Folsom's great little 7297 Chip Amp

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KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #540 on: 1 Sep 2016, 01:16 pm »
I have some bicycle tire tubes I bought a while back for clamping a large 2.8 cu. ft. speaker cabinet after glueing the sides and front and back together. I might try cutting a piece to fit on top of the transformer or gluing it to the case top above and see how it fits/works . I was thinking about trying that for the transformer base but decided to go with neoprene rubber washers instead

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #541 on: 2 Sep 2016, 07:13 pm »
Helping a friend build his Folsom; he opted for a few different components. Below are photos of it mounted on temporary test board being powered by a 24V switching PS. The extra long wires, cheap connectors, and PS just for initial testing. Final resting place will be in a nice aluminum case with a not yet built Antipole PS. It sounds great!







Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #542 on: 2 Sep 2016, 07:17 pm »
How does it compare to yours with different caps?

limits

Re: Folsom's great little 7297 Chip Amp
« Reply #543 on: 2 Sep 2016, 07:20 pm »
Wow, Larry--nice job!!

Are the Jupiter caps the 0.022 uf bypass caps instead of the smaller ones in the standard BOM?

Sure is purdy  :thumb:

Odal3

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Re: Folsom's great little 7297 Chip Amp
« Reply #544 on: 2 Sep 2016, 07:22 pm »
Nice :thumb:


Captainhemo

Re: Folsom's great little 7297 Chip Amp
« Reply #545 on: 2 Sep 2016, 07:29 pm »
Helping a friend build his Folsom; he opted for a few different components. Below are photos of it mounted on temporary test board being powered by a 24V switching PS. The extra long wires, cheap connectors, and PS just for initial testing. Final resting place will be in a nice aluminum case with a not yet built Antipole PS. It sounds great!







It looks great Larry  :thumb:
Really looking forward to hearing it and comparing with the Dodd prototype 7297 I've got now

limits, yeah the Jupiter's are the .02s and replace the standard bypass caps,  had a few pairs that I picked up on  sale a while back

jay

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #546 on: 2 Sep 2016, 07:51 pm »
How does it compare to yours with different caps?

Somehow I knew you would ask that. I just finished this morning, so I only have a few hours of listening so far. Certainly not enough time for it to settle in. I can't directly compare it to mine because it now resides a half a world away. However, I am in the process of building another. From memory only, I would say its a little brighter, not in a bad way, just notice the highs a bit more. Bass and mids seem the same from memory. So far I like the sound. Not better/worse, just a little different.

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #547 on: 2 Sep 2016, 10:16 pm »
The Nichicon Aluminum Electrolytic Capacitors - Leaded 35volts 220uF 85c 10x20 5LS are out of stock until December at Mouser
Any suggestions for a substitute ?
I applied parameter filters to something similar at Mouser and just came up with 2 different Nichicon models that are both out of stock

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #548 on: 3 Sep 2016, 12:38 am »
647-UPA1V181MPD

That should work fine.

mlundy57

Re: Folsom's great little 7297 Chip Amp
« Reply #549 on: 3 Sep 2016, 02:07 am »
Larry,

Looks good. You by-passed the Sonicaps with the Jupiter's above the board just like you would in a crossover network, correct?

What size is the heat sink?

Jay,

What do you think of the Jupiters as by-pass caps compared to Sonicap Platinums?

You got enough speakers for all your amps?  :thumb:

Mike

Captainhemo

Re: Folsom's great little 7297 Chip Amp
« Reply #550 on: 3 Sep 2016, 05:05 am »
Larry,

Looks good. You by-passed the Sonicaps with the Jupiter's above the board just like you would in a crossover network, correct?

What size is the heat sink?

Jay,

What do you think of the Jupiters as by-pass caps compared to Sonicap Platinums?

You got enough speakers for all your amps?  :thumb:

Mike

Hey Mike
I can't really do a direct comparison  betweenthe  Juiter and Platinum bypass yet...I haven't used them in identical positions.  But , from wht i have heard, I am a fan of the Jupiter's... I'm using  oe on the high pass bundle on the Otticas right now and the  high pass filter on a pair of Encores... both are bypassing  Gen1 Sonicaps.
If there had been more room and  no real  concern about expense, I'd have sent Larry a pair of either the  Jupiter 1.5 uF or  SC Platinum 1.5 uf's (not even sure ther eis any stock of the SCP 1.5's left, I beleive there are some 1.0's)and gone with no bypass cap, but  both opotions are big  and not exactly inexpensive.
Just had someone leave a pair of LGK's here for an extended  stay but i haven't had a chance to thry them  yet, kind of looking forward to that actually 

jay

mlundy57

Re: Folsom's great little 7297 Chip Amp
« Reply #551 on: 3 Sep 2016, 05:36 am »
Hey Mike
I can't really do a direct comparison  betweenthe  Juiter and Platinum bypass yet...I haven't used them in identical positions.  But , from wht i have heard, I am a fan of the Jupiter's... I'm using  oe on the high pass bundle on the Otticas right now and the  high pass filter on a pair of Encores... both are bypassing  Gen1 Sonicaps.
If there had been more room and  no real  concern about expense, I'd have sent Larry a pair of either the  Jupiter 1.5 uF or  SC Platinum 1.5 uf's (not even sure ther eis any stock of the SCP 1.5's left, I beleive there are some 1.0's)and gone with no bypass cap, but  both opotions are big  and not exactly inexpensive.
Just had someone leave a pair of LGK's here for an extended  stay but i haven't had a chance to thry them  yet, kind of looking forward to that actually 

jay

Jay,

I couldn't find any SC Platinum 1.5uF caps either which is why I asked about using 2.0uF the other day.

