Folsom's great little 7297 Chip Amp

Folsom · « **Reply #1300 on:** 14 Jun 2020, 12:46 am »

12v isn't enough for the amp. But I also wouldn't want to use a switch between PSU and amp because the voltage spike is dangerous to transistors.

If you had a hard switch that allowed 120v, and had a mini 12v power supply to run a relay for 120v to the amplifier transformer you'd be fine. That's kinda what amplifier companies do.

vilding · « **Reply #1301 on:** 14 Jun 2020, 11:48 am »

Ok....
I'll try to to push past my technical and linguistic shortcomings....

The switch is rated at 240VAC, the led at 12V(suppose DC since theres a battery in the wiring diagram).

I think this is might be it:
12vdc+ from smps to 4, 12vgnd from smsps to 5 for led.
230vac from wall via fuse to 2, 3 to smps +in.
Neutral from wall to neutral in smps.
Earth from wall to star ground
Earth from smps to star ground.
Done!

The other output of the smps is rated at 24VDC, but is adjustable some. Do I need to trim it down to 21? Will it hurt the amp if I run it higher?

Folsom · « **Reply #1302 on:** 14 Jun 2020, 05:41 pm »

No it won't hurt it at 24v but it'll make extra heat.

vilding · « **Reply #1303 on:** 15 Jun 2020, 09:47 pm »

Ok, so I worked it out, and now it makes music. It sounds freakin fantastic!

It has a pleasing, almost soft sound, without losing an ounce of clarity. Kurt Rosenwinkel's guitar solo on "Return of the prodigal son" with Brian Blade & the Fellowship band i so clear and precise. I hear all the little stuff he does and the decay of every note. And at the same time everything the band plays behind him is crisp, dynamic and incredibly well separated. And the bass is deep and strong with great body.
So far, maybe two hours in, at reasonable listening levels, it runs very cool. And it seems, as said by many before me, so much more powerful than 15 measly watts.

It's soon midnight in Stockholm, but I think I'll open a beer and make it a late night...

/Hilding

Folsom · « **Reply #1304 on:** 16 Jun 2020, 02:17 am »

vilding · « **Reply #1305 on:** 16 Jun 2020, 09:14 am »

uncola · « **Reply #1306 on:** 17 Jun 2020, 04:43 am »

hehe your amp looks so teeny on that giant amp platform. I'm always impressed when I put my folsom amp back in the system, I even used it to replace my IceEdge 1200as2 600 watt per channel amp in my small home theater temporarily and it had enough power to get as loud as I normally listen without strain. But I do use a sub at 80hz with high pass filter on the mains so that might help slightly

drmike · « **Reply #1307 on:** 17 Jun 2020, 11:28 am »

hello, are there any boards left?
thanks,drmike

vilding · « **Reply #1308 on:** 17 Jun 2020, 01:25 pm »

Quote from: uncola on 17 Jun 2020, 04:43 am

hehe your amp looks so teeny on that giant amp platform. I'm always impressed when I put my folsom amp back in the system, I even used it to replace my IceEdge 1200as2 600 watt per channel amp in my small home theater temporarily and it had enough power to get as loud as I normally listen without strain. But I do use a sub at 80hz with high pass filter on the mains so that might help slightly

Haha yeah, it was a tight fit, and a hellish job to put together and solder up, since it's just a two piece. Finicky, I think is the appropriate word. The amp itself on the other hand was a delight to put together.

WC · « **Reply #1309 on:** 17 Jun 2020, 05:35 pm »

Quote from: drmike on 17 Jun 2020, 11:28 am

hello, are there any boards left?
thanks,drmike

I have a set I could sell you.

sarora9 · « **Reply #1310 on:** 11 Jul 2020, 12:01 am »

I now have Folsom's newer 7293 amp, assembled by amp afficionado pinocchio who hangs out at diyaudio forum. (NB: pinocchio does not normally assemble amps for others. He did it for me because he was intrigued by the design and wanted to hear it for himself.)

