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Posted by on Mar 6, 2015 in Private |

Avalon VT 737 SP Babyface (Fast Attack) Mod

This is a reposting of the instructions formerly host at about how to mod an Avalon 737 channel strip for a faster, more musical attack. I do not know the original author’s name to give him credit as the original post was deleted, but this information may be useful to many Avalon 737 owners and so we thought it useful to repost it.

Avalon Vt -737sp ‘Fast Attack’ (aka: Babyface) Modification

Please Note: It is recommended that a qualified technician perform this modification. If you choose to perform this modification yourself, I can NOT be held responsible for damage to your unit.

Required Tools: Soldering Iron – Solder – Solder Wick – Allen Key -Phillips Screwdriver

Parts Required: 1 – 1µf 100V Electrolytic Radial Capacitor (which looks like this:)



1: Disconnect all cables from unit and remove from rack.

2: Place in a secure area and remove 12 Phillips screws from top cover – Remove cover.

3: Locate the Optical Compressor Board. It is in the front middle of unit, directly behind the VU and marked ASSY 5600 7374.737 Mod2

This photo shows the capacitor being replaced.

737 Mod1

4: Be sure to touch a metal part of the case to discharge any static you might have before touching any part of the circuit board.

5: Remove the two Allen Screws securing the board to the main circuitry.

Make note of the orientation of the board. Also note there are 2 washers, keep track of these for later replacement. The board is attached by two multi-pin connectors, simply pull upward in a straight direction to unseat and remove.

6: Make note of the orientation of the Capacitor on the board. The Gray stripe indicates the negative (-) polarity and the replacement MUST BE INSTALLED WITH THE SAME POLARITY.

737 Mod3

7: Turn the over and remove the solder holding the capacitor to the board. I recommend using solder wick with a soldering iron as it quickely and cleanly removes solder from boards.

8: When the capacitor is removed use iron and wick to clean any excess solder from the points on the board for easy installation of the new capacitor. – Check the rating of the removed capacitor. If it is 2.2µf 50V, replace with the 1µf 100V.

NOTE: Some older models have a 2.2µf 63V Capacitor. In these units a 1µf 63V Capacitor is recommended.

9: Install new Capacitor BEING SURE TO CHECK POLARITY. Solder in place (this takes very little solder, be sure not to use too much) and trim excess wire from board.

10: Reseat board, reinstall allen screw and washers. Replace top and screws.

Your Avalon 737 compression section is now ready for ‘faster’ fast attack.