AC30 Comparisons - C2/C2X Pros and Cons
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- Опубліковано 7 сер 2024
- A closer look at the Vox AC30 C2/C2X series' strengths and weaknesses.
Note: these amps have all been modded to the actual early '60s JMI circuit with the mistakes of each model corrected. Separate videos on each model will be uploaded soon that get into the strengths and weaknesses of each.
For more info, Subscribe to this channel, join us at PsionicAudio, or email us at info@psionicaudio.com.
Finally, someone who isn’t a hand wired snob and discusses the pros and cons of the circuit with an open mind
Very well explained and balanced viewpoint. A pleasure to listen to someone this knowledgeable.
Makes sense. I hated the normal channel on this amp. Super bright, and clean. I'd love to see a rundown of the AC15C1.
Thanks for the informative channel. I have owned and gigged a C2 with greenbacks for nearly 10 years now. Changed to JJ's when it arrived and it has been 100% reliable. I personally like the greenbacks, but the constant issue for many people is reading comparison reviews on the internet. There's a huge number of people who love the c2, but there seems to be a huge number of people who don't like the far eastern amps purely because of their origin. I understand your comments regarding the c2 not sounding like the original amps, but as you say, many of the modern features are really good. Thanks again for all the info.
From a tech's perspective, none of the various "reissues" get everything right. The C2 has too much gain. The CC is too bright/clean. The HW is harsh and over filtered. The TBX hums and buzzes. The Heritage is harsh and has an abysmal PCB.
All of these things can be corrected (I've even replaced the entire board on a Heritage). None of the flaws have anything to do with the country of origin.
It amazes me how many people use their iPhone to complain about Chinese products...
@@PsionicAudio Wonder why they use carbon comp resistors at certain parts? do they sound better?
between the CCW and the C2, which sounds better?
the thing that scares me about the C2 is the MDF construction.
someone locally is selling one in clean condition for $600
Please do a version of this with the AC30CC! Also I’m sure many would agree, no need to rush. I could watch these break downs for 30-45, even 60 minutes.
Next one that comes in will get a video like these.
Still my favourite amp. I change new tubes sound is perfectly done.
Great video! I have no idea where I'd take my amps to get this kind of thing done. Especially here in Virginia. Sub'd.
Very informative
Thank you for making this video. It was a really insightful delight to watch.
I love your channel and your honesty and expertise always shines through!
I have been gigging my C2 heavily for the past 10 years and it’s been such a great consistent amp.
I use a Variac set around 115/ 118V which gives a slightly “better” feel to it as well as an L pad type built in the cabinet attenuation device set at -3 db. I also by passed the bright cap on the Top Boost channel. All these simple “mods” make the amp usable for any size venue even though it is always a matter a small compromises but it works for me.
I replaced the tubes quite a few times and settled on Cv4004 Mullards preamps and TAD STR EL-84s which I am not to fond of in comparison to the TungSols.
Also replaced the Greenbacks with one G12H30 and a 12a125a Weber (kind of a nicer P12Q). A very surprising combination for many but works so well!!! I am not a technician but a player and those Chinese versions are great, a lot is of amp for the price and I am happy to know that as one of the very best technician out there you do share that sentiment.
Thank you again for making such videos.
@psionicaudio
Hi mate! I recently bought a 2nd hand Ac30C2 and all the pots were incredibly crackly, I've since cleaned with contact cleaner and it's almost rid completely of the noise, however the tremolo doesn't seem to working through the speakers. How is the tremolo powered or what sends a signal to the output? I'm not very tech savvy but would love your thoughts. Thanks.
Love your channel. Can you recommend any tech's in Southern UK?
A question about VVR’s if u have a minute? I tried one in a Hammond Ao44 rebuild with added preamp and PI tubes going into el84’s. It sounds great except no matter what I try, there’s still too much fizz. Is this just due to layout issues? Too close to the output transformer or something? The Ao44 chassis is VERY space limited. A VVR works GREAT in the Ao35 18 watt clone I built but just can’t tame the fizz enough to use in the Ao44. It’s a shame because it would really be cool in this amp that is relatively clean without one.
I have a circa 2010 AC30C2 that is stock aside from swapping out the Greenbacks for UK made Celestion AlNiCo Blues. Do I need to worry about the arcing issue you refer to on this amp?
