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cetoole

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Posts posted by cetoole

  1. Does anyone know if the gain is adjustable on this phono stage?

    Also what are the 9v inputs for (battery powered mode?)

    Nope, not without doing some serious recalculation of most of the resistor and capacitor values.

    The 9v battery inputs look to me like an optional replacement of the 1n4739 zener diode, for if you have objections to these parts. This is used as a voltage reference for the regulator. That said, this is just my guess looking at the schematic, which doesnt make it clear.

  2. so, I've been playing around with some diodes on a power supply and found some I like, but I think I'm cutting it too close with the current rating. The transformer is 82VCT 50VA R-core and I have a 300mA fuse on each rail after the main supply capacitance, which is around 3000uF per rail. I wouldn't expect any more than 300mA per rail, hence the fuse choice. That being said, there is in-rush and the like to consider, and blowing a bridge isn't too exciting in my book. So, without admitting how stupid I was, and how low I went... in your opinion, what's a good rule of thumb?

    Well, you dont provide all the needed information, so some assumptions must be made. I assume your rectifier is a FWB, though you did specify that you are using a 82VCT transformer. Also important, and my assumption is yes, but are you using a pure cap input filter? Finally, what is the DCR of your transformer? I would tend to guess maybe 10ohm or so, but it makes a pretty big difference. You can use PSUDII to get a pretty good picture of what is going on with your power supply. Rule of thumb though, I would stick with 2A rated diodes or higher, though I have used 1A rated diodes for extended periods of time with no ill consequences. That said, I can be a glutton for punishment.

  3. cetoole:

    I'm using the Fairchild FQPF2N60C in a HV regulator design. Pretty nice specs.

    I buy my heatsinks from R-Theta these days and absolutely love their service, but for the price this guy cannot be beat:

    http://search.ebay.com/_W0QQsassZbarrredboss

    Plus, he will custom cut the extrusion to whatever you'd like. Great guy to work with.

    Prices on those heatsinks looks good, but they are the wrong profile for efficient operation. I guess if he will cut them to around 3", they could work pretty well, though I dont know how you would go about mounting one of those. Anything that is not board mounted means more casework for me, and casework is the bane of my (DIY) existence, almost as bad as packing group buy stuff.

    I did look at that Fairchild part, but it doesnt have a P-Channel near equivalent.

    I've found that the mosfet as a pass device doesn't sound as good with the KGSS. I'm guessing it's due to the behavior of a vertical mosfet (BUZ90, IRFBC30, etc.) under (relatively) low current conditions. Does anyone have an opinion on this? There has been some stuff written on this, but obviously not in terms of audio...

    Lower transconductance maybe, giving higher output z? Are you using it as a simple source follower, open loop?

  4. I know, but then Colin said this:

    Colin is a bright guy so I assign a good deal of weight to what he has to say. Dr. Gilmore's thoughts would be greatly appreciated.

    Bright guy, hah. All I was looking at was that 800VAC*1.41/2 = ~564VDC, with a whole lotta ripple. I dont really feel that the R-Core I am looking at is perfect, but it seems pretty close, and still capable of providing significantly more current than is needed by the KGSS (which would allow one to bump up the output transistors' bias. I would use a bit different values if I were to get something custom wound though, though I am also planning to use different voltage regulators for all supplies. I would probably go for something like two windings of 280-0-280 at 100mA, and 18-0-18 at 250mA. The current ratings are kinda arbitrary.

    2sa1968's not needed for kgss. Think KGBH power supply.

    Front end fets can be matched from single devices if necessary, but

    lsk389 is a wonderful part.

    I am sure you are aware of this, but the KGBH power supply has double the 2sa1968 count of the KGSS supply, seen in the CCS biasing the zener string. Would be easy enough to change though. I dont have much experience in HV regulator design, but do you feel 500v parts gives sufficient margin. I am thinking parts like FQP4N50 and FQP3P50.

  5. The chassis is a bit of a pain so that might be left out but a common FPE design for the front panel might be a good idea to fit some chassis.

    The 2SK389 are a problem but can be substituted with MAT02's but the 2SA1968's a problem.

    For the case, the Nabu from Surplus Sales of Nebraska with a FPE panel would be a decent choice I think. MAT02 could work to replace the 2SK389, or the LSK389. 2SA1968 isnt difficult to find, just expensive. Check BDent, they have it in stock, and I have always had good luck with them before.

