Pars Posted March 10, 2009 Report Share Posted March 10, 2009 Not to be Debbie Downer here, but are you sure that you aren't kinda putting the cart before the horse here in terms of sequencing of what to buy/order when? It would seem to me that before you started lining up all these accessories (for lack of a better term), that until someone has built some DynaFET boards and determined current draws and thermals on the PSUs, etc. that you cannot guarantee that even the larger heatsinks are enough to support this? Or how many sigmas it will take for a given configuration? Or that the sigma will even work for this? Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 10, 2009 Report Share Posted March 10, 2009 I agree. 2 sigma22's can more than handle the power needed for this amp, the determining factor will be heatsinking. 1A per sigma(at 30V) is the limit with stock 1.5" aavids, and I don't think going with 2" aavids(the largest alternative I could find that will fit the pcb without alot of work) will improve much. A better alternative would be Conrad MF20-1F or angle aluminum to your choice of larger HS. Probably not that big of a deal with just headphone duty but like you say, no-one knows for sure what the power requirements will be for a fet board. Quote Link to comment Share on other sites More sharing options...
Icarium Posted March 10, 2009 Report Share Posted March 10, 2009 Yeah I've asked those questions to several parties including the board designer. There is no guarantee that even larger heatsinks will be enough essentially depending on how you bias... but heatsinks + heatsinking accessories are only ~10 bucks or less a kit so for me it's a trivial cost just to be safe. Yeah we explored whether it would be possible to do this with 2 sigmas as opposed to 4. Between me and the people I talked to 2 seemed to be enough. If it turns out to be more then I will order more. I had not heard that sigma22s might be not suitable period. Yeah it might make sense to order these things after the boards are prototyped... but one of my personal goals is to parallelize as many operations as possible and try to have as many parts on hand as possible before the beginning of summer to try and achieve an end of summer completion date if its at all possible. That being said jacob I think is going to release a release candidate board today I believe he said.. he was combing the thread to sweep for any recommendations he might have missed. He caught your latest one at the very least luvdunhill. He gave me some dimensions as well but they are on my home instance of AIM.. but it was slightly under 5 inches both dimensions. That being said as soon as the release candidate is deemed kosher by the group I intend to pin down a board maker and having prototype boards made. Who would be willing to build out a prototype board and test it? I believe luvdunhill has parts he can supply. I think he was hoping we could get 3 takers on this. Quote Link to comment Share on other sites More sharing options...
n_maher Posted March 10, 2009 Report Share Posted March 10, 2009 It would be the round hole cutter tech's opinion that at least one prototype might be a wise idea... Quote Link to comment Share on other sites More sharing options...
Icarium Posted March 10, 2009 Report Share Posted March 10, 2009 Yeah we want to do 3 I think... though I need to confirm that with luvdunhill again. Quote Link to comment Share on other sites More sharing options...
n_maher Posted March 10, 2009 Report Share Posted March 10, 2009 Prototype's aren't going to help much if you guys have already ordered thousands of dollars worth of parts. The lesson here is that these things take time, cost money, and shouldn't be rushed. At least that's my opinion, I can't keep up with this thread given my un-involvement but I'd just hate to see a bunch of you invest with unnecessary risk. Quote Link to comment Share on other sites More sharing options...
Icarium Posted March 10, 2009 Report Share Posted March 10, 2009 Nod.. that's good advice. I'm sorry if I rushed anyone or misrepresented risk. So.. I guess the main worry is that the design will not work and parts will become unnecessary/useless? How serious of a risk is that? Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 10, 2009 Report Share Posted March 10, 2009 Maybe we could agree to at least see if we could get at least 2 boards into someone's hands to do a test build and see if this thing is going to make music before any more $ is spent. I thought I read KG say that he had build a prototype somewhere. Quote Link to comment Share on other sites More sharing options...
naamanf Posted March 10, 2009 Report Share Posted March 10, 2009 For heat sinking the S22 I do think using something like the Conrad heat sink might be a better option due to the expected current demand of the amp. The trick is squeezing everything into one case. The 4U Hifi-2000 case might do the trick but I think it would be a tight squeeze. I don't think the S22s will be unusable because it's a pretty versatile power supply than can be used with other amps. All the parts for the amp board on the other hand... Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted March 10, 2009 Author Report Share Posted March 10, 2009 Prototype's aren't going to help much if you guys have already ordered thousands of dollars worth of parts. The lesson here is that these things take time, cost money, and shouldn't be rushed. At least that's my opinion, I can't keep up with this thread given my un-involvement but I'd just hate to see a bunch of you invest with unnecessary risk. Chris main point was the "accessories", and his main issue was the sigma22. I don't see any reason that this won't work, and Kevin and Ti have stated the same thing. Nate's point is more general. The parts and topology in this amp are very standard. I'm not sure I understand the risk. It's not like your going to find another JFET to use or something else more suitable for VAS stage. And the diamond buffer is pretty straightforward, wouldn't you agree? I would agree if we were ordering resistors, but it's not as if the semiconductors won't work in this topology. If you have a particular concern about parts and their intended use in the circuit, please let us know! Quote Link to comment Share on other sites More sharing options...
