Folsom's great little 7297 Chip Amp

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Nahuelitsn

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Re: Folsom's great little 7297 Chip Amp
« Reply #1360 on: 20 Mar 2021, 03:48 am »
I will Folsom!!I will !!! :lol: :lol: :lol: :lol:

Thanks for everything!!

vilding

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Re: Folsom's great little 7297 Chip Amp
« Reply #1361 on: 22 Mar 2021, 03:19 pm »
Hi again!
The amp is running smoothly and keeps remarkably cool with the 86-87db 6ohm speakers that are plugged in at the moment.
However, I have a slight ground hum.  You hear it when you're within a little over a foot from the speaker. Would you guys look at my layout and see if there are any obvious mistakes there? Or other ideas?


Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1362 on: 22 Mar 2021, 06:23 pm »
Wiggle all your IC's to make sure there is not change. A disconnected ground is a sure way to get a hum.

vilding

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  • Musician. Audiophile on a budget.
Re: Folsom's great little 7297 Chip Amp
« Reply #1363 on: 22 Mar 2021, 10:58 pm »
Ok, so I've been crawling around on the floor, wiggling, reconnecting, changing cables and swearing  :lol:
With just the phone plugged in to the amp, it's dead silent. The biggest cause of noise seem to be the dac, or it's power supply. When everything else is plugged in (dacs ic's still connected to preamp) and I pull the wallwart for the dac, almost all noise disappear. This kinda sucks since my listening is probably 75% through that thing.  :cry: Any ideas..? Been trying to read up some on grounding but don't really know what to make of it.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1364 on: 23 Mar 2021, 12:17 am »
So a loop is forming through the DAC.

Does the DAC have a 3 prong?

vilding

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  • Musician. Audiophile on a budget.
Re: Folsom's great little 7297 Chip Amp
« Reply #1365 on: 23 Mar 2021, 10:27 am »
No, it's a two prong double insulated little wallwart.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1366 on: 23 Mar 2021, 12:13 pm »
You could try this on the amp's ground between the socket and chassis. It'll reduce common mode noise, and ground noise.

You can test if it'll work by disconnecting the ground temporarily.


vilding

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  • Musician. Audiophile on a budget.
Re: Folsom's great little 7297 Chip Amp
« Reply #1367 on: 24 Mar 2021, 09:52 am »
Thanks! Will try but it'll have to wait until I need some more stuff from Mouser, or it will be one expensive little coil.  :icon_lol: I'm gonna try and troubleshoot using the guide from DIYA-member Bonsai. Simple enough even for me...  :P Listening to some Chris Potter on vinyl rn and the amp is dead quiet between tracks and sounds scary good.

SGI

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Re: Folsom's great little 7297 Chip Amp
« Reply #1368 on: 30 May 2021, 07:04 pm »
Anyone has another 7297 amp board / antipole board for sale?  My friend just built mine and he was testing it out w/o even fully broken in and now wants one!  :)  Please PM me or email me if you do have one.  Thanks!

Terry U

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Re: Folsom's great little 7297 Chip Amp
« Reply #1369 on: 10 Jun 2021, 09:09 pm »
I have a kit for a complete 7297 amp minus the case that I am looking to move on.  I do not want to separate the boards however.  Might you be interested in this.   terryu55@comcast.net

drew_t

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Re: Folsom's great little 7297 Chip Amp
« Reply #1370 on: 7 Apr 2022, 02:56 am »
I finished my build a couple of years ago at least. It's alternated between sitting on a shelf unused and being hooked up to one of my computers -- most recently the latter,  powered up for at least a few months 24/7. I noticed that the power LED was off yesterday. I checked the fuse, saw that it was blown, put in another one, turned it on, the power LED lit up, but I immediately heard a "zzzzttt" sound that lasted about a second, and the LED slowly faded out. 

I have never pushed this amp even remotely hard; it has not been exposed to power surges; it has not been dropped, gotten wet, or anything like that.  There are no scorched wires, burned components, leaking caps, bad smells, or anything else obviously amiss.  The power transformer is one of whichever Antek toroids were recommended. The fuse (same one that has been in it from the start) is a 1.6 amp one. I used one of the combination IEC socket/power switch/fuse holder deals (I know, I know, it's not a boutique audio-type part) and built the amp in an old computer case. 

Any ideas what the issue might be?  Could the Antek have just crapped out?  Should leaving the unit powered up for an extended period of time with the sound source (computer) asleep have done any harm?


lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #1371 on: 7 Apr 2022, 10:09 pm »
I suspect the IEC socket/power switch/fuse holder. Try disconnecting the Antec toroid from it's primary and secondary and power the primary with a different 120v source power cord, then check it's secondary output voltage (16-18v).

ctviggen

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Re: Folsom's great little 7297 Chip Amp
« Reply #1372 on: 23 Apr 2022, 07:30 pm »
Are these still for sale?  If so, where?

EJHickert

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Hi there! I have just joined Audiocircle and heard about this great little chip amplifier from GR research. I have searched on google for the circuit designed by Folsom with no success.

I would really appreciate it if someone could point me to the right location where I can purchase the circuit board and a really good power supply to run it.

Thank you in advance!

Eric

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1374 on: 14 May 2022, 10:11 pm »
Sorry I don't have any boards.