Vox AC15 Mod Guide

Vox AC15 Mod Guide

What follows is a retrospective journey of me and my Vox AC15 amp. Most of the mods I performed were inspired by the guide found here, so you should definitely check it out if you’re considering doing some mods of your own.

So I’ve had my trusty Vox AC15 amp for 5 years now… where does the time go!? Since buying it I have not once thought of replacing it, nor have I had GAS (gear acquisition syndrome) over other amps, like I’ve had with guitars and pedals. A lot of people think that the Vox AC30 is the superior amp to the AC15, and this might be true if you are gigging a lot and don’t have a good PA system, but in all other departments the AC15 is better, in my opinion. For starters, 15 watts of tube power goes a very long way; it is just as loud as my 100w solid state amp. With the AC15 I can barely get the master volume past the halfway mark if I have top boost on full. The AC15 has a lot less clean headroom than the AC30 and for me this is a very good thing as I can get to that sweet creamy overdrive much sooner, without having to blow the lid off my house. With the AC30 you really need to crank it to get to the good stuff or you have to resort to using an overdrive pedal, which denies you access to your straight up tube tone.

vox ac15

The AC15 is much better for recording compared to the AC30 because of it’s small size, it is also a whole lot lighter and easier to transport than the AC30, which is comparable in weight to a small elephant. The Vox AC15 is a lot cheaper than the AC30, and is cheaper to replace the speakers/tubes because there is half as many of both. Lastly, the AC30 has a tube rectifier while the AC15 doesn’t, this is both a positive and a negative for the AC15 as having a tube rectifier delivers better tone but also means that having the amp on standby can risk damaging it. I know this as I’ve read a lot of discussions about it on the net, my amp tech confirmed it, and my friend’s AC30 suffered a total meltdown because of it. Sure having a tube rectifier might lend the AC30 some slightly better tone, but at a large cost. Not being able to have the amp on standby while the tubes warm up can risk damaging the tubes, and they are expensive things to be constantly replacing. Also not being able to leave your amp on standby while you go off for a cigarette or something would be a real drag!

Even though the amp sounded brilliant the day I bought it, over the years I have modded the thing to really open it up and squeeze more tone out of it. The amp came stock with a Vox Wharfedale speaker, which sounded quite brittle at first as it’s a ceramic speaker and Vox’s are synonymous with Alnico speakers. But once the speaker broke in it really sang and I was more than satisfied with it. The AC15s don’t get made with these speakers anymore so chances are unless you have an old AC15CC you won’t know what I’m talking about. A lot of people hated the sound of the stock Wharfedales and replaced them without even letting them break in, which is silly. I did eventually change the speaker for a Celestion Blue, but more out of curiosity than necessity. However, I don’t regret doing so one bit, as it really improved the amp’s dynamics and tone and gave me a lot more response, clarity and note articulation. Below are some photos of the stock Wharfedale speaker and the upgraded Celestion Blue speaker.

The next thing I upgraded was the reverb as it was the only thing stock in the amp that I didn’t dig. It was too ‘surfy’… turning the dial anywhere past halfway would wash out the guitar’s sound and make it sound thin and distant. Not the hallmark of a good reverb. I replaced the stock reverb tank with an Accutronics 8EB2C1B Reverb Tank which set me back $25, quite a worthwhile investment I think. It was a laughably simple matter of unplugging the old reverb tank, and plugging the new one in. When you open up the back chassis of the amp, you will see a black pouch, open it up and there is where you’ll find the stock reverb tank. Once I replaced the stock reverb with the Accutronics tank the difference was substantial. If you’re going to do anything to this amp make sure it’s the reverb; it is such a cheap and easy fix and it makes the amp a whole lot better. The stock reverb on both the AC15CC and AC15C is rubbish. Below are pics of the two tanks.

