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- เผยแพร่เมื่อ 17 ก.ย. 2012
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Teardown Tuesday.
What's inside an Sydney CityRail Train PA Amplifier.
And an extensive tutorial on the design of the power amplifier system from the designer himself, Doug Ford:
www.dfad.com.au
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Doug Ford helps create another great video!!! Thanks Doug!
Dave + Doug is an excellent combo.
Omg look at the silkscreen art of the trains on the PCB. The female one in particular... I cracked up laughing once it twigged
I think this is my favourite vlog ever... Doug Ford is awesome! I mean... don't get me wrong, I love watching Dave's usual vlogs, but I really enjoyed Doug's incite!
Love the silkscreen of the two train engines in love. Good sense of humor.
Yep, and he's been in some of my other videos too. More to come!
It's always great to watch someone explaining their work when they also obviously enjoy what they do and enjoy showing off their work. More like this please.
A couple more videos coming up with Doug yapping on the whiteboard and me behind the camera...
Can we have some more of Doug's lectures because he is a good at teaching on thee internet; I can listen to him for hours
Wish Doug would make his own channel. Love to know some of the cool shit he has made throughout the years.
I still really enjoy this video! Watched it a few times over the years!
Great video. Doug Ford is a gentleman and an analog genius.
I love the format of this video, with the designer present too :o) You should do more of these Dave if you can. Don't understand half of what is talked about but fascinating none the less to see somebody go through the reasons as to why something is designed that way :o)
Incredible teardown, it really helps a lot the original designer to explain all the decisions and trade-offs.
This the "Ducks Guts" of teardowns! User and designer, nothing better.
Best teardown so far! Analog such as life.
Great stuff.
Fascinating and hilarious at the same time! Well done Doug and Dave.
Bloody good tear down! we need more of this kind, Dave!
@40:44 - When he described the reliability and life cycle of the JS-920, it reminded me of the Peavey CS 800. The CS 800 is arguably the most durable and reliable power amplifier ever made in the U.S. They started production of them in 1984 and most are still in working condition to this day. They are BEASTS. They weighed a ton and would take any punishment that you could throw at them. They are TRUE 400 watt RMS per channel and VERY over-designed, both electrically and mechanically. I currently own six of these amplifiers, which I had purchased from a studio, which we had done a lot of recording at, and was going out of business. They are in perfect cosmetic condition and, besides some re-capping and cleaning, I’ve had to do no other work to them. Anybody who has been in the music industry for at least a couple of decades truly appreciates these amplifiers. There are higher power amplifiers out there, but when reliability is your main concern, people still fall back to these amps. (Within limits, of course. These won’t power a stadium show.) They are what legends are made of. Peavey also went on to make other great amps, (like the PV-1200, which I own two of) but they still aren’t the ‘tanks’ that the CS 800’s were. I would have hated to be a roadie that had to move a rack of these amps around!!! LOL Here’s a link to the manual, for anyone not familiar with them: assets.peavey.com/literature/manuals/80300068.pdf
Traynor was the equivalent for guitar amps, the creator often testing his amplifiers by throwing them from 2 story buildings on concrete floor.
Excellent video, Dave. Thanks Doug.
Best teardown Tuesday yet!
Favourite teardown!
That was so interesting. Has to be the best yet, by far!
Doug Ford, what a champ! I still have 4 of his Jands 920's punishing musos weekly, also double as a nice boat anchor.
Damn that was a good mimicry of railway station sound
Made y day dave, brilliant work!!
Fascinating video! Doug is a genius for sure! Great to see him again :-)
Doug is a super cool guy. You boys must have some good talks!
These guys are amazing, thanks for the information.
Passion and magic - it was a pleasure watching! Engineering feast.
Got a Jands JD1 from the early 80s and a early 90s Jands 4Pak, both with Doug Fords name. Great units!
Great Teardown! Very interesting!
Oh, this episode is really great, very inspiring indeed!
I would love to watch more from Doug and his projects in the future. =)
Very informative.Thanks Dave!
Just great, thanks Dave
Wonderful video! You cannot do better than to get the original engineer to describe his design. I loved it.
