Folsom's great little 7297 Chip Amp

Folsom · « **Reply #1240 on:** 23 Sep 2019, 10:23 pm »

Quote from: DeeJayBump on 23 Sep 2019, 05:30 pm

What size screws/bolts should be used for mounting the PCB? And what kind + size board standoffs?

Thanks.

I use M3 for everything.

DeeJayBump · « **Reply #1241 on:** 24 Sep 2019, 12:22 am »

Quote from: Folsom on 23 Sep 2019, 10:23 pm

I use M3 for everything.

Thanks.

jonny5 · « **Reply #1242 on:** 18 Oct 2019, 06:24 pm »

I'm a longtime tinkerer with electronics and audio gear, but this is my first full solid state build.

Everything is still burning in, but to echo prior comments, it sounds fantastic.

#4 screws work just fine as an alternative to M3 screws - I used #4 for little stuff and larger screws for any part of the build that didn't require screws that small.

The cheap W226.5×H70×D271mm case on eBay makes a fantastic case for the build:
https://www.ebay.com/itm/252579253474

Pics with the build in that case are below.

Folsom · « **Reply #1243 on:** 19 Oct 2019, 02:52 am »

Very nice.

uncola · « **Reply #1244 on:** 19 Oct 2019, 07:32 am »

That’s an awesome looking amp... so compact yet neat

jmc207 · « **Reply #1245 on:** 19 Oct 2019, 12:28 pm »

Quote from: uncola on 19 Oct 2019, 07:32 am

That’s an awesome looking amp... so compact yet neat

Yes, awesome, and almost like it's been vacuum-packed.

lacro · « **Reply #1246 on:** 19 Oct 2019, 04:32 pm »

Very nice work!! The case you used is similar to the one we used to build Peter's amp, but different dimensions. The price is right for either one especially considering you don't need to buy a heat sink. BTW/ what input caps/bypass caps did you use?

rollo · « **Reply #1247 on:** 19 Oct 2019, 05:42 pm »

Looking good. Yet to hear one however people who have liked it.

charles

jonny5 · « **Reply #1248 on:** 19 Oct 2019, 10:29 pm »

Jantzen Z-Superior caps with Miflex KPCU copper foil bypass caps was what I decided. With the layout, size of capacitors was potentially limited, haha.

I originally had doubts that I could find a cover that could fit the Antek 1218 transformer yet had adequate clearance for the layout in the case. Once I had all the parts in hand, it looked like a 120x57mm toroidal transformer cover would just barely fit and do the job.

Peter J · « **Reply #1249 on:** 20 Oct 2019, 03:24 am »

Well done!

mresseguie · « **Reply #1250 on:** 20 Oct 2019, 06:42 am »

Jonny5,

That internal shot sure is nice looking!

Question: Is there an advantage to using a toroidal transformer over another transformer? My Folsom's chip amp uses 'another', but I don't know what to call it.

Michael

poseidonsvoice · « **Reply #1251 on:** 20 Oct 2019, 02:09 pm »

Jonny5,

Great work

. I like the shielded toroid as well. The stainless steel shielding minimizes noise from the toroid. Hopefully it came with electrostatic shielding to minimize capacitative coupling from the primary to secondary which you should connect to chassis ground.

Nearly all my builds use a stainless steel toroid cover plus electrostatic shielding. Antek supplies them. For my super high end builds I custom order from Toroidy.

In my experience, less noise = more low level detail, and a smoother sound to boot.

Best,
Anand.

jonny5 · « **Reply #1252 on:** 20 Oct 2019, 03:42 pm »

Yeah - you can’t see it in the picture, but the transformer shield wire is grounded to to the chassis ground.

Antek’s own transformer cover wouldn’t fit in that case without grinding it down to be several millimeters shorter. The cheap Chinese cover from eBay cost considerably less, didn’t require modification, and had a mounting setup that was easier to tuck wire under the cover.

Aluminum provides no magnetic shielding, so if you want to go crazy like I did with that build, a bit of steel sheet to cover the underside of the transformer to complete a more complete box to shield the external magnetic field of the transformer more thoroughly.

Other people can answer the question about trade-offs between transformer types better than me - I went with the toroidal transformer to fit in the case because I was trying to make the build as compact as possible.

drew_t · « **Reply #1253 on:** 21 Oct 2019, 12:28 am »

Quote from: jonny5 on 18 Oct 2019, 06:24 pm

The cheap W226.5×H70×D271mm case on eBay makes a fantastic case for the build:
https://www.ebay.com/itm/252579253474

Why is it that Chinese vendors will sell you almost anything you can think of with free shipping, but if you want an empty, presumably unassembled and flat-packed aluminum box, they invariably quote very high shipping charges?

Very nice build, jonny5.

DeeJayBump · « **Reply #1254 on:** 24 Oct 2019, 01:54 pm »

Excellent build, jonny5, thanks for sharing.

AKLegal · « **Reply #1255 on:** 30 Oct 2019, 07:02 pm »

Are the boards for these still available? I read through the thread but I cant really tell.

DeeJayBump · « **Reply #1256 on:** 30 Oct 2019, 11:11 pm »

Quote from: AKLegal on 30 Oct 2019, 07:02 pm

Are the boards for these still available? I read through the thread but I cant really tell.

Yes :

https://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu.html

AKLegal · « **Reply #1257 on:** 31 Oct 2019, 10:02 pm »

^^^Much Appreciated

Wind Chaser · « **Reply #1258 on:** 1 Nov 2019, 05:28 pm »

Rather than digging through this gigantic thread is there a website with all the essential information like specs, power supply requirements etc that is easily accessible all on one page? TIA

AKLegal · « **Reply #1259 on:** 1 Nov 2019, 05:56 pm »

Quote from: Wind Chaser on 1 Nov 2019, 05:28 pm

Rather than digging through this gigantic thread is there a website with all the essential information like specs, power supply requirements etc that is easily accessible all on one page? TIA

I ended up getting the newer ec7293 amp instead of the 7297. The specs for the 7293 are here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html