kevin gilmore Posted November 27, 2011 Report Posted November 27, 2011 This has been needed for a while. For those with problematic DAC's that put out a bit of DC, and balanced headphone amplifiers happy to amplify said DC and produce differential DC on the output... http://gilmore.chem.northwestern.edu/protector.jpg This is the one case where ti kan's protection board does not work, unless you want to use 2 of them.
justin Posted November 27, 2011 Report Posted November 27, 2011 don't you mean Balanced Headphone "Protector"
johnwmclean Posted November 27, 2011 Report Posted November 27, 2011 Nice one! I've been looking around for an external solution, with the thought powering from a wall wart. Good to use with unfamiliar equipment and of course not having to chuck one of these in every amp would be a bonus.
cobra_kai Posted November 27, 2011 Report Posted November 27, 2011 Do you have a schematic view you could post? I like the approach, comparators instead of Ti's summing amp. I see you used the same 1.6 Hz lowpass filter - I found this a little too sensitive on the epsilon12 and was getting a lot of false cutouts so I ended up lowering the cutoff to about .7 Hz and the gain on the summing amplifier from 10 to 5, which should make it cutout when it sees about 140 mV of DC offset. I'm not sure which did the trick as I did them at the same time.
kevin gilmore Posted November 27, 2011 Author Report Posted November 27, 2011 (edited) don't you mean Balanced Headphone "Protector" oops, so i can't spell. I'll fix it later. Its not like its already etched into a front panel. We can adjust the comparator window as necessary, as well as the filter. Ceramic caps up to 4.7uf in that lead spacing i believe. Putting the thing in a small box with a female and male 4 pin xlr's on tails plus a cheap wall brick should take care of those pesky massively overpowered things from my friend in skokie that seems unable to comprehend DC servo's. Edited November 27, 2011 by kevin gilmore
justin Posted November 28, 2011 Report Posted November 28, 2011 so you could have two products....RSA The Protector and The RSA Protector
Pars Posted November 28, 2011 Report Posted November 28, 2011 Might be more symmetrical as RSA The Protector and The Protector from the RSA... A schematic would be nice also
kevin gilmore Posted November 28, 2011 Author Report Posted November 28, 2011 (edited) I can't find the schematic. Seriously. I must have left it at home. Will draw it up again and post soon. here is a fresh version http://gilmore.chem....u/protector.pdf For DC, it triggers on anything over +.5VDC and -.5 VDC Detect time is 75 milliseconds. For AC, at 20hz, it triggers on 5 VRMS. Edited November 28, 2011 by kevin gilmore 1
swt61 Posted November 29, 2011 Report Posted November 29, 2011 I have a name in mind for this one. Going with the protection theme, how about the 'Gilmore Looking Over Valuable Equipment' or G.L.O.V.E. ?
justin Posted November 29, 2011 Report Posted November 29, 2011 is there some way to make this uncompatible with Ultrasones? 2
swt61 Posted November 29, 2011 Report Posted November 29, 2011 is there some way to make this uncompatible with Ultrasones? No, but he could make it incompatible. 1
UFN Posted December 23, 2014 Report Posted December 23, 2014 (edited) Old thread, sorry: Kevin, do you have a schematic for the current version of this board? //UFN EDIT: Oh, and some BoM-questions: 1) I assume the diodes are just standard 1N4148/1N914? 2) Is the 47uF cap supposed to be ceramic or similar since it hasn't got the same footprint as the electrolytics? Edited December 23, 2014 by UFN
kevin gilmore Posted December 23, 2014 Author Report Posted December 23, 2014 not sure where the schematic is, will look later 1n914 or similar 47uf non-polarized ceramic
GrindingThud Posted December 24, 2014 Report Posted December 24, 2014 Should I have one of these on the Balanced Dynahi, or is it ok to run without one?
kevin gilmore Posted December 24, 2014 Author Report Posted December 24, 2014 high powered DC amplifier. More than capable of frying headphones if you put dc in the input. Protection circuits always a good idea
GrindingThud Posted December 24, 2014 Report Posted December 24, 2014 Should be plenty of room in the case, I'll need to get one of these built up. . Might try and squeeze one in my dynalo build too. Thanks.
jose Posted December 24, 2014 Report Posted December 24, 2014 (edited) Dr. Gilmore. Can I use this on my Balanced Dynahi (last versión)? I suppose that I can used this on the output or it's not necessary? Edited December 24, 2014 by jose
Pars Posted December 24, 2014 Report Posted December 24, 2014 See posts 14 and 15. I presume this is used like Amb's in that you put it between the amp output and the phones?
jose Posted December 24, 2014 Report Posted December 24, 2014 (edited) See posts 14 and 15. I presume this is used like Amb's in that you put it between the amp output and the phones? OK, you are right, but if you have a servo on the output ( I don't know if on other Dynahi versión has servo) when you add this board, you are duplicating the protection. Not? Really, Is it necessary two protecction on the output? Edited December 24, 2014 by jose
kevin gilmore Posted December 24, 2014 Author Report Posted December 24, 2014 servo has a limited range and is slow
jose Posted December 24, 2014 Report Posted December 24, 2014 servo has a limited range and is slow Thanks Dr. Gilmore. For broken the servo protection, really you need a offset very high or a very deep signal. Not?
GrindingThud Posted December 25, 2014 Report Posted December 25, 2014 I've got a bunch of BC546B left over from the Dynahi PSU, would that be suitable in this circuit?
kevin gilmore Posted December 25, 2014 Author Report Posted December 25, 2014 no bjt's on that circuit board anywhere
GrindingThud Posted December 25, 2014 Report Posted December 25, 2014 (edited) What that N channel on the board that drives the relay? http://gilmore.chem.northwestern.edu/protector.jpghttp://gilmore.chem.northwestern.edu/protector.pdfhttp://gilmore.chem.northwestern.edu/dynapower2.jpg Edited December 25, 2014 by GrindingThud
kevin gilmore Posted December 25, 2014 Author Report Posted December 25, 2014 (edited) new board uses 1 x 2n7000 http://gilmore.chem.northwestern.edu/protector3.pdf Edited December 25, 2014 by kevin gilmore 1
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