Quad 405 Information Page

Click here for the renew/upgrade instructions.

Renew and upgrade kit. This kit will make a very dramatic difference in the sound of your amp. It comes complete with instructions. After 20 plus years of heat and use, several of these components need replacing on all Quad 405 and 405-2 amps. It also replaced the crappy DIN connector with gold plated RCA connectors. The kit consists of two of the followings items: power supply capacitors (upgraded to 15,000uf 63v, replacement for capacitors C2 C5 C8 C10, Resistors R7 & R8 and upgraded op amps by Burr Brown along with the small capacitors for stability, and new gold/Teflon RCA connectors. The new caps will eliminate noise, hiss, and distortion and the new Burr Brown op amp will make the amp really "sing". The new RCA connectors will allow you to use higher quality RCA terminated interconnect cables. The cost of this kit is $99 (US, Canada, Latin America, Europe, Far East, Middle East, Asia). You can either do these yourself if you have good soldering skills, or I can perform them for $150 (labor).

Click here for renew/upgrade instructions.

Original sales brochure

This is a link to the original Quad 405 sales brochure.

Click on the photo to send me an email.

Are you having problems with your amp? Need advice or help? Want to upgrade? What usually breaks? What are common replacement part numbers? Email and I can help you.

With the right upgrades, these Quad 405 amps sound extremely good and modern, and they compare sonically to the best audiophile amplifiers.

Click here for customer testimonials!

I have a Quad 405 for sale. It is serial number 11519, but has the last generation 405 circuit boards installed. They are 12368 issue 9, which is the last ones prior to the 405-2s. The renew/upgrade kit has been installed with new power supply capacitors, C2,C5, C8, and C10, and also new Burr Brown op amps. The two output devices, tr9 and tr10 has been replaced with matching pairs of Motorola MJ21194 which have increased current capacity. The DIN plug has been replaced with Canare gold/teflon RCA connectors. The amp is wired for muliplte voltages, as originally designed. The faceplace and heat sink is in perfect condition which looks like a 10/10 and the top and side pieces havd been resprayed and look like 8/10. The amp sound fantastic! The price is $499 plus shipping.

http://www.quadesl.org/Amplifiers/amplifiers.html

http://stereophile.com/interviews/522/

MAC MOD 405
The respected audio designer Steve McCormack (USA) soon realized that the basic concept of the Quad 405 ("Current-Dumping") was great, but the idea was destroyed by crummy parts and a drastic protection circuitry. In consequence he offered a modification kit for the 405. The ultimate Mac Mod were mono amps. The modification contained the following changes :

· Current Limiting removed

· Improved IC fitted (LM 318)

· Faster Drivers ( Motorola MJE 15031 )

· Faster Output Devices ( Motorola 2N3773 )

· Improved Resistors (metal-film 1% by Resista Mk3 or Corning RN-60 )

· Improved Capacitors (Wonder Caps, Wima, dipped mica)

· Improved Wiring (Audioquest) and Plugs (Tiffany)

The Mac Mod 405 surpasses the original 405 in every respect : It was a great sounding amp which could compete with the most advanced high end amps in these days. Harry Pearson of the "Absolute Sound" magazine wrote an enthusiastic review about it. I still regard it a pity that Quad-UK did not overtake the Mac Mod as standard, because the improved 405 is an exceptional amplifier. The only caveat about the complete Mac Mod is, that the ultimate version (= mono amps) has too much power for the delicate ESL-57 (protection circuitry mandatory !), though power output is quite right for the ESL-63.

Bernd Ludwig Text File and Schematic

This page is an extremely comprehensive Quad 405 modification document (plus other related info) that was very kindly sent to me by Bernd Ludwig. Please remember all audio equipment contains high voltages so only undertake modifications if you know what you're doing. Version June 2005.

Mono-block instructions

This is a link to a two page instruction for mono-blocking your 405 or 405-2. By monoblocking the amps, you will get double the current capacity, but still retain the 100 watt at 8 ohm output. I have several mono-blocked amps, and they do sound better. My B&W Nautilus 805 speakers are bi-amped and my matching Focal transmission line subs are mono-blocked. So I use a total of 8 channels of Quad 405-2 amps for my stereo listening. Do not even ask how many channels for my whole home theater system!!

The Canadian version of the amps did not come with a variable input voltage selector. They came fixed at 110 volts and had a more robust wiring and also an extra set of fuses. Click on the picture to the left to see the Canadian version of the power supply and how to wire it.

This is a pdf file of redrawn schematics from http://www.dc-daylight.ltd.uk/index.html showing the evolution of 405 and 405-2 schematics.

Here is a link to the 405-2 modifications page at http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/QUAD/QUAD-405-2-Modification/QUAD-405-2-Mods.html

This is a pdf file for the 405 Owners Manual

This is a pdf file for the 405-2 Owners Manual.

405-1 pdf file schematic

405-1 hi-res schematic jpg

405-2 pdf file schematic

405-2 hi-res schematic jpg

This is an article by Max Dubious titled "Pooging The Quad 405: Chicken Salad from Chicken Bleep. It is a nice article on updating the venerable Quad 405 and 405-2 amplifier.