Can I hook up a headphone amp to my integrated?

Hi Al…yes that is your number 4 approach.  I will either do that and get a headphone amp that has two inputs; or get one with the pre out and hook it into my amps pre in.  I talked to my LM 518 amp dealer and he didn't see any problem with either approach (he probably liked the pre amp approach a little better and didn't think it would degrade the internal pre amp any).  I mentioned above that I emailed Woo Audio.  They suggested the WA6-SE or WA22 over the WA2, didn't really give a reason.  Suspect it was related to power.  They also said they could add a pre out to either one if I wanted.  So right now I'm leaning toward the WA6-SE with or without the pre.  It has two inputs so I can just use the splitters you suggested above, or add the pre out.  Anyway, thought you might be interested in their response.  Before you responded I was pretty much in the dark on this, and now feel I have a pretty good understanding thanks to your feedback…thank you!

But let me ask….why is it that you can't just hook up a headphone amplifier to the line in inputs on the integrated, like you do a phono amp?  Just curious :)

But let me ask….why is it that you can't just hook up a headphone amplifier to the line in inputs on the integrated, like you do a phono amp?  Just curious :)

Inputs receive signals; outputs provide signals.  If you connect two inputs together neither input will receive anything.  In the case of the phono preamp, you are connecting its output to an input of the integrated amp.

I'll take a look at the WA6-SE later today, and provide any comments I may have.

Regards,
-- Al

Hi Mike,

The WA6-SE looks like a fine choice in all respects, as far as I can see, aside from the possible slight inconvenience of having the input select switch on the rear rather than on the front. And based on the specs power would not be a concern at all using it with the LCD-3.

Given the moderate 110 ohm impedance of the LCD-3, by the way, it would probably be worthwhile to try connecting the headphone to both the high impedance and low impedance outputs of the WA6-SE, if you purchase it, and use whichever output sounds best.

And as I said with respect to the WA2, using approach no. 4 (splitters on the outputs of both source components, connected to both the integrated amp and the headphone amp) should work fine with the WA6-SE.

Regards,
-- Al

Thanks again.  Woo Audio replied that the WA2 is an OTL and is not good for the LCD-3 but for 200-600 ohm impedance, so that's that.  I'm leaning towards the WA6-SE and will probably have them add a pre-out ($125). Then I can either use that, or just do your approach 4 if I don't like what the preamp does?  

I haven't seen many other headphone amps that offer that flexibility? If you or others know of some I'd love to hear what they are.

Thank you Al…..Mike

Hi Mike,

I’m wondering something about the addition of a preamp output to the WA6-SE, that you may want to ask Woo about. If instead of using my approach no. 4 you were to use that output of the WA6-SE, connecting it to the input of the power amp section of your LM integrated amp, you would of course be using the WA6-SE’s volume control to control the volume when listening via speakers. So in order to silence the headphones when listening via speakers, and possibly also to prevent overdriving the headphones when listening via speakers, I presume you would have to unplug the headphones from the WA6-SE. