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Running a Poweramp without fan?

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Running a Poweramp without fan?

Postby Sam Spoons » Tue Jul 07, 2020 2:23 pm

As I mentioned over in the lounge I have just bought a Studiospares Trojan 600 power amp as a temp replacement for my broken Quad 522. It's cost me £50 off ebay and I plan to use it with my final remaining pair of passive speakers when the return of the Quad makes it redundant.

It's too powerful really for the Kef 104 aBs but I will run it at an appropriate low level*. It was a bit of an impulse buy and what I didn't think of before pressing the 'bid' button was if it had a fan :blush: needless to say it does, and it's a noisy bugger. Given that I'll be running it at about 20% power I'm thinking I'll be safe disconnecting the fan and running it without. I'll keep an eye on temperature until I'm happy it's ok but what do our techies think, safe or silly idea?

* hopefully self noise an issue won't be an issue but if it is then the above question becomes moot and I'll revert to the old HiFi amp I've been using for since the Quad went TTU.

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Re: Running a Poweramp without fan?

Postby Hugh Robjohns » Tue Jul 07, 2020 2:29 pm

Sam Spoons wrote:Given that I'll be running it at about 20% power I'm thinking I'll be safe disconnecting the fan and running it without. I'll keep an eye on temperature until I'm happy it's ok but what do our techies think, safe or silly idea?

Unless the quiescent current through the output stage is silly high, which isn't likely, it should be fine. Just keep an eye on the heatsink temperature the first few times you use it.
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Re: Running a Poweramp without fan?

Postby Matt Houghton » Tue Jul 07, 2020 2:37 pm

If you find you *do* need the fan at those levels (which, like Hugh, I doubt... but if anyone other than you goes near the thing I wouldn't bet on), you can probably replace the stock ones with much quieter types, perhaps fitted with a speed control.
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Re: Running a Poweramp without fan?

Postby James Perrett » Tue Jul 07, 2020 2:40 pm

I'd say it totally depends on the design. I have a PA amp where the fan kicks in from time to time even with no signal. If they've used minimal heatsinking it is possible that it could get pretty warm from just the quiescent current although hopefully things aren't that marginal.

When I first saw your post on the other thread my first thought was "rip the guts out and put in some Hypex modules".
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Re: Running a Poweramp without fan?

Postby Sam Spoons » Tue Jul 07, 2020 2:46 pm

Thanks Gents

I suspect if anybody turns it up enough to need the fan I'll be picking bits of Kef driver cones out of the carpet for months.

I'll connect it up and see how it all goes.

James, I'm hoping to get the Quad 522 fixed, it has so far defeated two local engineers and I'm waiting for Quad to answer an email. I have a sentimental attachment to the 522 as I bought it many years ago and it has served as FOH PA amp and then studio monitor amp until it started giving problems a year or two ago. Not sure I will go the Hypex route if Quad can't fix it, it won't be the same amp (am I beginning to sound like Arpy here.....). If it goes that far I'll probably bite the bullet and buy the KH120s at last.
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Re: Running a Poweramp without fan?

Postby Martin Walker » Tue Jul 07, 2020 3:14 pm

I'm with Hugh and Matt, and have actually performed the deed on my own power amp, whose fan started out whisper quiet many years ago, but more recently whirred like a trooper when it slowly started to rotate.

I just cut one of the wires to the fan, taped it up for safety's sake, and then monitored heatsink temperatures carefully for the next few days during normal use.

The only time it got rather hot was when I turned up some heavy music ra ther louder than I normally would because I was about to go into the kitchen to have a peppermint tea - by the time I went back in some ten minutes later (and the music was too loud in situ) the heatsinks were rather hot, but still nowhere near a damaging level.

The main thing is that my studio power amp is now whisper quiet.

Result!


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Re: Running a Poweramp without fan?

Postby Folderol » Tue Jul 07, 2020 3:14 pm

I'm a bit puzzled, that you say people are having difficulty with the Quad. I don't know the amp in detail, but I didn't think it was a particularly complex one. What exactly is the fault?
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Re: Running a Poweramp without fan?

Postby Hugh Robjohns » Tue Jul 07, 2020 3:59 pm

That was going to be my question too!

The 522 is based on the Quad 606 and 306 amplifiers -- which are just updated 'fixed' versions of the Quad 405-2 -- except that the 520 (et all) have doubled output transistors instead of the triples in the 606.

It's all pretty straightforward and familiar technology, with readily accessible spare parts.

Lots of good info and recommended updates here:

https://quadrevisionspot.blogspot.com/2010/04/revision-of-quad-520f.html
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Re: Running a Poweramp without fan?

Postby Sam Spoons » Tue Jul 07, 2020 5:36 pm

That was my feeling, but it goes a little beyond my tech capabilities. Either way one channel is noisy, (crackles, possibly oscillation but it's a long time since I had it powered up). The last guy said there is something causing a couple of components to fail causing the problem to return after a short time powered up.

Now I've opened it up myself I'm a little disappointed at the quality of workmanship inside, though it's not possible to know who to blame. PCB's are a bit of a mess with several repaired tracks (likely a consequence of a catastrophic failure at some time but I don't recall ever killing it dead during my stewardship).

Will talk to Quad tomorrow and see if they can fix it. If not, maybe the DIY/Hypex route could be a goer.
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Re: Running a Poweramp without fan?

Postby ef37a » Tue Jul 07, 2020 5:47 pm

I agree, it should be fine for 'domestic' levels without the fan.
I tend to think fans in audio gear are a bit of a design fail? They can be a way to cheap out on heat sink capacity as mentioned or as an attempt to make gear more compact than is sensible.
Over time the fan or its filter gets clogged and loses efficiency first then stops. You cannot rely on Joe Pub' to clean things! (I used to service M/W ovens) A fan might be allowable in my view if it is intended as a last but one remedy for overheating but then you are relying on it starting up after perhaps years of being dormant although you can have a timed 'run at power up' circuit.
The LAST ditch heat detector is a fusible link in the mains transformer.

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Re: Running a Poweramp without fan?

Postby Folderol » Tue Jul 07, 2020 5:49 pm

I hesitate to suggest this (with all the other stuff I've got going on) but rather than have it slaughtered, if you can get it to me, I'll have a look at it.

P.S
I won't even suggest you buy a Yoshimi Pi to test the result :lol:
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Re: Running a Poweramp without fan?

Postby Sam Spoons » Tue Jul 07, 2020 7:18 pm

Thanks for the offer. Apparently Quad were most unhelpful when the most recent tech phoned for advice. I'm happy to give them a ring first to see of they are willing to fix it?

Attached some pics, both channels have had significant work over the years have a look and you may change your mind ;)

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Re: Running a Poweramp without fan?

Postby Sam Spoons » Tue Jul 07, 2020 7:51 pm

The studiospares amp is relatively modern (still current) and the fan is a plug in job so super easy to disconnect and the heatsink has a thermistor attached and overheat protection so I feel pretty safe running it sans fan.
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Re: Running a Poweramp without fan?

Postby Folderol » Tue Jul 07, 2020 8:33 pm

Looks a bit scruffy, but mostly its flux residue not cleaned up. I've seen much worse than that.
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Re: Running a Poweramp without fan?

Postby Sam Spoons » Thu Jul 09, 2020 5:22 pm

The Studiospares amp is plumbed in and running happily with it's fan disconnected. A bargain for £50 IMHO. :D
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