The next thing I replaced were the tubes – even though the stock tubes sounded great – as they were starting to lose their juice and so I figured I’d change them. The Vox AC15 amps have four tubes: two 12AX7 tubes in the preamp section, and two EL84 tubes in the power amp section. The preamp tubes control the top boost (overdrive) while the poweramp tubes control the master volume. There are two types of natural tube amp distortion: preamp distortion, which is the overdrive you get at low volumes, and poweramp distorion, which you get when you crank the amp as loud as you can. The way Vox AC15 amps work is there is a master volume and an overdrive (top boost) volume, if you have the overdrive volume on full and the master on low you’ll get a nice preamp distortion, while if you crank both high you’ll get poweramp distortion, but you’ll also get noise complaints. The 12AX7/EL84 combo is really, really sweet. The amp came stock with a Sovtek and a Tung Sol 12AX7 and 2 Electro Harmonix EL84s, these are all great tubes. I replaced the preamp tubes with 2 Tung Sol 12AX7s and the power amp tubes with JJ’s. Tubes in a Vox AC15 don’t need biasing so getting an amp tech to install them is unnecessary, it’s terribly easy ands worth learning how to do as you will do it once a year or so, depending on how often you play. The preamp tubes are in little metal canisters, you simply twist them and pull to reveal the tubes and then you just yank them out. The poweramp tubes are in a metal chassis, they needs to be unscrewed with a screwdriver, then you simply remove the metal conductor wire, pull out the tubes and put the new ones in the slots, being sure to line up the pins with the holes. Pics below.

Before I put everything back together and tested the amp I performed the ‘bright cap’ mod. The bright cap is a tiny capacitor on the circuit board which gives the amp way too much treble in my opinion, it made using my Electro Harmonix Big Muff in particular sound sharp and tinny. The op was as simple as finding the cap, desoldering it, and then pulling it out with pliers. Pics below.

The last picture shows the final mod I performed, which was purely cosmetic and I figured i may as well do so something to really make the amp mine. I took out all the black knobs, put white ones for the top boost channel and the master volume and put brown ones for the tremolo (which sounds amazing in this amp by the way!) and reverb. I also stuck a Grateful Dead sticker on the front, cos I love the Dead!

After everything was finished I screwed the back board back on, turned the amp on and was greeted by a sharp hissing sound; it sounded like a snake had made its way into my amp. I took the amp to a tech and found that the problem was the JJ EL84 tubes were defective. Moral of story, don’t buy JJ Tubes. The tech replaced them both with Sovtek tubes which sounded ok. He also charged me $80 for them, on top of the $150 for the hour. Biggest waste of money ever. Just so you know, all the mods I’ve discussed so far went down on the same day, which is why I had to take the amp to the tech as i wasn’t sure what part of the process was causing the hiss.

I played with this tube setup for a couple of months before the 12AX7 Tubes started to go microphonic (hissing sounds, learned this term from my tech – expensive new knowledge), so I replaced them with the stock 12AX7 tubes I had initially took out, and they were fine for a week or so, but my tone gradually  became more distant to the point where I had little to no overdrive. Just so you know, I play the guitar quite a lot so if you only play occasionally you might not have as much trouble with tubes as I did. I eventually decided to take the plunge into the NOS tube world (New Old Stock), as these tubes are unanimously praised as having superior longevity and tone. NOS tubes are tubes from as far back as the 60s, which haven’t been used and are out of production. Back in those days tubes were very abundant and were made more effectively, but after the digital boom they went out of production. That is until companies realised there was a guitar tube market, which is why modern day tubes are literally pumped out in factories like clockwork, which produces inferior quality tubes to drive a profit.

NOS tubes are fairly expensive, but after fitting them in I believe they are worth every cent. I bought my NOS tubes from kcanostubes.com, which has a wide variety of NOS and ANOS tubes (Almost New Stock) that are cheaper than their NOS counterparts, yet still infinitely times better than the current production ‘cheap’ tubes (ok, maybe I’m exaggerating a little!). NOS tubes average around $30-150 per tube depending on the brand, while ANOS tubes are generally half the price. New production tubes however are usually no more than $10 a tube. I ended up purchasing 1 NOS RCA 12AX7, 1 ANOS Mullard 12AX7 and 2 NOS Tesla EL84s (Tesla is the company that JJ’s eventually took over, and fucked up.) The Teslas were actually quite cheap for NOS at only $38 each! Pics below.

