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Quad 405-2


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Hi, I just bought the said power amp. It came from a studio where it was used as a headphone amp so it wasn't driven hard. The seller who has now become a friend told me that it sat for a few years, but before that, it was only used half a dozen times. When testing with my xiang sheng dac-01A moded to work as a pre amp & Yamaha ns-344 monitors, it was silent. No his splat or buz. Tonally, it sounds wonderful and natural. Unsure of the input voltage going in from the pre. I could test it with my hand held scope ( a car audio special) that I have laying around from those days but I am waiting for my quad 66 preamp & controller to arrive from Europe. My friend tells me that even though it sounds healthy and nice, he has a concern that the power caps might degrade quickly due to age amoung other components as well. He suggested changing them or getting it checked out. What do u think? My conundrum is, do I risk tinkering with what a appears to be a healthy amp just because & waste money or is it really a necessity?

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The first rule of service is:

 

'If it ain't broke, don't fix it.'

 

That said, there are a number of modifications that can be performed on the Quad 405 to enhance sound quality. Certainly a test of the main filter caps would be in order, but it is likely they will measure OK. More likely, the small electros on the output boards will require replacement though. Taking mods further requires considerably more effort and will likely cost more than the amp is worth. For some owners, this is inconsequential. 

 

Provided the load is easy, the old 405 is not a bad old amp. 

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I really need an honest clean and harmonically accurate amp to check my mixes on. I can't afford active genelec 10 or 12inch 3 ways so passive is my comprimise. My Yamahas have 10 inch drivers & have worked well to check bottom end which is what I need. It has translated well in mixes. They are made from the same material as the legendary NS10m which, is not possible to source hence the reason they are no longer produced. These 10 inch version offer a midrange driver & same tweeter. Like the NS10m, these yamies are time coherant and image bloody good but, unlike the NS10m which are rubbish for leisure listening, these are quite nice. In my professional opinion, the NS10m tweeters were crossed over at 2k, (poor tweets) no wonder they were harsh. Thats another discussion for another day. I'm not an electrical engineer but I am handy with an iron & have a couple of small projects under my belt, a couple of mic preamps. When I look at the open pics of the quad 405-2, those large caps don't look too challenging to replace.  :unsure: I can replace components if I know which ones. I'm ok with schematics. Question is, is that enough to attempt to upgrade to more modern components for better sonic performance or should I bite the bullet and fork out the cash? 

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I was planing to do an upgrade on mine a while back but never went through with it.

Here is an upgrade kit I considered

http://www.ebay.com.au/itm/Quad-405-DIY-Upgrade-kit-BHC-Aerovox-capacitors-/200407529887?pt=LH_DefaultDomain_123&hash=item2ea938399f

 

If you do a search on DADA Electronics, I think they have lots of info on the Quad amps.

Edited by rocky500
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I really need an honest clean and harmonically accurate amp to check my mixes on. I can't afford active genelec 10 or 12inch 3 ways so passive is my comprimise. My Yamahas have 10 inch drivers & have worked well to check bottom end which is what I need. It has translated well in mixes. They are made from the same material as the legendary NS10m which, is not possible to source hence the reason they are no longer produced. These 10 inch version offer a midrange driver & same tweeter. Like the NS10m, these yamies are time coherant and image bloody good but, unlike the NS10m which are rubbish for leisure listening, these are quite nice. In my professional opinion, the NS10m tweeters were crossed over at 2k, (poor tweets) no wonder they were harsh. Thats another discussion for another day. I'm not an electrical engineer but I am handy with an iron & have a couple of small projects under my belt, a couple of mic preamps. When I look at the open pics of the quad 405-2, those large caps don't look too challenging to replace.  :unsure: I can replace components if I know which ones. I'm ok with schematics. Question is, is that enough to attempt to upgrade to more modern components for better sonic performance or should I bite the bullet and fork out the cash? 

 

Depends. Replacing caps is easy. Doing a full upgrade is MUCH more challenging. It will likely require more experience than you've listed. As for replacing the main filter caps, refer to my original comment. 

 

'If it ain't broke, don't fix it.'

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Depends. Replacing caps is easy. Doing a full upgrade is MUCH more challenging. It will likely require more experience than you've listed. As for replacing the main filter caps, refer to my original comment. 

 

'If it ain't broke, don't fix it.'

 

Surely the age of these it is time to look at replacing some of the caps inside a component like this?

Edited by rocky500
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Surely the age of these it is time to look at replacing some of the caps inside a component like this?

 

If you read my original comments, you will see the answer to that question.

 

To paraphrase:

 

* Replace the small caps.

* Check the big caps and replace if necessary. Big caps can last a long time. Particularly, if the amp is kept cool (which will tend to happen if it is not connected to speakers and/or used infrequently). 

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I had my both my 34 and 405 re-freshed/overhauled by DADA electronics, good service and your amps will be like new sounding (or better).

 

There's a mod for the FM4 tuner too which does away with the battery for the pre-sets (as the batteries can leak). My battery was changed by Quad in the UK before I came to Oz so I didn't bother with this mod but might in another year or two.

 

The 405 service can also include better amp/speaker terminals.

 

34 and 405 will be coming up for sale soon to assist with the purchase of Harbeths.

Edited by cookster
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