ART PRO MPA II MODS

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Warning!!!: Art uses VERY small traces that can be easily damaged by improper soldering techniques. Take extra care with these units!
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Channel 1:
Tube MoD: - Replace the tubes with a better quality 12AX7 tube (mullard, tung-sol, rca, whatever)

IC MoD:
- (Input board) Replace u200 with a gold contact ic socket and change the chip to: OPA2132, opa2134, OPA2107, LT1358, or LME49860NA (My fav)
- (Main board) Replace ic's u301, u302, and u305 with gold contact ic sockets and change the chips to: OPA2132, opa2134, OPA2107, LT1358, or LME49860NA (My fav)
- Bypass the modded IC's V+ and V- (pins 4 and 8) with a .1uf film capacitor to ground

Capacitor/resistor MoD:
- (Input board) Replace c209, 210 with 100u 100v bipolar nichicon caps
- (Input board) Replace r217, and 218 with 10 ohm metal film resistors
- (Input board) Replace r216 with a 150 ohm metal film resistor

- (Main board) Replace c224 with a 2.2u film cap 5mm pin placement
- (Main board) Replace c301, 306, and 328 with 22u 35v bipolar caps
- Bypass those caps with .22u film caps
- (Main board) Replace c302, 304, 305, 308, 312, and c332 with 220u 10v bipolar caps
- Bypass those caps with .22u film caps
- (Main board) Replace r214 with a 33 ohm metal film resistor
- (Main board) Replace r212 with a 1k metal film resistor
- (Main board) Replace r300 with a 3k metal film resistor
- (Main board) Replace r311 with a 4.7k metal film resistor
- (Main board) Replace r314, 317, and 331 with 10k metal film resistors
- (Main board) Replace r323 and 328 with a 20k metal film resistor
- (Main board) Replace r363 with a 240k metal film resistor

Input transformer MoD: - You could add a input transformer (600:600) but the variable impedance wouldn't function correctly since you would have a fixed impedance set by the transformer.

Output transformer MoD: - Add a 600r:600r transformer between the output board. Cut the ribbon cable and wire the Transformer in line. (Input from the main board, Output to the output board)
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Channel 2:
Tube MoD: - Replace the tubes with a better quality 12AX7 tube (mullard, tung-sol, rca, whatever)

IC MoD:
- (Input board) Replace u201 with a gold contact ic socket and change the chip to: OPA2132, opa2134, OPA2107, LT1358, or LME49860NA (My fav)
- (Main board) Replace ic's u303, uu304, and u306 with gold contact ic sockets and change the chips to: OPA2132, opa2134, OPA2107, LT1358, or LME49860NA (My fav)
- Bypass the modded IC's V+ and V- (pins 4 and 8) with a .1uf film capacitor to ground

Capacitor/resistor MoD:
- (Input board) Replace c221, 222 with 100u 100v bipolar nichicon caps
- (Input board) Replace r248, and 249 with 10 ohm metal film resistors
- (Input board) Replace r247 with a 150 ohm metal film resistor

- (Main board) Replace c225 with a 2.2u film cap
- (Main board) Replace c315, 320, and 329 with 22u 35v bipolar caps
- Bypass those caps with .22u film caps
- (Main board) Replace c316, 318, 319, 322, 323, and 333 with 220u 10v bipolar caps
- Bypass those caps with .22u film caps
- (Main board) Replace r245 with a 33 ohm metal film resistor
- (Main board) Replace r243 with a 1k metal film resistor
- (Main board) Replace r343 with a 3k metal film resistor
- (Main board) Replace r355 with a 4.7k metal film resistor
- (Main board) Replace r358, r361, and 377 with 10k metal film resistors
- (Main board) Replace r347 and 369 with a 20k metal film resistor
- (Main board) Replace r364 with a 240k metal film resistor

Input transformer MoD: - You could add a input transformer (600:600) but the variable impedance wouldn't function correctly since you would have a fixed impedance set by the transformer.

Output transformer MoD: - Add a 600r:600r transformer between the output board. Cut the ribbon cable and wire the Transformer in line. (Input from the main board, Output to the output board)
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PSU MoD: - Change the diodes to Fast (UF) diodes
- Bypass c100, 101, 125, 126, and 127 with .1u film or ceramic caps
- Bypass c300 and c314 with .1u 250v film caps
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Disclaimer: I encourage people to DIY and I'm here in a informative role.
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Here are some images:
       
VLA 2 MOD Modification repair

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