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Old 11th June 2006, 01:47 AM   #1
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Default Cheap Gemsound Amplifier

Hey, I recently purchased a cheap gemsound amplifier on ebay. It works decently however, when there is a constant noisy hiss in the background. Is this just from cheap parts used or is it faulty? The music sounds good (Not Super High Quality).

I say noisy hiss becasue its not like a regular hiss it almost sounds as if the hiss was encoded to a really low qualty Mp3 and them played back.

If this is just cheap components is there any thing i can do to reduce it of make it less noticable? (Circuitry or AC filter)?!? I'm kind of new to this topic... but fimilair with audio...

Any help would be greatly apreciated. (model number is EXA3950)
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Old 11th June 2006, 11:06 PM   #2
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I have been doing some research on google and found some posts where people say that gemsound uses cheap (thus noisy) components.

Am i correct in assuming that, there is no resonable cheap way of fixing this?
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Old 22nd June 2006, 01:48 AM   #3
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Can anyone give me any advice on this??

Could it be as simple as adding a DC filter or perhaps a different power supply?
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Old 22nd June 2006, 02:08 AM   #4
anatech is offline anatech  Canada
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Hi sound_prodigy,
I'm guessing no one is familiar with it. Do you have a manual or schematic. Finding one may get things started for you.

Also, do you have an oscilloscope? Does it run warm / hot? It may be oscillating.

-Chris
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Old 23rd June 2006, 06:04 AM   #5
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no experience with them directly, but i see their stuff at radioshack all the time. a house brand, i assume.

i would start with a major power supply upgrade. how good can the PSU really be at the prices i've seen their stuff for new? not very. beef up capacitance and add some bypass caps. for upgrading typical consumer midrange stuff i just use cheap RS mylar caps and they do the job pretty effectively.
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Old 23rd June 2006, 02:02 PM   #6
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Hey,

Thanks for the input. I will try and do some testing. I have attached a schematic... it is not very clear I'm not sure what good it will do. I have emailed them asking for a higher resolution copy which I will post if I get it.
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File Type: jpg exa-3950.jpg (87.6 KB, 1527 views)
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Old 23rd June 2006, 02:18 PM   #7
Wynand is offline Wynand  South Africa
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I think I've read that metal film resistors are better than carbon resistors, at 0.06 cents each thats a cheap swap.
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Old 23rd June 2006, 02:56 PM   #8
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here are some pictures from within the amplifier.... the power supply looks to be extream bottom of the line.

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Old 23rd June 2006, 05:56 PM   #9
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i don't have an osciloscope. But if the amp were oscilating wouldnt the output be weak?... I have an unrepairable marantz 510m, Missing one of the main drive chips, would the preamp or possibly the power supply from it be any use to me? I am going to check the outputs on the power transformer, but if anyone already knows what they are that would be extreamly helpful.
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Old 23rd June 2006, 06:57 PM   #10
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Default gemsound amp

This thing looks better then I thought it would! Looks to be a true 160 to 200 watts per channel, and probably about 350 to 400 bridged, by the outputs and transformer rateings.
Rewire the thing, get the signal line from the power lines, get read of all that AC line sitting on top of the right amp board ect....
looks like typical cheap construction, look for resistors in the low signal line that are sitting with an extra inch of lead length on the output boards, stuff like that, then look at 1% metal film in critical circuit areas, it a straight forward design no surprises.
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