Great job Doug . I remember the Jands amps , boy they had balls ! I remember the rock and roll amps , was one of them called JS600 ? I ran one into a dummy load and even into 8ohms it did over the ratings and hardly got warm , very impressive !
J600 would be the one you are thinking of. There was also the J300 in that series. That was late 1970s. Early 80s the new J series came out, J400, J700 and J1000
Very cool video! You two seem to have a lot of fun together! The bus system at my University uses GPS to figure out what the stops are. No more manual speech. It's great! They also track all the buses to find out where they need to compensate for frequencies of stops. Amazing!
Tons of theory and history. This is a proper teardown.
Fantastic video, really enjoyed it.
Two thumbs up to EEVblog and Doug.
awesome teardown!
Really enjoyed that!!
In the UK, the vast majority of cities only have heavy rail commuter rail networks (London, Glasgow, Liverpool, Leeds, Cardiff and many more). Birmingham, Edinburgh, Manchester and Sheffield have both, and Nottingham has no real commuter heavy service but does have an extensive light rail system.
Has to be my favourite engineer ever Doug Ford, I looked for those Jands amps...Holy shit they are AWESOME!!! One I saw looked like it had been to the moon then to the bottom of the Marianas trench then dragged on a rope across Africa by a truck and it was still in A1 condition under the lid. And beautiful too (in it's own way) - just like Doug..
Heavy trains in "Trójmiasto" (Tricity) Poland as well. It's called SKM.
Cheers!
Excellent video! Thanks.
Nice teardown, even better with the guest :0D
I would love more industrial stuff!
I wrote a software simulation of the Virgin Voyager trains in the UK that was based on the schematic diagrams of the train. By the time we'd finished the engineers could connect a real train door, etc to it and test it which was pretty cool. The wiring of a train is a bit mental :-D
man, I wish I could run a screwdriver as fast- or talk as fast (20:30-20:40), Or know as much as Mr. Ford in the areas he is knowledgeable in. Listening to the two of you talk, while not quite Greek to me is certainly Spanish... That is to say- I understand many of the words and a little bit of the context but it's pretty difficult... If I have to apply it or explain it to someone else.
Anyway; I thank you, as your videos alone are responsible for most of my knowledge of electronics and, ..Well., things that relate- Like half of everything else... In the universe.
Peace be upon you, sir.
1:07:10 What a wonderful self-pwn there, Dave! Didn't you do a bit on jFET active probes about a year before this?
In addition to microphone preamps, the input stage for practically any instrument amplifier (guitar, violin, mandolin, bass) needs to be hi-Zed, which means either jFET or triode (the thermionic equivalent), which is why the LM072 is ubiquitous in guitar effects. A low impedance BJT presents an unacceptably heavy load to such low-current voltage sources. This is a great example of why EE video bloggers should have at least a passing interest in analog electronics.
omg we need more doug!
43:12 the old ones only get binned when both the output transistors and the power supply transformer shit themselves. Valve amps are never discarded, they are so expensive to make we always fix them.
Excellent!
listen up @ 0:41:00 Hey...that was my business for 5 years back in the mid 90th, PA & light rental comp...And this is what exactly is one of my favorite hobby right now: restoration / rebuilding vintage Tube PA(!!) systems - like the philips EL64x5 Tube PA amps (35W to 140W) and make them usable again for serious HiFi.
During my rental years i serviced a lot of 2sk135/sj50 mosfet amps and recone a lot more speakers as well ;) One can´t imagine what could happen to things in the PA biz....
The best answer to that is "it depends". Older tube integrated PAs are good candidates for conversion, but in general the following concerns are still considered (at minimum):
Input impedance, Output impedance, Tone network/EQ values.
If it uses balanced inputs, you may have to isolate those inputs to use them with the guitar.
So yeah, it's possible to make a PA into a guitar amp, but it's not strictly "one cap" to do so. It depends on the amp.
@50:20 Carriage wash fluid will normally be intensely alkali with high electrolyte content. No wonder that plus 100+v DC = fireworks
Wow those power transistors!!!!
i've still got a Jands J600S stereo power amp - its extreamely good.
I watched the whole thing. Wife is mad. Thanks Dave.
