Folsom's great little 7297 Chip Amp

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rtate

Re: Folsom's great little 7297 Chip Amp
« Reply #1000 on: 6 Dec 2017, 12:31 am »
Yes , there are slots below and the cove is completely vented as well.
I built 2 identical amps just because they were not very expensive and I just like to build stuff.
I have lined the inside of the chassis with duct seal just to deaden it a bit. I will take more pictures later.

I repurposed the heatsinks from some equipment at work. I have had the amp on for about 6 hours and the heat sink still feels like room temperature. Although I am in the garage and it is cooler out here.

Is there a circuit drawing of the amp out there that I could look at ?
I really would like to see what is causing the hum.

Once again  a Big Thanks to Folsom for putting this out there for us !!

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1001 on: 6 Dec 2017, 01:16 am »
It's just from an incomplete circuit. At that point it is very vulnerable to outside fields like 60hz. With interconnects attached you just have bigger antennas when the circuit isn't complete. Don't worry about it.

Check out the TDA7297 data sheet. There just isn't anything in particular. As long as you followed my instructions for isolation, you're all good.

mlundy57

Re: Folsom's great little 7297 Chip Amp
« Reply #1002 on: 17 Jan 2018, 01:15 am »
The BOM calls for .022uF by-pass caps on the input caps. Would other values like .01 or .047 work? If so, what would the trade offs be?

Mike

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1003 on: 17 Jan 2018, 11:01 pm »
Any will work. I wouldn't call any a "trade off" exactly. The value of the capacitance only ultimately matter in the sense that the total amount needs to be high enough to not cut off bass. Once you're there it doens't matter if you have 2 million uf or just 2 uf.

But what you can do is calculate the corner frequency to see where the bypass capacitor will effect. The R value is 25k - 30k, you can try both. The 7297 chip lands somewhere in that range.

mlundy57

Re: Folsom's great little 7297 Chip Amp
« Reply #1004 on: 17 Jan 2018, 11:58 pm »
I’m wondering about the value of the by-pass caps that go under the board.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1005 on: 18 Jan 2018, 10:01 am »
They are in parallel to the ones on top. The capacitance is cumulative. Signal will be split between the two except where one has rolled off and the other has not.

mlundy57

Re: Folsom's great little 7297 Chip Amp
« Reply #1006 on: 18 Jan 2018, 01:48 pm »
Ok. Thanks

WC

Re: Folsom's great little 7297 Chip Amp
« Reply #1007 on: 21 Jan 2018, 06:01 pm »
Is there an issue with only using the 7297 to power one of the two channels? I am building way more amps than I have speakers to power, so I was thinking of using only one channel of a stereo amp to power my center channel. Wasn’t sure if the amp would have an issue with it.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1008 on: 21 Jan 2018, 07:07 pm »
That's fine. You can also connect it so both channels provide their current, to the single signal.

zek

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Re: Folsom's great little 7297 Chip Amp
« Reply #1009 on: 21 Jan 2018, 08:26 pm »
That's fine. You can also connect it so both channels provide their current, to the single signal.
And how to connect speaker terminals - in parallel (L+ and R+, L- and R-)? :?

WC

Re: Folsom's great little 7297 Chip Amp
« Reply #1010 on: 21 Jan 2018, 09:07 pm »
Ok, can you send the + and - from a balanced signal to the amp and combine the speaker outputs to get a single channel output to the speaker?

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1011 on: 21 Jan 2018, 10:15 pm »
Yes the speaker outputs go in parallel. The inputs would be too, but you can use only one set of caps if you tie the channels together after the caps. (look carefully, may not be the holes your think)

 Not sure what you mean balanced signal to the amp, it cannot take balanced inputs.