I'll take it that L20D is fine with with 70-0-70VDC ps for 4ohm speakers and the max power will then be 324W.

Would linear ps or smps be best for the L20D? Consensus seem to favor smps for the hifimediy and Sure Tripath amps. Trevmar did you use smps for your L20D distortion measurements?
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Old 17th August 2011, 12:42 PM   #34
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Location: Maryland, USA
I too would love some suggestions on a good source for a power supply for 8ohm operation of the L20D. Is there a better value than the Connexeletronics SMPS800R @ +/- 72v?
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Old 21st August 2011, 05:45 AM   #35
trevmar is offline trevmar  United States
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I just posted more accurate intermodulation and harmonic distortion test data for my L20D in this other thread here at DIY:

Distortion Tests - HifimeDIY T2 / LJM L20D / SURE TDA7498

Thanks to ljm_ljm for a really great design
.
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Old 21st August 2011, 02:05 PM   #36
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Location: Powell River, BC Canada
Quote:
Originally Posted by trevmar View Post
ljm_ljm,
I was just looking at your Chinese language forum, and there is discussion there about piracy of your boards and design. Are the Ebay boards (from Hong Kong) pirated? Is there any way we can buy boards so that you get the benefit? All I could find were Taobao stores, which are hard to arrange payment and shipping for somebody who is not in China.

Also, on 1 July 2011 you posted the following comment on your Chinese language board "This is not the maximum power. Goal is to IRAUDAMP9 1200-1700W power." Have you had any further thoughts about a super big amplifier?

Thanks for all you have done for the DIY community.
.
It would sure be good to get a response on whether the Ebay boards will benefit ljm_ljm.

Besides the previously linked zoe_tsang boards 2pcs L20D IRS2092 200-250W X 2 Class D amplifier sc | eBay for $37.10 I also found this zoe_tsang board L20D IRS2092 IRAUDAMP7S 200-250W X 2 Class D amplifier | eBay for $39.50.

Wondering which is newer - they are both L20D. Noticed a copyright date of 2008 on the latter but not the former. Also on the latter Ebay listing there is a schematic showing a couple of auxiliary boards: what appears to be a capacitor board and a speaker protection board.

Rod
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Old 21st August 2011, 03:29 PM   #37
trevmar is offline trevmar  United States
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The dual board appears to be two L20D side by side, but with attribution to IR, not ljm_ljm. Since it is not identical to the IR reference board (see iraudamp7s.pdf) I would stay away from it. There is so much skill which goes into the layout of a board like the L20D - and ljm_ljm's "just works fine" so I would suggest staying with it.

The newer double board does appear to have larger have 100V bypass capacitors on it, this may be something you want to take up with Zoe, as I think her boards are custom made (probably by some Shenzhen artisan) after receiving an Ebay order. Not sure though...

The boards I tested were from the first auction, which is clearly marked as an ljm_ljm design, replete with his 'head' logo. It matches the photos he posted in this thread.

UPDATE: on closer examination it appears the newer dual board is pretty close to the IR reference design, but has some switches missing and terminal input blocks instead of RCA jacks. I still would go with ljm_ljm as it is good, and you can control single-point earthing with that single board. I used single point earthing (at the main power supply ground) when testing the distortion curves I just published.
.

Last edited by trevmar; 21st August 2011 at 03:34 PM. Reason: I noticed error
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Old 21st August 2011, 05:14 PM   #38
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by nwboater View Post
It would sure be good to get a response on whether the Ebay boards will benefit ljm_ljm.

Besides the previously linked zoe_tsang boards 2pcs L20D IRS2092 200-250W X 2 Class D amplifier sc | eBay for $37.10 I also found this zoe_tsang board L20D IRS2092 IRAUDAMP7S 200-250W X 2 Class D amplifier | eBay for $39.50.

Wondering which is newer - they are both L20D. Noticed a copyright date of 2008 on the latter but not the former. Also on the latter Ebay listing there is a schematic showing a couple of auxiliary boards: what appears to be a capacitor board and a speaker protection board.

Rod
Nice to your attention.

The two are all I have provided.

L20D is the first one, mono versions, I design.

Another double track is provided by the company of IR sample, it has more restrictions.

Including the voltage, over-voltage protection, and the output of the dc disconnect PWM protection function.

Suitable for a double track the amplifier. Or, more like IRAUDAMP7 reference version of friends.

It is also very low distortion, I believe that IR engineers can be fully play AMP7S-200 performance.

Also thank their reference version of the design let me get reference model.
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Old 21st August 2011, 05:21 PM   #39
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by trevmar View Post
I just posted more accurate intermodulation and harmonic distortion test data for my L20D in this other thread here at DIY:

Distortion Tests - HifimeDIY T2 / LJM L20D / SURE TDA7498

Thanks to ljm_ljm for a really great design
.

I have found this article carefully read.

This is to let people feel very good test, and the result is the normal course.

I also for these AMP often tested.

Purpose is to improve, to improve the performance of the amplifier now.

I often think about these distortion or sound the reason of its changes, I think I may never

Have satisfied.

Thank you very much for your objective comments and test, I very like to test, whether the result is good or bad.

That is very meaningful.
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Old 21st August 2011, 07:59 PM   #40
trevmar is offline trevmar  United States
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Quote:
Originally Posted by ljm_ljm View Post
I often think about these distortion, or sound, the reason .. for .. its changes, I think I may never .. be .. satisfied.
Yes, I know the feeling You can be flattered that the L20D is the first amp I have not felt tempted to 'tweak' components or design, or even layout (grounding). The L20D was stable, solid and reliable, from the time I unpacked the package which arrived in my mail. I am very impressed.

As you say, IR has a wonderful chip-set now, which is going to help define the standard of performance for switching amplifiers over the next few years. Thank you very much for your stable layout which introduced me to their excellent chips.

I visit China frequently, and have been to Chengdu many times to visit colleagues at West China Hospital. It is a nice city, not as active an electronics market as Shenzhen, but still I spent many hours wandering through it.

Thanks again
.

Last edited by trevmar; 21st August 2011 at 08:14 PM.
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