VOX AC30 Amplug modification

[shadowfan]

I just bought one of these little gems and can't put it down!

The AC30 emulation is uncanny, what with available overdrive (which I don't use, as I play clean) and tone.

I plug it into the output of my ZOOM 508 effects box and into a pair of noise cancelling SONY headphones. It's heaven:...no feedback (from my better half, that is).

The unit is somewhat flimsy, however and I am thinking of modding it into a nice little metal box, with input/output jacks as well as a DC jack and normal size pots.!
The main problem I see is replacing the thumwheel pots (VOL/GAIN/TONE) with the panel mounted ones; removing the PC board mounted ones looks like it's going to be a bear. They have 5 lugs, though I suspect the outer ones are just for mounting on the board. But it's tight in there!
An additional output jack will be installed in parallel with the existing one but with with an attenuator resistor, for use as a line out into my Laptop (with Audacity)...my laptop does not have a line input, only a MIC level one.

Any thoughts on this? Has anyone done it yet?

[aunchaki]

No thoughts, but I hope you take pics as you go. I'd like to see this job in progress. Good luck!

[Frontier9]

Is there any space between the pots and the board? If the pots are standing off of the board on their lugs, maybe you could clip the lugs and use them as solder points. I like your idea very much, it would be cool to put two or three varieties in one box!

[JohnnyCrash]

Originally Posted by Frontier9

Is there any space between the pots and the board? If the pots are standing off of the board on their lugs, maybe you could clip the lugs and use them as solder points. I like your idea very much, it would be cool to put two or three varieties in one box!

Great idea! If you're replacing the pots anyway, you might as well clip the old ones if possible.

Two or three Amplugs in one durable box... Frontier9, you're a genius!

Very cool ideas...

[Ben Harmless]

This does actually sound kinda cool, but I can't even figure out how to open mine up!

There appears to be a small screw in the plug housing, but while it feels like it's turning, it doesn't seem to loosen. I peeled the label off the inside of the battery compartment - that's the board. The sticker on the front isn't hiding anything good, and though I did pop off the Vox logo on the front, that's no help either - but it's kinda cool to have a little gold Vox logo.

Thoughts?

[JohnnyCrash]

Probably typical plastic construction.

Use a small flathead to gentley pry the seam apart? IDK.

[shadowfan]

To open it up, first remove the small phillips head screw just above the phone plug. Then progressively pry open with a small screw driver. With the battery compartment open, you can separate the 2 parts of the shell enough to start prying the thing apart.
WATCH OUT for 2 things, though: 1:the battery terminals fit in slots in the cover, and 2:, be careful to clear the 3 pots' thumbwheels when you lift the cover off. What I call the cover is the part that holds the phone plug. The PC board is in the front section

As for the pots themselves, it looks like the only way is to de-solder them using solder wick. There is not enough post height to just cut them off, remember this PC board is of the surface mount type and is 2-sided to boot, hence my aprehension so far.
Also I don"t know if the value of the pots is marked, so, to measure them out of circuit presupposes they are not destroyed in the process of removal.

As I write this, I just opened it up again, and I observe the following:

The 1/4 plug is actually wired (black=GND, red=Signal); I would use the wires for a 1/4" jack, most likely a switching type for the power leads (leave the PC mounted switch in the ON position. The leads on the LED can be cut flush with the LED body and the stubs used to connect leads to a new outboard LED (watch for polarity).

As for the existing jacks, I'll leave them alone, and run short leads to connect small plugs (stereo, I think) to 1/4" jacks. (for once radio Shack may come in handy, they have these plugs--get the cheap ones as you don't need the shell).

Back to the pots: Very risky to try to remove then (looks like their back may be glued to the board) but perhaps an Xacto knife with a fine saw blade could be used to carefully cut off the legs (they don't go through the board); removing the wheels can be done by grinding the central rivet with a small burr on a Dremel--or they can be left alone (does not really matter since the pots will be out of the circuit once the legs are cut); the trick will be to solder leads to the board to reach the new pots without causing solder bridges.

Anyway I want to enjoy it as is for a little while before I don my surgical mask :). But yeah, I will take pictures when I do go ahead with the project. I need to order the box (Small bear).

