|23rd May 2019, 06:17 PM||#1|
Folsom EC7293: PVI Powered Frontend Amplifier, 60/120w 8/4ohm, 0.0005% THD
**Updated: Lower distortion with a slightly different board.
**Updated 2: Distortion is even lower than before, found a piece of steel was interfering with previous measurements. (thought it was tinned copper)
Alright everyone! We’ve got the redesign done.
(Image of prototype)
The EC7293 uses 2 chip amps in parallel for high power with a discrete error correction frontend which reduces distortion; and has very low memory distortion. High sensitivity makes it perfect for a variety of sources with 8ohm and 4ohm speakers.
Input impedance: 27k
Distortion 1K; 8ohm; full power w/Antek AS-3225: <0.0005% (immeasurable by us)
Board size: 6.25x2.25"
*****There is not a mirrored left/right set because it would screw up the feedback layout*****
Discrete front end: 4 transistors
PVI: The frontend uses a photovoltaic power supply for galvanic isolation of the signal path. It uses a G4 LED bulb with a current source to disable the onboard driver of the G4.
High power: These are running in "modular" mode so that they can handle a 4 ohm load with some dips, while providing substantial power with a max output current of 20A. The Antek AS-3225 is a great fit for 60/120w. More power may be possible if you follow the guidelines of the TDA7293 datasheet and make provisions with higher voltage capacitors, and larger heatsinks.
Terminals: Happy to say we've found some that are based on a copper metallurgy, that accept decent sized wire, and don't strip too easily (I can torque them pretty good with screwdriver) that the boards are made to fit, and I recommend in the BOM.
Input Capacitor: This one is less sensitive to capacitors compared to the DIY7297. It has provisions for the same PHE426 and other caps. There is a slot-hole next to the pads so you can zip tie on larger caps and it has extra pads on the bottom to connect off board/long input capacitors.
CFC, smart PCB layout, & Copper Pours: Trace routing is optimized to improve performance and the power capacitors are placed for field cancellation (CFC); and copper pours are used for lower inductance.
Dualpole PSU PCB
Board Size: 4.25x3"
CFC, smart PCB layout, & Copper Pours
Via holes for snap caps
RC and bypass: dampen the transformer & reduce noise
Suggested implementation with EC7293:
**2U may work in dual mono with two smaller (shorter) transformers
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. I'm hoping to see a lot more than 12x. To anyone that liked the DIY7297, this one is better, simply better.
EC7293+G4LEDR PCB $45ea (you'll need 2, to make a stereo amp)
DualPole PSU PCB $40ea
Shipping USA $8
Shipping International $16
And it will come with a BOM and some build details.
Last edited by Destroyer OS; 5th April 2021 at 03:55 AM.
|24th May 2019, 05:42 PM||#6|
Join Date: Nov 2007
Oh my gosh! The documentation quality is so much better.
But, you really could have bragged up the output linearity instead of understating it.
Per each channel, four made-for-audio output fets in addition to an EC circuit!
Sure has clear and evident means-to-work.
Also, it is at fairly big scale, but if you wanted to know when you have enough, this will do it.
|24th May 2019, 05:58 PM||#8|
I updated the graph to the 8ohm, I accidentally put up 4ohm. This one isn't as hard to read, either.
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