IRS2092 cheap

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Kjeldsen

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#1
#3
For a few shekels more...

You could buy some allegedly genuine L25D's which at least look like the pair I just installed in some dead B&K amps from here:

Assembled mono L25D Power Amplifier board IRS2092 IRFB4020PBF (one channel)-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group

The amps arrived <way> ahead of schedule - taking just 4 days via Canada Air Post, where packed as if they expected someone's sadistic uncle to give them the 'Fragile' treatment - and, amazingly enough they both came up flawlessly with less than .05 V DC offset, and appear to be running in quite happily on +/- 65VDC from the B&K's stupidly oversized, but fairly unsophisticated. linear power supply.

For the money, these are fairly decent little modules, they seem to have few vices, where painless to install, and promise much more than I expected.

Cheers

Jim
 
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#4
A quick sub-note, on moderately efficient speakers (Mission 771, about 88dB/1w) I can hear some white noise at about 2" from the woofer with these amps.

This is acceptable for my uses, but if you've 90 dB efficient speakers, this background might be an issue.

Jim
 
#6
FLASH! Martian-Logans nuke L25D

Dr Jim said:
A quick sub-note, on moderately efficient speakers (Mission 771, about 88dB/1w) I can hear some white noise at about 2" from the woofer with these amps.

This is acceptable for my uses, but if you've 90 dB efficient speakers, this background might be an issue.

Jim
Click to expand...

A follow-up report - after 6 months of pretty hard use driving a pair of modified Martin-Logan Sequel II panels both L25D amps began to go into what I believed at the time was overcurrent protection mode at relatively low power levels - measured 92dB @1 meter running REW sweeps

The symptoms were a sudden loss of output on one channel, the amp's blue LED would flicker briefly and then the signal would return on the affected channel.

Both of the panels have been modified for use with external crossovers, so I band-aided the problem by using external 50W non-inductive resistors to increase the panel's static resistance to 3.8 ohms or roughly 5 ohms impedance.

This 'fix' allowed for significantly more headroom - enough that I saw no reason to try to find the new protection event levels - the panels played more than amply loud enough.

I would have continued bumbling along fat, dumb, and happy, but I scored some of Rod Elliot's very decent P101 amp modules from a DIY user and decided to shift the L25D's away from the very reactive electrostatic panels down to drive the 18" Eminence Sigma woofers in our floor-mounted infinite baffle manifold and use the P101's to drive the panels.

The P101's drove the M-L panels quite nicely, are very quiet, and give the panels an ethereal delicacy that the L25D's lacked.

OTOH, the L25D's were unlistenable on the efficient (99dB 1w/1m) Sigma 18's - I expected some white noise, but with the woofers in the floor behind a couch, thought it would be inaudible.

What was VERY audible was the 400mv of roughly 120Hz ragged sine wave coming from one of the amps - looked at grounding and install issues, pulled the amp and ran it on two different power supplies - one linear, one SMPS.

Same result, even with a 20K resistor across the input and an 8 ohm dummy load on the output it still showed this odd-looking waveform.

My hunch is that I've either cooked the inductor (the board underneath looks a bit toasty), punctured a cap, or possibly damaged an IRFB1420 - because the protection circuit kicks in at pretty low levels(e.g. less than .5 volt drive) if I use a 4 ohm dummy load.

So, it looks like even moderate use with reactive 4 ohm loads can possibly cook one of these amps - I'll dig a little deeper over the next few days and see what I find.

Cheers

Jim
 
#7
I think we are talking about the same amp as in this thread?

http://www.diyaudio.com/forums/class-d/275915-200w-irs2092-amp-20-a.html

So far, my experience has been very positive. Sounds very clean and can drive 95dB sensitive pro audio speakers to some insane loudness levels for home use.

The trick is to find a low cost dual rail power supply, which this Abletec for $20 in the US with free shipping from PE (for >$100 orders or $6 otherwise) seems to provide. One of these supplies can power two of the monoblocks, so for $60 you have a stereo 200w/ch amp that sounds quite clean.

https://www.parts-express.com/ablet...-14a--53v-at-14a--75v-at-16a--56v-1a--129-147

Also available via eBay at

http://www.ebay.com/itm/251804683031
 
#8
#10
irribeo said:
For use with MartinLoganlike load you'll need other mosfets, if I read referencedesign correctly with 4020 only 8 ohm stable.
Click to expand...


I recalled it was mentioned in some threads some time ago that this amp is not suitable to drive loads that have large variation of impedance. The LJM design (your amp) is basically the IRAUDAMP7, which was "supposed" to drive 8 ohm load. However, in LJM's web store, the output power at 4 ohm was also listed - implying that the amp is stable at 4 ohm.

Regards,
 
#12
I don't feel like IRAUDAMP7 cannot push loads of 4ohms. i built IRAUDAMP7D and it gives out more than 500watts in bridge mode (@ 8ohms) clean without any hiccups. output is clean sine wave. only thing is i have used t106-2 cores for output filter and i have no heating issue of output inductor. i tested the board on 10hz freq and after the rated output the amp goes on protection mode. all test were done on a resistor load.
 
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