Thread: Difference between these two TDA7850 amp

Hi, i was just wondering with the amp with denoiser. how would you hook up a heaphone jack to it? Im looking at hooking up a laptop. will this work ok? and can someone comment on the sound quality. thanx

Originally Posted by Alfredbra

Hi, i was just wondering with the amp with denoiser. how would you hook up a heaphone jack to it? Im looking at hooking up a laptop. will this work ok? and can someone comment on the sound quality. thanx

It's a 4 channel amp so you if you only have one headphone output, you can get a stereo headphone splitter. As far as hooking it up to a headphone jack - the amp comes with a 8pin JST connector with wires - you can see the pinout on the ebay post (note that the inputs are 1-2-4-3, for some reason). Just solder up those wires to a headphone plug and you'll be all set.

Originally Posted by TheMadTinker

I ordered the same TDA7850 with the DeNoiser Function you are showing last week, But I'm in Canada, and there is a looming postal strike, I don't know when I will receive it.
It shows coming with a heatsink and tube of glue, is this sufficient if mounted in the open behind the LCD in the dash?
Also, circuit board diagrams on the site show a standby a mute function, I have a M2-ATX with a line that is suppose to go to the amp to prevent popping, are you using either the standby or mute for this purpose?
Thanks

fyi the reason vin works is you're opening the transistor on the pins which control the stand by and mute. You can see your voltage gets applied to the gate of the transistor.

Originally Posted by nivanov

Hey! I did buy this amp on ebay and it does a decent job, and it doesn't get that hot. However, I found another amp on ebay on the same chip - search for "TDA7850 with denoiser". It has ground loop isolators onboard along with other noise suppressing circuitry. I'm not sure what the quality of it is, though - I just ordered it several days ago, so I should be getting it in about 2 weeks. It also costs $25 shipped, so I figured I'd give both of them a shot.

For the amp you have listed in this thread, I recommend you get a northbridge heatsink and thermal-epoxy it to the chip. I used Arctic Silver epoxy and it works really well. One thing though - make sure the amp and the heatsink fit OK - that epoxy is permanent

EDIT: Here's a pic of the other amplifier:

Hey I wound up with the same TDA7850 with denoiser, how in the world did you connect that 8wire input to motherboard? any advise would be greatly appreciated

Originally Posted by mikemui128

Hey I wound up with the same TDA7850 with denoiser, how in the world did you connect that 8wire input to motherboard? any advise would be greatly appreciated

Take a look at this post on my build. Basically, the 8 wires you get are In1, Ground, In2, Ground, In3, Ground and In4, Ground. They correspond to 8 output channels - Out1, Ground, Out2, Ground etc. Basically, you can use:

Input 1 - Front Left
Input 2 - Front Right
Input 3 - Rear Left
Input 4 - Rear Right

...in a 4 speaker configuration, and make sure outputs go to appropriate speakers in your car. So in other words, you use 2 headphone jacks, as you can see in my picture. If your motherboard only has 1 output, you can merge Input 1 and Input 3, and Input 2 and Input 4, so both Front Left and Rear Left speakers will play the same sound, same as Front Right and Rear Right. If you do that, you only need 1 headphone jack, and you would just plug it in directly into the motherboard. Alternatively, you don't merge inputs, and use a headphone splitter from radioshack that would essentially do the same thing.

Thanks thats perfect info, hate to sound stupid but my m2-atx-hv didn't have instructions, on j6 pins it says amp remote and ground, is this the ports that plug in power to the tda7850, if it is, why didnt they just call the ports amp power?

Originally Posted by mikemui128

Thanks thats perfect info, hate to sound stupid but my m2-atx-hv didn't have instructions, on j6 pins it says amp remote and ground, is this the ports that plug in power to the tda7850, if it is, why didnt they just call the ports amp power?

No, Amp remote is a trigger wire that turns the amp on and off to prevent amplifier thump. This amplifier can be powered from an unregulated 12V source, like your ACC line.

Originally Posted by nivanov

No, Amp remote is a trigger wire that turns the amp on and off to prevent amplifier thump. This amplifier can be powered from an unregulated 12V source, like your ACC line.

Thanks Nirmov, you have been great help.

2 last questions,

Only because Im not great at soldering and splitting wires, can I just cut the 12v and ground from a Molex thats connected to the m2-atx to power the tda7850? wouldnt that work and also not require a relay because the m2atx would power the computer first, if I still need a relay, where did you get the relay for the amp?

Thanks again

Originally Posted by mikemui128

Thanks Nirmov, you have been great help.

2 last questions,

Only because Im not great at soldering and splitting wires, can I just cut the 12v and ground from a Molex thats connected to the m2-atx to power the tda7850? wouldnt that work and also not require a relay because the m2atx would power the computer first, if I still need a relay, where did you get the relay for the amp?

Thanks again

Damn, that's the most anybody has ever mangled my username

Yes, you could certainly do that. In fact, using a regulated 12V line is better than unregulated. However, you need to look at the total power consumption. I've put a 5A fuse on the amp line, and it hasn't blown, so it's safe to assume the amp will use less than 60W (12V * 5A). M2 can give up to 140W, so that leaves you with 80W. If the rest of your system can be safely powered by that, I'm sure you'll be ok. I wouldn't push the power supply to its limit though.

You might or might not need to use a relay - it really depends on your hardware. I used a relay because when the AMP was powering up, it would make a loud static hiss noise that would go away in a second. Because of that, I made sure to start it muted, and then unmute it by using a USB-controlled relay. You can find that relay on ebay - just type in "usb relay".