Quad 405 -- upgrade options??
I just unpacked an old quad 405 that I haven't used for a couple years.
I really like the sound. I'm using with a pair of Paradigm mini monitors and an old Paragon system E tube preamp.
Although the amp is working fine, I've read many companies online offering "renew/refurb" kits and services that will vastly improve the amp. There is quad405.com and quadmod.com and an english company called net that offer upgrade kits- also on ebay...
This is appealing but I'm worried to buy some "home brew" mod that may change the character. Can anyone suggest a worthwhile mod or have any experience with this.
maybe i should leave it stock...I'm willing to put a little $ into it if new components will really improve the sound.Any advice.
thanks , nico
The "Mac Mod" designed by Steve McCormack (of McCormack Audio) addresses the primary limitations of the early design: dreadful first generation LM-301 op amp, poor coupling capacitors and current limiting circuit intended for the Quad electrostat). Read the reviews of the result.
Originally Posted by darkwavo
If it were me, I would replace the caps, with the same or better quality caps. I think this would give you the best bang for your buck without changing the sound, since caps do degrade over time. You could change out the op amp next, this may or may not change the sound of the amp. You could put in a ic socket for the op amp, if you should decide you'd like to do an A/B comparison between the two.
You can get the caps from Parts Express.
The op amp from Allied or Newark Electronics.
Is this the upgrade you were talking about?
If you really like the sound, why touch it?
Originally Posted by darkwavo
I have an old Quad 303 and I've read several positive magazine reviews of these upgrades but unfortunately they have never mentioned the condition of the un-modified Quad amplifer with which they were comparing it. Was it fresh from a full factory service and working to specification or an old tired one in need of a service?
I get mine serviced by Quad about every ten years and the improvement after a factory service is quite obvious, as others have said, capacitors will degrade with time.
I know that Quad upgraded the 405 to mark 2 specification after a fairly short time, so if yours is a mark one there is the potential to upgrade to mark 2 spec.
That fixed only one of the three inherent problems - the current limiting circuit. You must not have ever owned a component using an LM-301 op amp. MUCH better exists today.
Originally Posted by Chas Underhay
Thanks for all the responses.
Has anyone had experience with the offered refurb kits?
If I were to send it to someone (U.S.) to check on it , who is reliable and good tech?
Take care of that 405!
I have owned a brace of new 405-2 since purchasing them in 1984. There is one good modification based in the USA and several in Britain and a few terrific ones in Belgium where the market for old QUAD equipment is always going strong. Go to the following site:
Having had them done I can say these people know what they are doing and are not simply amp hot-rodders, They respect the qualities of the 405-2 and make it sing as sweetly as any amp available to day in the $4k range. Do not alter any circuitry that was made to couple to the ESl series of loudspeakers or you will regret it. Someday a nice pair of ESL-63's or 988's may come along and the mating of these speakers with a 405-2, 34 pre and FM-4 tuner is really a thing of beauty to listen to.
For those who doubt the capabilities of upgraded 405-2 to the richest community of audiophiles in the world, you can see them selling used in Hong Kong for as little as $800 US and as high as a recent one that sold for $3600.
Anyone who wants to rid themselves of old Quad equipment can reach me at: email@example.com
to discuss what you have.
Good luck and happy listening,
Dr. P. Venkmann
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