Author Topic: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w  (Read 901 times)

Offline Folsom

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Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« on: February 27, 2018, 12:59:09 PM »
'm happy to say Folsom has a second amp design to get into the world of DIY. Firstly we're talking more power! Nextly is this is an advanced design for people whom are ready to jump into a more complicated project. But there are rewards for your work!

Here is what it looks like (click on it). The final rendition you'll get will be slightly different, as it is getting a few tweaks.



Now let's talk some features:

"Feedback"
: It uses 4 transistors to compare, and correct. It actually helps improve phase in higher frequencies. It isn't an act so much of getting an average, as it is an act of fixing - as a crude way to compare it to traditional feedback. Because of how this work it has an extremely pleasant sound that may remind people of tubes, perhaps related to a function of improving linearity.

Feedback power
: In order to help keep distortion low, it needs an independent source for power. It has provisions for a 9v battery that will last a long time (months). But it also has provisions for solarcells. If you want to use the solarcells it will be up to you to figure out how to power them, and get enough juice into them. I will help some, but the default supported feature is a 9v battery.

Distortion: I don't have the equipment to check really low distortion, but can tell you it is somewhere 5-100x better than the standard TDA7293.

Dual Chip Power
: These are running in "modular" mode so that they can handle a 4 ohm load with some dips, while providing substantial power. I'm using a 330VA 25VACx2 transformer, available at Parts Express. At 35vDC +/- it can put out up to 60/120w 8/4ohm. That is the max.

Terminals
: Happy to say I've found some that are based on a copper metallurgy, that accept decent sized wire, and don't strip too easily.

Input Capacitor: This one is less sensitive compared to the DIY7297. It has provisions for the same PHE426 and other caps. There is a hole next to it, to zip tie on larger caps and it has extra pads on the bottom to connect external caps.

CFC & Copper Pours
: Like all other Folsom projects, it has capacitor field cancellation built in, and copper pours for lower inductance.


*There is not a mirrored channel because it would screw up the relationship to feedback.


Recommended PSU
: You'll want 18-24kuf per + and - supply. I believe due to size I'll have to come up with a new one that is like the Antipole in that it'll have CMC's, TO-220 diodes, and some big old snap caps.

Heatsink: You're going to need more heatsink capability than the DIY7297! It dissipates a lot more idle heat. Any amplifier enclosure with finned side walls should work great if you can fit everything in it.

Cost to build: It's about $200-250 worth of Mouser parts (80v and 50v caps are necessary with the transformer voltage for full power). $70 transformer. And this enclosure should be sufficient if the PSU isn't too large. And whatever for binding posts, RCA's, jacks, and such. (mine right now is on my test piece of plywood, which I guess is an option too)

And it will come with BOM's & Build documentation just like the DIY7297



Price & Amount needed to Print:

In order to print these up so I don't run out the day after, I need a commitment of 12x, two EC7293 boards and one PSU board. What I'd like to see is around hopefully 30-50 orders right away, because, well, it's awesome.

Please See here for pricing and joining the GB.


I think this is going to be a very popular board. The DIY7297 is still really popular, and still a great amp that crushes anything near it's price point up into the thousands of dollars... It's a really great starter project. But the EC7293 is a big upgrade in many ways - one thing I still like about the 7297 is that the texture is perhaps the best available among any amplifier on the planet. I haven't got to compare the new EC7293 head to head with as many high dollar items as I did the 7297, but I can assure you, the value is going to be absurd. Think like you could replace VAC statement amps without batting an eye.

« Last Edit: February 27, 2018, 01:07:53 PM by Folsom »

Offline Folsom

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #1 on: March 09, 2018, 03:05:32 PM »
Here is out sim for what the error correcting feedback can do for differential voltage error. It mirrors what we checked with a O-scope and signal generator.


Offline Nick B

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #2 on: March 09, 2018, 09:31:38 PM »
Well, Iím interested, but have never been involved in a project like this and Iíd have to have someone build it. The idea is to eventually replace a modded McCormack DNA 1.0 amp thatís been a great performer for me.
So, if you could answer a couple of questions:
1) can you provide a brief summary of the sonic character of the 7293 vs the smaller, less powerful 7297
2) AN member Gary used a 12 volt Batcap battery to power his chip amps....can you describe what battery would be necessary for the 7293 and how it would function as to AC recharging etc
Nick
ICEpower 1200as2 stereo amp
Audio Hungary APR 204 preamp
KEF LS 50 speakers
Border Patrol SE dac
Auralic Aries Mini
Roon & Tidal
Don Sachs phono
Basis Ovation turntable
Graham 1.5 T tonearm
AT-ML150 cartridge
PI Audio Uber
All cables by Gary A

