I bought a Burgundy VOX AC10C1, during Black November 2020. My ex-wife commented it is a good-looking amplifier. Nice glass-topped coffee table base?

I bought it having no VOX-sound experience, and internet research indicated that it should be a fun amplifier. Initial impressions? It is LOUD. 10 Watts? It also has an abundance of low-end. I am currently using it in a small-ish bedroom (3 x 3 ½ meter), and cannot evaluate it at higher volumes. I normally play with the Gain at about 8 – 9 O’Clock, master Volume at 12 O’Clock, and have settled on Bass at 8 O’Clock, Treble at about 09:30, Reverb at about 08:30. (The faceplate is not numbered.) This is with DiMarzio PAF 36th Anniversary humbuckers and a DiMarzio Red Velvet single coil in my Ibanez Jem Jr, with guitar volume around 5/10, tone 3-7/10. Turning the Gain up to 3 O’Clock, I can barely crack open the master Volume, sounds OK for slightly fuzzy/distorty sound. Would be fun to evaluate at higher volume levels. With the Gain low, the master Volume does not really make the amp louder above about 2 O’Clock. The amp can get very Boomy as well as very Ice-picky. Easy to get flubby and incoherent bass.

Specs – Vox VX 10 (Celestion) speaker (16 Ohm), two 12AX7 valves in the pre-amp, two EL84 valves in the power amp. Gain, Bass and Treble controls, Reverb level, and master Volume, claimed 10 Watt output. Back panel says “220 – 230 V AC 50/60 Hz 100 W”. I have not yet measured wall Voltage here, but it would be the usual 240+ VAC, thus the amp will be running hot.

I refer you to TDPRI, where there is a 40+ pages thread on this amp, under VOX AC10C1 owners club. I did get some good information off other pages as well, where tech-minded posters gave information on the silicon stuff and circuit design. This amplifier is well documented.

Also visit “The VOX Showroon”, hosted by North Coast Music, for infornation and pictures: “VOX AC10C1 Amplifier Under the Hood”. (Copyrighted material.)

The owners posting on the internet are almost unanimous in praise for this low-cost (?) Chinese PCB semi-hybrid amp.

The construction is weird: The chassis is an “L” shaped plate, screwed to the cabinet on top (two screws) and to the back cover (nine screws) for support. It is solid. The power valves hang upside down right behind the speaker magnet, on a PCB separate from the main unit, attached to a bent-out section of the chasis plate. No ventilation holes. The main unit PCB holds the pots, pre-amp circuit and two 12AX7 valves, sitting in a horizontal position, one under the Gain pot, the other between the Reverb and Volume pot. No ventilation holes. The reverb module PCB is piggy-backed on the main PCB. Valves plug into sockets, the power valve sockets are screwed onto the chassis plate, but all the socket pins are soldered directly to the relevant PCB. Long-term ability of the solder joints to handle vibration has not been reported on yet.

Cooling seems to be a joke, a small slot at the bottom rear, a rather small grill vent on the top above the speaker. There is another slot in the front bottom, but the speaker frame covers a lot of that one. Care has been taken with insulation material between the chassis plate and the back cover. Cooling is very much a “smoke stack” affair. The chassis plate at the power valve end gets quite hot to the touch (at low volume playing!), and I cannot see this layout being beneficial to long term component bliss. Cabinet is said to be MDF. Neat covering all round, even the back panel is covered.

I shall post photos of the inside when I open it up again, to swop valves and fit a modified back panel.

The signal path is based on the VOX Top Boost circuit, and uses a LND150N3-G MOSFET for the first gain stage (gain about 100?), and another as signal boost (gain of 5?) prior to the phase inverter, after the digital reverb module. The first half of the first 12AX7 is used as an amplifier stage after the Gain pot, the second half of that 12AX7 is a cathode follower feeding the tone stack.

So – Input goes to the LND150, through the Gain pot, the first 12AX7Y, tone stack, from the treble pot the signal goes through an op-amp (NJN2115, running at 5V) to the digital reverb module, exits through yet another NJN2115, goes into the low-gain booster LND150N3-G, into a 12AX7 phase inverter. The master Volume pot is between the phase inverter outputs and the EL84 power valves. The amplifier is Cathode biased. Unfortunately, no Tone Cut control. This should be easy to implement on the connecting wires from the power amp module to the output transformer.

Interesting, the LND150N3-G MOSFET runs on the same voltage rail as the 12AX7, and is wired similar to a valve. Apparently this small signal transistor acts just like a 12AX7 valve in the first gain stage, and is good for adding gain to any valve amp. Problem being, one cannot swop out another spec/gain value valve to alter gain, and the VOX AC10C1 PCB uses surface mount components, so swopping out capacitors and resistors to change gain and voicing is out of my capability – initial gain is pretty much fixed for life. Sad.