All I can say is WOW, the difference was night and day. It was as though a thick blanket was taken off the amp, and that’s saying a lot considering to my ears the amp sounded outstanding before I even put the new tubes in! Even my older brother, who doesn’t know anything about tubes or guitar tone, walked into my room while I was playing and told me my amp sounded amazing all of a sudden. NOS tubes apparently last a lot longer as well as they were built to last, so I definitely think they are a good investment. If you want to go the NOS route, but don’t have the money then you have a nice alternative. Buy only 1 NOS 12AX7 tube and put it in the V1 slot (the tube to the very left), as the V1 slot produces the most dramatic differences in tone. If you shell out $30-100 on one of these tubes then you will really do your amp and your ears some favours. In my opinion it is important to play with the best tone available to you as it encourages you to play more – good tone keeps you in front of your amp grinning with satisfaction at how good you are sounding. Good tubes also greatly improve dynamics, which enables you to hear tiny differences in picking attack. As for the 12AX7 in the V2 slot, and the two EL84 tubes, check out these sites for some solid reviews on what cheap new production tubes are available: (I can vouch for the Tung Sol 12AX7s, they sound great)

  1. 12AX7 Tube Reviews
  2. EL84 Tube Reviews

UPDATE: 10/04/2012 – Someone in the comments section asked me if I had any recordings of the amp pre-mod and post-mod to compare, but considering the modding process happened gradually over time I don’t have any accurate recordings of the amp pre and post mod. I did, however, record myself directly before and after I replaced the stock tubes with NOS, and have uploaded them for you to listen to. In all of these recordings the amp is post mod, with the Accutronics reverb tank and broken in Celestion Blue speaker. The recordings don’t do the sonic differences justice in my opinion as I was playing very loud and had the mic (from my iPhone) quite far away from the amp… take my word that it sounds much better in the flesh. Each recording is played with my Gibson SG 61 Reissue, with the first three stock/NOS comparison recordings being played   with the bridge, middle, and neck pickups in that order. I was in a hurry to record these (hence the sloppiness) as I wanted to get it over with so I could jam with my mate and really enjoy the tubes. The wah demos are taken from two jams we did that day, one quick one before the tube change and one long one after. Also note, these were recorded over a year ago, and so are not representative of my current guitar playing 😉

Stock tubes

  1. Had to Cry Today – Blind Faith
  2. No Quarter – Led Zeppelin
  3. Politician – Cream
  4. Crossroads – Cream
  5. White Room Jam – Cream (Wah demo)

NOS tubes

  1. Had to Cry Today – Blind Faith
  2. No Quarter – Led Zeppelin
  3. Politician – Cream
  4. Crossroads – Cream
  5. Black Magic Woman Jam – Fleetwood Mac (Wah demo)

Unfortunately I didn’t record any clean samples, as I was in my obsessed with Clapton phase at the time and was mainly playing the amp overdriven. I can assure you that the amp delivers very articulate cleans though, worlds better than before I did any mods. The overdrives sound a lot more organic to my ears after I did the mods and especially after I changed the tubes. The speaker and reverb tank change also made a massive difference. Listening to the two wah demos you can clearly hear that the stock tube wah is quite muffled while the NOS tube wah is very dynamic and clear. Also note, that it has been over a year since I’ve replaced the tubes with NOS, and they are still sounding just as good as the day I put them in!

Thus ends my modding journey, my Vox AC15 has new life breathed into it and I will never consider replacing it. If you are looking for a new amp, make sure you look at the new Vox AC15C1, these amps are exceptionally good, and don’t even need a speaker change as they come stock equipped with a Celestion G12M Greenback speaker, which is a legendary sounding speaker (I have one installed in another one of my amps). These are the speakers that were used primarily in the 60s Marshall amps used by Cream, The Jimi Hendrix Experience, and The Who. If you’re looking for the creamy overdriven sound of Eric Clapton or Jimi Hendrix, then look no further than the Celestion Greenback. I hope this has been of some help to someone out there in the big old internet. If you have any questions or suggestions please don’t hesitate to ask. Finally be sure to check out my mod guide on the Vox AC4TV!

UPDATE 12/12/12:

Vox AC15 with external 1x12 cabinet
Vox AC15 with external 1×12 cabinet (the acoustic is a 1974 Japanese made Martin Sigma DM5 – it sounds as good as a Martin D-18!)

