ART PRO VLA I 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!
- The stock switches on the Pro VLA 1 are very cheap, don't close properly, or are intermittent. Recommended replacements on the bottom of the page.

Notes: The ART Pro VLA is a very good compressor right out of the box (VLA II is better) 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 ($150 -$200 or so retail, $100-300 MOD, Time.., so $250-$500 total). Not to throw you off but you could just buy a better compressor for that...
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Note: Channel 1:
Tube MoD: - Replace the tubes with a better quality 12AT7 tube (mullard, tung-sol, rca, whatever)

IC MoD: - Replace ic's a2, a3, and a5 with gold contact ic sockets and change the chips to: lt1358, opa2132, opa2134, 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: - Replace c29, 28, 30, 41, 42, 43, 17 with 22u 50v bipolar caps
- Bypass those caps with .22u film caps
- Replace c21, 23 with 47u 35v bipolar caps
- Bypass those caps with .47u film caps
- Replace r31 with a 2.2k metal film resistor
Vactrol/Opto MoD:
- (Main board) Change the Optical cell to a VTL5C1 (Faster Response, "Grabs" more)
Your Ratio 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. Solder the out(+) of the tranny to where pin 7 of A5 would go or at one of the junctions where r63, c39 and pin 7 meet. Solder the out(-) to a ground point near the chip (r59, r78, r81, r80, or c37). Make sure this point is on the ground. Use a Ohm meter.

Output transformer MoD: - Add a 600r:600r transformer between A2 and 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: - Replace a7, a8, and a10 with gold contact ic sockets and change the chips to: lt1358, opa2132, opa2134, 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: - Replace c53, 59, 54, 46, 52, 63, 64 with 22u 50v bipolar caps
- Bypass those caps with .22u film caps
- Replace c65, 67 with 47u 35v bipolar caps
- Bypass those caps with .47u film caps
- Replace r124 with a 2.2k metal film resistor
Vactrol/Opto MoD:
- (Main board) Change the Optical cell to a VTL5C1 (Faster Response, "Grabs" more)
Your Ratio 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. Solder the out(+) of the tranny to where pin 7 of A7 would go or at one of the junctions where r122, c61 and pin 7 meet. Solder the out(-) to a ground point near the chip (r118, r135, r138, r139, or c57). Make sure this point is on the ground. Use a Ohm meter.

Output transformer MoD: - Add a 600r:600r transformer between A10 and 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 c8, c10, c24, c25, c36, and c50 with .1uf 63v or higher film/ceramic 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 R13 to 4.7k metal film
- Add a 5.6v zener in series with the 47v zener d14
- 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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Replacement Parts:
- SD 740 vu meters off of ebay work as replacement ART Pro VLA 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 will have to take the lens off of the old meter, throw away the lens from the new meter. Put the old lens in the bezel (Black plastic piece from the faceplate of the VLA) and line it up on the new vu meter. Now tape and/or glue all the sides of the new vu and old lens together (not the bezel, bezel is just used to hold everything in place).

- Pushbutton switches: 4mm pin placement. The stock VLA (1) pushbutton switches are horrible in my opinion. I would recommend the gold contact for the bypass as audio goes through this.

DPDT - ALPS - SPUN191400 (VU, Attack, Release)
DPDT - C&K - F2UEE (Silver contact) (VU, Attack, Release)
DPDT - C&K - F2UEEAU (gold contact) (VU, Attack, Release)
4PDT - ALPS - SPUN19C400 (bypass, link)
4PDT - ALPS - SPUN194700 (bypass, link)
4PDT - C&K - F4UEE (Silver contact) (bypass, link)
4PDT - C&K - F4UEEAU (gold contact) (bypass, link)
- EG4807-ND - CAP PUSHBUTTON ROUND GRAY
- EG4806-ND - CAP PUSHBUTTON ROUND GREEN
- EG4805-ND - CAP PUSHBUTTON ROUND RED
- EG4804-ND - CAP PUSHBUTTON ROUND BLACK

Here are some pictures from some mods.
HERE!!! https://www.facebook.com/media/set/?set=a.638317159595287.1073741842.478520652241606&type=1&l=12a169d4cb

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