ART Levelar Mods

Warning!!!: Art uses VERY small traces that can be easily damaged by improper soldering techniques. Take extra care with these units!

Notes: The ART Levelar is a good easy compressor. (VLA I and VLA II have more options) 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.

Tube MoD: - Replace the tube with a better quality 12AT7 tube (mullard, tung-sol, rca, whatever)

- Replace ic's u1 and u2 with 14 pin gold contact ic sockets and change the chips to: MC33079, LME49740NA, OPA404, or OPA4227
- Bypass the modded IC's V+ (pin 4) with a .1uf capacitor to ground

Capacitor/resistor MoD: - Replace c13, c14, c17, c19, c23, c28, c29 with 22u 50v bipolar caps
- (Optional) Bypass those caps with .22u film caps
        - Option 2 - Instead, Replace those electrolytic caps with a 10uf 5mm spacing film cap (10u = MKS2B051001N00MSSD or MKS2B051001N00JO00). No need to bypass those with smaller film caps.
- Replace c31 and c32 with 47u 35v bipolar caps
- (Optional) Bypass those caps with .47u film caps
- Replace c30 with a wire jumper or a 22u 50v bipolar cap. Wire is better.
- Replace c18 with a 1u or greater film cap (Depends on what you can get to fit)

Vactrol/Opto MoD:
- (Main board) Change the Optical cell (U3) 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. 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. Remove c17. Solder the out(+) of the tranny to the (-) pad of c17 Solder the out(-) to a ground point near the chip. Make sure this point is on the ground. Use a Ohm meter.

Output transformer MoD: - Lift one side of r27 and r28. Must be the side that is not at the junction of c31 and c32. Add a 600r:600r transformer. Tranny in(+) will go to r27. Tranny Out(+) will go to the vacant pad of r27. Tranny in(-) will go to the lifted lead of r28. Tranny out(-) will go to the vacant pad of r28.

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

Higher Voltage MoD:
Note:These are calculated values, I have not done this mod myself. If you do this, make sure to check the voltages with a voltmeter.
- Replace R51 with a 22k metal film
- Add a 5.6v zener in series with the 47v zener CR9
- Replace R52 with a 14k metal film
- Replace r16 with a 100k or 150k metal film resistor to provide more voltage to the first gain stage of the tube + reduces noise, lowers gain.

Disclaimer: I encourage people to DIY and I'm here in a informative role.
_______________________________________________________________________________________________________________________________________________ Schematic PDF


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