luvdunhill

heh. There are a lot of other (reasonable) 0.200" options out there, like the Phoenix 0.6W MRS (I think?) series and the blue Vishay series. You can also tombstone larger resistors. If this isn't all that interesting to people, now's the time to speak up. Jacob: Can we remove the ground plane from around the output pad and up, so there isn't any chance of the L-bracket scratching through the solder resist layer? For the large output resistors, I like the Panasonic ERX series, which are available in 1W-3W. http://www.panasonic.com/industrial/components/pdf/AOA0000CE18.pdf What are you thinking for the caps? Something like Nichicon UHE 50V, perhaps? http://products.nichicon.co.jp/en/pdf/XJA043/e-he.pdf I'd also add some film bypasses, something like Wima FKP2. There is a 10nF/63 DCWV that is PCM 5mm 5.5mmx7.2mm that might work well

I think it would. At least that was the case when I played with it on a design I've been working on. I found a good write up somewhere in the documentation for the Leech amp I'll find and post. I pretty much followed the concepts like a recipe and it worked perfectly. Also accounts for phase issues, though in a slightly less elegant way.

a LPF would also require recalculating the global compensation cap, right?

Basically, the input JFETs need to be just like the Vas duals, except the 4-pin side needa to be placed back to back (i.e. one rotated 90 degrees) and the pins 5mm away from each other. Like this: -0-0-0- 0-0-0-0 -------- 0-0-0-0 -0-0-0- where the distance between the second row of text and the fourth row is 5mm.

the input JFETs are not correct. They should be layed out just like the 7-zip packages.

Pete: We all appreciate your enthusiasm, but you do realize that the lead time for the parts (then resulting matching) will be the long pole in tent here? We will have plenty of time for the boards, trust me

For balanced I'd recommend 160VA 2x30 VAC. I'm planning on using Plitron 057017201. I don't understand all the consternation about a single box build. Look at the number of power amplifiers out there that don't use shielding and using much larger transformers... not all that many two box power amplifiers out there. Anyways, if we need to agree to disagree on this one, I'm fine with that. The group just needs to come up with a recommendation, preferably a single model. I think the SumR toroids are a "good value". I have a custom unit sitting right here in front of me and have another large 2x18VAC unit as well. I'm still waiting to hear back on some more of the semiconductors. Interestingly enough, I have a friend within Renesas that I had no idea he worked there. Small world. Lead time is pretty long (~8 weeks), and that's what I'm trying to work around now. Chris, thanks for your help with the board quotes. I say we just call it $15 per board and use the extra money as a deposit on shipping and packing supplies as well as funding for the prototype boards. I'd rather estimate high. That leaves the rest of the work for me in firming up estimates on semiconductors and heat sinks so we can take deposits for those. I'm waiting to hear back from 2 more bids before balancing cost versus lead time At this time, we can target firm quotes for the end of this next week.

yeah, that and things like Caddock MK-132, Vishay VSH/VSC and S102, and Texas Components TX2352/TX2575 ...

yup, also check out the heat sinks towards the start of the thread for the desired orientation for the input JFETs and VAS BJTs. Also, I vote for adding 0.2" pitch footprint for the resistors... in fact, what about a combo 0.2" and SMD footprint? I think that would be sweet.

doesn't look like it to me ... He just used that footprint on the silk. Notice the connections between the 2SC3381 and 2SK389.

If the layouts will work for the dual parts, they will work for the heat sinks as they were made to retrofit a pair of single devices into the dual package. I suppose I'm confused here? I'll look at it again tonite, as I gotta run.

yup, looks right. I'm confused why these heat sinks won't work? The 2SC3381 is "BCE ECB" so just flip one of the devices and things should work, just like with the JFETs. I hope I didn't miss anything.

