Craig Sawyers Posted September 7, 2010 Report Posted September 7, 2010 Welcome to the wonderful world of transistors, here one day and gone tomorrow... Over the years so many useful devices have just vanished. Dangerously unprotected MOSFETs from Siliconix that were essential in certain CCD designs - long dead (came with a wire clip shorting the leads together. Solder in and then remove clip). Sensible dual FET's like the 2SK389/2SL109 - dead. Now pretty much the only 900V PNP - dead. Next on the death list will be components with leads, with surface mount being the only game in town. Lead free solder? A complete sham, which subject I can wax lyrical on at length. One audio manufacturer I know has a reel of lead free solder on the bench for audit purposes, and then uses Wonder Solder or some such leaded solder in building the gear. Don't even get me started on the name change game - Hitachi to Renesas, Motorola to ONsemi, HP to Agilent to Avago. Without even considering the number of useful products that have gone the way of dust as a result of Vishay's quest to own every brand going - then doing "product rationalisation". <soap box mode> = "off"
Inu Posted September 7, 2010 Report Posted September 7, 2010 How about 2SA1831? Not isolation package and Vceo & Vcbo are 100v lower than 2SA1968LS but cob is smaller than 2SA1968LS. 50pcs (= minimum order: >$50) @$1.41 100pcs @1.06 http://www.tenfourltd.com
luvdunhill Posted September 7, 2010 Report Posted September 7, 2010 How about 2SA1831? Not isolation package and Vceo & Vcbo are 100v lower than 2SA1968LS but cob is smaller than 2SA1968LS. 50pcs (= minimum order: >$50) @$1.41 100pcs @1.06 http://www.tenfourltd.com Makes a better CCS I've found when I've used it. The lower voltage is the issue for these guys..
spritzer Posted September 8, 2010 Report Posted September 8, 2010 It would limit the voltage to 400V but I've been using them in the BH PSU's for years now with good results.
ujamerstand Posted September 8, 2010 Report Posted September 8, 2010 Excuse my ignorance, what are the advantages of running the PSU at a higher voltage? I tried searching, but nothing came up. :s
spritzer Posted September 8, 2010 Report Posted September 8, 2010 More voltage swing and higher slew rate and the biggest factors.
luvdunhill Posted September 8, 2010 Report Posted September 8, 2010 It would limit the voltage to 400V but I've been using them in the BH PSU's for years now with good results. wimps try them in a BH circuit, they work and sound nice... haven't blown up either... Anyways, I'd probably just stick with the MOSFETs or design another CCS (pentode CCS for a SS amp anyone?).
spritzer Posted September 8, 2010 Report Posted September 8, 2010 I do have a bunch of them and I might try it with slightly lower rails just to be on the safe side, +/-380V maybe.... I like crazy ideas like that. I want to do a single ended SS amp with an output transformer for Stax one of these days...
monsieurguzel Posted September 8, 2010 Report Posted September 8, 2010 I'm be very interested in a board set and a kit of parts also if i'm not too late Thanks for everything Kevin!
justin Posted September 9, 2010 Report Posted September 9, 2010 They will all work well for the front end, it's not picky in terms of Idss. I'm guessing Kevin won't support the Toshiba parts on his PCB, so that leaves the Linear Systems parts. I believe the A parts show less noise. There was an article in AudioExpress than confirms this, if my memory holds. the article i read in audioxpress was called "Noise Measurements of the LSK389B Dual JFET"
luvdunhill Posted September 9, 2010 Report Posted September 9, 2010 the article i read in audioxpress was called "Noise Measurements of the LSK389B Dual JFET" that's it. Then there was a addendum / letter to the editor in the next issue that expanded the topic a bit.
Uncle Erik Posted September 10, 2010 Report Posted September 10, 2010 If it isn't too late, please count me in for boards and the kit, too. Thanks, Kevin.
FrankCooter Posted September 11, 2010 Report Posted September 11, 2010 Welcome to the wonderful world of transistors, here one day and gone tomorrow... One of the major reasons I don't use them in audio circuits. I find it ironic that it's often easier to source a 1920's tube than a 1990's transistor. The tubes don't blow up either. A transistor is a switch, a tube an audio device , let each do it's thing.
luvdunhill Posted September 11, 2010 Report Posted September 11, 2010 A transistor is a switch, a tube an audio device um, no? let me try: Tubes first application was rectification and radio wave detection. (Germanium) transistors first application by the folks at Bell Labs was indeed an amplifier.
kevin gilmore Posted September 11, 2010 Author Report Posted September 11, 2010 tubes sure look like switches to me... UNIVAC 1101 - Wikipedia, the free encyclopedia 2700 tubes in fact. Each dual triode was a flip flop.
GreenLeo Posted September 11, 2010 Report Posted September 11, 2010 Hi, this is first post here. May I have a board and a kit? How much do they cost in total? I may want to have spare set but it seems that I have missed it after reading all the pages.
spritzer Posted September 11, 2010 Report Posted September 11, 2010 Tubes = valves to the rest of the English speaking world.
wink Posted September 12, 2010 Report Posted September 12, 2010 Sacres cows to the golden eared brigade.
Pars Posted September 12, 2010 Report Posted September 12, 2010 Two stupid comments, one bumping a 6 month old thread? methinks
crappyjones123 Posted September 12, 2010 Report Posted September 12, 2010 are the through holes for the transformer/volume pot/etc a certain standard distance apart? i ask to see if those hand terminal blocks could be used (ones which get soldered on to the board and the wires get screwed into the block. after having to solder and desolder and solder and desolder and solder and desolder again and again while using the wrong fuse (needed to use slow blow in stead of the supplied fast blow with the crack amp...) i really missed having those screw on things. just a little though in case the bom is still fluid. would help us noobs a lot while troubleshooting. if it is more of a personal preference then i wouldnt mind being told what exactly the thing is called so i can start looking for it.
kevin gilmore Posted September 12, 2010 Author Report Posted September 12, 2010 standard terminal blocks with .2 inch pin spacing on all connections to both the amp boards and the power supply boards. No pot on the production version.
crappyjones123 Posted September 12, 2010 Report Posted September 12, 2010 hmm (just went back to the bom). would one need a preamp of sorts for volume control? or could a pot be added to the amp itself somewhere along the way? any way to use the bottlehead crack as preamp in case one is required? wondering if i could do without having to buy more gear.
spritzer Posted September 12, 2010 Report Posted September 12, 2010 The pot is simply added between the input terminals on the chassis and the input terminals on the board, just like it is on the Crack you built. I would recommend a 4 gang pot and XLR inputs even if you are using SE only since these can be a pain to add later on. If you want to have both XLR/RCA inputs then you need to have a switch to ground the - part of the amp when running it SE (XLR/RCA adapters do this already so no need to worry about it). I for one use a 4PDT ON-ON switch on my amps so the two inputs are isolated from one another but you can just use a 2PDT switch if you do not want that. There is also the option of using bridging pins as you can see on many power amps. 1
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