Folsom's great little 7297 Chip Amp

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jtwrace

Re: Folsom's great little 7297 Chip Amp
« Reply #40 on: 8 Nov 2015, 01:13 pm »
OK, so if battery power is 24Vdc what is the current requirement?

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #41 on: 8 Nov 2015, 01:46 pm »
The transistor that feeds the DC to the supply capacitors and chip, controlled by the other transistor and TL431 for voltage regulation. The numbers and letters there punched into Mouser would have led you to one. It also requires a small heatsink on it.


Actually I did try finding the number at Mouser, but no luck? Is that the transistor you are supplying?



[/quote]

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #42 on: 8 Nov 2015, 01:54 pm »
Here's one in Ireland. I'll link to comments if he posts them publicly. (He says it's much more impressive than his Amp Camp Amp)



It looks like he left the 12 Oscon's proud of the board. Is that suggested to prevent possible shorting of the caps aluminum case?

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #43 on: 9 Nov 2015, 08:40 pm »
Actually I did try finding the number at Mouser, but no luck? Is that the transistor you are supplying?

Try 863-D45H11G

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #44 on: 9 Nov 2015, 08:44 pm »
It looks like he left the 12 Oscon's proud of the board. Is that suggested to prevent possible shorting of the caps aluminum case?

No idea what's up with that. I noticed as well. Perhaps his technique isn't down-pat.  I apply solder, then hold the unit with my hand, pressing on the cap gently, and touch the joint again. The capacitor goes into place, and when I release the iron it stays. That way when I do the other lead on it, it's in place. After the second is done, I typically add enough to finish the first joint/ clean it up.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #45 on: 11 Nov 2015, 03:15 am »
OK, so if battery power is 24Vdc what is the current requirement?

It's possible to run as low as 4.3a, but I would have more available, personally. The chip is regulated (internally) at 2A x 2, and the capacitor multiplier uses just a tiny bit.
« Last Edit: 26 Feb 2018, 05:29 pm by Folsom »

Odal3

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Re: Folsom's great little 7297 Chip Amp
« Reply #46 on: 18 Nov 2015, 03:51 am »
I've got batteries ordered with the intent to put two 12v's in series to get 24V (that the US Post Office lost yesterday in shipping-althought the torn and crushed box was delivered sans batteries :cuss:).  I have to call after 4PM today to get their official runaround about why it's not their fault.

Any updates how you like the 24V?

S Clark

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Re: Folsom's great little 7297 Chip Amp
« Reply #47 on: 18 Nov 2015, 04:00 am »
Any updates how you like the 24V?
Afraid not.  While mounting it in a case, I managed to blow out the chip, so it's down for now.  Hopefully by the end of the week I'll have something to report.

Vapor Audio

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Re: Folsom's great little 7297 Chip Amp
« Reply #48 on: 18 Nov 2015, 04:14 am »
I can't believe that I haven't yet posted my thoughts after Folsom was so kind to let me live with his prototype for a few weeks.  My sincere apologies, I should have posted weeks ago. 

My thoughts on the amp were first that it seems much more powerful than the spec would suggest.  It controlled and drove our Perfect Storm White, Arcus, Cirrus Black, and Uber Aurora all with ease.  The first impression was clear and open, great soundstage and layering of images in the stage.  Independent stage elements were easily discernable and separated in space.  There was a nice sense of ease in that the details were delivered without any edge.  The amp was an especially nice match for the Arcus, there was plenty of current to drive them to quite high levels, and the Folsom amp really added an extra layer of presence through the mids and upper mids. 

From 100hz up I'd say this amp was very good in all phases, and excellent in some.  The amp was completely non-finicky, giving predicable results on many different speakers.  It ran cool, is a great manageable size, and his case was actually quite nice as well.  My only negative was bass was noticeably truncated on the Perfect Storm.  Folsom said he was going to chance some cap values to help alleviate that, but I haven't heard it since those changes were made. 

I do plan on having my own pair of Arcus setup permanently in a room here, and when I do plan to have one of the Folsom amps in that room as well. 

Peter J

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Re: Folsom's great little 7297 Chip Amp
« Reply #49 on: 18 Nov 2015, 05:58 pm »
I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #50 on: 18 Nov 2015, 07:02 pm »
I can't believe that I haven't yet posted my thoughts after Folsom was so kind to let me live with his prototype for a few weeks.  My sincere apologies, I should have posted weeks ago. 

