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Robinette Box Speaker Amp to Headphone Interface - Page 2

post #16 of 23
Thread Starter 

Robinette Box with Only 4-Pin XLR Output

Robinette_Box_XLR.png

This adapter will work with single-ended and balanced output speaker amplifiers.


post #17 of 23
Thread Starter 

Robinette Box with Only TRS Output

Robinette_Box_TRS.png

This type of adapter is only for amplifiers that have their negative speaker terminals tied together (common ground).

post #18 of 23

Are these boxes available to purchase somewhere or does someone have one for sale?

post #19 of 23
Thread Starter 

No, they're pretty much for DIY'ers.

post #20 of 23
Gotcha, well I appreciate the easy to figure layouts. I should be able to rig one up and see how it goes.
Quote:
Originally Posted by robrob View Post

No, they're pretty much for DIY'ers.

Anyone ever try them with Class D amps?
post #21 of 23

Rob,

I appreciate the work that went onto your Box, and may build one.

I have a couple questions which I will split into two posts.

 

I tried several L-Pad calculators for loudspeakers found on the internet, and all agreed: for 8 ohms and 12 dB attenuation the resistors should be 6 ohms and 2.68 ohms, not 6 and 2. I upped the headphone impedance in your calculator to 1000000 ohms, to simulate an open, (no headphone connected). I changed the amp impedance a lot, up and down. In all cases I got only small changes. No or small changes are good. But the results for R3 being different is puzzling.

 

So I am wondering, how did you arrive at your L-Pad calculations?

I suspect there is more going on here than meets the eye.

 

 

I do realize that speakers and headphones usually have a reactive component and being “in the ballpark” is often fine. However when tuning my speaker crossover, padding my tweeter to match the midrange, I found 0.1 ohm of difference, out of about 1.5 ohms, made the sound “snap” into focus (like focusing a camera lens). It was startling. This could not be calculated easily: it was found by trial and error. (The amp then was a Yamaha SS receiver of good quality, not tubes, but this "focus" persisted with any amp I used.)

 

BigAud


Edited by BigAud - 1/16/17 at 2:51pm
post #22 of 23

Rob,

Have you compared the sound of your L-Pad network to a simple series resistor, for use with a stable solid state amp?

I am currently using a (upgraded) vintage 50 watt per channel SS receiver and its circuit goes from speaker out, through a 470 ohm resistor for each channel, to the headphone jack.

 

I am wondering if I would get any improvement by getting fancy, i.e., building a box, or at least an L-Pad?

 

 

BigAud

 

PS. Love your “People for the Ethical Treatment of Plants” Web page. Reminds me an email I wrote some years ago calling for “Plants Rights”. :-)

post #23 of 23

how could I also implement a volume pot?

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