It would have been easy to implement a “normal” channel around the Top Boost circuit, if the PCB allowed it. Should have been designed in, even if it would have been a solid state channel. Might have been beneficial to be able to switch out (bypass) the reverb PCB and anciliaries as well. A Tone Cut control would be easy to do, but there is no space for that pot on the control faceplate. “High / Low” inputs? Never used the “low” input on my other amps, so not missed. With the gain turned up high, the master Volume pot is a bit scratchy low down, with little effect just off zero, a sudden “switch on“ and a bit sensitive at low volumes. Yes, one can play at low volume, but it would be nice if the master Volume was more controllable at low settings.

I did remove the back cover to hear “open back” tone, I do think it is slightly better, but, of course, louder with two open sides on the speaker. (Phase cancellation? Never experienced that yet.) Did not do much to reduce the Bass response, just more “open” and slightly less “boom”. I shall at some stage make up a vented back panel to do a proper evaluation.

The internal depth is just enough to accommodate the speaker and the power valve bracket. A deeper speaker with bigger magnet will hit the power transformer, and press against the power valve bracket. No fitting Celestion Golds. Or Blues. It accepts Greenback, Creamback, V-Junior, and speakers with less than about 110 mm depth. Some owners have relocated the power valves and transformers, or spaced out the back panel, to allow the fitting of “better” speakers. But, many owners report that the stock VX 10 is fine. I cannot comment, being unable to push the amplifier, and I only have a few hours soft playing on it. Could be less boomy, and I did not look at the circuit close enough yet to see if this is speaker/cabinet derived, or just a capacitor/resistor choice somewhere in the signal chain. Not that I would know. There are some gripes about the speaker being 16 Ohm, though, with some owners threatening to fit 4/8/16 Ohm output transformers.

All this has lead to a silly desire for a wired, turret board VOX. The AC4HW, or the AC15HW? (Many owners say that the Class A AC4HW, even with the 12 inch Greenback, is “thin”, the push-pull AC15 having a fuller, stronger tone.) They apparently have better cabinet construction (Birch ply), and there is the ability to “easily” swop out components as required/desired. (The current AC15HW has no Reverb tank, or Tremelo effect, no effects loop. It has separate Normal/Top Boost inputs, both channels having a High/Low option - a switch between all the options, would be good).

I would enjoy to have a turret board version of this AC10C1, with both normal and top boost channel (on a switch), tone cut control, with valves all round, by-passable real spring reverb tank and effects loop, slightly deeper, open back cabinet allowing for speaker choices. Ten inch speaker is fine. But that is just a smaller (and much lighter) AC15C1? Ah well. Would be fun. I am open to offers to build me one, though.

Photos, did not want to load.

Yup, that is the cooling inlet.

No numbers. Go by ear.

That is an awesome write up. And congrats on the new amp. Sure is smart looking. My experience of vox is that the treble and mids need to be turned up quite high to solve the boominess. Either that or an eq pedal to try adjust for it. I do lile el 84 amps though.. congrats. I have a roadblock by JP le Roux which allows for a bit more volume..but not much.

Enjoy.. really cool amp

I have been very slow on all my projects. I have sourced some 10 mm MDF (asked for 12 mm...) to make up an open back rear panel. I made up a chassis support panel while I use the original back as a cutting/drilling template. Not tested yet.
I can report that the spurious noises and whines reported on the websites reared it's head here. In all fairness, I bumped the amplifier off it's trolley onto it's back, ouch, so may have shaken a valve a bit. I plan to install new valves, will see if that helps.

The noise, soft high-pitched sound, not related to a specific guitar, but pickup output might have an effect on severity.
I have checked Eishkom value here to be 230 VAC, but do not monitor it regularly. I should.

The speaker is the Celestion Ten 30 with a Vox sticker on. This is Celestion's entry level 10 inch and although great value there is definitely room for improvement.
https://celestion.com/product/ten-30/

The next step up is the VT Junior which will tighten up the bass end, sound "sweeter" clean and have more balls overdriven.
https://celestion.com/product/vt-junior/

First prize if it fits would be the G10 Creamback which is just better all round.
https://celestion.com/product/g10-creamback/

The last special edition AC10C1 I know of, comes with the Creamback and JJ valves. I have been looking at that one for a while, but in 8 Ohm. Looks like I shall have to order two 10 inch Creambacks, 8 Ohm and 16 Ohm, when funds allow. I was not too impressed with the 10 inch Greenback, the Creamback might be better to my ears.

Greenback vs Creamback is a lot to do with the amp and guitar characteristics. Creamback is warmer with a smoother top end, Greenback very detailed tops but can get shrill when pushed.

JGP

I have had chance to put a few hours on it with the open back as above. It is very loud, It has heavy Bass. My concern with the Creamback would then be the better low frequency response. I can see from the Frequency Response chart it should have more "sparkle" than the Greenback too. Cannot see the amplifier becoming more bass-heavy than it is, but I guess it could.

I fitted a G10-Vintage to my Laney Cub 10, which was reasonably "dark" with the Tube Ten speaker, and that worked well. The Vox AC10C1 is already rather "bright" unless one turns down the Treble a lot, and the G10-Vintage might be too bright for this amplifier.

