There is no op amp under the heatsink that I can see from peering underneath with a flashlight. Are you saying that it is internal to the 2092 and is behind an input cap and probably a value of 3.2k? Why have a 100k resistor on the input then? Just to drain things? Once I get the proper +/-52v power supply I will test it and compare signal out vs v input.
There's an 'OTA' (like an opamp but with a current output) inside the IRS2092 and that's being operated just like an opamp in inverting mode. With an inverting mode opamp the input impedance is determined by the input resistor - that's normally 3k3, there's also a cap in series with this to give roll off at LF.
So yeah I rather suspect the 100k you measured is a drain resistor for the input coupling cap.
Assuming that the impedance is as shown in the application circuits (3k3) then those using an opamp to drive it will probably benefit subjectively from biassing their opamp into classA with a current source on the output. Or using a discrete classA buffer.
So yeah I rather suspect the 100k you measured is a drain resistor for the input coupling cap.
Assuming that the impedance is as shown in the application circuits (3k3) then those using an opamp to drive it will probably benefit subjectively from biassing their opamp into classA with a current source on the output. Or using a discrete classA buffer.
You cant tell by looking if components are quality or not.
A lot of fakes look just like originals.
The only way to get quality is to buy from top quality vendors.
Forget ebay and Chinese sources and buy from RS and Farnell.
Here though we're talking about a built up PCB, not components. So do RS and Farnell sell stuffed, working classD amps?
It would be useful given that you mention amps blowing up due to poor components to have links to those instances so we can all see the details - then we may get an idea of vendors to avoid, and which failed parts to pre-emptively swap out.
It would be useful given that you mention amps blowing up due to poor components to have links to those instances so we can all see the details - then we may get an idea of vendors to avoid, and which failed parts to pre-emptively swap out.
wonder how it and the ps compare to a nu1000? (I'd trust the little XLS moreso than the inuke) Behringer iNuke NU1000 Amp Amplifier Fan Swap How To w/ PICS - Page 12 - Home Theater Forum and Systems - HomeTheaterShack.com
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I have bought about a dozen cheap Chinese amps, none have blown up. All have actually worked well and sounded quite decent, and sometimes sound better with an upgrade in stock power rail electrolytics swapped for Panasonic FM's or OSCON's. When input coupling caps are poly films or SMT's I leave them alone. I have swapped them in the past and have not been able to tell a huge difference. We will see how these fare as they are my first "high power" amps that are well above the 50watt range.
Certainly a Crown XLS or iNuke will be better quality in general, although, they too are made in China. But for $19, I am not going to complain about quality. The visual quality is quite extraordinary for a $19 cheap Chinese PCB in fact.
Certainly a Crown XLS or iNuke will be better quality in general, although, they too are made in China. But for $19, I am not going to complain about quality. The visual quality is quite extraordinary for a $19 cheap Chinese PCB in fact.
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I have a pair on the way now - 88rmb each plus 10rmb shipping.
IRS2092´ó¹¦ÂÊ·¢ÉÕ¼¶ÒôÏìµ¥ÉùµÀdÀàÊý×Ö¹¦·Å°å³ÉÆ· 200WºÃÒôÖÊ-ÌÔ±¦Íø
IRS2092´ó¹¦ÂÊ·¢ÉÕ¼¶ÒôÏìµ¥ÉùµÀdÀàÊý×Ö¹¦·Å°å³ÉÆ· 200WºÃÒôÖÊ-ÌÔ±¦Íø
Is that a similar strategy to what's being done with the opamps in the tda1387 x8 DAC?
And I assume if your upstream component (DAC, preamp, dedicated buffer) does something like this, you don't need to do it again in the amp?
I first started dipping my toes into DIYAudio a few years ago with IRS2092 amps from Class D Audio. There's a huge thread about these over on AudioCircle: $175 Class D amp--120 wpc. Of course the Chinese boards are even cheaper (but are they just as cheerful?
).I had two of the SDS-470 amps, which is the highest-powered one (600 WPC at 4R). Heat was an issue when I jammed the amp board in small case with a Connex SMPS800R PSU. A bigger/better heatsink plus moving into a bigger case (with better ventilation) seemed to fix the heat issues.
I sold both of them. One was a spare, the other was used in my living room as my main amp. I replaced it with DUG tpa3116 dual mono boards. This isn't my critical listening rig, so I didn't do any real A-B comparison. My goals were something physically smaller, more power efficient, and less heat production. A success on all counts, and I didn't notice any obvious change in sound quality (but again, I didn't spend a lot of time looking for differences).
Anyway, back to the original topic: attached is a close-up pic of the input side of the Class D Audio SDS-470 amp board. Not the best picture, but maybe enough for keen eyes to get an idea of how the "state of the art input stage" is implemented. This picture was taken from my AudioCircle Gallery; there's some other pics in there that might be of interest.
If anyone wants, I can look through all my photos at home and see if I have any better pictures of this amp module.
Attachments
Yes - though there the current source bias current is determined by the DAC chips' output current (8mA in total). Here its determined by the maximum current required into the 3300R load (which will be lower, around 1mA since it has 1VRMS input sensitivity).
Right - if your output buffer can cope with the low impedance load in classA, no need for further buffering or adding a CCS.
I have been thinking of getting a pair of IRS2092 amps andhave my eyes set on this
L20D ¶¥¼¶Êý×Ö¹¦·Å³ÉÆ·°å 200-250W *2 8Å· IRAUDAMP7 IRS2092-ÌÔ±¦Íø
Yes it costs 46 RMB more (< 8 US$) for a pair, but it is a proven board by LJM and a number of people on this forum have provided favourable reviews on this board. Interestingly, no SMD (I think) all through hole components.
Regards,