Boss Auto Wah AW-2 Mods

[chassit]

Haven't been on the forums in a while because of work, but came across an AW-2 today at a yard sale for $20.

I'm looking at doing at least the "Instant Attack" and "Triangle LFO" mods I found at http://autowahmods.blogspot.com/.

Anybody know anything else I can do to it?

[Mark Hammer]

R27 (1k) and R28 (68k) set the attack and decay times, respectively, and C15 (can't quite read the value, but I'm guessing 1uf) is the averaging cap.  Dropping R27 down to 330 or even 100R would shorten attack times, and increasing either C15 or R28 will lengthen decay times.

[chassit]

Thanks for the assistance. But are you following the schem at that site for these values? The author of that site used a schem for the Boss TW-1 rather than the AW-2.

According to the schem at http://www.eserviceinfo.com/downloadsm/41767/Boss_AW2.html those values don't match up. If this is the actual schematic, am I correct in translating what you used (R27, R28, and C15) as R14, R19, and C7 respectively? The values and arrangement seems right. In this case, are you suggesting changing out R14 rather than R20 for the "Instant Attack" mod (http://autowahmods.blogspot.com/2009/08/instant-attack-mod.html)?

Thanks

[Mark Hammer]

Thanks for correcting my error, and for the link.  That fills a gap in my Boss schematic collection!

You are correct, the component numbers I indentified in the TW1 correspond to the ones you identified in the AW2.

R14, since it precedes C7, determines the charge-up time for C7.  You are correct in finding the conspicuously large value of R20 something to wonder about.  IC3a essentially buffers the envelope signal prior to being mixed with a DC offset and the LFO, in addition to providing a little more ripple-rejection, via C10/C11 in the feedback loop.  The negligible value of R14, when added to R20, makes IC3a a more-or-less-unity-gain stage (especially when you factor in component tolerances).

Note the pre-emphasis in the envelope follower section, provided by R10/C6.  This provides for greater sensitivity in the rectifier for stuff above 1.8khz.  Smart.

I have a Boss RPH10 desktop phaser that I have modified to include envelope following.  It has a sluggish response, by design.  One of the neat things that lets you do is use the overall average picking strength to effectively shift the sweep range in real time.  If the response time is too fast then the envelope follower doesn't sum with the LFO as smoothly.

You may want to try the same experiment here and see if it provides any advantage or viable options for you.  For a slow/fast option, I'd suggest having a 4u7 cap in parallel with a 100k-220k fixed resistor as a switchable replacement for the existing 1u/68k combination.  the 1u/68k is better suited to using the envelope follower on its own, while the longer decay time of the other combo is better suited to using the envelope follower as a complement or adjunct to the LFO.

[Electron Tornado]

Talk about reviving an old thread.....

Taking a look at the TW-1 schematic: http://autowahmods.blogspot.com/2009/08/schematics.html#start
There is a "Peak" control on the TW-1 that isn't present on the AW-2. Has anyone tried modding the AW-2 with that control?

Link to AW-2 schematic:  https://www.eserviceinfo.com/downloadsm/41767/Boss_AW2.html