Played an Ibanez RG570 through it, the one with the standard pickups I mangled last year. The VOX does make a huge difference to how those "dead" pickups sound. Almost tolerable.

I guess I shall fit a G10 Creamback, 16 Ohm, and replace the valves with JJ's (5751 and 12AY7), while I am at it.

Fun amplifier, just too loud.

I have been playing this amplifier almost exclusively, evaluating it. Not been playing much, though. I had a lot of fun with the RG652 guitar with the “Air – ified” pickups. What I did perceive, is a bit of lack of coherence at lower frequencies, it can get a bit flubby(?), and does not stay “tight”. More time, with more guitars, required to evaluate this. I also need to get back to the Laney Cub 10, just for a sonic baseline adjustment.

This amplifier does not lack for bass response in my playing environment, I normally turn down the bass knob a lot, sometimes play with it at about 8 o’clock or below. Which alters something in the midrange. Small tweaks seem to have very audible effects on that. My ears do not like a lot of hard treble, so I sometimes turn down the treble knob to that level as well. There is indeed many good tones to be had out of this amplifier, if you enjoy twiddling knobs all the time. I do not. What I do find (still learning about guitars and amplifiers, remember), is that playing the low E string to try and set the Bass knob, and playing the high E string to tune up Treble, does not work. Will need to play a third fret G-barre for the Bass setting, and a twelve fret chord for the Treble setting, trying to balance out a pleasant sound profile with nice mids.

If this is all speaker related (it is not), I require a speaker with tight bass response, not flubby and loose, smearing chords about. And the speaker has to have a sweet top end, no harsh treble. While retaining “sparkle”. And, I need a hand-wired amplifier to test voicing by playing with different capacitors and resistors.

And, OOH!, what fun to turn open the "Gain", unfortunately I then have to turn down the Master Volume a lot, and cannot open up the guitar much, but, what fun.

modulator this mod to the back wont stop heat transfer along the chassis panel and then upwards r=to the control plate...

Cerise
Despite our reservations about the closed cabinet and heat issues, as far as I know, no problems has been reported on that owners' club pages. And as people have indicated on the internet, a better design would push the amp into AC15 price range.

As for opening the back to manage heat, a lot of small amplifiers (and many larger ones) has the tubes hanging upside down behind, and close to, the speaker magnet. Most of these has a C-channel chassis, so the heat conducts upwards to the top, via a reasonably closed-box, unventilated area where the electronics sit, to the control plate. In the AC10C1 that path is a long one. In the rest, it is a few centimeters at most. As an example, the Laney Cub Ten is open back, with no vents on top. It gets warm to the touch, but not hot. At least the Vox has a vent at the top, sited so that the airflow has to go past the electronics. The heat will conduct up via the chassis plate, yes, but it will run much cooler than the closed box. I would like to invert the power valves, and have them sit on top of the bracket, just to get the heat off the sockets and PCB, and to get the valves away from the magnet.

These amplifiers have been in use for several years, I have not read about any blow-ups or fires. Would I have bought a "better" one at a substantially higher price? No. I would then have invested in an AC15 Handwired instead, that would have been the price bracket. Would I like to have a handwired AC10C1, all valves and no MOSFET? Very much so, but it would really be an AC15 with a off-spec (10kOhm) output transformer and 10 inch speaker, in a not much smaller box. The compromises to get this thing so small and handy is not optimal, but it seems to work sort of OK.

guidothepimmp what are your thoughts on the Reverb on this? I find it somehow 'phoney' in a way ..if I can put it that way; like using a reverb pedal .

Cannot say I am afraid. My experience has been with the ac30 and to be honest, i cannot recall interrogating it far enough to have an opinion on the reverb. I do like the timbre of a vox though.

I have ac30/ dc30 clone type amp built by JP le Roux which is 15/30w switchable, but it doesnt have a reverb, so i run a reverb pedal through the fx loop. I do recall that putting an eq pedal on either did bring a gorgeous sparkle to the amp (ac30 included), almost like it woke the amp up.

JGP good call.. my clone os paired with a heritage. Great sounding speaker. Open back cab for what its worth

modulator You find yours bright? mine's bass heavy...especially with humbuckers. I've read others feel the same. Mine came with a Greenback 10 " "and I've not even tried the stock speaker. it can be loud..depends on the size of house/room you have! Valve amps without power scaling are loud even at 10 watts. top end is good with a few adjustments- with that speaker. This is better suited to single coils -a Strat or Tele rather than LP or SG. You can get some good sounds out of it but it takes getting used to...

Cerise
The amp is bass heavy, yes, even with an open back. My ears perceive brightness, leading to listening fatigue. With the VOX AC10C1 I turn down the treble. With the Laney CUB 10, I needed to turn up the tone, eventually fitting another speaker. Still dark-ish. The Ibanez TSA 15 head is dark. Not related to bass-heavy. The AC10C1 has plenty bass and treble, to my ears.