Offline dBe

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #3 on: March 10, 2018, 08:14:15 PM »
Well, Iím interested, but have never been involved in a project like this and Iíd have to have someone build it. The idea is to eventually replace a modded McCormack DNA 1.0 amp thatís been a great performer for me.
So, if you could answer a couple of questions:
1) can you provide a brief summary of the sonic character of the 7293 vs the smaller, less powerful 7297
2) AN member Gary used a 12 volt Batcap battery to power his chip amps....can you describe what battery would be necessary for the 7293 and how it would function as to AC recharging etc
Nick
I will be happy to do your build, Nick.  This amp will be a much better choice than the 7297.  No worries:  we have your back here!


Offline Nick B

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #4 on: March 10, 2018, 08:35:48 PM »
Well, Iím interested, but have never been involved in a project like this and Iíd have to have someone build it. The idea is to eventually replace a modded McCormack DNA 1.0 amp thatís been a great performer for me.
So, if you could answer a couple of questions:
1) can you provide a brief summary of the sonic character of the 7293 vs the smaller, less powerful 7297
2) AN member Gary used a 12 volt Batcap battery to power his chip amps....can you describe what battery would be necessary for the 7293 and how it would function as to AC recharging etc
Nick
I will be happy to do your build, Nick.  This amp will be a much better choice than the 7297.  No worries:  we have your back here!

Thanks, Dave! Iím really looking forward to this amp.
Nick
ICEpower 1200as2 stereo amp
Audio Hungary APR 204 preamp
KEF LS 50 speakers
Border Patrol SE dac
Auralic Aries Mini
Roon & Tidal
Don Sachs phono
Basis Ovation turntable
Graham 1.5 T tonearm
AT-ML150 cartridge
PI Audio Uber
All cables by Gary A

Offline Folsom

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #5 on: March 11, 2018, 06:16:13 PM »
Well, Iím interested, but have never been involved in a project like this and Iíd have to have someone build it. The idea is to eventually replace a modded McCormack DNA 1.0 amp thatís been a great performer for me.
So, if you could answer a couple of questions:
1) can you provide a brief summary of the sonic character of the 7293 vs the smaller, less powerful 7297
2) AN member Gary used a 12 volt Batcap battery to power his chip amps....can you describe what battery would be necessary for the 7293 and how it would function as to AC recharging etc
Nick

1. It's better :rofl: instruments can be more bold. There is a little more magic, a little more character, timbre, bass goes farther, deeper, with inefficient speakers. I'll report more before long (playing around in music room, playing with solarcells)

2. You'd need something like 7 batteries in series, the last one could be 6v, if you wanted full power. They would have to be pretty decent sized to make sure they can pump out up to 9A or so, continuous, without sagging real bad to keep full power. Your stereo room would look like the trunk of a lowrider. You'd use a switch to turn on a series of 24v, 12v, and 6v chargers when you turn the amp "off" from listening - you'd probably put them on on some relays powered by a walwart.
« Last Edit: March 11, 2018, 06:23:03 PM by Folsom »

Offline Nick B

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #6 on: March 11, 2018, 06:26:57 PM »
Well, Iím interested, but have never been involved in a project like this and Iíd have to have someone build it. The idea is to eventually replace a modded McCormack DNA 1.0 amp thatís been a great performer for me.
So, if you could answer a couple of questions:
1) can you provide a brief summary of the sonic character of the 7293 vs the smaller, less powerful 7297
2) AN member Gary used a 12 volt Batcap battery to power his chip amps....can you describe what battery would be necessary for the 7293 and how it would function as to AC recharging etc
Nick

1. It's better :rofl: instruments can be more bold. There is a little more magic, a little more character, timbre, bass goes farther, deeper, with inefficient speakers. I'll report more before long (playing around in music room, playing with solarcells)

2. You'd need something like 7 batteries in series, the last one could be 6v. They would have to be pretty decent sized to make sure they can pump out up to 9A or so, continuous, without sagging real bad to keep full power. Your stereo room would look like the trunk of a lowrider. You'd use a switch to turn on a series of 24v, 12v, and 6v chargers when you turn the amp "off" from listening - you'd probably put them on on some relays powered by a walwart.

