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So I clipped the bright caps on my Vox AC15C1 (C4, C8, C67), but I have decided that I prefer the sound of the stock amp. Fortunately, I only clipped one leg on each capacitor, so they are all still attached to the circuit board. My question is, would reversing this modification be as simple as soldering the leg of the capacitor still attached to the circuit board to the wire sticking out of its end (see picture below), or will this risk damaging the capacitor in someway? Also, can I go straight into soldering this, or do I need to take certain precautions (draining capacitors, etc.) before doing so to prevent the risk of electrocution? If so, how exactly do I go about doing this?



Thanks, I am relatively new to electronics and soldering, but I would like to learn how to do this kind of stuff myself.

You realise you could be open to castigation for what I've seen RG Keen call the BUMS - blind urge to mod syndrome

If you're adept with a soldering iron a botch job may be possible if you've left the lead sticking out the end of the cap long enough. If it's too short chances are you will really struggle without burning the caps... possibly fatally. Is it a modern pcb amp? If so the pcb and other components are likely to get in the way and there's a good chance of at least some 'collateral damage' with the iron even if you succeed. It may all work again, but you could make a bit of a mess (whether that bothers you or not I don't know).

I doubt from what you say you'll be adept enough with an iron though - so the recommended solution has to be to desolder the cut caps and replace them with new. This could be a bit of a time-consuming job - you'll have to dismantle and maybe desolder things to get the pcb out.

You really shouldn't go inside any amp without taking the recommended precautions you can easily find googling the topic (making sure the reservoir/filter caps are drained).

It's just common sense, not over precaution. Study the schematic if you can find it - are there drain resistors in the HT line? If you don't know what they are at least do enough reading before you go inside. Make sure you've a decent multimeter that you can rely on to measure voltage in caps and watch it drain away.

Did I mention a modern, mass produced pcb amp has a good chance of being a pain when undertaking anything of this nature? They're designed to be produced and assembled... but seemingly not to work on again... probably just to throw an entire pcb away and replace with new if a problem arises during guarantee (if not just replace the entire amp - it's likely cheaper than repair work).

You might be able to make good your previous mods without removing the PCB if your soldering skills are good enough, but be very careful not to apply too much heat to the short lead in the board. There is a good chance of melting the solder holding it into the PCB causing the lead to move or drop out completely. You will then have to remove the board to solder in a new lead (or preferably capacitor) and to make sure the old lead is not shorting something out.

So if this were your amp, what would you do?

I just want to put the caps back into the circuit as easily and quickly as possible. I'm not too concerned if the soldering looks ugly, but I don't want to do anything that will create new problems for me.

Without photographs it's not possible to give reliable suggestions I don't think.

How long is the lead left on the cap itself - where did you snip? Did you take a section of lead out or just snip it?

Things you could think of trying - IF the caps were raised high enough from the board to begin with and you've enough lead...

1) Wrap a piece of solid core wire - as thick as the original lead - around the piece still stuck in the board at one end; bend this upwards and wrap around the piece of lead still on the cap. In other words: connect both ends together with a jumper lead that will physically hold both parts in place, so that when you add solder the piece stuck in the board cannot drop out as Fred pointed out could happen.

2) If there's enough lead left just to push the end of the cap down so both sections of lead reconnect and are pressed against each other - attach something like small forceps or heat sink to the lower-most part of the lower section of lead so there's no risk of it falling out. Add heat and solder.

3) If there's space - and there's enough lead sticking out the board at the snipped end: cut the caps out completely leaving two poking up leads. Get new caps of same or more voltage rating with long leads. Physically wrap these leads around the 'posts' you've been left with. Add solder.

But this is just guessing what you could try without pics - or knowing the space you've got to work in... I'm guessing it could be quite condensed and crowded in an amp like that.

Ideally - it may be a lot easier to take the pcb out.


...or build a Rangemaster/Treble Booster perhaps and leave as is

I've no idea why this mod is undertaken - or much about the actual amp - to be sure that would be a solution though

Okay, thanks. These seem like some useful approaches. I will look into it more once I see how much of the leads I have to work with. I only clipped them (didn't remove chunks from the wire), so hopefully some of these options might be possible.

The bright cap mod is very common with the AC15C1. These capacitors preserve the high-end frequencies of the amplifier at lower volume levels, but as a result it makes dirt pedals running through the amp sound shrill and brittle. Removing the caps from the circuit did help improve the sound of pedals quite a bit, but it took away that signature Vox high-end jangle. From what I've read, most people are happy with the mod, but I'd rather just play the amp without pedals and keep what makes it unique.

If I were putting it back to standard, assuming that there is sufficient clear space to get an iron tip in and there was enough lead sticking out of the board, I would :-

Make sure that the leads are scrupulously clean (shiny clean*), push the cut end of the cap down so the leads are parallel and touching, then go in with the iron quick and hot. One quick dab of solder so there is no damage to either the capacitor or PCB board, and no time to conduct enough heat to melt the original solder joint.

*I use an typists eraser (but I don't suppose you can get them now). They look a bit like a fat pencil with a very thick centre of a rubber compound loaded with sand. I push the lead I want to clean into the rubber compound end and twiddle the eraser round a few times. It cleans all the oxide and crap off. The capacitor would stand bending up once to clean it's cut lead.