I can only guess what you're doing, hence the recommendation of the second item which seems to have no relation to what you asked for

something like this? eBay Motors: Universal cd-rom drive controller with remote for diyer (item 290293563954 end time Mar-04-09 06:10:19 PST) and perhaps this: http://cgi.ebay.com/Hard-disk-IDE-MP3-Controller-Board-with-LCD-Display-DIY_W0QQitemZ190283472765QQcmdZViewItemQQptZAU_MP3_Players?_trksid=p3286.m20.l1116

guys I may not be around here much today and tomorrow. If possible, I'd love to have the owners of the various sourcing efforts drop in a rough estimate in the next few days so we can get some commitment by the interested parties, as we may be looking at some lead time for some of the semiconductors to keep prices down. Also, there will be another run for the dual heat sinks and that will take time as well. Then there is the board finalization and fabrication. As soon as we can get these items moving, the better, as we could be talking 4-6 weeks easily. The next steps forward as I see it is a rough cost with a few options, then a final commitment to at least the above costs (boards, semiconductors, and tiny heat sinks) then finally a deposit made for the above items. Chris: as far as the boards go, I think a rough cost based on the board size in the original files would be good enough for now. Looks like 50 is a good number. If/when Jacob Potter wants to get involved, you guys can go to town on the boards. Naaman: I'd prefer a single box version if the chassis is large enough. I see no reason to waste performance of a low output impedance power supply on 3 feet of wire and a bunch of connectors. However, I'm usually alone in this opinion. I'll leave this direction up to you for estimation purposes. It's not a super critical decision at the moment, as long as the committing parties are away of the potential cost and labor associated with 2 boxes. Also, I'm of the opinion that the bigger the heat sinks the better, so perhaps we can offer two size of cases, one that caters towards the 4-channel / speaker amp builds and one for the 2-channel builds.. again, your call.

...that and there would be a lot of heat to deal with both in the amp and the power supply.

FWIW, I think it will take some work to make this amp stable with lower gains.

I dunno, we like need wire and you seem to always have a lot of it lying around ... I can always give this one to someone else if you aren't up for it!

I don't want to be accused of only selling boards after all

luvdunhill - 8 - 4 Naamanf - 6 - 4 looser101 - 4 - 2 n_maher - 4 - 0 Digipete - 8 - 4 Pars - 6 - 2 Fing - 4 - 4 Asr - 0 - 4 Stretch - 0 - 4 PFKMan23 - 0 - 4 Icarium - 4 - 4 Dreadhead - 0 - 4 ok, here's what I'm thinking in terms of responsibility: luvdunhill - JFET / MOSFET matching and device procurement pars - boards / BJT matching looser101 - BJT matching Naamanf - Cases / heatsinks / mounting hardware / IO Boards (including jacks) Digipete - passive component procurement and matching n_maher - internal wiring procurement and distribution Icarium - toroid procurement and distribution ?? - power supply (sigma22) kitting <everyone else> - shilling and general "investment protection" I think the rough plan would be that all the boards and power supplies are built and tested. Cases would be speced out so that things are pretty much plug and play with no soldering required. The I/O board would contain PCB mount jacks and probably there would be a front and rear panel board that would be scored and could be broken out. Wires from each PCB would be pre-soldered by the builder/tester and then just connected to the IO boards. The boards would already be connected to the angled aluminum (done by the builder) (edit: maybe this is a bad idea, but this shouldn't be that hard for the end user to do as long as the devices could be protected in transit) and then this angled aluminum would just be screwed into the already tapped heat sinks. I'm not sure to what extent this is feasible, but sounds like a good idea to me. This way the cases would just be shipped once to the organizer and then a second time to the end-user who would just assemble things together. Comments?

yeah, that would be the idea. I need to noodle on a plan a bit more... T The boards with the on-board sinks are just not acceptable to me. I have a feeling that they cannot handle enough heat (especially not in the configuration with doubled up devices) and plus they cannot accommodate the external mounting scheme, as they are turned 90 degrees.

nope, the version with external heat sinks. See post #1.

just a pin limit.

As for other group buys tagged on to this, I'll leave that up to whomever gets assigned that particular piece of the build. Still working out the assignments

Break the mold and use diptrace. Everyone's doing it. Sensible defaults to boot!