Quad 405 Component Service / Upgrade

A good friend of mine, a HiFi buff and keen music listener and drummer, has asked me to service his Quad 405-2. This amp has a great reputation for a good reason – it sounds great, especially for its time of design and manufacture.

Electrolytic capacitors don’t last forever and may even leak after a few thousand hours of use – I can see some of them in his amp are bulging at the top which is a sure sign they need replacing. Plus there are other areas I can see that look wrong to me:

1. I’m not keen on the cheap connection wire used, especially the screened cable for the low level signals.
2. The low level signal wire is laced into a wire loom along with power leads and high level signal wires. It may look tidy but that’s not great for the signals. Personally I would lace the power leads (+Ve, -Ve and 0V) to reduce interference and increase common mode rejection but the low level signal leads I would leave lose and messy to keep cross coupling to a minimum. I would also take a more direct route to keep signal lead length to a minimum. Also ,call me obsessive, but I would keep all wire lengths to be exactly the same, not different for left and right channels.
3. The is only a four way DIN connector for the input. Whilst I have no dislike of this type of connector, the fact is it is not in common use these days. So I will install a couple of decent phono / RCA connectors in parallel with the DIN.
4. The 4mm banana output connectors are rather cheap and nasty with nickel plating and provide no acceptance for bare wire.  They will be replaced.
5. The internal cabling from the power supply and the signal cabling connect to the amplifier printed circuit boards via nickel plated, mini spade connectors. This connection makes servicing and amp board replacement much easier. However, the boards only need a service every 10 or 20 years at most (the ones I am looking at are around 35 years old and they still work) and it is not a much more difficult job having the wires soldered direct to the boards. We all spend a lot of money on highly expensive and exotic signal leads and have no idea that inside our cherished amp the signal are passing through a shitty piece of nickel plate.
6. There are other components that could easily be improved upon.

My friend seems to think I could perform this service for others. I am starting to wonder if he is right. If you are interested in having your Quad 405 power amplifier serviced and / or upgraded let me know via the Contact page (link at the top). This could be a good way to help finance the development of the Liquiphonics HiFi system.


About Matal

Hand made HiFi, photos, a friends poetry.
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