Fantastic! :D
Excellent "yup-to-speetch" ratio Dave! :D
i have been on the kscr sets before and i have heard them rattle around and i wondered what the amp was
Loved the teardown, now to pay for watching it instead of doing homework
Very interesting !
Nice!
Don't get the schematic but the person that designed it. Brilliant! :)
Being legally blind myself I know what Doug's talking about towards the end of the video when he's talking about the blind man suing CitiRail, I know how important it is that public transport providers and drivers announce upcoming stops along the line, because those of us with disabilities really rely on public transport because it's the cheapest way for us to get around independently of others.
This was really fantastic. I think I still would have liked to hear Dave's own reverse engineering, then this as a second video
I have acquired a Jands s920 recently
thats a damn smart amp you got ther omg
Yeah, that used to be the industry name for it when they found out what Beryllium did!
If it's a local amplifier to each speaker then you don't need to overcome any poor connections or induced noise. You can send power and signal down the same two wires.
I would really love to get one.
1) PA amps require microphone inputs. Most hi-fidelity microphones require 48V phantom power supplies. Guitar pickups have a high-impedance connection.
2) Guitar amps are designed with a fairly large amount of allowable distortion compared to other amplifiers.
Dave, I'd love to see a schematic of the voltage spike generator Doug described. I'd like to build one but I didn't quite follow his description.
It's only a problem of cost rather than it not being possible. It's easily possible to have an amplifier local to each speaker or car.
22kg for a jands 920? gilding the Lilly there Doug, they are about 30kg! still know of one in use, amazingly robust amps; an Oz rock legend, :)
Superb. The 'duck's guts' video.
The comments about the FETs struck home slightly... back when I was a staff engineer at a radio station in Tampa, the group got tired of the terrible sounding agc and limiter they had. Pumping and all sorts of nasty sounding stuff... I got tasked with designing a new limiter, so a few fets and some op amps to the rescue.. with the fets in the feedback and so on to crop the gain down... Could adjust the rates of change and all that rot. Sounded better, but the radio station got sold before we could rack it and put it in service.. no idea where that thing is now... (The station moved from the bayshore royal hotel into a site downtown on top of a bank with a brand new state of the art transmitter and new studios in the neighborhood of Tampa International Airport... ) --- could do about 20 minutes on how they managed to get jet engine sounds out of their studios....
So here is the deal: I read your story earnestly... It's the least I can do; and, I dig Florida- I've never been there. Do you still live there? or work there? how be the ocean and the fish? ... those last two would be my areas... But there is more-
I have an ulterior motive: I am experimenting on the TH-cam algorithm, and its' response (responses) as it (they) relates (relate) to my commenting on a video... and, not that he needs it but it's good to alert the algorithm that it should put Dave's stuff up all over... Because he's cool, and knows what the f^&k he's talking about.
May peace be upon you, sir.
@@primateinterfacetechnologi6220 I left Florida back in the very early 90's. I've been back a couple of times for very short periods. (My aunt called me with a big problem with her computer... Was dead... So I drove down to the St Pete area and found the power cord had left the back of the computer. That was my last trip to the Tampa area. (Geeks can have techno impaired relatives...)
@@Billblom Yes they can... I even have a few techno impaired friends... I think... I can't think of who they are though. If you ask me it's a survival skill... You know; understanding the world around you at least enough so you don't walk off a cliff cuz you didn't understand gravity or run over a family of 26 because you didn't realize that the brakes in your car can fail under certain circumstances... actually, somebody not having a basic understanding of physics and biology and stuff is a liability... to themselves and those around them.
Some individuals who, with a bizarre and suspicious level of ignorance, continually put themselves up for a Dunning-Kruger award, even believe that the earth is flat or that there's no such thing as penguins (Just a whole bunch of species of "penguin like birds" which merely resemble the penguins... that don't exist...) thus annoying normal people with their ridiculous blathering, to no end...
most certainly...
peace.
