Jackson Ampworks ‘Britain’
Hello, welcome back to the blog. We are now offering world-class (non-warranty) service & repairs to the range of valve (tube) amplifiers from Jackson Ampworks of Keller, Texas USA. We should point out that we have no official relationship with Jackson Ampworks, so we cannot accept any warranty repair claims without the endorsement of their Australian distributor.
Jackson Ampworks ‘Britain’ amp head
We recently serviced the Jackson ‘Britain’ amp for one of our customers, who is a guitar tutor and professional player – the amp is featured in the accompanying photos. The Jackson amps are built in Texas, but are British-voiced. The concept of the Jackson ‘Britain’ is broadly similar to our own Richards ‘Expressionist’ amplifier models – there are two discrete preamp channels, voiced as per vintage VOX amps.
Jackson ‘Britain’ rear panel removed
CH-1 is based on the EF86 pentode preamp valve (tube), and CH-2 employs the more familiar 12AX7/ECC83 valves and is effectively the top-boost channel. The EF86 is famously rather prone to microphony in guitar amps, but sounds absolutely wonderful in the right situation. The ‘Britain’ power amp section is switchable between a pair of cathode-bias EL84 valves for low power, and a pair of fixed-bias EL34 valves for full power.
Jackson ‘Britain’ chassis
The Jackson amp is very compact – about half the size of most comparable amps, ie amps in the 30 to 50 watt range. This amp depends absolutely on forced-air cooling for its survival, so if the fan ever stops working the amp needs to be serviced a.s.a.p. Some of the amp functions normally carried out by passive components appear to be implemented with the use of solid-state devices, which are mounted to vertical heatsinks, also in the forced-air cooling path.
‘Britain’ chassis: front view
Fortunately, for this service job there was nothing more serious than some noisy valves, which we replaced accordingly with a full check & test. The only problem we encountered was that the light aluminium chassis was quite resonant, at a frequency that was very close to the resonant ring from certain brands of EL34 power output valve that we tried in the amp. This was so noticeable that we substituted several brands before settling on the least resonant combination.
Jackson ‘Britain’ underneath the chassis
Finally, we were happy with the end result and our customer was pleased to get his amp back, working correctly again with unwanted noise at a minimum. You can see from the photo to the right that the amp is indeed hand-wired and the chassis layout is very tight indeed. Access to some components is limited or not possible at all without stripping out the electronics from the chassis.
Jackson ‘Britain’ chassis
Hardware components are by Carling, Switchcraft, Alpha and others – the standard of electronic components is also good. So there we have it – our very first experience of servicing the Jackson Ampworks product ! These amps look and sound great, but are relatively new to the Aussie music industry so we cannot pass any comments with ref to long term reliability issues. If you are in New South Wales and own a Jackson amp that needs servicing, please contact us @ ivan@ivanrichards.com
June 5, 2014 at 4:04 am |
Read your post on Jackson Ampworks Britain. Can you tell me the brand of preamp and power tubes this head uses? I don’t see any branding on the tubes themselves; do you know if they are custom made by JA or a typical high-quality, like Mullard, Amperex, EH, Ei, etc. thanks
June 5, 2014 at 10:56 am |
hello Mark – I cannot recall but they were standard current production valves; the biggest problem I had with that repair was the combined resonance of the (EL34) output valves and the lightweight aluminium chassis which was really quite resonant; I ended up installing several different brands of EL34 until I found a pair that worked for this amp; luckily I was stocking several different EL34 options at the time of repair; IR.
November 21, 2014 at 8:53 am |
To all: the amp in question was a Jackson Ampworks Britain V3.0; I checked my invoice for this job and the valves installed on the day were Mullard (current production) EL34, which gave the best result in this amp out of all the brands in stock at that point in time. IR.