luvdunhill Posted January 12, 2011 Report Posted January 12, 2011 I see. The holes next of the connecters are for the plastic standoff? those specific connectors have anchors that fit into the PCB in those holes for added support.
Kerry Posted January 12, 2011 Report Posted January 12, 2011 Marc's right. I haven't added holes for the standoffs just yet. Also, the AC on this will need 2x 330VAC CT, 1x 140VAC, 1x 28VAC, and 1x 28VAC CT (not counting the filiment windings). This uses less power than the original BH, so I was thinking of doing it in one transformer. For the bias, it uses a similar doubler to the orginal BH, with a bit more capacitance, and then the IXCP10M90S against some zeners (same as the T2). It supports two taps out, Stax Pro for the higher and it has an option for what the lower one is (500V - for HE 90 or 240V Stax Normal).
justin Posted January 12, 2011 Report Posted January 12, 2011 The two of you, and you both know who i'm talking about... Knock it off with sticking chassis in ovens where you cook food. Seriously... There are VOC's... Even in the water based stuff. you think the coatings on some Made in China oven tray/pan are safer?
Craig Sawyers Posted January 12, 2011 Report Posted January 12, 2011 The two of you, and you both know who i'm talking about... Knock it off with sticking chassis in ovens where you cook food. Seriously... There are VOC's... Even in the water based stuff. Um - if they are volatile, they aren't going to stick to anything. And they are going to come off anyway even if you air dry it on a sunny day outside. And with the extract hood going they aren't going to give me a solvent high
spritzer Posted January 12, 2011 Author Report Posted January 12, 2011 The two of you, and you both know who i'm talking about... Knock it off with sticking chassis in ovens where you cook food. Seriously... There are VOC's... Even in the water based stuff. Didn't you once say I should do stuff like this in the bakery ovens...?
Craig Sawyers Posted January 12, 2011 Report Posted January 12, 2011 Didn't you once say I should do stuff like this in the bakery ovens...? Ah - so that is why the judges chose your cake as the winner - they were on a solvent high! Better than ground up pot
spritzer Posted January 12, 2011 Author Report Posted January 12, 2011 Sssshhhh, it was supposed to be a secret special ingredient....
kevin gilmore Posted January 13, 2011 Report Posted January 13, 2011 here is the first cut on the all sand version. i synthesized it, and everything looks good. The semisouth parts are NOT cheap... http://gilmore.chem.northwestern.edu/t2schemsand.pdf what i would still do is replace all remaining 2sc3675's with 2sc4686a and replace the fet and led's in the batteries with the precision regulator and change R34,R34 as necessary to bring the battery in the range of 640V. And likely make Q23 a darlington out of a pair of 2sc4686a. +250 volt supply modified to make +150v, and cascode with 2sc3840. Overall, less power due to no filaments, but more power in the outputs, making the thing still dish out just about as much heat.
Craig Sawyers Posted January 13, 2011 Report Posted January 13, 2011 here is the first cut on the all sand version. i synthesized it, and everything looks good. The semisouth parts are NOT cheap... http://gilmore.chem.northwestern.edu/t2schemsand.pdf 20mA standing current through the output devices - wow! Twice the T2 value. WOOF... And likely make Q23 a darlington out of a pair of 2sc4686a. Or reduce R39. My 2sc4686a have a low voltage gain of 25, or about 30 at ~600V. Conditon for operation is that the base current of Q23 plus the equal currents through Q20 is the current through R39. So say 10uA through each half of Q2 = 20uA plus 5mA/30=200uA about. So R39 would have to be halved in value (in the T2 the current through R39 is 100uA). Or chose the operating voltage of Q16/17 bases to double the voltage across R39 and so double the current through R39, and keep value at 62k. Just saves another transistor is all. the thing still dish out just about as much heat. Which all goes into the heatsinks. I make that an additional 9W dissipation for each sink. Sounds like a helluva good project to me. And although the power MOSFET's are expensive, they are certainly going to be less expensive than the tubes and teflon sockets, and also saves the cost of a third transformer for the heaters.
jcx Posted January 13, 2011 Report Posted January 13, 2011 how much is too much R_DS_on? looks like they may have a lower C part SJEP170R550 IXYS IXTP02N250 looks better parasitic C wise but 450 Ohms, enhancement mode - adding bias not too hard - now listed at distributors but not stocked I plan to "totem pole" cascade 2x IXTP01N100 depletion mode devices - stocked and cheap power budget could be helped by going push-pull with modulated current source - but getting away from "T2"
luvdunhill Posted January 13, 2011 Report Posted January 13, 2011 yes, yes, yes can this be scaled down to fit in a Pico Slim chassis?