Today I purchased an external 1×12 cabinet (Vox V112TV) for my AC4TV combo, and put a Celestion G12M Greenback in it and have been using it with my AC15! It is incredible, it now sounds like I am playing on a completely new amp. Not only does my AC4TV sound galaxies better with the cabinet than it did previously, but my AC15 has opened new doors of tonal possibility. The extension cabinet is closed back, which really sounds great with a Greenback (Greenbacks don’t sound so good with open back cabs), while the VOX AC15 is open backed and has the Celestion Alnico Blue, which sounds great in open back cabs but not so good in closed backs. The back of the AC15 has two speaker connection sockets, one for the internal speaker and one for a extension 16ohm cabinet. The speaker in my AC15 is 16ohm and so is the one in the cabinet, and I can play through either one at 16ohm, or both in parallel at 8ohm each by flicking the impedance switch. The Greenback hasn’t broken in yet, but when it does I will upload some recordings of me playing through the Celestion Blue by itself, the Celestion Greenback by itself, and both of them in parallel, both with clean and dirty tones.

Stay tuned!





61 responses to “Vox AC15 Mod Guide”

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  2. bornkiller Avatar

    That’s not a bad price considering they are like 17 hundy here…..Even after the currency conversion .

    1. endofthegame Avatar

      The amp in the link you showed me is a Vox AC15 twin – it has two speakers as opposed to the one in my amp, hence why it’s a lot more expensive. Honestly, I much prefer this amp with one speaker. Two speakers means I have to play louder to get good tone, and the amp is already ridiculously loud as it is!

  3. David Avatar

    Great post thank you. I love mu AC15C1 but I have a clicking sound when using my Telecaster (not usually with humbuckers). I took it back to the shop and asked them to look and they couldn’t reproduce the click, although I suspect they never bothered to look! Also, I find the amp a bit muddy with loud OD using a jemini pedal – any suggestions,? Many thanks, DR

    1. endofthegame Avatar

      Might be a problem with the tubes but I’m not sure. Best to record the sound next time you hear it and take that to the amp techs. The amp will be muddy if you use top boost on top of the pedal. Turn the gain on the amp down, and the master all the way up, then turn your pedal on and adjust accordingly. It could also be the pedal – tube amps prefer organic sounding OD pedals over sharp and shrilly distortion pedals.

      1. David Avatar

        Many thanks for your prompt reply. I’ll give that a go.

      2. David Rosen Avatar

        Thanks for the tip. Tried it at home and your suggestions have made a big difference. Much obliged. Looking forward to trying it at band rehearsal this Monday. May I ask, have you ever added a cabinet to the AC 15 and if so, what would you suggest? I have looked at the Vox 112 NT cabinet but haven’t tried it. Do I have to change anything on the Amps if adding an extra cabinet?

  4. endofthegame Avatar

    Great, glad it worked! I haven’t attached my AC15 to a cabinet… yet. My mate has an AC30 head and cabinet, and if I were to get a cabinet I would definitely get the one specifically designed for the AC15/30, but that just boils down to personal preference/aesthetic appeal. The AC15 uses one 16ohm speaker. If you use a 2×12 cabinet then you would want both speakers to be 8ohms each, thus totaling 16ohms; there is a switch on the back of the amp that allows you to switch between 8 and 16ohms. So the only thing you would have to do, I imagine, apart from plugging it in, would be to flick that switch to 8ohms. Best to double check with your amp tech before taking my advice though, as I have never done it.

    1. endofthegame Avatar

      Also you have to consider whether a cabinet is necessary before you go ahead and purchase one. The reason I bought a combo amp and not a head/cabinet was that I was looking for portability. If you have band practice at your place, and your amp can’t keep up volume wise with your bandmates (unlikely!) then go ahead. But if you have to lug your combo amp (which is already hugely heavy), along with a cabinet containing two heavy alnico speakers (very, very delicate) it’s going to cost you money, time, and piece of mind. Try turning your master and top boost on full, your house will fall down. The amp is loud enough as it is.

      1. David Rosen Avatar

        I agree completely apart from 2 vital factors:
        1. GAS
        2. The lead guitarist bought himself a MESA Boogie and then had the nerve to buy a matching cabinet, which looks very nice and blows everyone away! Even my very loud AC15 is no match for that.

        Appreciate the advice. Will learn to use the 15 fully before thinking of any changes.