A lot of people don’t realize that Celestion’s best speakers are undoped. Standard green backs are doped but there are some that are not such as the Marshall G 12 C. Much smoother response; less ice pick and more detailed mid range. The blues are undoped. All the heritage. Sound good in just about every configuration including open back.
You have to check the opamp datasheet because some opamps are made to be stable at unity gain, others at higher than 1.
My Orange Tremlord 30, has solid state rectification, then all tube reverb and trem with EL84s.
What happens when the built in rectifier goes out how would you fix that. I have a ac30ce thats blowing ht fuse after standby is turned on
I know I'm late to the party but what are you thoughts on the head version of this? It has a reactive load attenuator
Thank you again for your tips, this is the model I own and have been gigging with for 12 years in sotck forms (recently I've just changed the only plate resistor that measured 100 with the 220), good to know that the abscense of the choke and the solid state rectifier don't really prevent this amp from sounding like an AC30, so the only things to fix it and bring it into TBX/JMI territory would be converting the ladder thing into treebranch and getting rid of all the transistors that go from the top boost channel to the phase inverter included reverb and loop FX?
Listen to the video again. They are opamps, not transistors, and no, you do not want to remove them!!!
Most amp techs cannot change the opamp section to unity gain. I'm not going to share what the changes are - anyone qualified to make the changes won't need my notes, and anyone who would need them has no business fixing fiddling with that circuit.
Sounds like you already love your amp - you don't have to change anything if you already love it.
@@PsionicAudio yeah I listened to the video, English is not my native language so I sometimes have trouble to fully understand when it gets "too technical", no need to have your notes, just trying to understand the differences with all these models and how they compare to the so praised TBX or even the traditional JMI since people tend to think those are the best ones, often for the only reason they were still made in the UK, and consider the newer ones worse becuase they're made in China. Yes I'm pretty happy with it, just wonder if it can get better with some simple mods, as I said in the other video I felt like the BM model (the one with the single knob) had some smoother and warmer mids than my C2X which sometimes tend to sound a little more scooped especially when I gig outdoor or in larger stages in general (I gigged with both in exactly the same venue), I know it's natural that the amp would lose lot of the warmer freqs outdoor being open cabs without walls arounf it, but I had the feeling the BM and TBX did a slightly better job in preserving them, not sure if it's down to some different components or anything else, some people even think the birch plywood of the TBX and BM (or even the CC2) resonate better and make the amp sound better as opposed to the MDF one of the C2X, but I never really believe the cab wood would play a big role once you're in a noisy stage with a drummer.
I apologize - you write like a native English speaker, so I didn't know.
I haven't noticed any difference in the sounds of the different cabinets, though I usually just get the chassis in.
None of the various RI cabs sound as good as the old JMIs. But that's a relatively small part of the puzzle.
@@PsionicAudio Thank you for the compliment, I've been a good student of English for sure, but some technical insights could be too much even for me :D if you don't mind, I'd like to ask you one more thing about something you said that wasn't quite clear to me, you said that the normal channel of the C2X was made after the vintage AC30/6 Treble model? hence too bright and too much clean headroom?
Yes, it's modeled on the AC30/6 Treble amp's normal channel.
Thanks for these videos Lyle, it's an education!
I have the CC2 and have done many of your mods to it. I find the Normal channel too bright with the brilliance switch engaged so I am going to the capacitor mods you suggest. I know the 100pf cap will make it less bright when the switch is engaged but how does the mod effect the sound when the cap is switched out of the circuit? I am guessing this is where the 68pf cap comes in to play?
Thanks in advance.
Thanks! On the CC normal channel, you want to jumper the 330K resistor, replace the 250pf cap with 100pf, and put a 68pf across lugs 2 and 3 of the Normal pot (middle and right looking at the back). You can do this without removing the pots board. You need good resoldering braid for this.
@@PsionicAudio That's fantastic, thanks for the info. Jumpering the resistor will affect the overall gain available on the channel so will only really come into play when the amp is turned up to gigging levels? Is that right?
Thanks again!
No, it will give the Normal channel more gain, regardless of the Master Volume series.
