luvdunhill

that's not any red polish, that's conformal coating... ok, nail polish. Anyways, I guess I'm curious to know if: A.) Kevin's new all DHT amp uses HV opamps B.) If the older DC coupled version, perhaps with DHT output, is worth building Obviously, there's only one person who can answer this

Found some sockets for the Brown Burr op-amps. $27 each though ...

KBI for the win. Nice derailment!

If this is the case, just ensure you don't have too much gain in your system, then the steps will feel just right at lower volumes.

just use a hair dryer to shrink it back a bit or a heat gun if that doesn't work

right now it's more like: $300 in plane tickets $150 in hotels $100 in food 1,000 hour honey-do list when I return = not worth it

how does this guy have zero posts?

While this might be an issue in theory, I've found not so much in practice with the TVC or autoformer approaches. Just careful system matching is all that's really required. For some reason, coarser steps do not feel as course with the inductive approaches, I'm not sure why that is, but it seems to be the case to me at least.

I know most of the Muse Electronics devices have 1.99 Vrms output on the balanced outs. I was on a similar quest and settled on one of their players and am very happy with it.

oops, yes you are correct. I looked around at Mouser some more and decided to change to the PM series. I don't think we need much capacitance here really. I've decided on these to prototype with, and feel free to use larger ratings / larger sizes. The PM series is a very good performer by the way, and usually better than the HE series, if I recall. I'm choosing these values as there are equivalents in the Elna Silmic II line as well (my favorite electrolytic) 647-UPM1K221MHD6 647-UPM1V471MHD6 good catch. The most recent version of the board was changed to a 0.1" pitch TH cap instead of the SMD pad. good catch again. I think 2.5mm, 5mm, and 7.5mm will all fit. Seems that the cap you recommended should fit fine, I'll add it, unless anyone sees something we don't ... yeah, I was thinking about using a pair of the 0.47uF for the larger caps and a pair of the 0.01uF for the smaller caps. I think I'll change all four to be the Wima FKP2 and while I'm at it increase them to 100V caps. no, you've been super helpful! I very much appreciate the feedback, and it goes without saying that the rest of the group buy members do too! updated BOM: http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=69a573ab56

Final prototyping BOM: https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=69a573ab56

don't Google around for DIY options then A Microprocessor Controlled Here's a different approach though: Tube Tester analyzes tubes by Transcendent Sound

couldn't be any more expensive and not use a wall-wart. Duh.

you mean the non-cancer causing ones? Quite a few actually. You have to be very careful using Kapton film. How thin are you considering going? Remember, now you have three thermal junctions as you need interface material on both sides of the Kapton (edit: depends if you consider Kapton rigid, like mica. I do.). Also, look at the thermal conductivity of Kapton, not just its thermal resistance. In this comparison, Kapton performs pretty marginally. You can help things out by going thinner, but once you look at how thin you must go, it begins to be a non-option. Just as an example, compare AL2O3 pads to Kapton and you'll see what I mean. Just drill a hole at an angle under the device and use a thermocouple. That's the most accurate I've found.

you mean the non-cancer causing ones? Quite a few actually. You have to be very careful using Kapton film. How thin are you considering going? Remember, now you have three thermal junctions as you need interface material on both sides of the Kapton. Also, look at the thermal conductivity of Kapton, not just its thermal resistance. In this comparison, Kapton performs pretty marginally. You can help things out by going thinner, but once you look at how thin you must go, it begins to be a non-option. Just as an example, compare AL2O3 pads to Kapton and you'll see what I mean. Just drill a hole at an angle under the device and use a thermocouple. That's the most accurate I've found.

My datasheet (RCA Receiving Tube Manual 1966) says 250V max plate voltage in a class A1 amplifier. So, I say .... pony up and do the video!

yeah, the datasheet says up to 11.5mm max tab diameter, see how they jut out a bit further in? The pad widths are available in 1mm increments, so 12mm, 13mm, or 14mm would be the reasonable choices. Better than hand trimming the pads, right?! I'm betting they are simply non-RoHS devices. The ones I have were dropped shipped from Renesas and have different case markings. I'll post a pic sometime soon.

what about a 12mm wide pad? datasheet for MOSFETs with case dimensions: http://documentation.renesas.com/eng/products/transistor/rej03g0122_2sj76ds.pdf

Those have the older package markings, they're probably Hitachis (or an eariler non-RoHS version I suppose). Anyways, so, does that mean there is 0.02" between the two devices? wowza, I would have guessed more. Thanks again!

shit, I didn't even think about pics... definitely, dew eet!

Here's the really counter intuitive thing I've found. Two 6" x 6" heat sinks perform better than one 6" x 12" heat sink (assuming same type, and for argument's sake there is a single output device in the center of each 6"x6" and spaced out similarly for the 6"x12" heat sinks), even when strapped together like proposed in that GB.

I was wondering if Pars or Jacob or perhaps someone else with Dynahi boards could answer something for me. What is the maximum width of a thermal pad that could be used and there not be any overlap between the pads? Not that this is bad, but looks kinda funny and is wasteful. I'm talking with a company that makes isolation pads that perform orders of magnitude better than the products available at Mouser / Digikey. To give you an idea, thermal conductivity of 8.0 W/mK and thermal resistance of 0.07 K/W. This is around 8 times better than for example Thermalsil III... and so far I'm seeing around a 8 degree temperature drop which is consistent with this. This is rather amazing result, IMHO (think about how much larger heat sink you would have to use to get this sort of drop!)... Since we're going to have to order pads anyways for the part kits, I was considering using these ... I'd have to get them custom cut, and there is a lead time, but I think it would be worth it for those interested.

please repeat for the 6S4A

it may take a while to get through to the seller. I think you could use the F5 boards I sold you, but try and get the devices as far as possible apart, or look into using heat spreaders to make sure you are using the depth of the heat sink to its maximal potential. Also, consider looking at the more exotic isolator materials, as I'm finding these to be an excellent performance increase. As long as you're not absolutely set on hitting the bias used in the First Watt, I think you'll be okay. If you actually going to do the math instead of a simple "hand test" after the fact, remember you have to derate the Conrad heat sinks as the C/W is quoted at a much higher ambient temperature than you want to run your devices at (80 C). One you start to really look at the numbers, (and appropriate implications due to the fact that powder coating doesn't perform as well as anodizing) these IMHO are not optimal for use in a power amplifier. But given the caveats above, you should be okay. edit: The R-Theta GB (which is ending soon, as is under the title Aavid Thermalloy), IMHO would be a better choice for a F5.