The 7293 is freakin' amazing. In my system I have had over the years a Sim Audio moon entry level (back in the aughts), a decent EL34, an audio GD integrated, and most recently AVA hifi's SET120 (same circuit as their SET 400). The Folsom 7293 is from another planet, combining fantastic soundstage/prat/clarity with a very nonfatiguing sound. Another builder at diyaudio forum finds it superior to Cherry Maraschino and Hegel 360. The thread is here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html

My system: Roon Rock -> Bricasti M5 streamer -> Bricasti M1 SE dac -> Folsom 7293 -> Spatial X3.

Folsom · « **Reply #1311 on:** 11 Jul 2020, 02:22 pm »

Thank you for the kind words!

vilding · « **Reply #1312 on:** 17 Jul 2020, 02:34 pm »

Newbie problems....

Haven't run mine in a while, and when I started it, it has a nasty ground hum. It is somewhat under control when playing music from my macbook pro unconnected, but gets worse if I touch the metal of the computer and much worse if I plug it in to the wall.
Where do I search and what do I search for..?

HT cOz · « **Reply #1313 on:** 17 Jul 2020, 07:37 pm »

Quote from: sarora9 on 11 Jul 2020, 12:01 am

I now have Folsom's newer 7293 amp, assembled by amp afficionado pinocchio who hangs out at diyaudio forum. (NB: pinocchio does not normally assemble amps for others. He did it for me because he was intrigued by the design and wanted to hear it for himself.)

The 7293 is freakin' amazing. In my system I have had over the years a Sim Audio moon entry level (back in the aughts), a decent EL34, an audio GD integrated, and most recently AVA hifi's SET120 (same circuit as their SET 400). The Folsom 7293 is from another planet, combining fantastic soundstage/prat/clarity with a very nonfatiguing sound. Another builder at diyaudio forum finds it superior to Cherry Maraschino and Hegel 360. The thread is here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html

My system: Roon Rock -> Bricasti M5 streamer -> Bricasti M1 SE dac -> Folsom 7293 -> Spatial X3.

Pinocchio builds are amazing, do you have pics of your amp?

Thanks,
Robert

sarora9 · « **Reply #1314 on:** 17 Jul 2020, 07:46 pm »

Quote from: HT cOz on 17 Jul 2020, 07:37 pm

Pinocchio builds are amazing, do you have pics of your amp?
--Robert

Pinocchio posted pics on the diyaudio thread starting page 15. Yeah, I am lucky he agreed to build it.

ctviggen · « **Reply #1315 on:** 17 Jul 2020, 08:04 pm »

Quote from: sarora9 on 17 Jul 2020, 07:46 pm

Pinocchio posted pics on the diyaudio thread starting page 15. Yeah, I am lucky he agreed to build it.

That guy has real oscilloscopes and signal generators, and a nice lab.

ostvald · « **Reply #1316 on:** 18 Jul 2020, 10:29 am »

I've started my 7297 build.
Will post here some photos, comments are welcomed and appreciated!

2109 chineese case

almost done with the PSU board

Should bend chip pins 180 degrees cos the board is to be mounted on the chassis side

Almost populated amp board

Amp board mounting

The workplace on the kitchen table

lacro · « **Reply #1317 on:** 18 Jul 2020, 01:59 pm »

Good job on the implementation of the chip on the bottom of the amp pcb. That will make it a lot easier to fit everything in that case

Folsom · « **Reply #1318 on:** 18 Jul 2020, 02:08 pm »

I truly wish they sold chips like that...

ostvald · « **Reply #1319 on:** 18 Jul 2020, 02:22 pm »

Quote from: lacro on 18 Jul 2020, 01:59 pm

Good job on the implementation of the chip on the bottom of the amp pcb. That will make it a lot easier to fit everything in that case

lacro, was inspired by your builds

it's gonna be pretty tight even with the board on the side. Doesn't fit otherwise if using 200VA transformer.