  6. Grawk did point me towards this thread, and it is true, I am gathering parts for my own KGSS build. The unavailability of the 2SK389 isn't a big deal for us, as we don't need a P-Channel equivalent. Linear Systems makes a part called LSK389 that is, in their words, an improved second source replacement for the 2SK389. Seems like a good part to me (only have used them once so far though), and that is what I will be using for my build. BDent has all of the other transistors needed, though I have decided to change up the voltage regulators to something that doesn't use the 2SA1968, as they are bloody expensive. Anyone building this amp based off the schematics on headwize be aware, the power supply, as currently drawn in the article library, has some dangerous problems with it. Last I checked, an 800vct transformer with a FWCT rectifier isn't safe to use with a 450v rated capacitor input filter. Right now, I plan to use R80-46 from diyclub.biz, a 100VA R-core transformer with 300v-0-300v at 80mA,0-6.3v at 2A, 0-18v*2 at 1.2A, and 0-12.6v at 1A. It is $35, and the shipping quote I got to the USA is $30. I am gonna try and shoehorn it into a 12"x8"x2.5" Par Metals case (Nate will recognize it I suspect). Undecided at this point about doing it on protoboard or making a PCB, but I am leaning towards PCB right now. Their boards arnt the best I have seen, but I could probably get a PCB for this for $50 shipped from Advanced Circuits, on the student discount. Gonna stick with board mounted heatsinks though, probably 2" tall SK129 profile. Volume control will almost certainly be a 50k Alps RK40, using a differential shunting configuration. Only part I am not sure about really is the headphone connector (this amp is for ESP950, though I may reterminate for stax).

  7. Looks like my rig will look like this:

    Dynamic: DA10 >> Balanced 650

    Stat: DA10 >> KGSS >> 007 and 404

    So I guess its "really" just one rig but with a nice dynamic option ;)

    Now thats the correct way to look at it. Now, since we have already determined that only one rig isnt enough, you should probably get another k1000 rig.

  8. Hmm, dark, probably some of the following counts, but "dark" can be subjective. Following is a list of what I love :dance:.

    Opeth - All but Damnation and Ghost Reveries, Meh

    Edge of Sanity - Only have Crimson, Crimson II, and Purgatory Afterglow, but damn, they are amazing

    Bloodbath - All three CDs are good, been enjoying Nightmares Made Flesh a lot more lately

    Dark Tranquillity - Too many CDs to list, but all pretty good I think, though different

    Dan Swano - Moontower: Great CD, not too dark in my mind though

    Shape of Dispair - Angel of Distress:, Pretty good Cd, normally would be way too slow for my tastes, but its just so gcaptivating

    Agalloch - Pale Folklore: Same as above, quite captivating

    Katatonia - Brave Murder Day: Slowish, but captivating, dont care for the newer stuff so much

    Death - Symbolic, The Sounds of Perseverance

    Plenty more, just cant think now, I need sleep.

  9. It won't. At the most basic level, the codec as a whole is not in the same league and neither is the supply voltage. Sticking a pair of Black Gates on the Photo, the worst-sounding iPod to date (my only experience is since the 3G though) sounds a bit perverse to me, that's all I can say.

    Sounds odd to me too; since you pretty much have to use the imod with an amp, why not just get a 5G, dc couple it (remove all output caps from the ipod), and then use the input caps of your choice, in the amp of your choice, where there is going to be much more available space, so if black gates arnt your trip, you can use metallized polypropylene film caps, or maybe even film/foil (large value caps arnt needed when its going to an amp instead of directly driving headphones to avoid bass rolloff).

  10. cetoole, you rock!

    I have no idea why I couldn't find those on Mouser before. Thanks!

    -Ed

    Sometimes mouser's seach seems screwy to me, I had one day I couldnt even locate the Nichicon UPW caps at all using it. Resistors are the other thing I dislike there, its a pain to search for different values, as unlike digikey, they dont have a filter list for the parts they stock.

  11. For those that have not been following Tangent's thread on Headwize.

    http://headwize.com/ubb/showpage.php?fnum=3&tid=5806

    No more board chopping in half, and apparently bye bye to the TLE rail splitter (yay).

    Yeah, I have been following it, looks pretty cool so far.

    Now where can I order some SMD 0.1% thin film resistors?.......

    -Ed

    Mouser, check the Vishay Dale TNPW line, or do a search for "vishay dale 1206 thin film".

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