        Thanks again


  5. endofthegame Avatar

    GAS comes and goes, but I know what you mean…. I’ve bought a lot of gear purely out of GAS. One day I’ll want a telecaster and the next a les paul – there’s no end to it! Good luck with the cabinet hunt, make sure you fill it with some good speakers.

  6. C.J. Avatar

    Great info!! Just got a AC15C1 and got tube porblems already.
    Shall retube and do the bright cap thing.
    Thanks for taking the time to share your experience!

    1. endofthegame Avatar

      Yeah the stock tubes are pretty crappy. Best to replace them ASAP anyway! Enjoy your new amp!

  7. Megalofisak Avatar

    Thank you for posting this great and informative guide. I have a red VoxAc15 that I purchased in march of 11 and was curious about any kind of mods for it. The one that I felt needed changing was the reverb and its nice to see that you switched that. How did the reverb sound once you switched it out?

    1. endofthegame Avatar

      The difference was night and day. Considering how cheap the replacement tank was, and how easy it was to replace, i’m surprised they don’t just build them stock with the better reverb tanks. The stock reverb drowned out most of my notes and was pretty much useless to me anywhere past 12 o clock on the dial. The new reverb is much better, a more even and less washed out tone.

  8. SAO Avatar

    Thanks for all the information, very helpful. I bought a used/stock ac15c1 yesterday and I’m just trying to make it through the day and get back to playing. I like the idea of NOS or ANOS but am wondering how much being matched pair/sets come in to the mix. You talk about just replacing one at a time, is it a huge drawback, not having them matched?

    1. endofthegame Avatar

      The only tubes I get matched are the EL84s. I always have two different brand 12AX7s in there, so those are the best ones to replace individually. If you’re on a budget you can just get some cheap Sovtek EL84s and 1 NOS 12AX7. The 12AX7 in the V1 slot does the most for your tone.

      You don’t have to go the NOS route. Tung Sol 12AX7s are pretty good non NOS tubes. I find that NOS don’t break as often though, I only have to replace them like once a year or less and I play a lot! The stock tubes I was replacing every few months.

      1. SAO Avatar

        Thanks. Are you saying that an NOS in the 12AX7 V1 preamp position is the best tone for the buck, say compared to two NOS tubes on the EL84 power side? I’m always on a budget but I don’t mind a little extra cost if it makes a big difference. I’m looking to replace all the stock tubes to improve the tone without changing the Vox sound too much. I’ve read that new tubes will take some of the muffle from the top boost and maybe produce a little more headroom on the clean. I’m thinking anywhere between $100-$175. That should be enough, right? I really like this amp for my Pearless Songbird (hollow body casino) but I’m really impressed with the matching between my AS Tele and the Vox.

    2. endofthegame Avatar

      Yeah, a NOS in the V1 will give you the most bang for your buck. But if you prefer to play clean you will appreciate changing the EL84s more than the 12AX7s. The 12AX7 tubes are for the top boost channel, replacing either of them will greatly diminish the stock ‘muffle’ as you put it, and will also mellow out some of its harsh trebles. The EL84s are for the master/normal channel, and putting NOS in those slots will give you a more articulate clean channel, and will also smooth out the overdrive to an extent.

      My favourite NOS EL84s are the Teslas; they are only $30 each (cheap for NOS) and are well worth the investment. Try those out, and replace the 12AX7s with Tung Sols (not the NOS ones). That will yield you the greatest tone reward for the smallest amount of money. The Tung Sols are about $10 each I think.

      If you want to shell out a bit more get either a Mullard or RCA 12AX7 (NOS or ANOS) and put it in the V1. Leave the Tung Sol in the V2. By the way, if your amp ever produces a cracking or hissing sound, or if you ever have any problems with it, 95% of the time it’s a faulty tube. NOS tubes last a lot longer than new production, so they pay for themselves in the long term.

      1. endofthegame Avatar

        Also if you want your tubes to last longer it’s important to always flick the standby switch before you hit the power switch, and then turn the standby off once the tubes have warmed up (usually 20 seconds or so). If you don’t then you risk the tubes overheating. This isn’t necessary when you’re turning the amp off though, just hit the off switch and they will cool down just fine.

