Your questions answered
We guide you through the most commonly asked questions about your VOX product.
Can you tell me about my amplifier and when it was made, from the serial number? |
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Anyone who knows the history of Vox or has read through the Vox Chronicles section on this website will known that Vox has had several changes of ownership and various manufacturing facilities over the decades. Unfortunately, there are no manufacturing and serial number records from any of the previous manufacturers of Vox and therefore we can not supply any information on older Vox amplifiers. The best source of information of this type can be found in the book, The Vox Story by Dick Denny & Dave Peterson. |
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What valve types should I have in my AC30? (Not Custom Classic) |
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There have been several different design variation of AC30 over the decades and the valve types have changed accordingly, but the traditional valve line-up in the original and the recent AC30 design (1993 -2004) is:
The standard AC30's made during the late 1980's used ECC83 valves for the entire pre-amp section. The AC30 Limited Edition and Vintage models made by Rose Morris during 1990 -1992 had the following valve line up:
The Vintage model with reverb (1991 - 1992) had two additional valves for the reverb section:
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< view our spare parts page for ordering > | |
What quality of valve should I put in my amplifier? |
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There are many valves available from music retailers and specialist valve suppliers that make various claims about sound quality, testing and matching etc. However, the most important issue is reliability and when purchasing new valves always check what warranty is available (normally 3 or 6 months). Good quality valves can cost more but are the best way to ensure trouble free operation and good performance. |
< view our spare parts page for ordering > | |
How often should I change the valves in my amplifier? |
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This obviously depends on how often your amplifier is used, but with average use, the power valves should last between 1 - 2 years. The pre-amp valves do less work inside your amplifier and should last twice as long. However, this is only a general rule that considers the average wear on a valve and it must be appreciated that the life expectancy of a valve can be indeterminate. This means that no matter how much care and attention goes into making an amplifier and selecting good valves, a valve can suddenly fail and need replacing earlier in its life. Most guitar players will accept the fact that their guitar strings wear out or can snap unexpectedly, and will need replacing. The same consideration should also be given to the valves in your amplifier. Over a two-year period, you are likely to spend more on regular string replacement than on a new set of power-amp valves. Also, most players carry a spare set of strings in their case ready for the next string change. At some point it is likely that your amplifier will need some new valves, so it's good advice to carry some spare valves and fuses as well. |
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What is the procedure for changing valves? |
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First ensure that the mains lead is removed and that the valves are cool then remove the chassis. On current AC30 & AC15 you should remove the captive nuts on the side of the chassis before attempting to slide the chassis out, otherwise you will damage the vinyl on the inside of the amplifier. Remove old valves and insert new valves. Always make sure that the pins of the new valve are perfectly lined up with the valve based before pushing the valve in. This is especially important for pre-amp valves where the valve and valve base can easily be damaged. When changing power valves, always replace the whole set and never mix valves from different manufacturers. There is usually no bias adjustment on AC30s and AC15s. |
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The Vib/Trem channel on my AC30 is not as loud as the other two channels, is this normal? |
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Yes, there is less gain on the Vib/Trem channel and that is normal. |
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Can I connect my AC30 to another or an extra extension speaker cabinet and if so what should the impedance be. |
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The current AC30s have the internal speakers connected to a jack on the underside of the chassis. You can connect other speaker cabinets to the chassis output, but always make sure that the total impedance load connected to the output is 16 ohms otherwise you will damage your amplifier. Traditionally AC30 have a fixed 16 ohm output impedance and the two internal speakers are both 8 ohm wired in series. Some AC30s had 4 and 8 ohm output taps from the transformer available inside the chassis but you are advised to seek the help of a qualified amplifier technician to make use of this. |
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My AC30 is dead! Should I start changing valves? What should I do? |
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You should refer servicing to your dealer or a qualified technician. But if you really must attempt your own repairs here is some useful advice. First be aware that there are high voltages and potentially lethal electrical currents inside the AC30 chassis. Please take care when removing the back panel and working on the internal circuits. Fuses are the first items to check then the valves. We recommend that you download the troubleshooting guide for more details. |
< download troubleshooting guide (PDF) > |