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bss epc 740/780

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jonminns View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonminns Quote  Post ReplyReply Direct Link To This Post Topic: bss epc 740/780
    Posted: 08 August 2009 at 5:17pm
Afternoon all

I don't know much about these amps, i've seen pics of them around here a while back but searching turns up no results

Are they particularly heavy? What's reliability, power etc like, must be 10 years old?

I remember seeing a picture of someone using a 780 to run x1s

Cheers

Jon
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JaKe Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2009 at 6:07pm
have you tryed searching the forum, there has been some discussions on these in the past.
My opinion is they are nice amps but not the most reliable.
First made about  20 years ago IIRC.
Brit Row had shed loads for their turbo rigs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote james folkes Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2009 at 7:18pm
the electrical power converter series of amplifiers were, at the time of making, some of the most ambitious pa amplifiers ever built. packed with innovative technology, there is an awful lot of stuff crammed into those 2u chassis, they do indeed weigh a ton too. there aren't that many people who even know how, let alone enjoy repairing them, but i totally lust after them nevertheless. i wanted to get a pile for the martin modular rig from brit row, but they'd all gone before i got the cash together.

by modern standards they aren't insanely powerful, a bit over 1k a side into four ohms for the 780, but the spec is absolutely off the charts compared to almost anything you can buy today (like damping factor >1800), they control cones very well. at lower power levels they operate at pure class a topology, but then gets to class a-b as it gets above 20 something watts a side. as suitable for the studio as they are for the stage, they even come with a fan defeat switch to keep them hush-hush, no worries about overheating though as they have excellent protection circuits and you can keep an eye on the temperature with handy gauges on the front. behind the electrostatically charged dust filters you'll find little switches that configure the protection systems for 4 or 2 ohm usage.

when they were released a hi-fi magazine tried some out to see if the claim that a pa amp was suitable for the studio could possibly be justified, the verdict was: sell everything else, buy bss epc!

the manual is available from the bss website, it makes great reading. well, i think it makes great reading, but then again i do read operating manuals as a leisure activity.

james.
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2009 at 7:37pm
I have 2 of brit row's old epc780's since 8 months now of almost weekly gigs, running sub at 2.66 ohms a side/lo mid at 8 ohms, i've had no issues and the sound is nice. Can't wait to get 2 more sub bins and unleash the 2 ohm power frankly!
things to know:
1. no bridge switch and external bridging isn't reccomended due to independent power supply design
2. they are deeper than standard rack cases
3.Microcontroller in power supply will stop amp turning on at all if anything is wrong, this can be a pain in the arse if it happens unexpectedly. Includes shorted outputs and worn out fans etc.
4. shorted outputs: also note the heatsink coils just inside the rear vents are live when the amp is on and an errant strand of speaker wire can cause a small bang and the amp to go into protect. As i found out :) No damage though, protection system works
5. the psu's can be switched for 2 ohm or 4 ohm operation - the 2 ohm setting lower voltage rails a little in exchange for more available current. running always on the 2 ohm setting causes the amps to get warmer. however the handy temperature gauge will let you know if it's too hot.

I did meet one old monitor engineer who used racks n racks of them for oasis tours mid 90s. He said they toured with a BSS tech. The reason he gave was the power supply issue - if one wouldn't turn on one day it was given to the tech to get repaired for the next show. Apparently this was common enough to make it worth the tech being on the tour! Hasn't happened to me yet though and mine are just in a basic rack sleeve, not much portection, get chucked in vans a lot.....
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djeddie Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2009 at 9:39pm
Was offered some of these for my F2 rig. Decided to stick with my SR707 and PPX's as they were lighter to lift! Bloody nice amps though. I'm off to eat some spinach and see if they're still up for grabs.
Chas n Dave : it's like Drum and Bass but with beards.             E=mc² ±3dB
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyamp Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2009 at 10:03pm
are they mos fet?
a wise man changes his mind a fool does not.
http://www.matrixamplification.com/
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2009 at 10:41pm
Originally posted by james folkes james folkes wrote:

tbut the spec is absolutely off the charts compared to almost anything you can buy today (like damping factor >1800), they control cones very well. 
i actually noticed this. when the amp is off, 18" cones bounce and go boing when tapped. when amp is on, they go rock solid. first time i noticed i assumed i'd toasted a coil and came near to ripping the cone out to have a look! class a kicks arse
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shagnasty Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2009 at 1:54am
I think I posted this when someone else bought a few a wile ago, but, just in case... Rear racking is not optional on these beasts, they are very well made but 30KG plus of amp swinging on a 2U panel will trash it big style... Make sure you have the proper rack strips at the back to bolt the babies to!
 
Not putting more than 4 in a rack is a plan as well unless you have a forkilift!!
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave M Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2009 at 9:19am
EPC 780 weighs 25kg, mostly contructed using 2mm and 1.45 steel plate. Power is 1000W 4Ohm, 1500W 2 Ohm - copper heat sinks with biscuit fans, MOSFET output stage (IRF740s I think). Dual switch mode power supplies, The EPC760 where optimised for high frequency reproduction.  The last few made left the BSS factory at Potters Bar around 1995. I modified at least a 100 as BSS still came up with fixes for problems up until aroung 1999. The guy aound is to repair and maintain these amp is George M of DBA based in Baldock, he is the ex BSS service engineer and has exensive knowledge of these amsp and has some spares whcih inlude graded MOSFETS. I really liked these amsp and owned a few, i thought these amps sounded great and mine never missed a beat - fitting the correct fan filter material helps keep em cool and these need washing out often!

Cheers  Dave
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRE4U2NV Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2009 at 1:05pm
GEORGE ClapHug
IM SO SECRETIVE BUT I CANT TELL YOU WHY
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Dr T View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dr T Quote  Post ReplyReply Direct Link To This Post Posted: 20 September 2009 at 5:25pm
Afternoon to everyone, just a "newbie" on here , but long in thr tooth otherwise.
I like to spend my "free time" fixing dead amps for the challenge of it, between lugging the working ones in ands out of gigs. So here's a plea fromthe heart, I've read up what i can on the EPC 780, I'd like to fix the one that was donated to me, any suggestions for where i might get technical info/circuit diagrams, or am i just wasting my time?

Dr T
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Phil B View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil B Quote  Post ReplyReply Direct Link To This Post Posted: 20 September 2009 at 8:46pm
As said before on this thread...contact George M


http://www.dba-uk.co.uk/

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