New AC15C1 2010 Mods - Pictures and description - Clips

[Slaymoar]

** Disclaimer: Do this at your own risk. Do not attempt it if you do not know what a filter capacitor is, looks like, and how to drain them. If you absolutely need these mods and cannot perform them, a competent tech should be able to execute this quite easily. **

 

The goal of these mods are to restore this already great amp to AC30-like preamp. The preamps are already very similar, but these mods will implement the extras available on the current/previous AC30 lines. They are handy to toggle so you can still maintain the original AC tone, while adding flexibility to better accommodate your own setup.

 

To get into the amp, unscrew all these:

 

 

 

Inside:

 

 

 

 

Mod 1 - Bright cap mod:

 

This mod will allow you to use a much larger spectrum of pedals in front of your amp.

 

 

 

 

1. Remove C67 - 10pf ground (Reads 100)

 

It is located near the Top Boost volume knob. It is used to kill high end harshness. It is there to counteract the harshness which is brought on by the 120p cap, but is no longer needed when removing the 120p. This 10p capacitor was not part of the original AC15/30 schematic either.

 

2. Remove C8 - 120p high pass (Bright cap - Reads 121)

 

It is right next to C67. It is the capacitor that adds tons of sparkle when the top boost volume is low, and the master is high. It is a nice touch, but also kills any chance of most pedals sounding good in front of the top boost.

 

 

 

 

Mod 2 - AC30 tonestack mod: (Original vintage tonestack setup for AC15/30)

 

This one is a little tricky, since there are no spaces on the board to solder a jumper wire off the bass tone pot. I improvised something that works well. The sound difference is night and day. It provides a much bigger spectrum of tones. The treble and bass become much more "extreme". You will notice a boost of low end in your sound as well. I keep my bass around 3-4. The biggest difference for the bass control is from 0 to 4 - then there is not much difference between 5 and 10. The biggest difference for the treble control is between 5 and 10. From 0 to 4 only changes the mid range response slightly.

 

1. Remove capacitor C67 10p. You will be using the lug where there is no trace leading anywhere, which is ground. To verify, use multimeter on "beep" mode and verify ground once capacitor is removed.

 

2. Cut about 8" of 22awg hookup wire - do not use bare wire. Start by bending one end (crimped) and stick it in the tiny hole under the bass tone pot. If standing behind all the pots, its the first lug on the left - it is the lug that DOESNT have a trace going to the treble pot. You will notice a tiny hole where the wire will fit. Its a bit crowded, but its possible to solder there.

 

3. Cut the wire so it has a bit of slack to reach the C67 ground lug - I suggest more slack if you plan on adding a switch. Crimp it, and bend it so it doesnt flick out of the grounded hole. If uncertain, verify its the proper hole by checking ground with the big green ground wire/nut.

 

*OPTIONAL - Not shown in picture*

 

*4. Add an SPST switch near the tone controls. Once the AC30 tonestack mod is completed, as long as you have plenty of slack left, you can cut the wire in the middle and attach each end to an SPST switch to toggle between standard and custom.

 

 

 

Mod 3 - Normal channel -> Bright cap mod: (AC30 already has this selectable)

 

This is the easiest mod, which only involves getting rid of a single capacitor. It is a 120p cap which bleeds treble through the signal when normal volume is low. This is especially crappy if you plan on using distortion or some boost pedals. It darkens the tone a bit and helps tame the high end. ** I suggest using an on/off switch for this mod so you can keep the original Vox chime.

 

 

Simply remove Capacitor "C4". I will later add a mini SPST toggle switch and a quality mica 120p cap to be able to toggle between normal and bright. This mod will also be shown here.

 

 

 

Updated Jul/29/2010

 

 

Toggle switches: (from left to right)

 

Standard / Custom voice, Bass cut, Normal/Bright

 

[groovetube]

dope ideas

[Slaymoar]

(toggle switch hookup soon)

[Slaymoar]

[Johansolo]

i was literally planning on buying a vox night train head today (thanks to a casino outing last night)

...now you have me thinking about getting a AC15 instead

 

damn you.

 

great work btw:thu:

["sasquatch"]

sounds good, but you need to make some clips w/an sm57

[Sheik_Yerbouti]

Sounds great, man, I'll bet it sounds really good in the room!

 

One thing, though. If you EVER film yourself playing "Sweet Home Alabama" again, so help me GOD, I shall visit you in your sleep!

[Slaymoar]

Thanks guys! I'll try not to play sweet home again...

 

I'm on a good path with this, although I am still not happy with the gain sound. I want to tighten it a bit more and then add some blistering high mids to it. Still have some combinations to try...

 

-D

[JPIndustrie]

Thanks for this, I'm looking to get more out of my AC15C1 now!

[Mr_Wonka]

I can just buy a line6 pod and get that same tone. what a waste of time and money. the tones were weak.

[Slaymoar]

 

I can just buy a line6 pod and get that same tone. what a waste of time and money. the tones were weak.

 

 

Cool, go buy a pod and have fun.