Pricewise I think the 1.5uF Jupiter copper foil wax caps are about $145 each while the SC Platinum 2.0uF are $224 ea.

These amps start out pretty reasonable but it's easy to run the price up pretty quick.

I look forward to hearing your impressions of the LGK (1.0's I take it?). 

Mike

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #552 on: 3 Sep 2016, 11:54 am »
Larry,

Looks good. You by-passed the Sonicaps with the Jupiter's above the board just like you would in a crossover network, correct?

What size is the heat sink?
Mike

Mike,
 Yes the caps are piggy backed per Jay's request instead of soldering them on the bottom pads.

The heat sink is the one recommended in the BOM. It's from heat sink USA 3.5" long x 3" tall.

Captainhemo

Re: Folsom's great little 7297 Chip Amp
« Reply #553 on: 3 Sep 2016, 04:15 pm »
Jay,

I couldn't find any SC Platinum 1.5uF caps either which is why I asked about using 2.0uF the other day.

Pricewise I think the 1.5uF Jupiter copper foil wax caps are about $145 each while the SC Platinum 2.0uF are $224 ea.

These amps start out pretty reasonable but it's easy to run the price up pretty quick.

I look forward to hearing your impressions of the LGK (1.0's I take it?). 

Mike

Mike,  are you wanting this amp to be able to  play full range ? I know the  10 uF's would be fine with your  Wedgies or the Ottica MTM's I sent down.  At 25kohms input impeence, the calcualtor says  you'd have a -3db point of 6.37 hz (seems low to me  but ? )... I know Jeremy says  results may vary a bit but  for those speakers and your subs ability to play way  up, you'd be fine.
Other option is go  capless, as mentioned , your  Dodd  buffer  uses output caps so don't think there is any need to be redundent on the DC blocking unless you ara concerned about compatability or want the filtering from the caps.

Yes, those  speakers i mentioned  are the  LGK 1.0's, I may try and have a listen to them this weekend

All  these DIY builds  start off as inexpensive but CAN quickly ramp up.. amps speakers  etc, all can grow quickily but i guess without  trying the parts, one never knows .
I've actually been offered a  great deal on  a couple of 300VA 15V  transformers, they'd be over kill for this but I'm considering using one in place of he  Hammond if I go with the Antipole anyway, haven't decided yet  :scratch:

jay

mlundy57

Re: Folsom's great little 7297 Chip Amp
« Reply #554 on: 3 Sep 2016, 11:41 pm »
Mike,  are you wanting this amp to be able to  play full range ? I know the  10 uF's would be fine with your  Wedgies or the Ottica MTM's I sent down.  At 25kohms input impeence, the calcualtor says  you'd have a -3db point of 6.37 hz (seems low to me  but ? )... I know Jeremy says  results may vary a bit but  for those speakers and your subs ability to play way  up, you'd be fine.
Other option is go  capless, as mentioned , your  Dodd  buffer  uses output caps so don't think there is any need to be redundent on the DC blocking unless you ara concerned about compatability or want the filtering from the caps.

Yes, those  speakers i mentioned  are the  LGK 1.0's, I may try and have a listen to them this weekend

All  these DIY builds  start off as inexpensive but CAN quickly ramp up.. amps speakers  etc, all can grow quickily but i guess without  trying the parts, one never knows .
I've actually been offered a  great deal on  a couple of 300VA 15V  transformers, they'd be over kill for this but I'm considering using one in place of he  Hammond if I go with the Antipole anyway, haven't decided yet  :scratch:

jay

Jay,

I want at least the first amp to be able to play full range. That way I can use it with any of my speakers. I may build out an amp without input caps to see what it sounds like with the Dodd tube buffer. It looks like the output caps in my Dodd are Sonicap Gen1s by-passed with SC Platinums.

I'm going to build the amp and power supply in separate chassis. That way I can compare different amp builds without having to build multiple power supplies up front.  The first Antipole I build will use the Hammond but I may try a toroidal transformer in another Antipole later on.

Mike

ebag4

Re: Folsom's great little 7297 Chip Amp
« Reply #555 on: 4 Sep 2016, 07:16 pm »
I finally got around to building my amp and ps.  Question, having never used an insulator between a chip and a heat sink, should I pull what appears to be a plastic protection layer off the insulator?

Thanks,
Ed

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #556 on: 4 Sep 2016, 07:18 pm »
Are you sure there's not just two? I never had anything like that on any of the mica I ordered...

ebag4

Re: Folsom's great little 7297 Chip Amp
« Reply #557 on: 4 Sep 2016, 07:41 pm »
I did recieve two because I ordered two chips (just in case  :wink:), but what I am referring to is what appears to be separation of layers around the holes at at some of the edges.  I had a couple of pieces peel off but when they didn't pull off as a complete sheet but in shards I thought I should ask. 

Thanks,
Ed

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #558 on: 4 Sep 2016, 07:57 pm »
I really don't know, I didn't experience anything like that.

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #559 on: 4 Sep 2016, 09:27 pm »
I did recieve two because I ordered two chips (just in case  :wink:), but what I am referring to is what appears to be separation of layers around the holes at at some of the edges.  I had a couple of pieces peel off but when they didn't pull off as a complete sheet but in shards I thought I should ask. 

Thanks,
Ed

That's just a characteristic of mica, if you peel it, it will come off in flakes. What appears to be layer separations around the holes and the edges is normal. The thermal grease fills the tiny scratches you can't see or feel on the aluminum chip, and heat sink so you get the best thermal conductivity. The mica sheet electrically insulates the chip from the heat sink. Both sides of the mica should be glass smooth.

 If you peel off mica layers it will no longer be smooth, and you will lose some thermal contact with chip or heat sink. It may not be a problem, but be sure there is no electrical continuity between the chip and heat sink.