Net Audio Modified Quad 405-2 Amplifier
Having recently accquired an second hand Quad 405-2 on Ebay, we were interested to see what improvements could be made to what already sounded fairly impressive.
Having already upgraded our 405 with heavy duty loudspeaker binding posts, teflon insulated phono sockets, and replaced the internal wiring loom with a combination of pure silver PFTE wire for input signal and silver plated PFTE for all the power supply wiring, we thought it time to send our amplifier boards off to David Pritchard of Net Audio to see what further improvement could be made.
The basic upgrade costs £50 and involves replacing old signal degrading electrolytic capacitors with Elna Starget type and upgrading the op-amp (typically a TL071) with a Burr Brown OPA604, and a few other tweaks here and there to really make the amp sing. Whilst David had the boards, we thought it worthwile to upgrade the output transistors as well (£35) and also purchase the Dual Mono Power Supply upgrade which we would fit once we got the boards back.
Ten days later the boards returned and we carefully fitted the new power supply which was a fairly straight forward job given the excellent instructions on the website and then reseated the amplifier boards.
David did stress that it would take at least a week for the new components to burn in and he was not wrong. Although the amp was evidently more detailed than before, it seemed somewhat sterile at first but after a week this had all but disappeared and we have to say the sound from this little amp has superseded all our expectations. In short for an outay in total of £400, we now have an amp that can compete with the best under £2000.
These amplifiers are built to last and the upgrade path that Net Audio offers further enhances their status as a classic piece of British Hi-Fi.
This entry was posted on Sunday April 2nd, 2006 at 7:04 PM and is filed under Amplifiers. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response.
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7 Responses to "Net Audio Modified Quad 405-2 Amplifier"
Steve b Says:
November 25th, 2006 at 9:21 PM
"David did stress that it would take at least a week for the new components to burn in and he was not wrong. Although the amp was evidently more detailed than before, it seemed somewhat sterile at first but after a week this had all but disappeared and we have to say the sound from this little amp has superseded all our expectations.
What changes occur in the components during this time to make the sound less "sterile"?
Hi-fi insight Says:
November 27th, 2006 at 10:42 AM
Steve,
There was some really good information on the internet on why components such as capacitors (on of the main Quad 405 Upgrades) need time to burn. It was in relation to Black Gate Electrolytics but I am afraid I can no longer find it. There is some information on Wikipedia but there was more scientific documentation elsewhere.
It is odd that components behave in this manner but they just do. I have no scientific evidence on this thought but I also believe every other component in an electrical circuit effects every other one, so that a new component (such as a replacement capacitor) sounds different at first before the influence of the other components have had their effect on that particular one - hence influencing the overall sound.
If anyone else has any thoughts, then please feel free to comment.
Phil Says:
January 28th, 2008 at 3:52 PM
I'm sorry but you're talking rubbish. What 'beds in' after a week is your ears. And all this guff about silver PTFE wires - do you think they use this stuff in the recording studios? Of course not - they use 100s of meters of bog-standard copper wire to get the music onto CD. What difference is a few cm of expensive cable going to make? A big fat zero is what.
David mellor Says:
February 13th, 2008 at 9:03 AM
Well, that told him, didn't it?
David pritchard Says:
April 19th, 2008 at 10:14 PM
Dear All,
Out of interest the NET Audio - soon to be Quad Mod - 405 MK3 boards are now being manufactured. If Hi-Fi Insight would be interested in listening to a 405 MK3 amplifier for evaluation then I would be happy to post one to you for appraisal or/and the NET Audio 303 MK3 or Sonance MK3 DAC.
http://www.net-audio.co.uk/quad303mk3.html
http://www.net-audio.co.uk/quad405mk3.html
Many thanks for your past reviews - much appreciated.
Best regards
David
Harry denton Says:
January 12th, 2009 at 7:36 PM
Hi,
I have been reading your 405-2 mods I am trying without luck to find 2 power transistors for my quad 405-2 can't seem to locate can you advise
Yours
Harry D
Deal, Kent England.
Keith snook Says:
March 26th, 2009 at 1:01 PM
Phil
I agree entirely - More people need to stand up and point out that the emperor has no cloths - There are both long term and short term adjustments made by the lump between the ears - This was clearly demonstrated by the BBC (and others) when it was established that A-B comparison of speakers and sound sources could not be relied upon - I wonder what takes longer for the brain to decide - Is it the sound is getting better with time ? or is it when do I tell the wife how much I have wasted on these little capacitors ?
regards to any one who actually reads these comments