[shadowfan]

Here are 2 views of the open Amplug.

[shadowfan]

Damn, can't remember how to upload pix. Will try again.

[shadowfan]

Note the small pads where the pots are soldered (the outer ones are just mounting legs). Note the battery terminals on the RH photo: they fit in slots in the rear half of the shell. Be careful when you disassemble/reassemble. New power leads will be soldered to those springs (Polarity is clearly marked). You will need an outboard battery holder (you could use AA's instead of AAA's). Need to check for utility boxed with battery access. Will revert.

[shadowfan]

The box I have in mind does not have battery access (actually none of them do), but it would be a BB sized one from Small Bear (no affiliation) and they come in lots of flavors.

All the jacks are available there too, including a panel mount power jack.
The VOX logo will be re-used (it can be detached from the shell) and maybe even the Vox pattern "grill cloth" too (soak in water and gently peel off).

Need to find a 3V wall wart (but it must be filtered, otherwise filter caps must fit in the box); I suppose it should be regulated, but not sure.
I have a couple for a CD player that are 3V. If they don't induce hum, they'll do. Rechargeable AA's? don't know, they're 1.25V and I'm not sure that's enough. Wireless phone rechargeable packs will put out 3.75V and that may be too much unless I use a diode in series which should drop .7V. and a charging circuit would be easy to implement (one resistor + one diode).

Battery holder, LED and bezel, mini stereo plugs and, I think, knobs, from Radio Shack
1/4" jacks NOT from RS, they're crap

Potentiometer source will depend on values required.

[JohnnyCrash]

If you go with a diecast box the size of typical stomboxes, you may be able to fit a battery pad in there. If not, upgrade the size. Hammond boxes come in a wide variety of dimensions.

Also, if you plan on using batteries AND having an AC adapter, use a stereo input jack so that you can short to ground when unplugged to avoid wasting battery life.

[shadowfan]

As for the switch, shorting to ground would be OK IF signal ground and voltage ground are the same, which I should have checked while the thing was open. Otherwise I could use a pot mounted switch. As for the battery space, no problem; it looks like the PC board can mount vertically. If everything is mounted to the box, it's not a big deal to remove 4 screws for battery access.

Front of box: 1/4" input jack and PC board
Rear of box: Headphone jack (1/8" stereo), Line out (1/8" stereo) AUX in (1/8" stereo). Power jack on one short side.

Box top: Pilot LED, VOL(w/switch?) TONE and GAIN.

[shadowfan]

OK, I found out that the guitar input ground is common to power ground. This is good as I can use a stereo input jack as a power switch (ring and ground lugs would be shorted by a mono plug).

On the other hand the headphone jack and the AUX IN jack do not share ground, which implies insulated jacks (die cast box); it also kills the idea of an L-Pad attenuator for the Line Out I was planning (at least I think).

[Ben Harmless]

Hehe. I just set my guitar down with the Amplug still plugged in, and opened it up by accident. Still works though.

Those pots are going to be interesting to work around.

Oh, and I've been using rechargable batteries in mine since I bought it. I don't buy anything that cant take the rechargables anymore. I can't stand the battery money pit.

[shadowfan]

Harmless:

how long do your batteries last on a charge? Any problem with the lower voltage of NiCd's (I assume that's what you're using)?

[kynyrd synyrd]

hello shadowfan,
i own a vow amplug. while in use the headphone chord was bent, twisting the jack. my desire to pop it open lead me to this post. i want to possibly follow in your footsteps and build a stompbox enclosure. my question is, did you ever figure out the K values for the three pots? i'm sorry if that is not worded perfectly, as i am a novice tinkerer. links, or very specific parts descriptions would be most appreciated.

many many thanks,
kynyrd

[Delta63]

I've got to try this!

I think I'll do it with the lead, BASS, Classic Rock and the AC30

[kynyrd synyrd]

allright, another post in 2011 on this old thread! somebody set this stomp box up and post some good details please. i'd love someone to really explain the process of removing the potentiometers and what exact type to replace them with.

thanks!

kynyrd