Distortion Tests - HifimeDIY T2 / LJM L20D / SURE TDA7498

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Hello!, I'm sorry to use this tread but I don't know how to connect my new L20D ... The pinout on ebay page was not very clear... +70V to VCC+; -70V to VEE- and ground to PGND? The speaker + to OUT+ and speaker - to PGND?
Thank you a lot
max



In free time I draw a picture, may help.

By the way, power and voltage is connected.

L15D work 40 to 60 V DC (+-)125-150 W8R
L20D work DC 60-80 V (+-)200-250 W8R

According to from already the need to choose the better.
 

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By the way, power and voltage is connected.

L15D work 40 to 60 V DC (+-)125-150 W8R
L20D work DC 60-80 V (+-)200-250 W8R

So with +/-60V the L15D gives 150w/8R and the L20D gives 200W?

At the same +/-60V, what are their idle power dissipations?

Also another question, if I may - what is the connection between ljm_ljm and zoe_tsang?

I've looked through the latter's ebay listings, including the ones being discusses here, and can't help but wonder kind of quality/reliability can be expected for such low prices.

Assuming there's a reassuring answer, what are the pros/cons of the single-channel boards vs. the stereo ones?
 
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The boards I got from zoe_tsang both worked properly, but I swapped out the main filter caps for 100V low ESR types. They were only 63V, and high-ish ESR. Best to consider Zoe's as "bargain basement" prototypes, and check them over carefully. I certainly didn't throw mine straight onto 65 Volts, although I could have done so... Both of my L20D drove 6 ohms without a hiccup and put more than 200W into my 4 ohm dummy load, which was almost glowing red with distress :) I didn't have a larger dummy load. No problems with dissipation, the L20D heatsink was always cool-ish, no matter what I threw at it. I was very happy with them. The output ran to within a few volts of the supply rails, almost regardless of 4-8 ohm loads.

Before buying the l25D I would want to see if the heavier capacitive load on the PWM driver chip might lead to a little higher distortion levels. The L20D distortion was so low it was difficult to measure...

Single channel boards give you control of the grounding. If that is important to you, I count it as the single most important difference between them. My testing was with single boards, no trace of ground routing problems.
 
Is zoe_tsang the only source for ljm's design?

Or does replacing the filter and input caps pretty much take care of it.

Though I'd much prefer something ready to go, and with speaker protection.

Something else I'm curious about: How long did it take other people to figure out that "European" means ohms/resistenace? :)
 
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what's the maximum output current, and is there overload protection?
The IRFI4020 data sheet and application note (iraudamp7s.pdf) has all this information. There are both peak and average current rating for the MOSFETs there.

Be warned that the overload protection with the additional transistors in the app note is not implemented in the L20D, but the IRS2092 internal overcurrent protection mechanisms are still active.
 
The boards I got from zoe_tsang both worked properly, but I swapped out the main filter caps for 100V low ESR types. They were only 63V, and high-ish ESR. Best to consider Zoe's as "bargain basement" prototypes, and check them over carefully. I certainly didn't throw mine straight onto 65 Volts, although I could have done so... Both of my L20D drove 6 ohms without a hiccup and put more than 200W into my 4 ohm dummy load, which was almost glowing red with distress :) I didn't have a larger dummy load. No problems with dissipation, the L20D heatsink was always cool-ish, no matter what I threw at it. I was very happy with them. The output ran to within a few volts of the supply rails, almost regardless of 4-8 ohm loads.

Before buying the l25D I would want to see if the heavier capacitive load on the PWM driver chip might lead to a little higher distortion levels. The L20D distortion was so low it was difficult to measure...

Single channel boards give you control of the grounding. If that is important to you, I count it as the single most important difference between them. My testing was with single boards, no trace of ground routing problems.

L20D near power position has two 80 V150UF capacitor, they need more than compression VCC +
The voltage between GND.

Some 63 V22UF capacitance they work voltage is low, only need to more than 25 V is enough.

22 UF capacitance need high frequency, LOW ESR.

In addition L20D has a resistance, the default is 470 OHM. Can set PWM frequency

About 470 R = 550 K, 330 R = 440 K, 300 R = 400 K HZ.

:D
 
So with +/-60V the L15D gives 150w/8R and the L20D gives 200W?

At the same +/-60V, what are their idle power dissipations?

Also another question, if I may - what is the connection between ljm_ljm and zoe_tsang?

I've looked through the latter's ebay listings, including the ones being discusses here, and can't help but wonder kind of quality/reliability can be expected for such low prices.

Assuming there's a reassuring answer, what are the pros/cons of the single-channel boards vs. the stereo ones?

zoe_tsang was a good transportation network of dealers.

I know there are many inferior in China really fake parts and materials.

But I won't use these, I to the requirements of the quality of the very strict.

I'll in my products indicate the LJM letters. :drink:
 
New boards are updated

My later purchases of the L20D boards all come with 80v power caps and changeover to the bigger 2W resistors (3 per board).

My dc-coupled L20D approaches 200 hrs run in and seem to be still improving in sonics. Iirc ARC recommends 400 hrs or so on their Class D line which is IRS2092 based :)
 
OK, thanks.

I'm still very interested in the answer to these questions:

1. Is it correct that with +/-60V the L15D gives 150w/8R and the L20D gives 200W?

Perhaps the numbers approximate, or at different distortion?

2. At the same +/-60V, what are their idle power dissipations?

Thanks

In theory, the same voltage +-60 V.
Their output power will be the same.

But in +-60 V voltage and L20D will be more security. Not quite a higher voltage of the transistor and capacitors.
Also includes the resistance of the current size and power control.
 
True, the widerange speakers I stuck to my ear are 84dB/W, Peerless 830983, But they cover from 40Hz to 20K, as long as you don't want a lot of volume... and as long as you use a MiniDSP to equalize them :)

These days I myself would select a higher power, highly efficient amp (like the L20D) and a wider range, very low distortion, speaker :)

Still, 113dB/W is a pretty impressive achievement :)
.


Trevmar,

Can you point me to a thread that has the specs. on those PVC speakers you have in the photo.

I'd be interested in build a pair.

Thanks,

Allen ...
 
trevmar - Thanks so much for your testing and insight with the L20D amp and furthering this discussion and knowledge along. I'm just now reading this thread and others on the ljm class D design. As has been requested by a few other readers, it would be nice for someone to summarize what hacks/mods are essential, and what ones are so esoteric as to not make much of a difference in a typical listening environment.
 
Yesterday I assembled a double L20D in substitution of a T2.
The difference is audible, from my first impression beeing the TK2050 more "analytic"
or colder in the mid-highs than the IRS2092, the IRS2092 more "solid" or warmer in the mid-basses than the T2.

In the meantime I've put in place my old and faithful Denon SS amp and no, no comapraison, muddy bass and foggy stage.

My perfect setup would be a biamped system: a T2 for the tweeters (maybe with a waveguide), a couple of L20D to drive the woofers, all over an active Xover.
I think I've found my next project. Stay tuned.
 
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