speaker binding posts necessary to wire?

[Michael415]

I am finally building my amp and have gotten to the part of wiring the speaker posts and was thinking since I will never use this amp with speakers do I need to wire them up? Will it have any impact (besides the obvious no ability to power speakers).

[2wo]

Nope...John

[Michael415]

Thanks for the reply!
Getting excited to finally get this done!!

[Henry2011]

You are going to love your new amp! 

Concerning the speaker terminals, although open ended speaker terminals are no different electronically than unwired speaker terminals, I recommend wiring them up.  Different headphones require different loading.  Having the speaker terminals wired makes it very easy to optimize the loading to suit the headphones. 

For example, my Yamaha RH10MS headphones (Z=40ohm) sound their best (really, really good) with 10ohm to 25ohm resistors attached to the speaker terminals (with the resistors the bass is bottomless and very musical; without the resistors the bass lacks focus and is too boomy; other aspects of the musical spectrum are also enhanced by optimizing the loading). 

On the other hand, my Sennheiser HD600 headphones (Z=300ohm) sound their best (just this side of fantastic) somewhere between having open ended terminals and connecting 100ohm resistors across the terminals (I'm still searching for perfection).  With 10 ohm resistors installed across the terminals the HD600s sound like a bad set of Walkman headphones from the 80s.

Although the assembly manual still has instructions for installing 10 ohm resistors across the speaker terminals when speakers are not used, if you search the forum you will find several references to NOT doing this (theory vs practice as to what sounds best).  I think the best thing to do once your amp is up and running is to connect resistors of varying size (no less than 10 ohms) to the speaker terminals to optimize loading the amp for your particular headphones.  I use banana jacks and a variety of wire wound resistors from Radio Shack.  Be careful not to short the left channel positive output to the right channel ground.  Keep in mind that whatever you connect across the speaker terminals is in parallel with the two 120 ohm resistors and your headphones.

Happy listening!
Henry Moore

[Michael415]

Thanks Henry for the very detailed response!

[Doc B.]

One can also leave out the 120 ohm resistors connected to the headphone jack - just use wire in their place. Some users find that low impedance headphones sound better this way.

[Paul Joppa]

...
Concerning the speaker terminals, although open ended speaker terminals are no different electronically than unwired speaker terminals, I recommend wiring them up.  Different headphones require different loading.  Having the speaker terminals wired makes it very easy to optimize the loading to suit the headphones. 

For example, my Yamaha RH10MS headphones (Z=40ohm) sound their best (really, really good) with 10ohm to 25ohm resistors attached to the speaker terminals ...

This is the best, most practical suggestion I've heard for sensitive low-impedance phones - thanks for posting!

This approach will reduce the amp's output, so for those less sensitive phones that have low impedance and need more damping, follow Doc B's suggestion to bypass the 120 ohm resistor with some wire, or a smaller resistor.

Headphones vary widely in sensitivity and impedance, so optimizing for a particular set is always going to be an adventure.