I just bought one of these for a steal price, I think they are pretty close, but they are AC custom so I am not surprised they are not bang on classic AC30 amps, but was super surprised how good the amp did sound
what price? I talked somehow down locally for $600 clean condition
@@levijessegonzalez3629 little less than that, that is a good price tho, I got mine at a pawn shop, didn't know much other than a tube amp and it was rare in the British racing green and the price they gave the guy so didn't care except to make a little profit for the small time it was in there
Damn man that’s nice. I paid a pretty penny for my BRG ac30
@@tidymilk5162 yea they retail for 12-14 also was looking, I have the 4 channel not the two channels with the tilt type knob, I personally think it's closer to the old ones the 4 channel but never played a two so can't really say
The green was custom color too, expensive still, and rare, not number how many produced tho
Hello Psionic audio,
I recently bought a used ac30c2 and found your video talking about the mods for the amp. I was wondering, do you have a schematic for the mods so i can take it to my amp tech.
Great job on the videos and thank you.
Thank you, but I do not give out my mods.
@@PsionicAudio If you have a competent “amp tech”, he/she should be able to do most of the mods that are mentioned …The mods discussed here are explained well, and an electronic tech w/an associates degree should be able to handle as long as you/they have a schematic…
Hey Lyle, quick question. Patrick at Mercury Magnetics recommends their VXP-30 power transformer for the C2/C2X, so I assume that’s the one you use when you swap them out on these amps. My question regards the HT secondary voltages produced by the MM transformer. The C2/C2X schematic shows HT secondary voltages at ~265-0-265v, while the MM transformer datasheet says it produces 303-0-303v . When I questioned Mercury about adjusting the dropping resistors to compensate for the extra voltage, they told me “you can, but you don’t have to.” You’ve done a bunch of these, so I thought I’d ask... Is the extra voltage a big deal? Do the voltages fall in line under load after doing the swap, or do adjustments need to be made?
I haven't changed the PT on a C2 yet, so I don't have direct experience with that. But in general the only thing is be concerned with is the bias of the output tubes and would expect to change that one resistor as needed.
But a 10W resistor is 75 cents, so it would not be a huge concern.
I’m interested in the jmi mod. How do I get a quote from you?
Thank you for the video. I really enjoyed it as I am trying to learn more about amps.
I am looking for a new good gigging amp and very much feel the AC30C2 will be the one I choose……. Although I have a question. At the 10:22 mark you mention the solid state diode section. I just wanted to know if you consider this to be a hybrid amp like the Blackstar HT range or is it a proper valve amp?
Please forgive this is it is a daft question but I am not very well versed in the inner workings of amps. I just wanted to know if the gain/clipping in the amp is generated by the valves or do the diodes clip/overdrive the signal like they do in the Blackstars? Any help is appreciated. Thank you.
This is very much a proper tube amp. The solid state rectifier is a common choice in tube amps, like a Fender Twin Reverb or Marshall 100W Superlead. Both very much tube amps!
@@PsionicAudio Thank you for your reply. Is all of the gain in the amp generated from the valves? If so, what do the op amps you reference at 10:22 do?
The vast majority of the gain in the amp comes from the tubes. The opamps in the C2 are for mixing the channels, buffering the loop, the reverb circuit, and the trem circuit. In stock form the opamp path has a gain factor of 4. I change that to true unity gain so the only level increases in the amp are from the tubes.
They are very high quality opamps - no sterility.
@@PsionicAudio Thank you for the explanation. Greatly appreciated
Do your "JMI" mods sound better on the '30 vs the '15? Does it make any sense to go for the '30 in order to get the loop and just cope with the size? Can the '15 have the loop added for a relatively reasonable cost, in order to keep the more convenient package but with more pedal options? I really miss a loop on my AC15C1, at least inside my own OCD-type mind. I probably wouldn't notice it as much if only I had gotten an Excalibre to play with. Alas, a mind is a terrible thing... Posted from my wife's YT account...
I did a mod on a original CC that involved plate resistors, bright caps and a few other things. It was easy to remove the board with the pots , making the job itself easy. Was that something you posted? I didn’t change the effects loop cap though, access to that was more than I wanted to deal with, plus I wasn’t using it
The amp sounded amazing afterwards. It sounded as good as a Top Hat King Royal I had. Granted neither amp was my gigging amp, so maybe under fire it would have suffered.
