I removed the heatsink on my amp and yes, it is just a metal plate on show, no marks. No paste was used so no mess.
If you use the terminal block input terminals, then you bypass the 0.7uf input caps. No caps via this input..
There seems to be a constant background hiss from all channels, at all volume settings. I have tried different power supplies and it is still there..I dont think, IMHO, it is going to be a "hifi amp"
..
If you use the terminal block input terminals, then you bypass the 0.7uf input caps. No caps via this input..
There seems to be a constant background hiss from all channels, at all volume settings. I have tried different power supplies and it is still there..I dont think, IMHO, it is going to be a "hifi amp"
..Ouroboros said:
No such luck. Mine finally came today, so off went the heatsink and then on to desoldering the pins.
Here is what it says on the underside of the chip:
SDA-754
SS 07 08 31 15: 09: 25 5128
AC/HOT OK JUN SUN OK
My guess is that it is a module made for them by Monolithic Power. Sure-electronics has an amp board with the MP7220, and this looks like it could be a module made from 4 MP7782's. The MP stuff uses a single supply with analog input, and MP is one of the few that provides that combination.
I got the amp back together and hooked it up to a 12V supply to start out. The switching frequency is fairly high--up around 450KHz. That's higher than what Philips uses and less than Tripath, but it's in the range that MonolithicPower uses (400KHz-600KHz).
There's a fair amount of constant "hiss" in all channels that is probably due to the high gain of the module. I haven't measured the gain, but it doesn't take much input to saturate the amp. I tried bridging one of the 56K resistors with another 56K to cut down the gain, but it didn't seem to make any difference in the hiss. It's typical amplifier noise, but definitely more than what you hear from an LM3886 amp with Av=20. Shorting the input to ground doesn't make it go away, and it doesn't seem to be from the power supply (additional capacitance didn't help). The hiss level is different for each channel...hmmm.
I measured one of the output coils--looks like 12uH.
I'll give the amp a workout with real speakers later on, but based on what I've heard so far I expect the quality to be good.
There's a fair amount of constant "hiss" in all channels that is probably due to the high gain of the module. I haven't measured the gain, but it doesn't take much input to saturate the amp. I tried bridging one of the 56K resistors with another 56K to cut down the gain, but it didn't seem to make any difference in the hiss. It's typical amplifier noise, but definitely more than what you hear from an LM3886 amp with Av=20. Shorting the input to ground doesn't make it go away, and it doesn't seem to be from the power supply (additional capacitance didn't help). The hiss level is different for each channel...hmmm.
I measured one of the output coils--looks like 12uH.
I'll give the amp a workout with real speakers later on, but based on what I've heard so far I expect the quality to be good.
I am also slightly interested in maybe getting a couple of these for a quick and easy home theater amp. The hiss mentioned, is it quite noticeable? Or is it something more along the lines of what you would here from an off-the-shelf reciever (like pioneer, sony, yamaha, etc)? I'm not looking for the holy grail, just something thats 4ohm stable for not too much cash.
Hello, I have one of the 2 channel modules coming and Sure said in a reply yesterday that a new batch is being built and will ship asap.
Question for anyone....would a 24v 6a laptop barrel connector power supply be adequite in both powering and connecting?
Looks like a DC female barrel jack on the board.
Thanks
Question for anyone....would a 24v 6a laptop barrel connector power supply be adequite in both powering and connecting?
Looks like a DC female barrel jack on the board.
Thanks
Not all connectors that look like that are the same size. However, the one this takes is one of the most common sizes.
And the package included a connector if you're willing to splice the wires to it. See the photos.
6A is plenty.
The 24V might be fine, the question might be how well regulated the power supply is, since voltage can fluctuate well above the stated voltage on some; and what the real max voltage on the amp. Personally, I'd try it, but ....
The most important thing - make sure the polarity is center positive. That's most common, but not always the case.
And the package included a connector if you're willing to splice the wires to it. See the photos.
6A is plenty.
The 24V might be fine, the question might be how well regulated the power supply is, since voltage can fluctuate well above the stated voltage on some; and what the real max voltage on the amp. Personally, I'd try it, but ....
The most important thing - make sure the polarity is center positive. That's most common, but not always the case.
I would think that more voltage = more gain. What the relationship is, and how it affects distortion, I wouldn't know. That is, is the max voltage also going to push you into an area where the distortion is more than you want?
I'd also appreciate hearing from someone who knows (ie, not me), because I'm wondering if one way to manage the hiss/noise on this would be to use lower voltage if I'm not needing all the gain it's capable of. Less gain would let me increase the signal (to achieve the same comfortable listening level) and hopefully improve the signal to noise.
I spent another half hour or so listening using a 14V supply. On a bad source it magnifies every flaw (eg, a desktop computer with a very good but inboard sound card that picks up a lot of noise). Other sources (eg, mp3 player) were pretty clean on some music, but less so on others. Haven't sorted that out yet - by comparing the original on other gear, for example.
Not sure if it would matter but - I have it hooked up as 2 channel, channels 1 and 4, haven't tried any other combination.
Noticed that I have version 1.1 of the board, not 1.0 as shown in the PDF. Only obvious difference I saw was that the output channels are re-ordered (1 is where 4 was).
I'd also appreciate hearing from someone who knows (ie, not me), because I'm wondering if one way to manage the hiss/noise on this would be to use lower voltage if I'm not needing all the gain it's capable of. Less gain would let me increase the signal (to achieve the same comfortable listening level) and hopefully improve the signal to noise.
I spent another half hour or so listening using a 14V supply. On a bad source it magnifies every flaw (eg, a desktop computer with a very good but inboard sound card that picks up a lot of noise). Other sources (eg, mp3 player) were pretty clean on some music, but less so on others. Haven't sorted that out yet - by comparing the original on other gear, for example.
Not sure if it would matter but - I have it hooked up as 2 channel, channels 1 and 4, haven't tried any other combination.
Noticed that I have version 1.1 of the board, not 1.0 as shown in the PDF. Only obvious difference I saw was that the output channels are re-ordered (1 is where 4 was).
buzz1939 said:
Thanks... I may pick up the 24V supply then...
I think 2x12v batteries in series would be a bad idea, as fully charged they are around 14v, and 14+14 = 28v, which is too much voltage for this amp...
I guess I could wire in 3 diodes in series with the power cable, which should give 2.1v voltage drop... but I think it would be much less hassle running it straight from the 24v PSU.
Running it from a 12v battery would be good for in the car tho, or even in a portable boombox... I guess class D is ideal for portable us as it's very efficient.
Anyway, I'm rambling on now, I just have a quick question about bridging this amp...
Say I'm powering 2 x 4 ohm subs, and wire them up so they are bridged, would I have to input a signal just on channels 1 & 3, or would I have to supply an input to all 4 channels?
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