PFKMan23 Posted March 10, 2009 Report Share Posted March 10, 2009 Nod.. that's good advice. I'm sorry if I rushed anyone or misrepresented risk. So.. I guess the main worry is that the design will not work and parts will become unnecessary/useless? How serious of a risk is that? I think it's a very serious risk. That could be problems with the design that we haven't anticipated on a theoretical basis. Resulting changes from that may very well cause a modification that renders many parts useless, largely owing to the fact that we've been doing things in terms of a group buy. I think before we proceed any further we really should get a prototype going. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted March 10, 2009 Author Report Share Posted March 10, 2009 All the parts for the amp board on the other hand... CTC Blowtorches for everyone! Quote Link to comment Share on other sites More sharing options...
naamanf Posted March 10, 2009 Report Share Posted March 10, 2009 CTC Blowtorches for everyone! I do need a good pre.... Group buy!!!! Quote Link to comment Share on other sites More sharing options...
Icarium Posted March 10, 2009 Report Share Posted March 10, 2009 I think it's a very serious risk. That could be problems with the design that we haven't anticipated on a theoretical basis. Resulting changes from that may very well cause a modification that renders many parts useless, largely owing to the fact that we've been doing things in terms of a group buy. I think before we proceed any further we really should get a prototype going. Yeah that's reasonable. Okay prototypes first then anything else next. Looks like Luvdunhill will have parts at least for one board so we can prototype before the big shipment arrives. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted March 10, 2009 Author Report Share Posted March 10, 2009 Yeah that's reasonable. Okay prototypes first then anything else next I will prototype one channel and take it with my other projects up to Pete Millet to run through some tests. No promise on time frame though, as he's out of the country a lot and I have some other things that take priority. My one requirement is that we nail down the board dimensions and location of the output FETs and agree not to change those specs, if there is a second run. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted March 10, 2009 Author Report Share Posted March 10, 2009 I do need a good pre.... Group buy!!!! Colorado might work better for my version... you guys don't have to turn on the AC in March Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 10, 2009 Report Share Posted March 10, 2009 I don't see how KG could build a working proto and comment on the sound the way he did if there was a problem with the parts selection. However I have purchased pcb's that later had to be modded because of a very minor oversight by the designer. I am also willing to pitch in if needed just to have one or a pair of the final pcb tested just to make sure. Have you guys agreed on the final position of the ouput devices yet?(I am still trying to catch up on reading) Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted March 10, 2009 Author Report Share Posted March 10, 2009 Have you guys agreed on the final position of the ouput devices yet?(I am still trying to catch up on reading) yes, they will be compatible with the Dynahi boards. Thanks for the offer Quote Link to comment Share on other sites More sharing options...
Torpedo Posted March 10, 2009 Report Share Posted March 10, 2009 Ah good call.. if you want more diodes then adjust the numbers accordingly and then email me back the spreadsheet and then I'll send it to him to have him confirm and then we can do payment. His paypal address btw is: [email protected] Also.. were you guys doing separate payments or one big payment? If separate then it'd probably be good to email him a list of names so he can confirm that he's received all the payments. Oh yeah one last thing.. for the more than 2 kit buys (j4cobs and spains) wait til you hear confirmation from me to actually pay. He just let me know to wait until later today or tomorrow because he is receiving the larger heatsinks today so he can package it up and make sure that the shipping costs quoted are appropriate. You 2 kitters are fine though! I will handle payment for all 8 S22 kits in a single order, I'm arranging things with the other Spanish Gang mates. I will ask PICaudio about the power modules, I don't know if he wants to use anything special. Also comment him about the diodes. When all this is sorted out I'll PM you Icarium, so we can arrange payment to Jeff. Quote Link to comment Share on other sites More sharing options...
Icarium Posted March 10, 2009 Report Share Posted March 10, 2009 K thanks Torpedo! Quote Link to comment Share on other sites More sharing options...
Torpedo Posted March 10, 2009 Report Share Posted March 10, 2009 Are you referring to the sigma BOM spreadsheet? You will need either plain IEC power entry (with fusing, some sort of power switch whether it is part of the IEC or not is your choice) or a filtered IEC inlet. Also, it might be good if Team Spain were to include some spare current diodes of both flavors, as these are getting hard to find reliably, at least here in the US. Hi Pars, Would you be so kind to specify which diodes should we get for spares? I don't see them in the speadsheet, so my guess is that the Power module just comes with the units needed. Quote Link to comment Share on other sites More sharing options...
Pars Posted March 10, 2009 Report Share Posted March 10, 2009 781-J508-E3 781-J511-E3 Better would be 1n5307 and 1n5314s if you can find them (these are rated up to 100V). Quote Link to comment Share on other sites More sharing options...
Torpedo Posted March 10, 2009 Report Share Posted March 10, 2009 Thanks Pars. I've checked those in the spreadsheet and seem to be CR1, CR2, CR3 and CR4 so two of each per board are needed. How many of them would you suggest to get for spares, a whole set for each board? That's some dough. Quote Link to comment Share on other sites More sharing options...
Pars Posted March 10, 2009 Report Share Posted March 10, 2009 There's only 2 part numbers (a 2.4mA and a 4.7mA), so one of each should be sufficient, or maybe a couple of each to cover all of you. You could first check and see if these are readily available from whoever you guys order parts from (Farnell? RS?). I f you can easily get them, then don't bother. Quote Link to comment Share on other sites More sharing options...
digger945 Posted March 10, 2009 Report Share Posted March 10, 2009 yes, they will be compatible with the Dynahi boards. Thanks for the offer Doesn't matter to me. If I were doin it again I would cut the pcb off next to the output pads(so the pcb can be moved closer to the HS) and mount the output's directly to the heatsink, as I plan to do for this build. The angle thing just seems kinda cheesy to me, although it doesn't look too bad. Quote Link to comment Share on other sites More sharing options...
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