Craig Sawyers Posted January 13, 2011 Report Posted January 13, 2011 The semisouth parts are NOT cheap... Well, what are we talking - $30 each? So $120 for four. And that replaces four EL34's at $120 for a Winged C quad from Parts Connexion, plus
spritzer Posted January 13, 2011 Author Report Posted January 13, 2011 We could blow that on some silver WBT sockets!! Not that I don't have some of those...
kevin gilmore Posted January 13, 2011 Report Posted January 13, 2011 four per channel... So that's $240 for the output transistors. Going to need bigger heatsinks I wonder how many pieces of justin's new 5 inch heatsink i would have to buy... Nope, not doing this again. NOT doing this again. Someone find me a standard heatsink/chassis assembly that can dump about 150 watts of heat. I might be able to shrink the board to 12 x 12...
spritzer Posted January 13, 2011 Author Report Posted January 13, 2011 I'm sure we can have some heatsinks made for us plus some bolt on panels. 240$ for the transistors isn't that much when a quad of Mullard XF2's is ~400$. The transistors will last a good while longer and we can push more current though them...
Craig Sawyers Posted January 13, 2011 Report Posted January 13, 2011 240$ for the transistors isn't that much when a quad of Mullard XF2's is ~400$. The transistors will last a good while longer and we can push more current though them... Five years ago I arranged a seminar at the Rutherford Lab on the future of SiC electronics, then almost at a research stage. Astonishing how quickly this has progressed into real devices. The concept of a 1200V, 17A JFET that works at up to 175C is truly amazing. Note: JFET!!! We live in exciting times when leading edge semiconductors are not based on anything resembling conventional semiconductors. The next thing will be devices based on diamond - also addressed at the seminar - but three or four years behind SiC. http://www.e6.com/en/media/e6/content/pdf/The%20MIDDI%20Project.pdf
jcx Posted January 14, 2011 Report Posted January 14, 2011 the IXYS IXTP02N250 and a photovoltaic gate drive optoisolator wouldn't need 2x the bias and whatever extra current you're hoping for from SRPP connection to drive the ~200pF parasitic C of the Semisouth "normally off" fet if there is something "magic" about jfet vs mosfet parts then the "normally on", much lower C sje170r550 device could be biased - may only need ~100 uA forward current for ~10 mA Id, megaOhm bootstrap ccs + LED?
kevin gilmore Posted January 14, 2011 Report Posted January 14, 2011 This is not srpp. At least its not driven that way. Its the solid state version of grounded grid. If it was bipolar it would be called a common base amplifier. The capacitance while way higher than a tube would be is still not subject to the miller effect and hence its much easier to drive than you might think. The idea is to keep the sound the same which means keeping the same way the output stage works except with solid state. I likely need to add a gate resistor on the current source to keep it from oscillating. You could use the original current source with 2sc4686's with a bit more base drive current. The normally on part cannot be used as the gain stage because that messes with all the bias stuff elsewhere. The 2sj79 would not be able to drive it.
jcx Posted January 14, 2011 Report Posted January 14, 2011 ...The normally on part cannot be used as the gain stage because that messes with all the bias stuff elsewhere. The 2sj79 would not be able to drive it. I understand cascode drive, you have nearly 50 Vds on the 2sj79 so I don't see how operating points change with even 10 V difference in common gate pass device Vgs "normally on, normally off" is just a gate drive V offset and the pass Q Vgs, 2sj79 Drain V has little effect anywhere else in the circuit my ccs comments are a little confused - by "SRPP" I was thinking of modulated current source like the sim (just used parts already in Ltspice, think of it as "impedance scaled") by splitting the "current sense" R and adjusting ratio for equal current swing with jfet gm you nearly double current swing vs a constant current source - even easier with bjt device since you can usually ignore the Q's gm and just use equal R
kevin gilmore Posted January 14, 2011 Report Posted January 14, 2011 Yes, and by changing all the operating points, the sweetness of the sound may change. The 50 volts across the 2sk216 and 2sj79 seem to be the magic values where those parts sound the best. Lots and lots of things can be changed or simplified. And i encourage you to build one and test it.
justin Posted January 14, 2011 Report Posted January 14, 2011 hey guys, can we roll transistors? also will someone build me one for parts cost?
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