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.

don't you mean Balanced Headphone "Protector"

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.

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.

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, 201114 yr by kevin gilmore

so you could have two products....RSA The Protector and The RSA Protector

Might be more symmetrical as RSA The Protector and The Protector from the RSA...

A schematic would be nice also

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, 201114 yr by kevin gilmore

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. ?

is there some way to make this uncompatible with Ultrasones?

is there some way to make this uncompatible with Ultrasones?

No, but he could make it incompatible.

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, 201411 yr by UFN

not sure where the schematic is, will look later

 

1n914 or similar

 

47uf non-polarized ceramic

Should I have one of these on the Balanced Dynahi, or is it ok to run without one?

high powered DC amplifier. More than capable of frying headphones if you

put dc in the input. Protection circuits always a good idea

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.

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, 201411 yr by jose

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?

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, 201411 yr by jose

servo has a limited range and is slow

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?

I've got a bunch of BC546B left over from the Dynahi PSU, would that be suitable in this circuit?

no bjt's on that circuit board anywhere

What that N channel on the board that drives the relay?

http://gilmore.chem.northwestern.edu/protector.jpg

http://gilmore.chem.northwestern.edu/protector.pdf

http://gilmore.chem.northwestern.edu/dynapower2.jpg

Edited December 25, 201411 yr by GrindingThud

new board uses 1 x 2n7000

 

http://gilmore.chem.northwestern.edu/protector3.pdf

Edited December 25, 201411 yr by kevin gilmore