  9. SAO Avatar

    Thanks for the advice. I’ll think I’ll go with the NOS in V1 and then matched NOS pair for the EL84s. I’m looking at KCA’s availability. They don’t seem to have the $10 Tung Sols you’re talking about. Is there a one stop place that you like to go to?

    1. endofthegame Avatar

      KCA only sell NOS and ANOS if I remember right. I buy my new production tubes from tubedepot – http://tubedepot.com/12ax7.html – turns out they’re about $15 each

      1. SAO Avatar

        Thanks, I’ll let you know how it goes.

  10. moises Avatar

    Hi End…

    Im trying to do some mods to my ac30c2 that is similar to your model but my knowledge in that things is zero, so i need to know where are the plate resistors. could you help me if a send you a photo of the PCB?


    1. endofthegame Avatar

      Hi, sorry but the AC15 and AC30 have different PCBs so I wouldn’t be able to help you out. If you have zero knowledge in this department you should be taking your amp to a qualified technician.

  11. funnell86 Avatar

    I quickly read through your article. thinking about doing similar mods to my ac15c1. have you done any demos of your newly moded amp. my apologies if you’ve already posted them. I must of missed it. thanks

    1. endofthegame Avatar

      I did record some short before and afters but don’t know how to upload them…

    2. endofthegame Avatar

      I figured out how to upload the recordings and have updated the post to include them. I don’t have any of the amp before I did any mods so the recordings are all of the amp post mod, with half of them being the amp with stock tubes/new speaker and the other half NOS tubes/new speaker.

  12. paul Avatar

    how to make the orange Tiny terror sound more open and clean ? can change to gold lion 12ax7 tube do the job ? thanks

    1. endofthegame Avatar

      Replace one or both of the preamp 12AX7 tubes with 12AU7 tubes. These will have less gain and more headroom.

  13. Jo Avatar

    I’m thing about getting one of these bad boys. It sucks that the jjs didn’t work for you. They are the only tubes I use-mainly for the price-and I have not had any issues. But thanks for the info!

    1. endofthegame Avatar

      You will be very happy with one of these amps. It is a shame about the JJs as I’ve heard a lot of great things about them. At the moment the Teslas are sounding amazing, but I’m sure I’ll give the JJs another go one of these days.

  14. […] AC15 Mod Guide AC4TV Mod Guide […]

  15. Brad Avatar

    You have a bit of misinformation in your article. An amplifiers rectifier is not a part of its signal path. Its function within your amplifier is to convert AC current to DC current. The only effect a tube rectifier will have on your tone is to add compression while it struggles to supply your power tubes with the current they require when your master volume is dimed (voltage sag).
    Other than that, this was a very good article, after the mods I’ve made to my ac15 the accutronics reverb seems to be a good addition to the tone stack mods I’ve made.

    1. endofthegame Avatar

      Thanks for clearing that up. Admittedly I don’t know much about tube rectifiers as I have never owned an amp with one! I only went by what I had heard from others, which I am going to assume was false information. Cheers!

  16. John Peterman Avatar
    John Peterman

    Hi there. Thanks for taking the time to talk about all your modifications. Very good stuff here and motivated me to look at things differently. I don’t know too much about AC15’s or maybe I misunderstood something but I was wondering if you experienced any red-plating from your Tesla el84’s? And if so, won’t something eventually fail because of having too much voltage and if not, how did you get around that issue? Thanks so much for your time!! 🙂

    1. endofthegame Avatar

      Hi, thanks for writing. I’ve never experienced any red-plating with my Tesla EL84s, or any tubes in my AC15 for that matter…

  17. Mike Avatar

    I would like to buy a 149 dollar Orange Micro Terror and use just the speaker cab of
    my Vox AC15C2 so as to get a different tone and sound.

    Micro Terror MT20 can jack into the back of the external speaker jack and just leave the
    power off on the Vox amp, or do I need to buy a female jack with 8 connectors and hook up the
    speakers and Amp to that and when a mail jack is inserted, the amp gets separated from
    the speakers and no damage can occur ???? Thanks for help with this.

    1. endofthegame Avatar

      Sorry, I’ve never experimented with using the AC15 as an external speaker, only using an external with the AC15. So I can’t say if it will work or not, in either case it would be better to just get an external cabinet that way you can safely use it with both the Orange and the Vox.

