Audiolab 8000Q Preamplifier Repair

Lovely little preamp the Audiolab 8000Q. It’s really only let down by poor quality factory-fitted parts, particularly the capacitors.

This 8000Q came to me with a fault which would see it sometimes take a really long time to turn on. It would sometimes take up to 30 minutes to become operational after turn-on.

In this case, I found one definite and one possible fault. A couple of the small electrolytic capacitors in the multiple regulated power supply sections showed signs of damage. One was bulging and had clearly had a hard life, exhibiting low C and high ESR. I removed all of them.

Bad Caps…

The small capacitors used in the 8000Q are from a particularly shitful Chinese brand called Capxon. Capxon caps feature in some spectacularly cheap gear. This preamp wasn’t cheap, but the accountants saved a few cents on production costs by fitting the world’s worst capacitors! Not a smart move, but a common one.

I replaced all the small caps in the power supply for good measure. It’s likely they were all stressed due to ripple current, heat and age. Naturally, I used premium 105 degree, low ESR parts as replacements.

The second possible fault might be that one of the owner’s sources is feeding DC into the preamp. The control module inside the 8000Q senses any DC offsets and sends the unit into standby until the fault clears. I will have a better idea if that’s an issue when the owner tests the unit again in his system.

In the meantime, I’ve repaired the Audiolab and she is working perfectly again. A side benefit is that it now sounds even better than when it came to me!

The cleaned and finished amp!

Nicely laid out, the Audiolab 8000Q features all components except the toroidal transformer located on just one high-quality fibreglass PCB.

You can see unpopulated spots of the board for input transformers for an MC phono pre, if fitted. Note the neat, clean layout with almost zero wiring – very nice.

Board-mounted pot and space for MC step-up transformers. Note the quality board mounted RCA connectors and relays everywhere, for low-noise, high-reliability switching.

Digital control is under this RFI shield – again, a nice touch. The control unit detects DC offset, power supply issues etc.

This is where the trouble was. Note the multiple power supply regulators, very much like Naim use in their gear. The issue is that those small capacitors are the cheapest, low-quality ‘Capxon’ brand.

Spot the bulging one..? Nominally rated at 100uF, this cap tested at around 40uF and 2.5 ohms ESR. The ESR of the new parts was around 0.03 ohms for comparison!

Out they come, all of them…

Here they are, next to some of their replacements. As I always do, I used only premium replacements, many times the cost of the original parts, but always worth it.

Job done, all small power supply capacitors replaced.

Another view of the replaced parts