ART PRO VLA 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!

Notes: The ART Pro VLA II is a very good compressor right out of the box but it can be improved with better components. Depending on the level of mods and quality of parts these mods can have minimal to great effect on the sound of the unit.

- Change the tubes to non-chinese tubes. (minimal-medium effect)
- Just a IC change can clear up the unit (take out the mid scoop), while adding transformers will add the most "color".
- Cap/resistor changes will have a minimal effect while the opto change will "Grab" more.
- The higher voltage mod I haven't noticed any difference, but it can't hurt to have more voltage on the tubes.
- I haven't noticed much if any difference in sound with the PSU mod and IC bypass but it is better design and your unit will most likely last longer.
- The cost to buy a unit and mod is ($300 or so retail, $100-300 MOD, Time.., so $400-$600 total). Not to throw you off but you could just buy a better compressor for that...
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Channel 1:
Tube MoD: - Replace the tubes with a better quality 12AT7 tube (mullard, tung-sol, rca, whatever)

IC MoD:
- (Main board) Replace ic's a2 and a3 with gold contact ic sockets and change the chips to: OPA2132, opa2134, OPA2107, LT1358, or LME49860NA (My fav)
- (I/O board) Replace a5 and a11 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 capacitor to ground

Capacitor/resistor MoD:
- (Main board) Replace c17, c29, c42, and c43 22u 50v bipolar caps
- (I/O board) Replace c41 and c44 with 22u 35v bipolar caps
- Bypass those caps with .22u film caps
- (Main board) Replace c28 with a 47u 35v bipolar cap
- (I/O board) Replace c21 and c23 with 47u 35v bipolar caps
- Bypass those caps with .47u film caps
- (Main board) Replace r31 with a 2.2k metal film resistor and replace r56 with a 3k metal film resistor.

Vactrol/Opto MoD:
- (Main board) Change the Optical cell to a VTL5C1 (Faster Response, "Grabs" more)
Your Attack, Ratio, Release, and Threshold values on the case will not be accurate though. You'll have to dial it in by feel.

Input transformer MoD: - Add a 10K:10K input transformer on the input. Take out A5. Solder the input tranny in(+) to pin 2 of the xlr jack. Solder the in(-) of the input tranny to pin 3 of the xlr jack. Cut the white wire on the ribbon cable. Solder the out(+) of the tranny to the white wire going to the main board. solder - of the tranny to a ground point on the main board. Use a ohm meter.

Output transformer MoD: - Add a 600r:600r transformer between the output board. Cut the Yellow and green wires on the ribbon cable and wire the Transformer in line. (Input from the main board, Output to the output board) I don't recommend this mod unless you are using a line driver circuit or a DOA on the output to be able to drive the transformer.
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Channel 2:
Tube MoD: - Replace the tubes with a better quality 12AT7 tube (mullard, tung-sol, rca, whatever)

IC MoD:
- (Main board) Replace ic's a8 and a10 with gold contact ic sockets and change the chips to: OPA2132, opa2134, OPA2107, LT1358, or LME49860NA (My fav)
- (I/O board) Replace ic's a7 and a12 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 capacitor to ground

Capacitor/resistor MoD:
- (Main board) Replace c46, c52, c53, and c64 with 22u 50v bipolar caps
- (I/O board) Replace c6 and c63 with 22u 35v bipolar caps
- Bypass those caps with .22u film caps
- (Main board) replace c59 with a 47u 35v bipolar cap
- (I/O board) replace c65 and c67 with 47u 35v bipolar caps
- Bypass those caps with .47u film caps
- (Main board) Replace r124 with a 2.2k metal film resistor and replace r88 with a 3k metal film resistor.

Vactrol/Opto MoD:
- (Main board) Change the Optical cell to a VTL5C1 (Faster Response, "Grabs" more)
Your Attack, Ratio, Release, and Threshold values on the case will not be accurate though. You'll have to dial it in by feel.

Input transformer MoD: - Add a 10K:10K input transformer on the input. Take out A7. Solder the input tranny in(+) to pin 2 of the xlr jack. Solder the in(-) of the input tranny to pin 3 of the xlr jack. Cut the white wire on the ribbon cable. Solder the out(+) of the tranny to the white wire going to the main board. solder - of the tranny to a ground point on the main board. Use a ohm meter.

Output transformer MoD: - Add a 600r:600r transformer between the output board. Cut the Yellow and green wires on the ribbon cable and wire the Transformer in line. (Input from the main board, Output to the output board) I don't recommend this mod unless you are using a line driver circuit or a DOA on the output to be able to drive the transformer.
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PSU MoD: - Change the diodes to Fast (UF) diodes
- Bypass the V+ and V- with .1u film or monolythic ceramic caps
- Bypass c36 and c50 with .1u 63v film caps
- Add a 47u 100v cap to ground from B+ at r98. Bypass with a .1u 63v or higher cap
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Higher Voltage MoD:
- Reduce R201 to 4.7k metal film
- Add a 5.6v zener in series with the 47v zener
- Reduce r64 and r96 to 150k metal film resistors to provide more voltage to the first gain stage of the tubes + reduces noise, lowers gain.
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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:
   

Replacement Parts:
- SD 740 vu meters off of ebay work as replacement ART Pro VLA (1) meters. I haven't tried them as VLA II meters. You can get them for around $10 and have either a green or amber lamp (not led). The only flaw is that the outside lens is too big so you might have to do some metal work or tape on the lens from the old vu meter

- Pushbutton switches: 4mm pin placement
DPDT - ALPS - SPUN191400 (VU)
DPDT - C&K - F2UEE (Silver contact) (VU)
DPDT - C&K - F2UEEAU (gold contact) (VU)
4PDT - ALPS - SPUN19C400 (bypass)
4PDT - ALPS - SPUN194700 (bypass)
4PDT - C&K - F4UEE (Silver contact) (bypass)
4PDT - C&K - F4UEEAU (gold contact) (bypass)

Here are some pictures from some mods.
HERE!!! https://www.facebook.com/media/set/?set=a.638323189594684.1073741843.478520652241606&type=1&l=e019c82ff8
VLA 2 MOD Modification repair

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