      1. Patrick Avatar

        I was happy to find your article as I just purchased an AC15C1 for road use. I’ve been a Deluxe Reverb man for twenty years. I own a 1965 Blackface (not a reissue) and a ’73 Silverface. The ’65 has been my workhorse and it is awesome to put it mildly. However, I was becoming more and more anxious every time I’d take it out. The ’73 is a great sounding amp as well but much cleaner and I was having problems with too much stage volume by the time it started to break up the way I want. The master volume AC15 seemed a viable alternative and the price was right so I grabbed one new in the box. I plan to play it as is for a while until it breaks in before I start making changes. That said, the reverb mod seems a no brainer. The “brite cap” mod in particular intrigues me since I am having to adjust to the somewhat harsh treble response on the AC15 as compared to the high end sweetness of my Fenders. I’m sure I will get around to the tubes once I hear how the amp sounds responds when broken in properly. Onstage I run an Orange PCP 212 semi-open back extension cabinet containing two Celestion Vintage 30s. I use the extension together with the combo speaker and just stack to combo on the Orange. I like the fuller, less boxy low end response of this set up so the extra trip to the truck is worth it. Anyway, once I’ve lived with the amp for a while and made whatever changes I’m likely to make I will check back in with an “after” commentary. Peace.

  18. Alex Avatar

    All I use on my VOX AC15C1 amp is the normal(clean) channel and I was going to upgrade the EL84 tubes to the Teslas. I have a pedal board and always plug into the clean channel. I never use the top boost channel. So is there any reason for me to change out or upgrade the 12AX7 tubes in V1 and V2? Would I even notice it if they went bad?

  19. Steve McDevitt Avatar
    Steve McDevitt

    Thanks for posting lots of useful stuff on the AC15C1. Looking around at what’s available to be done, and your things are useful to know.
    On another note, your sound file’s, the 1st song you have listed for the different tubes,
    “Can’t Cry Today” ?
    I believe that is meant to be “Had to Cry Today”, 1st track on the Blind Faith album right?
    Just a minor little typo.
    I think you may have taken the first word from the 2nd song, “Can’t Find My Way Home”, and mixed it in with the title of the 1st song.
    Anyway, just for clarification. Sounds good !

    1. endofthegame Avatar

      Haha! Thanks for pointing that out, I think you definitely cracked the case of the typo. ‘Can’t Cry Today’ hahah, I blame Blind Faith for not sticking around long enough to make their song titles more memorable 🙂

  20. cbleick Avatar

    Regarding the Bright Cap mod, you cut out C26, but I see on other sites that the Top Boost Bright Cap mod means removing C8 and C67.


    Is this some kind of difference between AC15 model years? How did you come to determine that C26 is the bright cap? And does that affect both Top Boost and Normal channels?

    1. endofthegame Avatar

      My amp is an AC15CC (custom classic), the older model. The amp you linked to is an AC15C1 (custom 1), the newer model. The AC15C1 has a different circuit board and also an extra channel (normal channel) compared to the AC15CC. My amp doesn’t have a normal channel, so if yours does follow the instructions on the guide you linked rather than this one.

  21. msca8h Avatar

    Sorry dude. It is known that the Tube rectifier IN THE VOX doesn’t have any effects. I heard it’s because the AC isn’t really a class A amplifier. Also, the AC30 does not need a standby since it has the Tube rectifier. The Tube Rectifier will slowly warmup alowing the other tubes to warmup too

  22. henry Avatar

    Hello there. Great article! Very informative!!! I have an AC15CC1 and the tremolo has gone out. Any idea on how to fix that?

  23. Evan Avatar

    I ordered the reverb tank you linked. Installed it last night. I’m trying to make sure i’m not hearing things but is that link still good? I didn’t just order the same style stock reverb tank did I? I swear I’m hearing a difference.

    1. pimpfreud Avatar

      The difference between the stock reverb and the Accutronics one I linked is substantial. If you have to strain your ears to hear it then maybe you installed it improperly or got a dud?

  24. Brian Farmer Avatar
    Brian Farmer

    This is a great web page and detail. Thank you for taking the time to do this! Also, I have done all of these mods to my Vox AC 15CC. Preamp tubes to NOS makes the biggest difference IMO. Had replaced the Wharfdale speaker with a Greenback, but thought it to be too harsh, so just now replaced it again with the broken-in Celestian Blue and it is bliss!