1 Thatís a nice, confident answer 👍
2 Oh boy....how would I explain that to the mrs..... thereís gotta be a discrete, more compact way to do that.
Nick
ICEpower 1200as2 stereo amp
Audio Hungary APR 204 preamp
KEF LS 50 speakers
Border Patrol SE dac
Auralic Aries Mini
Roon & Tidal
Don Sachs phono
Basis Ovation turntable
Graham 1.5 T tonearm
AT-ML150 cartridge
PI Audio Uber
All cables by Gary A

Offline Folsom

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #7 on: March 11, 2018, 11:49:49 PM »
You can put the batteries in a closet? Outside?

I can't imagine any reason to use batteries.

Offline Nick B

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #8 on: March 12, 2018, 10:02:11 AM »
You can put the batteries in a closet? Outside?

I can't imagine any reason to use batteries.

My system resides in the living room. Neither my wife nor I want to look at multiple batteries or cables. But Iím sure thereís a nice solution available. Iím just not sure what it would look like, so maybe a pic of a similar setup would be helpful. The other thing I wonder about is a slight lack of dynamics if itís a battery operated system. I have zero experience with using batteries for audio, but have listened to Garyís battery-powered Temple chip amps and they were quite good.
Nick
ICEpower 1200as2 stereo amp
Audio Hungary APR 204 preamp
KEF LS 50 speakers
Border Patrol SE dac
Auralic Aries Mini
Roon & Tidal
Don Sachs phono
Basis Ovation turntable
Graham 1.5 T tonearm
AT-ML150 cartridge
PI Audio Uber
All cables by Gary A

Offline Folsom

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #9 on: March 12, 2018, 08:29:53 PM »
My solution is to just use AC.

Best talk to Dave about what custom solution he can build, because he's going to be doing the building. It needs +/- 35v rails, can sag to 30v, maxis out around 7A.

Offline Nick B

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #10 on: March 12, 2018, 10:02:30 PM »
My solution is to just use AC.

Best talk to Dave about what custom solution he can build, because he's going to be doing the building. It needs +/- 35v rails, can sag to 30v, maxis out around 7A.

AC would be fine if he can do it. Otherwise Iím sure I can make it look good somehow
Nick
ICEpower 1200as2 stereo amp
Audio Hungary APR 204 preamp
KEF LS 50 speakers
Border Patrol SE dac
Auralic Aries Mini
Roon & Tidal
Don Sachs phono
Basis Ovation turntable
Graham 1.5 T tonearm
AT-ML150 cartridge
PI Audio Uber
All cables by Gary A

Offline dBe

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #11 on: March 12, 2018, 10:46:48 PM »
My solution is to just use AC.

Best talk to Dave about what custom solution he can build, because he's going to be doing the building. It needs +/- 35v rails, can sag to 30v, maxis out around 7A.

AC would be fine if he can do it. Otherwise Iím sure I can make it look good somehow
Nick
Nick,  AC is the only way I would build this amp for you.  I can't imagine the monkey motion necessary to do DC.  Besides, Jeremy has come up with a tremendous method of building power supplies and I would not be so arrogant as to believe I have a better way.

I'll order my first boards from him tomorrow and see how it goes.  If it turns out to be what I think, I'll make it available to you and then build another for me.

The man does good work!
« Last Edit: March 12, 2018, 11:10:45 PM by dBe »

Offline Nick B

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Re: Folsom EC7293: Battery/Solarcell Powered Feedback, 60/120w
« Reply #12 on: March 12, 2018, 10:52:23 PM »
My solution is to just use AC.

Best talk to Dave about what custom solution he can build, because he's going to be doing the building. It needs +/- 35v rails, can sag to 30v, maxis out around 7A.

AC would be fine if he can do it. Otherwise Iím sure I can make it look good somehow
Nick
Nick,  AC is the only way I would build this amp for you.  I can't imagine the monkey motion necessary to do DC.  Besides, Jeremy has come up with a tremendous method of building power supplies and I would not be so arrogant as to believe I have a better way.

I'll order my first board from him tomorrow and see how it goes.  If it turns out to be what I think, I'll make it available to you and then build another for me.

The man does good work!

Oh yeah, Dave, now weíre talkiní! Iím really excited about the potential for this amp and itís for a great price as well.
Nick
ICEpower 1200as2 stereo amp
Audio Hungary APR 204 preamp
KEF LS 50 speakers
Border Patrol SE dac
Auralic Aries Mini
Roon & Tidal
Don Sachs phono
Basis Ovation turntable
Graham 1.5 T tonearm
AT-ML150 cartridge
PI Audio Uber
All cables by Gary A