Audiolab 8000Q Preamplifier Repair

Lovely little unit, the Audiolab 8000Q preamplifier. Unfortunately, it’s let down by poor quality factory-fitted parts, particularly the capacitors. In this article, I repair this very nice pre-amp.

This Audiolab 8000Q preamplifier came to me with a fault which would see it sometimes take a long time to turn on. I’m talking a really long time – 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 poor aging. One was bulging and clearly suffering, exhibiting low C and high ESR. I removed all of them.

Specifications, as always, from HiFi Engine:

Specifications

Frequency response: 10Hz to 20kHz
Total harmonic distortion: 0.007%
Gain: 15dB (line)
Input sensitivity: 100mV (line)
Signal to noise ratio: 97dB (line)
Channel separation: 100dB (line)
Output: 100mV (line), 0.5V (Pre out), 7.7V (Pre out Max)
Dimensions: 445 x 74 x 335mm
Weight: 6kg

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 and awful gear. This preamp wasn’t cheap, but the accountants saved a few cents by fitting the world’s worst capacitors. Nice work Audiolab.

I replaced all the small capacitors in the power supply, given that they were all so awful. 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 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 Images…!
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

4 thoughts on “Audiolab 8000Q Preamplifier Repair”

  1. Hi Mike, thanks for your quick reply. I am based in Wellington, NZ. So not within range. I am very confident I have the same issue, and its on my head if this does not work. For confidentiality on your solution, please could you email kylerichardnicol@googlemail.com – all I need to know is the types of capacitors you bought. In exchange, I will recommend you guys to my uncle and his family based in Perth, and also my colleagues based there. I can also let you know how my fix goes. Finally, if I ever move to Perth I will visit you guys! Any help would be greatly appreciated. Thanks, Kyle

    1. Hi Kyle, no problem and happy to continue the conversation here for now. Hope all is well over in NZ. In terms of caps, I just grab the parts directly from stock as I need them. I’m not quite sure what you are asking for – are you looking for the specific values of capacitors I used in this repair? If so, I couldn’t tell you because I can’t remember. I don’t make a list, I pull them from stock as needed. You have to remember I repair dozens of units a month and that repair was a year or two ago! It might be best if you call and speak to me directly on 0439 690 436, with the Australian codes in front of course. Look forward to chatting on the phone! Mike

  2. Hi, brilliant post. Any chance you could tell me what capacitors you have replaced? Any help would be greatly appreciated. Many thanks. Kyle

    1. Hi Kyle, thanks for writing and glad you enjoyed the post! It’s worth bearing in mind that each repair is unique and my best advice is to get this unit to me if you are within range, for proper diagnosis and repair. You wouldn’t want to base a repair on what I did here until proper diagnosis pointed in that direction. Are you local and in a position to bring her in? Regards, Mike.

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