My thoughts on the amp were first that it seems much more powerful than the spec would suggest.  It controlled and drove our Perfect Storm White, Arcus, Cirrus Black, and Uber Aurora all with ease.  The first impression was clear and open, great soundstage and layering of images in the stage.  Independent stage elements were easily discernable and separated in space.  There was a nice sense of ease in that the details were delivered without any edge.  The amp was an especially nice match for the Arcus, there was plenty of current to drive them to quite high levels, and the Folsom amp really added an extra layer of presence through the mids and upper mids. 

From 100hz up I'd say this amp was very good in all phases, and excellent in some.  The amp was completely non-finicky, giving predicable results on many different speakers.  It ran cool, is a great manageable size, and his case was actually quite nice as well.  My only negative was bass was noticeably truncated on the Perfect Storm.  Folsom said he was going to chance some cap values to help alleviate that, but I haven't heard it since those changes were made. 

I do plan on having my own pair of Arcus setup permanently in a room here, and when I do plan to have one of the Folsom amps in that room as well.

Ryan's correct. When he listened it had 1uf input capacitors. While the corner frequency was low enough, that's an electrical engineers wish, and not the reality. Since I've updated to 1.5uf sized input capacitors and the bass should have a -3db at 20hz like the chip is capable. But also I've begun bypassing this capacitor with a smaller one. There's far better detail, particularly in the information around what most people call detail.

Boy, I hope I get to hear some Arcus speakers with it! I can see how it would play quiet well with them. I love it's control it exerts for only being 15w. Another member might chime in some time, he said he doesn't think it has the highest dampening factor so one pair of speakers he tried it on, didn't give him the articulation in the bass that other speakers did. The good news is generally inefficient, moderately designed speaker drivers seem to behave that way. For example in a small/medium-small room with some 87db GR-Research speakers, you wouldn't be disappointed; but Danny's drivers have some careful attention paid that make them not as demanding on dampening, if I understand correctly.

I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/

They'll be printed. If the IndieGoGo didn't go through, I could still collect from those that paid, separately. A few more orders would fully pay for printing, since $500 isn't how much I have to have, but how much IndieGoGo requires.

The Antipole is good for a lot of projects, btw. It's got a wide range of capability.

ebag4

Re: Folsom's great little 7297 Chip Amp
« Reply #51 on: 19 Nov 2015, 06:49 pm »
I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/
Done, thanks for the nudge  :thumb:.  I have a couple 100ah Powersonic AGM batts ready to use but I am curious about Folsom's power supply.  I may build my amp to use either.

Best,
Ed

shadowlight

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Re: Folsom's great little 7297 Chip Amp
« Reply #52 on: 21 Nov 2015, 03:01 am »
Jeremy,

Can this be run as mono blocks in a single chassis?  2 x 7297 board and 2 psu boards but a single power cable?  If yes, what changes need to occur on the chip board?

lokie

Re: Folsom's great little 7297 Chip Amp
« Reply #53 on: 21 Nov 2015, 12:06 pm »
OK I'm in.

A DIY project I think i can pull off.

jtwrace

Re: Folsom's great little 7297 Chip Amp
« Reply #54 on: 21 Nov 2015, 12:22 pm »
It's possible to run as low as 2.3a, but I would have more available, personally. The chip is regulated (internally) at 2a, and the capacitor multiplier uses just a tiny bit.
So like 2.5A @ 24Vdc? 

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #55 on: 21 Nov 2015, 06:38 pm »
Well,

Yes you can. You can parallel the channels on each board but you may lose some detail. But it's best to match chips because the input impedance varies from chip to chip within 5k.

You can also just run one channel on a board.


Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #56 on: 21 Nov 2015, 06:41 pm »

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #57 on: 23 Nov 2015, 03:07 pm »
Jeremy,
 Do you think we will see the boards before the new year?

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #58 on: 24 Nov 2015, 02:05 am »
Unfortunately no. The IndieGoGo ends early December, payment takes 15 days, and printing takes two weeks.

If I had a way to get them out now, I would.

jseipp

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Re: Folsom's great little 7297 Chip Amp
« Reply #59 on: 24 Nov 2015, 03:31 am »
I'm in!