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 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.
Last edited by Sam Spoons on Tue Jul 07, 2020 2:23 pm, edited 1 time in total.
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.
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
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.
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".
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.
Last edited by Sam Spoons on Tue Jul 07, 2020 2:47 pm, edited 1 time in total.
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!
Martin
Last edited by Martin Walker on Tue Jul 07, 2020 3:16 pm, edited 4 times in total.
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?
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.
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
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.
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.
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
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
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.
In regards to getting the Quad fixed maybe ask over at the Vintage radio forums (vintage-radio.net), I', sure someone will either be able to fix it or give advice on what might be wrong and how to fix.
He's even developed upgraded, new boards for some amps. Antwerp seems to be Quad country. One collector spouts four Quad II sets, a dozen 303s and seven 405s, all of them driving Quad or IMF speakers. Most of them lovingly restored by Stefaan.
Last edited by cyrano.mac on Fri Jul 10, 2020 12:16 am, edited 1 time in total.
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
I was too... I spoke to somebody on customer service and left it with her after she promised to get an answer and call me. She phoned back later having asked the service department if they could help but no was the answer.
There's londonsound.com and DADA in Antwerp (probably a bit trickier to get it shipped) but I gave Will a get-out clause and he said he'd like a stab at it so I'd rather put some money his 'new gear fund'. I will converse further when he has had a look.
Sam, did you tell Quad that you had had another tech look at the amp? Even send those photos?
Some companies you see have a policy of not taking on products when someone else has 'had a go'. Harsh perhaps but I have seen some right butchery in the past and a tech can never be confident in guaranteeing the work. Yes, a block replacement of both PCBs would do it but likely to be uneconomic?
Even so, I would have expected a company of Quad's standing to take such a problem on the chin?
Hi Dave, No just asked a simple question "Can you repair my ex-BBC Quad 522?". They were unhelpful when the last tech phoned for advice (which seems odd if they are not prepared to attempt to repair it themselves) maybe they remembered his call? They just said "sorry, we can't service 522/BBC any more".
I didn't send the pics either but, it's probably inevitable that a 34 year old professional power amp will have been repaired at some point (even if it's just re-capping).
I had a quick look for replacement PCBs with a view to rebuilding it myself (I can solder but have negligible experience of faultfinding electronics) but it's probably too obscure.
There are a couple of 520s on ebay but buying another doesn't keep mine out of landfill, and it won't be my Quad 522 so I may as well stick with the Studiospares amp if mine can't be fixed
Ok Sam, well there is always the chance that the Studiospares bruiser will blow your Kefs?
Have you considered gutting the Quad and using the power supply with a pair of modules? I have an amp I built years ago with a pair of ILP HY60s. Served me well as a hi fi amp for many years. The mains traff is one I salvaged from a Philips VCR2000! The amp is not used at the moment but I have plans!
I'm sure Will will be able to sort it. As I said, it's really not that complicated an amp, and component parts are readily available. So as long as the PCBs aren't completely wrecked it should be fixable.
The 52x series was an unusual excursion for Quad and I don't think they made that many in comparison to their other lines... I'm disappointed that Quad won't service them...
I don't think you can get replacement complete amp cards for them like you can for 405s and so forth -- at least, I've never seen any online! -- so repairs would have to be component level rather than board swaps. But at least the schematics are available, and the technology is very similar to the 606/306 and derives from the 405.
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
ef37a wrote:Have you considered gutting the Quad and using the power supply with a pair of modules?
Yes, in the unlikely event that it does turn out to be irreparable, I'd do what James did with his broken 405 and rebuild using Hypex class-D power amp modules and associated power supply.
I have an amp I built years ago with a pair of ILP HY60s. Served me well as a hi fi amp for many years.
Me too! My university years music reproduction was with a home-built amp using ILP HY60s driven from a modified Sinclair discrete transistor preamp module, and working with a pair of Videotone GB3 bookshelf speakers! Front end was a Hitachie 3-head cassette machine and a modified alarm clock-radio, and in my last year I added a salvaged Garrard 301 with an SME 12-inch arm and Decca London cartridge! (These were quite literally thrown out of the university Students' Union's Hi-Fi society because they was deemed old fashioned! They threw out a pair of Tannoy Lockwoods too, but I didn't have space for them and a friend took them and kept using them for decades).
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
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?