    1. pimpfreud Avatar

      Awesome, glad to hear it mate! Yeah the Celestion Blue seriously is a dream speaker with this amp, it’s a shame the new AC15 amps don’t come with them. I honestly didn’t mind the Wharfedale once it was broken in, but the blue definitely blue (ha ha) it away. The NOS tubes do make a big difference, it’s a real shame it’s an impermanent/expensive improvement though…

  25. Chris Osterdock Avatar
    Chris Osterdock

    Great read – I really enjoyed this – I’ll be getting a VOX 151C from that VOX Showroom place where they will put in the UK blue – and of course test the tubes for microfonics etc. The funny part of this that you talk about – are the new manufactured tubes – I’m a newbie at guitar – however my hifi system is pure tube based (tube pre and tube mono amps) – and you are completely correct about the EH 12AX7s – my tube amps require two each for driver/phase splitter – very microfonic tubes – I replaced with NOS GE tubes – completely silent (I replaced two – and kept two EH tubes for the phase splitter) – I then ordered NOS RCAs from the same place as you – much better. When I replace the tubes in the new amp – NOS all the way.

    Thanks for the great writeup – and wonderful pictures!

  26. vincent Avatar

    Hi. thanks for the review! in my ac15ccx i also swapped the reverb tank with an accutronics. Result is much better than stock but still sound a little harsh for me. Is there a possibility to add a tone or even twang pot to the amp?? thanks for help. best, vince

  27. Gage Avatar

    Thanks for the info on the AC`15. It is a great amplifier. I did the mod from http://tonesmiths.wordpress.com/2013/03/28/5-steps-to-make-your-vox-ac15c1-or-ac15cc-sound-amazing/

    I grudgingly did it but omg it was like night and day. My amp came alive. The Celestion Bad Cat speakers are like a cross between a Celestion Blue and a G12M. Much better bass response and when I put in the PM tubes the amp had the best overdrive tones I’d heard from a Vox. The whole mod set me back a little over $200.

    Yeah, I’m not gassing like I used to for a new amp. I have an AC30 Brian May that I’ll probably be selling soon as its too darn loud and too heavy. I’ll trade a little loss of headroom with an AC15 for all the benefits you mentioned: easier sweetspot, lighter, better overdrive, manageable volume…

    Thanks again man. Good site. Gage

  28. John Burr Avatar
    John Burr

    Love what you did with the amp! I have an AC15C1 with the Greenbacks. Fixing to replace the tubes and the reverb tank with an 8EB2C1B tank. I was wondering where you got the Multi colored knobs. Thinking about getting some myself.

  29. Phil Avatar

    Have you tried pre amp tube substitution? My experience is Fenders & replacing 12AX7 in v1 with a 5751 or 12AY7 will give more headroom & more dynamics @ lower volume…

  30. Dave Avatar

    can i put a lead from my external speaker output straight into my BR800 on my VOX AC4

  31. Lewis Avatar

    how long does it take to break in the greenback speaker?

  32. kamarul Avatar

    when the master volume is only 30 percent on. and the top boost at 70 percent.. there is loud high noise. please advice. im blurred. already change new tube

  33. Syrus Avatar

    Simple solution for the AC30 Standby switch problem is to always leave the amp in ‘ON’ at the standby switch selector. Reason for this is that the Rectifier is also a tube and can’t conduct HT/HV without FIRST self having ‘warmed-up’ by heating the filaments with the LV.

    VOX simply put these standby switches on the AC30’s because of people getting used to the sight of having on and automatically assuming it ALWAYS a good thing. Same goes for True-Bypass vs Buffering. People yell and scream True-Bypass, but on the other hand praise KLON, ‘old ‘TS-808, Pete Cornish, etc. you know the lot. All are a keen-on a good buffer.

    Enfin. Nice write-up. Might be handy when I get my AC15CC in a few days, came here for the reverb tank part. Usually the first thing I swap on any and all of my amps.

  34. Tommaso Avatar

    Hi, nice mods ! Did you work also on a line out connection, pre-fader ? Thanks 🙂

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