kevin gilmore Posted April 2, 2011 Report Posted April 2, 2011 (edited) Lil knight among others have asked for an updated dynahi board. Here it is. http://gilmore.chem.northwestern.edu/dynahi8.zip changes, remove 2sk389,2sj109, add lsk389,lsj109 2sk170,2sj74 you can use opa445 instead of op27 and then you don't need the 7815 and 7915. 2sa1349,2sc3381 can be replaced with the single versions. I need to check this a few more times. unbalanced input, balanced output version coming soon. Edited April 2, 2011 by kevin gilmore
El_Doug Posted April 2, 2011 Report Posted April 2, 2011 aww, and I just last week finished procuring all the dual fets for my set of 4 rev. 1 boards :/ you're a true gentleman Kevin, updating this great amp for modern sand, for the sake of the community <3
n3rdling Posted April 2, 2011 Report Posted April 2, 2011 Perfect timing! I was going to build the old version. Anybody gonna do a run of boards? I'm in if so.
kevin gilmore Posted April 2, 2011 Author Report Posted April 2, 2011 (edited) working on the balanced board now. Its a low impedance input with nelson pass's supersymmetry. True balanced, and balanced or unbalanced input. here is the balanced version as a work in progress. I wonder what other case this will fit into http://gilmore.chem.northwestern.edu/dynahibal.jpg Ater that, i'll do up the dynafet boards. I'm once again on a roll, and maybe the wonderful crema out of my new coffee machine might have something to do with it. Slightly jittery though Need some more of blubliss's hand roasted bean... Edited April 2, 2011 by kevin gilmore
monsieurguzel Posted April 2, 2011 Report Posted April 2, 2011 Thanks so much Kevin! I'd also be super interested in buying a board once they're ready for a run.
purk Posted April 2, 2011 Report Posted April 2, 2011 Thanks KG. I'm in for a balanced version of the board as well.
Deadneddz Posted April 2, 2011 Report Posted April 2, 2011 Perfect timing! I was going to build the old version. Anybody gonna do a run of boards? I'm in if so. Perfect timing indeed... Count me in on this KG.
Lil Knight Posted April 3, 2011 Report Posted April 3, 2011 (edited) Thanks for the great work, Dr Gilmore! AFAIK, Ti has suggested some changes. Not sure if this applies with the current one. Parallel a 680R resistor and 10k Trimpots to adjust bias and offset, you should pre-set the trimpots such that you measure 500R across them after installing it on the board, along with the 620R or 680R resistor. This would then be the initial power-up setting. (setup procedure using them here) A 475 ohm resistor in series with the wiper to the amp board to buffer the board a bit from being shorted completely to ground (volume pot minimum condition) or connected directly to the output stage of the source (volume pot maximum condition).Optional (well it's all optional I guess, but this one especially?): Reducing the gain to 7 by changing the global feedback resistors to 1.21KΩ and 200Ω (from 2KΩ and 100Ω) and increasing the feedback compensation cap value from the suggested 33pF. Substitute the OP27 for a OPA134PA as it offers much lower DC offset. Kevin's schematic showed no input resistor to ground, but the board is laid out for a 10K resistor. If you have a <100K volume pot wired up at the input, then 10K is too low a value. Anywhere from 10K to 1M is more "the norm" for a JFET input amp. If nobody takes the job, I'm willing to do a small run of boards like last time. Edited April 3, 2011 by Lil Knight
kevin gilmore Posted April 3, 2011 Author Report Posted April 3, 2011 (edited) much closer now. Since its now supersymmetry, with 10k input impedance, some things have had to change. Will send to ti for comments. You can certainly reduce the gain now by changing the 200k feedback resistors and increasing the compensation caps. Obviously a 10k resistor in series with both inputs at all times. Same name, same place, for the board picture balanced schematic http://gilmore.chem.northwestern.edu/dynahiver2a.pdf Edited April 3, 2011 by kevin gilmore
ujamerstand Posted April 3, 2011 Report Posted April 3, 2011 (edited) Hurray for summer time! I'd love to get my sweaty paws on some pcbs. Looking forward to see the dynafet! Edited April 3, 2011 by ujamerstand
kevin gilmore Posted April 3, 2011 Author Report Posted April 3, 2011 Well the patent for super symmetry has run out, so i don't have to even ask nelson for permission... (not that i think that was ever a valid patent to begin with) Current board size 9.12 x 5.22 target board size 9 x 5 People really want to use HE6's as room speakers and dump 60 watts RMS into them, this will do the job for sure. The only right way i know of to do unbalanced to balanced, and balanced to balanced at the same time. opamps, bah humbug. If you go with the opa445 as the servo, you don't need the +/-15 volt regulators. Anyone want to suggest additional power supply capacitor sizes. I have plenty of room left.
digger945 Posted April 3, 2011 Report Posted April 3, 2011 Anyone want to suggest additional power supply capacitor sizes. I have plenty of room left. How about onboard shunt regs, one for each rail?
jcx Posted April 3, 2011 Report Posted April 3, 2011 looking in PAIR Nelson has paid up his maintance fees on 5,376899, 17 years from 12/27/94 issue date still gives him the rest of this year but from his various statements it seems unlikely that a "public domain" headphone amp project would be a problem for him
Lil Knight Posted April 3, 2011 Report Posted April 3, 2011 People really want to use HE6's as room speakers and dump 60 watts RMS into them, this will do the job for sure. Aww, so would this make the HE6 sound like a speaker from a distant of 12 feet or more? Need an overkill T2-like PSU too...
El_Doug Posted April 3, 2011 Report Posted April 3, 2011 Need an overkill T2-like PSU too... sigma22 not good enough for you?
kevin gilmore Posted April 3, 2011 Author Report Posted April 3, 2011 (edited) sigma22 not good enough for you? They would work just fine. But i want something that is compatible with my stack of machined brackets. getting close now. http://gilmore.chem.northwestern.edu/dynahibal1.zip trying to figure out which one of the 14 or so dynafets is the one i want to start with OH.. and this Edited April 3, 2011 by kevin gilmore
Lil Knight Posted April 3, 2011 Report Posted April 3, 2011 They would work just fine. But i want something that is compatible with my stack of machined brackets. Would the PSU has side heatsinks to match the amp or just onboard ones?
livewire Posted April 3, 2011 Report Posted April 3, 2011 (edited) OH.. and this Wow! I have that album. Your post made me dust it off and listen to the whole thing. The chilhood memories came floodin in... Oh and btw, it sounded great on my new amp! Now back to your regularly scheduled dynahi discussion. Great stuff! Keep it coming. Edited April 3, 2011 by livewire
kevin gilmore Posted April 3, 2011 Author Report Posted April 3, 2011 dynahifet in progress http://gilmore.chem.northwestern.edu/dynahifetbal.jpg because of all the power supply stuff all over the place, this might end up as a 4 layer board.
kevin gilmore Posted April 4, 2011 Author Report Posted April 4, 2011 first rev of both done. someone needs to do some serious checking on these. Both boards identical size with identical mounting holes and compatible with the T2 power supply angle brackets. http://gilmore.chem.northwestern.edu/dynahibal1.zip http://gilmore.chem.northwestern.edu/dynahifetrbal.zip
Lil Knight Posted April 4, 2011 Report Posted April 4, 2011 How much power does the dynafet consume? I haven't seen many impressions about the dynafet so far.
kevin gilmore Posted April 4, 2011 Author Report Posted April 4, 2011 dynafet a bit more because of the extra parts, but the bias is adjustable. Say 20 watts per channel. Dynahi is about 18 watts per channel.
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