@@primateinterfacetechnologi6220 Sorry about the Year Old response... Reason: Gmail and You Tube hid your reply for a long time. I left Florida about 20 years ago. It was an interesting place to live, but income was not great. I was primarily a computer / networking geek at the time, and the local wholesaler of computer gear (Tech Data) was generating several hundred CNEs every year. After 2-3 years, there were 500-1000 CNEs trying to make money off networks.. And almost all of them bought the Tech Data / Novell special where you could get 1 copy to run in house, and 2 for sale (100 user no less) for less than 50% of the first copy cost. Got a RFP for a upgrade of an existing network to 100 user from 50 user... Gave the company a quote for several hours of labor (backups being one of the first thing for safety)--- then the upgrade. Testing and so on. My quote was $100 above my cost on the Netware... and $70 an hour for the labor. About $800-1000 total as I remember. The company got a quote for $300 from one of the companies that had one of those copies on their floor plan, which was eating their profit margin alive.... No real experience at their end. I didn't get the sale.. and ended up moving up to Chattanooga to write code for an insurance rating company.. Then a year later, that company downsized, and I moved over to Charlotte to work for Microsoft... MUCH more profitable there....
I've only been to Florida twice since I left... Once to repair my aunt's computer.. and once for the Orlando Hamfest / Hamcation...
Great show! Get Doug to talk about guitar amplifiers next time :)
you'd have to amplify the line level input to a high enough voltage that it can over come poor connections, induced noise etc. locationing in each car, power supply etc. line transformers are alot cheaper.
also its 2 wires for all speakers, vs 4 or more.
33:00 - One of the major problems with these mics (or ANY mic for that matter). People tend to YELL into or talk too closely) them causing that metal backing to be hit, causing clipping. This is even BEFORE the signal reaches the preamp!
Ahhhhh discrete components does life get any better.
They had their time and uses, nothing wrong with them. I was just taking the piss out of Doug, who prides himself on being an analog designer.
New subscriber this is great!!!!
PS: PAs that use 1/4" phone jacks at high impedance (Hi-Z dynamic mic inputs) would be the closest to a guitar input. A lot of older PAs have those available.
at 55:35
I understand what the differential amplifier is.
I understand the left hand side of the diffamp is the input signal.
What is the "negative feedback" exactly on the right hand input of the diffamp?
Does anyone know who made the amplifiers of the oldest British Rail trains still on the GB network...? (HSTs, Sprinters, Pacers etc...?) It seems like they were solidly built too, as they all still work fine 30-40 years on, and in the case of the first two types with modern sources (TrainFX systems which can play any automated announcements from files, and have a wider frequency response than the microphones)
JFET's with pilot lights aka "choobs"... I get that, vacuum tubes!
Were these power amp given screw driver short circuit, and how long did amp last before it blow up ? I am surprised Jans Engineering did't go for well engineered class D mode digital power amplifier. You have forgotten that well worn out P.A systems usely go to E.Bay today or local church or mosque P.A
ive heard some rumours claimed itll be sufficient insert/add one cap (or maybe a couple only) to convert a PA to a guitar one
yeah ,the jacks is the same. maybe the impedance will be different ,i dont know..but the "hole" ,the jack looks the same
Dave, I have a question. On cars, trains, planes, and stuff, I always see the extensive use of single purpose cables. A lot of them actually. Wouldn't it be easier (and much cheaper) to just have one or two ethernet cables running along with the power cables, with every device having an internal IP address?
Certainly, I was mainly thinking of the links between the powered cars, which was the topic in the video at the time. :)
Thx Doug, I loved this!
PS. Dave at first 20-30min or so, you were interrupting Doug bit too much/promtly. It was bit hard to follow on video as I'm not native english speaker. Thx for the video Dave! +++
A teardown together with the man who designed it - only on the EEVblog :-)
Of course the last thing you want on a train PA is bad rails
(Sorry!)
folks, what does "public address" mean or stay for? if you do a test using an electric guitar: a tube PA amp Vs. its corresponding plane one (a Lead or Bass amp with just 1-2channels) both they fired up on 10 of volume and for many many hours (days?). so which amp will last more time,which one is the strongest/sturdest and which will get to melt transformers or components inside first?
maybe you can find out why some carriages are super distorted and others so quiet you miss we miss our station? ( well, that's what its like in the UK)
Does CitiRail design and build all their own equipment, including locomotives and rolling stock?