I put up a few of my mods on a forum, and now people ask me if I can do the "Lyle Caldwell mods."
Um, yes. ;)
Those mods are just part of what I actually do but they make a huge improvement in the CC.
Be aware that there is a typo in the mods being shared - says a 68pf cap across lugs 1 & 2 of the Normal volume. Should be across lugs 2 & 3.
I don’t have either amp anymore. I had a case of transformers snobbery and decided I needed to eventually hand build one with specific transformers. Maybe the Ken Fisher version with Pacifica. I built an Express with those
You mentioned the Night Train series. What are your thoughts on those amplifiers, specifically the 50 watt heads? I love a Vox sound but I am open to trying something new (or rather, discontinued) like a Night Train.
Avoid. Poor construction, hard to service, meh sound.
@@PsionicAudio Thank you for the reply. I guess I'm sticking with the AC30C2/CH, my opinion being based on your informative videos, of course.
@@PsionicAudio hi sir, I really enjoy watching your content and learn a lot from your videos. I really wanted to understand why you would say Night Trains have a poor construction. I use a Night Train 15 Combo G2 with a Greenback and haven't really had any issues so far and to be honest it sounds amazing. I get really great Vox cleans and a pretty solid High gain in the Girth channel. Its a proper 2 channel amp. The normal/bright channel sounds clean. Maybe not pristine clean like a Vox but that's what I like about it. It has its own tone. Plus you get a boost switch on the normal channel which makes it sound even better. Construction wise, i do not know how different it is from a VOX AC15 combo but looks quite similar to NT15 combo.
Can you tell me what about its construction you dislike and why you feel the tone is not great ? I picked it up because I felt it was great. Would love hear your side and learn from you.
Sorry for the long post ,sir.Just curious.
Also, if you don't mind. I need your advice.I want go for a 50w head or a combo next which is not super expensive. I am fine.if it's discontinued. I just want it to be versatile and not a generic sounding like a Vox AC or Fender twin.
I run my rack effects into the normal channel on my AC30C2 because it seems like it has more clean headroom and the top boost channel I feel like I can never get the tone stack set right either too much bass or treble. Is it easy to make the bright cap switchable on the Normal channel?
Easy for a good tech who can work on a PCB without damaging it. The tonestack on the TB channel needs to have the Bass pot wiring changed to JMI spec, otherwise it fights you. A good tech can compare the schematics and know what to change. I don't want to tell all of UA-cam to start cutting traces, because most people aren't qualified and would just damage their amp. Or electrocute themselves. Or both.
@@PsionicAudio would you say the tight switch that you install gives the amp more definition in the bass? I guess the thing I don't like most about the AC30C2 is the lack of definition in the low mids and bass. The low E on my Tele doesn't sound like a string being plucked, it just booms, there is no string attack like my Super reverb which has tons of bass too,
A fixed bias Super Reverb with more filtering will always have more defined bass than an AC30.
A great AC30 will have a softer low end than a Super Reverb. That's part of the charm.
BUT...
The stock output transformer in the C2/C2X isn't great. That doesn't help.
And the C2 has Greenbacks in an open backed cab, which is a recipe for weak low end.
The blues in the C2X are better in that regard.
My tight switch rolls off lows, like the second channel of a Marshall JTM-Plexi (not as extreme though).
@@PsionicAudio I put an Alnico Blue in it recently and it was 100% better. I'm definitely getting another one.
I don't like amp sag. When I hit a note or a chord I want the sound to come out immediately through the speakers. Therefore I prefer a solid state rectifier. And one that doesn't cause sag.
I wonder what makes the AC30C2 loop noisier than the AC30CC loop like you said.
Looking at both of the schematics (which I am happy to share), the C2 loop is the exact circuit as the CC on the -10dB switch position.
Is the -10dB position on the CC noisy?
Thanks
I think it’s the longer signal run past other stages. You can move the connecting wires and lower/increase the noise in the C2.
@@PsionicAudio Thank you so much!
Does anyone know if the effects loop is buffered? Or, in case I'm asking the wrong question, would I want to put a buffer at the beginning and/or at the end of my effects chain when using the effects loop?
It’s buffered low impedance.
