quad 405 - A Restoration story...

[Wakefield Turntables]

So I bought a Quad 405 off the forum just for the hell of it.


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I had some time spare at work so I decided to get the old IPA out and the clean the old thing down. Yep, it was dirty. It powers up and has no hum. I cant test it yet as I need to make a 4 pin to RCA lead.

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Here's the old beast after a clean down.

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Here's a crappy kettle lead I found in my bottom drawer. This will either be replaced with a spare shielded Isotek lead or I may even hardwire the Isotek lead onto the PCB.

[walpurgis]

Well it looks alright Andy. Keep at it and you could have a nice result. :)

[DarrenHW]

Nice! If you plan on using it with your Croft (which I'd wholeheartedly recommend) you may want to look at changing the input sensitivity of the 405. I've been playing with mine recently and (with my Croft) have had excellent results at 1.5V (R6 = 100K, R4 = 6K8, C4 = 150nF), IMO the Croft has way too much gain for the standard 0.5V sensitivity. I don't know what your ATC pre is but 405's work well with a passive, Marco brought round his Tisbury round and it worked very well. Enjoy!

[Wakefield Turntables]

Nice! If you plan on using it with your Croft (which I'd wholeheartedly recommend) you may want to look at changing the input sensitivity of the 405. I've been playing with mine recently and (with my Croft) have had excellent results at 1.5V (R6 = 100K, R4 = 6K8, C4 = 150nF), IMO the Croft has way too much gain for the standard 0.5V sensitivity. I don't know what your ATC pre is but 405's work well with a passive, Marco brought round his Tisbury round and it worked very well. Enjoy!

Excellent advice. I'm probably gonna raid the DaDa electronic webshop at some point. I just want to have a listen to the "Quad Sound" and then mod. I had a complete Quad 77 setup at one stage which got sold off, it will be interesting to see how it compares with the 77 stuff. I do indeed intend (initially) to use this with the Croft, then maybe if its very lucky it might get a go with the ATC. The whole thing is an experiment really to see what drives the Tannoys better, valves or SS. I also fancied a bit of box swapping.

[brian2957]

I'd be interested in how you get on with the 405 Andrew . I've had one of these on my radar for a while now .

[Wakefield Turntables]

I had a rummage around my spares box today and managed to find a few bits that are probably going into the 405.

1. Some solid copper OEM speaker binding posts
2. A screened Isotek mains lead, probably hard wire this in.
3. Some solid silver (1mm) teflon wire, this will probably go into the speaker binding posts.
4. Some nice silver plated RCA's or some Eichmann silver bullets for the 4 pin to RCA lead.

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[Wakefield Turntables]

I've now made up a decent mains lead. The Quad's plumbed into the valve system with black rhodium twist doing duties as speaker cable. Still no 4-Din to RCA adapter so that's been ordered. Looks like this example was made in 1979 this should give me the info to research the various PCB versions. So cant do much more now until new lead arrives.

[Barry]

Why don't you open it up and have a look at the number printed on the two PCBs? I have a copy of the Quad service manual, so can give you chapter and verse as to the mods and updates.

[Us-&-Them]

I like to see old stuff restored - keep the info and photos coming :)

[Wakefield Turntables]

Why don't you open it up and have a look at the number printed on the two PCBs? I have a copy of the Quad service manual, so can give you chapter and verse as to the mods and updates.

You asked for it! I'll get some phonots tonight if I get chance. The transformer says Jan 1979. Altough TBH Barry I think the Dada electronic PCB kits have pretty much done all the mods that I'll need to do. It will be useful however to see how Quad upgraded and optimised the circuit as the years passed by. ;)

[Barry]

I'm not sure the mods DADA incorporate, apart from upgrading the IC and some of the capacitors, and replacing the components in the bridge for higher tolerance versions. There were small circuit and some component value changes made by Quad in later versions.

I have three 405s: a heavily modified 405-1, following suggestions by Keith Snook; a lightly modified final-version 405-2, and a NET-modified final version 405-2 with twin power supplies.

As I'm away from home at the moment, it will be a few days before I can give you the information you seek.

[Wakefield Turntables]

A little detective work shows it looks like I have the M12368 issue 9 or 10 PCB's fitted inside my little 405. I've also been trawling the net for the best web resources and happened across Keith Snook who Barry mentioned a few posts ago. I've decided to give Keith a call and seek his opinion on the best way to mod the 405. Who know's if I'm lucky I might get a fully Snook'd 405 :lol:. I've left a message so we'll see how this goes.

[Wakefield Turntables]

New lead turned up today so should be able to get some noise out of the old bugger.