Folsom's great little 7297 Chip Amp

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AKLegal

Re: Folsom's great little 7297 Chip Amp
« Reply #1340 on: 21 Dec 2020, 06:06 pm »
That will not work because the outputs are balanced of the 7297. You can't combine them.

One could do this with four of your 7293 boards correct?

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1341 on: 21 Dec 2020, 08:44 pm »
I would not go as far as to make a claim that something could be possible that is untested thus far... (and if possible how much modification it would take)

The easier thing to do is just use an input transformer that turns balanced to single ended, and eliminates the need for an input capacitor.

AKLegal

Re: Folsom's great little 7297 Chip Amp
« Reply #1342 on: 21 Dec 2020, 11:02 pm »
Thanks.  I'm not really interested in further modding my amp anyway.  Just trying to learn a bit more.

vilding

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Re: Folsom's great little 7297 Chip Amp
« Reply #1343 on: 23 Feb 2021, 04:16 pm »
Ok. So i put the amp on a board, went over all joints and connections and all seemed fine and it made the music. Happy moment! :)

I then moved the amp to a new case, connected everything and started listening. It held up fine and sounded great at low levels for maybe two hours. At that point I turned it up a bit, maybe halfway on the pre, and it started to distort badly, then flail back and forth between distorted and quiet music and after maybe ten seconds of this going silent. No more music... The chip was cool to the touch. One of the resistors (big one) was a little warm but nothing bad. I measure 22.4 vdc in to the amp, zero volts at speaker output. No speaker posts or connectors touch the chassi.
I'm starting to give up on this DIY thing at this point... :´(


So I almost gave up and did other stuff for a while, after being quite discouraged by the struggles of amp building. I still have the big EC7293 waiting for me as well...  :o

I´m posting a few pics. My suspicion is that I might have fried a transistor or so, but I´m not sure how to measure for it. My biggest scare is that I somehow damaged the chip, which would really, really suck. I'm hoping for you guys experience and patience to help med put this together. :)
Cheers!









Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1344 on: 23 Feb 2021, 04:50 pm »
Where are the two capacitors that go next to the DC input?

vilding

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  • Musician. Audiophile on a budget.
Re: Folsom's great little 7297 Chip Amp
« Reply #1345 on: 23 Feb 2021, 05:33 pm »
Feeling stupid now, but were they not optional for rf screening, or have I burnt my chip to crisp....  :|

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1346 on: 23 Feb 2021, 05:37 pm »
Sorry, what are symptoms again?

They are not optional.

Can you see a gap between all the chip pins? It's pretty hard from the pictures to tell.

BTW I can't reply to noreply emails. My email is folsom.jeremyh@gmail.com

vilding

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  • Posts: 98
  • Musician. Audiophile on a budget.
Re: Folsom's great little 7297 Chip Amp
« Reply #1347 on: 23 Feb 2021, 05:42 pm »
Ok. I'll mail you. :)
No, there are no solder bridges. It looks a little messy but thats mostly flux... It played for a few hours on low volume, and when I turned it up, it started to distort badly and then went real quiet fo a few secs before it went silent.