@Psionic Audio Thanks Lyle. I didn't expect you to be monitoring the comments, that's why I threw my question out there to the gallery. Thanks again. As an amp user with little to no knowledge about the innards, I greatly appreciate your videos.
Really enjoying watching your AC30 videos. I was wondering in your opinion, between the TB/TBX, CC2, C2, and HW, which one, in stock form, sounds like it has more clean headroom before any breakup? I used to own a CC2 and felt that it wasn't great for clean headroom. I tried a TBX way back that I felt was much better for that, but those are hard to come by now. I haven't had a chance to play the C2 or HW yet, due to covid. I know AC30s will all break up after a certain point, since they're not super loud and clean amps, but just wondering if one is better for that, according to your ears.
Thanks!
It's a little deceptive, because the various models use different taper pots. The CC has more clean headroom than the TBX, but the TBX volume pot has to be at 11:00 to be like the CC at 10:00. So visually, the TBX breaks up "later" but the actual circuit of the TBX breaks up earlier.
Note: this all can be tube dependent. 12AX7s have a nominal gain factor of 100. Actual 12AXY triode gain factors vary from 70-110.
Thanks for this videos on the AC30´s. Can I ask you a question? I keep reading that this amp (AC30C2/C2x) is self biasing. But I´ve been told to take the amp to a tech if I wanted to change the EL84´s, which is something that have to do. What´s your take on the subject. I have an AC30C2x that needs an output tube change. Can I do it myself? Thanks
Cathode biased = "self biased." You don't need a tech, so long as you have a matched quad of EL84s. Most good tube vendors match at no additional charge. Just make sure the pins line up before pushing them in the sockets.
@@PsionicAudio thank you so much for your response. I was gonna get a matched squad of JJ's. Any power tube brand that you would recommend that gets along well with ac30's?
JJs *from a good vendor* are a great inexpensive choice. Don't buy on eBay, etc. Use a real tube vendor that does real testing. I would recommend The Tube Store and Tube Depot.
@@PsionicAudio thank you!
@@PsionicAudio May I ask you one more question regarding ac30 tubes? you really seem to know your way around them and though everything is subjective and opinions may vary I would love to know your opinion about 12ax7 tubes in the v1. I can´t find any good recordings comparing stock tubes to any other brand. What would you say it´ll sound better in a C2x? I can´t afford NOS tubes really. I can get a Tung Sol, Mullard, JJ´s....any other in that price range that you would recommend? Thanks again.
I never bonded with my AC30 C2. To me it sounded one dimensional and didn't have that sparkle as the old ones from the 60s had. The TB channel also was very dark, which surprised me tbh. I'm sure there are many happy C2 users though.
The stock TB channel has a little less brightness due to some snubber caps I didn't get into in the video. They are gone after my mods. The stock higher filtering also affects this.
@@PsionicAudio Ok, thanks for the clarification. 👍
I noticed that warmth on the bright channel. It helps the amp sound more to my liking than the TBX or Ac30CC amps I’ve had before. So far in the C amps I like the AC30C2 better than the AC15 C1. The AC15 CCX I had, all stock had the best sound in stock form of any of my Vox Amps. The AC30C2 is almost as good and that’s plenty for me.
although he said it's modeled after the treble TB/6 I also find the amp to be rather dark, especially the normal channel, the TB channel can be equalized though, funny how the TBX get so much more love despite being much darker than the C2.
I like vox
I wish you lived in Scotland. I would have you mod mine. I don't know a single decent amp tech within a 50 mile radius.
Thanks! I don't know if it's feasible for you, but I can recommend Roland Lumby in Manchester.
Lyle, do you ever see issues with the op-amps or the 1000uf/35v caps in the 27v supply in the AC30C2?
I've got an AC30C2 that is not passing signal past the U5B op-amp, and R106 and R103 are getting hot enough to turn a little brown (part of the +27v supply). This section of the circuit is a little outside of my expertise, but I'm working to learn more about op-amps with regard to trouble-shooting.
I have not run into any problems with the LVS caps or opamp, but any electrolytic can fail - sounds like something is drawing too much current there. More likely the caps than the opamps.
@@PsionicAudio Thank you Lyle. I’ll check those four filter caps on the low-voltage supply.
Do you have a preferred make/model for lower voltage electrolytics?
