My design L20D IRS2092+IRFI4020H 200W8R

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trevmar

Member
Joined 2011
Bernie7, IMO the T2 is really good enough for a quality audio system. It is clean enough so that it will be hard to find any speakers capable of distinguishing between the T2 and the L20D. However, the L20D measures cleaner, especially at high frequencies and high powers. I will use the T2 as a knock-about portable system run from my (Apple) 24V 2.65A power brick, and the L20D in the aluminum casing holding my main stereo amplifier. I want to get the SURE working for a suitcase-portable system I have designed, so I will get a real TDA7492 chip from Digikey or Mouser tomorrow, and replace whatever chip SURE supplied in the board :)

You know, the L20D performance is so good that it is really going to be hard to beat. Ljm_ljm has produced a board which is really stable, a very nice package indeed. And inexpensive as well :) It doesn't have all the protections of the T2 (speaker relays, etc) and that is just about the only way I think it could be improved. Other than increasing its power to kilowatts, of course :)

As for power supplies, you don't need as high a supply voltage to pump power into 4 ohm as you do into 8 ohms, but you need twice the current. The 4020 output chip on the L20D is optimized for high voltage, not high current.

As for pushing the specs a little, one tends to be cautious in view of the lack of speaker protection relay on the L20D. I am adding a board to do that for me :) But if you take 150 watts as the maximum real-world 4 ohm output (which is the number I would start with), you only need about 25 Vrms into the 4 ohm speakers to achieve that. You should be able to get that from a 40-0-40 power rail. Because it is a switching amplifier you can probably fudge it from a 68-0-68, but there will be higher peak VI values floating around, and the amplifier will not be operating at maximum efficiency. Look on pages 9,10,11 of the iraudamp7s data sheet and you will find curves using 50-0-50 into 4 ohms, for example (but they use a different FET in the lower voltage configurations than the 4020).

Hope that helps.
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trevmar

Member
Joined 2011
I explained the issues with low impedance loads in my post above. IR took the attitude that if you didn't understand why there were issues, they were not going to bother with any explanation. You can see the curve I supplied for distortion vs power into 4 ohms, it goes out to 150 watts, but it was not taken with a 70-0-70 supply :) .
 
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Bernie7

Member
Joined 2008
Ok gotcha about the specs.

What would happen if I used a 68-0-68 ps on a L20D? 200-300W demand would rarely ever happen and only on transient peaks, but if it does happen would the IR chip blow or just run out of breadth?

Reason I'm pursuing this is I already have a good linear Hypex 68-0-68VDC ps and using something else for my 4ohm speakers would be a deal breaker.
 
T

trevmar

Member
Joined 2011
If it were me, I would use it. The advantage of switching amplifiers is their ability to give good efficiency over a wide range of operating conditions :) Your 68-0-68 would probably drop a little under full load, and you very rarely would peak to full load in any case. Just be very careful that your 4 ohm speakers don't drop below that impedance, due to poor crossover design, or whatever. If you are driving a bi-amped speaker (active crossover) then the 4 ohm speaker will measure a much higher impedance throughout most of its range, in any case :)

But please don't sue me if the sub-$50 L20D boards can't handle the strain :) :) :) Expectations have to be realistic :) :) And don't forget to buy a speaker-protector relay board :) :)
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T

trevmar

Member
Joined 2011
That is a reasonable assumption. Remember that the output inductor averages the output current between the switch and your speaker, so if you aren't driving more than 150W into your 4 ohm speaker too often, you should be keeping the average switch current below 9 amps.

Mind you, I would like to hear what 150W sounds like into a tweeter. Let's see, 85dB efficiency at 1W, 125 dB at 100W, I guess 125dB is still reasonable :) :) :)
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nwboater

Member
Joined 2010
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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ljm_ljm

Member
Joined 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.
 
B

Bernie7

Member
Joined 2008
ljm_ljm said:
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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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?
 
N

nwboater

Member
Joined 2010
trevmar said:
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.
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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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trevmar

Member
Joined 2011
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.
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L

ljm_ljm

Member
Joined 2006
nwboater said:
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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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.
 
L

ljm_ljm

Member
Joined 2006
trevmar said:
I just posted more accurate intermodulation and harmonic distortion test data for my L20D in this other thread here at DIY:

http://www.diyaudio.com/forums/clas...y-t2-ljm-l20d-sure-tda7498-3.html#post2679941

Thanks to ljm_ljm for a really great design :)
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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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trevmar

Member
Joined 2011
ljm_ljm said:
I often think about these distortion, or sound, the reason .. for .. its changes, I think I may never .. be .. satisfied.
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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 :)
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