[wwit]

Hey thanks for these mod idea's

 

I bought my AC15C1 2 weeks ago knowing that it was a good amp for a reasonable price, but had rooms for being a much better amp for a little more money and a little elbow grease.

 

First thing I did was get rid of the junk stock tubes. I swapped in JJ's from Eurotubes. I went for the 3 high gain and balanced preamp and 2 standard powertubes. Made a great difference. No more death rattle or microphonics and a nice overall boost.

 

But still too much high end. To brittle ice picky ear shattering top end from this amp. Dig into the strings and it beacame unbearable to play.

 

This is where the bright cap mods come in. I had read this thread a few weeks ago and decided to remove the C67, C8 and C4 caps last night. WOW what a difference. Gone is the ear splitting sharpness on the high end. Nice thing is that it still sounds like a Vox, but now its like a Vox on Marshall flavored steroids.

 

Im going to order some gold pin and standard preamp tubes from Eurotubes in the near future to experiment with. But as it is now, Im realy digging this amp as is.

 

[Fendert]

Wow good thing I stumbled on to this!

[owen1358]

Hey wwit i just got an ac15c1 and im thinkin about doing these mods, i was just wondering if you have any clips of what the amp sounds like with the mods? thanks- owen

[scud133]

where is the link for the clips

[Slaymoar]

No clips were added, but all the mods were made. I don't have the amp anymore, but a switch to the top boost channel for 120p and 1n were added and were very awesome sounding.

[chrisjnyc]

Digging this one up.... Any other mods for the AC15C1?

[guitargeek93]

I am about to do these mods, but I don't quite understand the toggle switch hook up except for the second one. I would very much appriciate it if you would expound on the other two a little. Can't wait to try the mods!

[98 les paul]

Can anyone recommend a vendor for purchasing the switches for this mod?

[Slaymoar]

BTW, for what it's worth guys, I highly suggest changing those crappy stock coupling and tone caps with proper poly caps. They definitely make a difference in sound, remove the muddyness of the stock noisy components.

 

 

 

Fluid gain mod:

 

At the electrolytic capacitor "C7+" Add a 1u 100v, or 2u2 100V cap across it for less muddyness in gain. Using 2u2 will have a bit more effect on the sound, but not enough to really notice between 1u and 2u2. You would need an A/B.

 

Where I get them: Capacitors -> Mallory 150 series -> 1u 100V

http://turretboards.com/

 

The best way is to remove the electrolytic, add the mallory across it in a vertical manner - kind of like picture:

Add it across the electrolytic in parallel, then resolder the electrolytic to the board. You can also choose to buy your own fresh electrolytic with longer leads to work with.. anything from 15u to 30u (50V) low ESR will work fine.

 

Same thing can be done with the other electrolytic C14 for V2. However, someone needs to verify that C14 is indeed connected to the kathode of V2 to confirm C14 is the proper cap to do this to. I no longer have the amp sadly.

 

Low end control mod:

 

C6 is responsible for the amount of low end that makes it to the gain stages. More low end will give it more bark, low end, and sound best with pedals. To achieve more low end, replace this 500p with a larger value like 1n or 2n2, more than 5n will start not having any effect at all, just full out nasty flabby sound at that point - that some people like, but it now begins to leave the Vox sound realm.

 

If you lower the value from 500 to 250p or lower, you will shift the mid character and lose some low end and it probably won't be as desireable. You can experiment though, why not. If you plan on trying seleral values, you can even solder two 4-6" hookup wires and use them to swap caps until you are happy with the sound.

 

 

Midrange gain boost:

 

This increases the gain of the amp, but also decreases the pedal friendlyness. If you don't use pedals, this might be useful to you:

Add a 1n cap across C8. I recommend using an SPST switch to be able to toggle it. This will add high some good midrange, and will have less of an effect once your increase the gain past 12oclock.

 

 

Tonestack mods:

 

I need a series of high resolution closeup shots of the board to be able to tell which caps do what... if someone cares to post some? Thanks

[Firedogx]

Hate to resurrect this thread, but I decided to do the mod! I was wondering if grounding the bass pot to C67’s ground was absolute. I decided to ground it to the chassis (shown here: https://m.imgur.com/054sNNv)

 

The mods work, however I am getting some noise now. I’m not sure if the mods caused it or my guitar, because with no guitar plugged into the amp I get a normal amp “shhhhhhhh” sound. But I get a “zzzzzzz” sound from both channels on the amp with a guitar plugged in. Touching my guitars pots can cause crackling too.

 

Since the mods are for the TB channel, would it affect the normal channel? Did I screw up by grounding it to the chassis? Was wanting to post on some forums looking for advice before taking the 2000 screws off the back of the amp and checking myself.

 

Have a Video:

[cann29120]

hello , how to see a photo please

 

[Phil O'Keefe]

hello , how to see a photo please

 

You can thank Photobucket for the missing photos... they changed their policies and don't allow embedded photos on other websites anymore. Since this thread is several years old, the original poster may not see your post and so you're probably not going to be able to see the photos... sorry about that!

 

 

[cann29120]

ok ,Thanx Phil

i do the change on my amp ,,,,, Great , really !!

but no more reverb ?

by:rawk: