AC30cc2 & C2, also AC15C1: my mods

[TmcB]

As you know I have an AC30, and I've been modding it over time to see how good it can get.
This post is really just for posterity for myself rather than anything else.

Here's the list of things I have inflicted upon this poor thing so far

• – Made a junction box for the speaker wire/reverb cable to connect to and attached it to the chassis - essential to save headaches and swearing when changing tubes or speakers
  
  – Swapped out reverb tank for an Accutronics one (replaced R18 with a 28K, added a 470K resistor across lugs 1 and 3 of the reverb drive switch, replaced pan with Accutronics pan # 9EB2C1B)
  
  – Fixed the FX Loop (C109 to 2.2uf)
  
  – Sped up the Tremolo (changed R38 to 27K, R37 to 100k)
  
  – Added more gain to the normal channel, changed the brilliance switch caps to be useable (removed and jumpered R49, C12 to a 100pf cap, and then put a 68pf cap across lugs 1 and 2 of the Normal volume pot)
  
  – Changed the treble cap in the top boost channel, and the one on the TB vol pot (c13 to 68pf, c16 to 47pf)
  
  – Removed Top Boost Cathode Bypass cap for tighter bass, more headroom on the TB channel (removed c9)
  
  – Changed the Plate resistors for more gain, and more vintage spec (replaced R6 & R7 100k Plate Resistors with 220K Resistors)
  
  – Changed the screws out for ones that don't strip instantly
  
  – Swapped out all the caps in the signal to Mallory caps (C11,C14, C15, C17, C18, C19, C20, C23 to Mallory equivalents)
  
  – Changed crappy Wharfedales out to Alnico's, settling on the classic 2x Celestion Blues (great combinations included 2x Greenbacks, Silver + G12H30, Silver + Creamback, Silver + Blue, Gold + Blue, 2x Gold - favourites were blue + gold, 2x golds, 2x blues)
  
  – Changed tubes to JJ power + rectifier, Sovtek preamp (Sovteks were surprisingly good, although I have some Tung Sols to try, and a Weber Copper cap for if the rectifier goes)

If I discount speakers and tubes, it was probably $80 of parts and 2 hours of time which has been time and money very well spent

The biggest fixes tonally have been the speakers and bright caps, the rest is cumulative or just fixing things for better utility for me.

Only one last thing for me to swap out really, and that's the OT

[olegmcnoleg]

Very interesting, thanks for posting this Tony, it is a useful resource.

[null_pointer]

So if I read that correctly, you have 3 inches of tolex and the handle left of the original amp...

[TmcB]

Ha!

Surprisingly less action in real life than it looks when written out. Most of this is because my ac30 is a very early one, mid production the hardwired speakers & reverb, effects loop, trem, and tube things were fixed.

[StrummersOfThunder]

Nice work!
I did a fair bit with my ac15.
Im sure the speaker change was like lifting a pregnant manatee of the amp.

[weltall89]

Owner of 2 modded AC30ccs here. It really is a great amp once it has been subjected to some of these mods. Seems to have a bad rap, and I have owned the newer AC30 Custom and found that to be inferior - even stock.

I actually found that changing to 68pf for the TB Channel has made mine too dark once the speakers were broken in. I am going to change it to 100pf. I enjoy a cutting tone, so it's all personal taste.

I am undecided about the OTs, some say it's like night and day, others have told me it made barely any difference at all.

[alanp]

Something I always wonder about...

If these mods make it such a better amp...

Why in hell do Vox not do this, stock?

[Bg]

To be honest, once those wharfdales are worn in, they aren't that bad. I think a lot of people swap them out before giving them a chance. I always preferred greenbacks in mine, but the wharfies weren't bad once they bedded in. Not the best in the world but not shite either, happy to have another pair if anyone wants to gift them to me

[TmcB]

Something I always wonder about...

If these mods make it such a better amp...

Why in hell do Vox not do this, stock?

Then they wouldn't have a reason to come out with the C2 series! There are a few mods there that are purely because it's a very early run cc2 and they got fixed later in production, like crap tubes, wrong fx loop cap value (schematic typo), trem speed, hardwired speakers, the rest are gravy.

I honestly think that with the cc2, they did a lot of great bells and whistles like input linking, tube bias, EQ response switching, and filter switches but offset the cost with cheap speakers. They also somehow didn't get that the way they did the standby would eat recipients but they were responding to consumer demand.

They responded to consumer demand again by removing the bells and whistles, changing from an input link switch to hi/Lo inputs per channel,changing to solid state so people could use stand by, mounting the tubes fender style so they're easier to get to, and most importantly, proper Celestion speakers (greens or blues).

Sounds great on paper but they cheaped out on the cab (mdf vs cc2 Birch), removed the option for a tube rectifier (them feels mang), put the tubes in a position that will bake the PCB over time (heat from all tubes goes straight up to PCB, will surprised if things don't go pear shaped later), removed the cool functionality like filtering and wattage select and the simple input link.

I think you get a better amp out of the box with a C2, but you can make the cc2 an amazing amp for less money.

[TmcB]

Owner of 2 modded AC30ccs here. It really is a great amp once it has been subjected to some of these mods. Seems to have a bad rap, and I have owned the newer AC30 Custom and found that to be inferior - even stock.

I actually found that changing to 68pf for the TB Channel has made mine too dark once the speakers were broken in. I am going to change it to 100pf. I enjoy a cutting tone, so it's all personal taste.

I am undecided about the OTs, some say it's like night and day, others have told me it made barely any difference at all.

I'm exactly where you are, I think they got a bad rap due to wharfdales (which aren't terrible, but I think they made more sense on paper than in real life with the amp), the unnecessary Standby, and to a lesser extent poor choice of value for the treble bleed caps.

I hear the same thing about OT's, either it really helped and was awesome, or it did sweet FA.

[TmcB]

Thought I'd best to update this to match the newer AC30

The AC30cc2 and AC30C2 Preamps are almost exactly the same, apart from the the C2 series doesn't have the switches and have chosen far more sensible values for the treble bleed caps etc. The problem is mapping them to the new board...which I've done The CC2/Lyle Caldwell mods references are on the left, the C2 on the right

Plate resistor mod:
R6 & R7 = R14 & R12 respectively. However, R14 is already 220k so all you have to do is change R12 from 100k to 220K

Normal channel gain increase:
R49 = R13 – jumper this for more gain. The treble bleed cap on the normal channel is C18, stock is 120pf if you wish to muck around with that. (Mod changes this cap to 100pf, and has a "brilliance" switch that puts a 68pf cap in parallel with the 100pf)

Top Boost treble cap:
C13 = C15 (stock 120pf) tweak to taste (68pf?) or remove

Tone stack tweak
C16 = C23 (stock 56pf) -> 47pf

Removal of Top Boost Cathode Bypass cap
This is the U2 mod - the Edge's amp doesn't have this cap and it makes for tighter bass, more headroom/lower gain on the TB channel.
C9 = C18 (kinda nice to put on a switch)

Coupling caps - change them out to Mallorys/Sozos for corksniffery good times
C11 = C7 (.047uf)
C14 = C38 (.022uf)
C15 = C28 (.022uf)
C17 = C45 (.1uf)
C18 = C48 (.1uf)
C19 = C51 (.1uf)
C20 = C50 (.1uf)
C23 = C80 (.0047uf)

If you liked the Custom/Normal switch you could lift the leg of R47 that connects to the bass pot. Then you'd put a switch between the bass pot and R47 - the custom setting on the AC30cc2 disconnected the bass pot from being connected to ground, the normal connected it to ground.

This is currently all theoretical and I'm just some guy on the internet so poke your own amp with the hot thing at your own risk.


Also, I'm actually a major fan of the C2 amps as they are so this is just for shits and giggles

[Anvil Amps Alan]

These Vox amps regularly come to me with shorted 5AR4s.
I routinely add diodes in series with each of the two AC HT leads entering the rectifier.
This cures the problem and prevents AC on the caps in event of the rectumfire going shorted.
You still get the sag, but the amp is tuned for minimum smoke.

[TmcB]

Thanks former self!

[Bg]

I modded my ac30 by buying a laney vc30 instead.

really juicy cleans once I chucked a eminence legend in.

Did that amp turn up or did you tell the sender it didn't and then offer it for sale at a later date?

[TmcB]