Robert M
pfm Member
Thinking about it now, I think i was checking it's resistance.
Amp explosion!
- Thread starter foxwelljsly
- Start date
linnfomaniac83
I bet you can’t wheelie a unicycle!
I work with a lovely big JBL PA 2-3 nights a week so my idea of ‘quite loud’ is probably also most people’s deafening… I don’t tend to thrash the hifi too much though, I get my fix with this lot… definitely does loud without a struggle!
foxwelljsly
Me too, I ate one sour too.
I work with a lovely big JBL PA 2-3 nights a week so my idea of ‘quite loud’ is probably also most people’s deafening… I don’t tend to thrash the hifi too much though, I get my fix with this lot… definitely does loud without a struggle!
I would, but I think even my very laid back wife would object.
Arkless Electronics
Trade: Amp design and repairs.
A valve amp couldn't go DC into your woofers and valve's don't have a secondary breakdown failure mode which is probably what caused this.
linnfomaniac83
I bet you can’t wheelie a unicycle!
Might need quite a big valve amp to do party levels though!
foxwelljsly
Me too, I ate one sour too.
@Arkless Electronics As someone that knows what they're taking about, do you think the 104.2 that was connected to this channel when it failed will be toast?
Arkless Electronics
Trade: Amp design and repairs.
russel
./_dazed_and_confused
Have a Quad 405 with Netaudio boards which I have been using with Kef 104.2s. Listening pretty loud, but not excessively and Today crackling noise, smoke and this happened. Never had this happen to me before. Was listening to a mono album and the other channel is fine. I don't have another amp to test my speakers. Anyone know if that speaker might be toast?
The OPA627 is a very high performance device and requires a reasonable knowledge to implement properly to avoid instability which may have been the failure mode.
Arkless Electronics
Trade: Amp design and repairs.
If it took full DC for more than a couple of seconds or so then yes it's toast but we don't know that this happened.
Others have described up thread what to check but basically stick yer hand in through the port with a torch and check that the bass drivers are free to move and without making scraping noises. If then should be alright. You can back this up with the battery test up thread but if it passes the first bit here than prob it's OK.
If in an early 405 case then there should be a DC protection module behind the speaker terminals. On later models it was on the PCB. What you have there is not really a 405 but a no holds barred modified version. The lack of fuses is a bad idea! The T0220 package not on a heatsink could be an SCR for DC protection as on proper 405... or maybe not... There may or may not be Safe Operating Area protection on the board but any amp with only one pair of output transistors and capable of 100W into 8R is not suitable for thrashing into 4R. This is why Quad were so conservative with the SOA protection on the original MkI 405.
foxwelljsly
Me too, I ate one sour too.
Pretty much what I thought. Luckily, the drivers all feel fine. And I honestly didn't think it was THAT loud, guv.
linnfomaniac83
I bet you can’t wheelie a unicycle!
Absolutely… I’m sure a trio of Prima Evo 400s would really boogie in my active system… so would my electricity meter!Such things exist
Love or hate Linn power amps (I know where you stand on this), they don’t dissipate a lot of heat in use unless you’re thrashing them to within an inch of their lives… hard to do in a three way active setup, your ears fold first, 6 x 90w into 8r is plenty!
foxwelljsly
Me too, I ate one sour too.
More importantly, I'm not going to be able to listen to the mint first German (Deutsche Grammophon) press of Sabbath's Volume 4 with Vertigo Spiral label that landed on Friday until Rob gets my 606 back to me.
If anyone's interested, this is the track that killed my amp ... (Mint stereo first US pressing, of course)
If anyone's interested, this is the track that killed my amp ... (Mint stereo first US pressing, of course)
linnfomaniac83
I bet you can’t wheelie a unicycle!
Sometimes amps just sh!t themselves… one of my first amps as a teenager was a Technics SU-8080 (quite a high end late 70s/early 80s integrated), I was just listening to the radio at low volume whilst studying (for a C&G electronic servicing diploma ironically) when it suddenly fell silent and started releasing its magic smoke… was fun to fix because the original transistors were long obsolete, got it fixed at college though!
foxwelljsly
Me too, I ate one sour too.
That's a coincidence. I bought a SU 8080 off e bay for a song for a mate of mine about 15 years ago. It's still going strong in his workshop. Big beastie.
linnfomaniac83
I bet you can’t wheelie a unicycle!
It was a nice old powerhouse of an amp, I replaced it with an Arcam Alpha 8r because I’d got it in my head that British kit was better, and the smokey Technics was a catalyst to make me go and buy one… it wasn’t better, although to be fair the Arcam was £380 in 2000… the Technics cost about that in the late 70s, when an LP12 with a decent arm and cartridge also cost that much, it wasn’t a fair contest.
Arkless Electronics
Trade: Amp design and repairs.
It can happen like that yep.
russel
./_dazed_and_confused
The original Quad 405 is capacitor coupled to the speaker so if the net boards are the same it should provide a high degree of protection, it’s likely they will have ditched that arrangement like I did with mine.
Arkless Electronics
Trade: Amp design and repairs.
Eh??? No it's not! Are you thinking of the 303? 306 et al have a kind of "floating ground" with a "synthesised 0V" for the circuitry which can protect the speakers but not the 405