I always use Nichicons or Panasonics.
What those IC's for?
Some are mixing the channels, some are the effects loop, some are the reverb circuit, some are the tremolo circuit.
They are good IC circuits.
Can you make these videos for a Vox AC15c1?
If a client brings one in. But they are essentially the same amp as the AC30C, just with different transformers and two fewer EL84s.
@@PsionicAudio would you recommend similar mods?
@@o0SLAVIK0o1 it's tricky. Most amp modders have no business changing amps, and a surprising number of "amp techs" don't know how to work on PCBs without damaging pads and traces.
So if you bring the amp to a very good tech, he or she can compare the C1 schematic to the actual JMI era AC30 Normal with Top Boost schematic and will know what to change, particularly on the first stage of the Normal channel and the Bass pot wiring in the tone stack. Let them know to increase the screen grids to 1Ks and to reroute the heater traces beneath the first two filter caps (hidden surprise there). A really great tech can also make the opamp stages unity gain (most amp techs don't speak opamp, so...).
But better to keep the amp stock than to bring it to an unqualified "tech."
@@PsionicAudio What kind of radial electrolytic capacitors do you recommend to use for filter caps. Also whats the best tone capacitors to use in a vox ac15?
Is there a schematic online for this model?
Yes, I found one at least.
@@PsionicAudio do you have a link? I only found a schematic for the power section, I want to see how they wired the silicon diode rectifier bridge.
Shoot me an email at info@psionicaudio.com
@@PsionicAudio ok just emailed you
I'm bordering on doing to R6 and R7 mod to my CC2 but also kinda worried I might damage it 😬
I've soldered plenty of Guitars but never a circuit board
It's tricky. If you have a good temperature controlled soldering station (not just a plug in iron) and good desoldering braid you can see my video on a Deluxe Reverb RI s few weeks back for the techniques. But if you don't have the gear, don't even try.
PS on the CC series you don't have to remove the pots board to access the main board. Many do, and they eff up the dress nuts on the pots board.
@@PsionicAudio OK, thanks for the info. I think I'll not bother trying myself as my soldering iron is just a basic one that I use for Guitars. It does that job fine but I'm far more wary of Circuit boards. I'll need to try and find a decent tech. The guy you mentioned in Manchester might be feasible as I could just send him the chassis. I'll need to look him up. All this info is great by the way, enjoying watching it all.
I've also it a HW AC15 that I've never been completely satisfied with. Only bought a used CC2 recently and it feels totally differnt and sounds very different to the HW1X that I've got. The normal channel on the HW is just too damn dark even with the tone cut wide open.
The CC2 is a lot better to my ears although I've improved it by installing an Alnico Blue and Alnico Gold but I really would like to have those resistor mods done.
@@PsionicAudio took your advice and have a tech going to do the resistors on my CC this Friday. Looking forward to finding out the difference it makes. The guys on the Red Special forum tell me it's a great mod so can't wait to hear it. 👌
I think some of the audio is out of sync with the video on this.
In your opinion, which one sounds better stock? the ac30c2 or ac30cc ?
In stock form, the C2X, at least the Top Boost channel. The stock Normal isn't great on either.
- WRT Opamps, NJM2147 are a cheap junk, poor performing opamp that can handle high voltage rails, which is why they used them.
- They are very slow (SR = 0.5v/uS) , very low OP drive current , running internal transistors at a few micro amps.
I upgraded my AC30CC2 to Burr Brown opamps but had to a/ lower the voltage rails and b/ use SMD to DIP adapters which was a slight PITA. The amp sounded better for it though.
You gotta wonder why the techs at vox can't identify these things but this guy can. You'd think they would change it.
They hire EEs. Who haven't really studied valve technology, as it's ancient stuff. They don't understand heat or vibration. They don't know all the ways amps fail. And honestly the EEs getting hired at Marshall, Vox, etc aren't the cream of the crop the days - Google and Cisco etc get the top of the class.
@@PsionicAudio interesting, I didn't know that. You have to wonder though, if I'm the head of Vox amps and I see a tech who can easily identify issues and recommend mods that are clearly what the end users want and that work, I would be employing him as a consultant for future models.
Please download your knowledge into my brain.🙃😄
Bloody hell is there no reliable amp?
too many chips in there