Quad 405-2 ... a bit warm?

[mikmas]

just received a later model 405-2 via the post today.

Sounds bracingly marvellous listening to a Bach solo violin concert from the Beeb3 website but after 20 mins is a bit warmer than I'm used to with my 303 (not hot, just warm on the cooling fin side)

Anyone with experience can confirm if this is normal :)

[Gordon Steadman]

just received a later model 405-2 via the post today.

Sounds bracingly marvellous listening to a Bach solo violin concert from the Beeb3 website but after 20 mins is a bit warmer than I'm used to with my 303 (not hot, just warm on the cooling fin side)

Anyone with experience can confirm if this is normal :)

I suspect it's normal. My 405 used to get quite warm but the 303 stays resolutely cool no matter how hard I drive it.

[Desmo]

Yes the 405's do get warm to the touch, as does the 306 - not so hot you can't touch them, but noticeably hotter than the 303 does.

[spendorman]

Yes, I too confirm that is normal. Have 405-2 and several 303's

I think the Mk1 runs cooler. In 1987 I converted my 405 to 405-2 with a new Quad conversion kit, I noticed that it ran warmer than before the conversion.

[Barry]

Agreed, the 405-2 runs hotter than the 405-1 (probably due to a change of bias), and both run hotter than the 303.

As long as you can still continue to touch the heat sink fins without discomfort, after the amp has been in use for an hour or two (or even longer), I wouldn't worry. All my solid-state preamps and power amps run warm.

[mikmas]

Thanks for all the confirmations chaps - you are all stars :youtheman::respect:

figured that might be the case but as with every dive into the unknown the nagging doubt voice takes over - now to enjoy :cool:

[DSJR]

The 405-2 relaxed the current limiting a little over the series 1 (and revised the amp board layout again). The two I had ran very warm and the second got too hot to touch when driving ATC 20's to high levels on a regular basis - cough... Quad did admit to designing the case too small I recall. The longer it's on, the better it sounds I think, as both of mine had a slight 'sting' at hf for a while, which totally disappeared after a few hours' use.

[spendorman]

A handy gadget that gives an indication if the quiescent current is high or low, is a plug in watt-meter. I bought one recently and the results were quite surprising. I have not recorded them, but remember that the lowest power 303 measured 8W, another one 12W, and I think, but not sure, the 405-2 was something like 25W.

This is the same as the one I bought:

http://www.ebay.co.uk/itm/ENERGENIE-Energy-Saving-Power-Meter-for-any-UK-Household-Appliance-UK-/351293240990

[DSJR]

The 303 I had, which had been rebuilt by the previous owner, ran ever so slightly warm, but as said above, had no temperament otherwise. can't wait to get it back :)

[spendorman]

The 303 I had, which had been rebuilt by the previous owner, ran ever so slightly warm, but as said above, had no temperament otherwise. can't wait to get it back :)

I have mentioned this before (I think), on the 303 is a large series transistor that controls the output of the stabilized power supply. Any voltage dropped by this will cause heating of the heatsinks. Depending on which secondary tapping on the mains transformer has been used, the heating of that transistor will be different. My very early 303 used a lower voltage tapping, so not much voltage to be dropped by the transistor, so not much heat generated. My later 303(s) seem to use a higher voltage tapping, so more voltage to be dropped by the transistor, so more heat generated.

[Idlewithnodrive]

Quite normal :)