(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
Gain: 32db
Distortion 1K; 8ohm; full power w/Antek AS-3225: <0.0005%
A short review.
At 8ohms:
At 4ohms:
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.
Distortion: <0.0005%
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"
TO220 Diodes
CFC, smart PCB layout, & Copper Pours
Via holes for snap caps
RC and bypass: dampen the transformer & reduce noise
Suggested implementation with EC7293:
- 18000uF to 24000uF per rail
- Antek AS-3225 transformer
- Keratherm insulators from DIYAudio store. (Chip tabs are 1.1” apart).
- Heatsinks need to be larger than used on the 7297, nearly any enclosure with heatsinks for sides should work
- 3U enclosure from DIYAudio store is a good fit. **
- 2x Duapole's for dual mono with 2x transformers (Antek AS-2225)
**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'd like to see 12x pairs to get this going. 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.
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Parts to populate both amp boards is about $130 + $8 hardware + $10 LEDs + $10 pvi cells. Each PSU board is $38~ to populate. Then add in your choice of input capacitor, enclosure, wire, and connectors.
I think this post would give you an idea of what a beautiful build would could come out to. One can spend less going with 1 transformer and 1 PSU ($100 min less not including shipping). You can use different chassis parts, different wire.
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