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  • GB#2: Folsom EC7293: PVI Powered Frontend Amplifier, 60/120w 8/4ohm, 0.0005% THD

GB#2: Folsom EC7293: PVI Powered Frontend Amplifier, 60/120w 8/4ohm, 0.0005% THD

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Destroyer OS

Destroyer OS

Member
Joined 2005
#1
EC7293-glow.jpg

(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:
EC7293-THD-8ohm-2.png


At 4ohms:
EC7293-THD-4ohm.png


EC7293-Amp-GB-PREVIEW-1.png


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.


dualpoleppv.png


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.

DeeJayBump 2,2
SAinet 2,2
shacketf 2,2
myl 2,2
mctavish 2,2
Stephen S. 2,2
jameshillj 2,0
drkingweeb 2,2
HaflerDh500Fan 2,2
genjamon 2,2
angchuck 4,1
Click to expand...
 
Last edited:
#8
asuslover said:
I would like to know how much the components from your suggested BOM will cost , so I will have an idea about the total cost of this amp,
Thanks
Click to expand...

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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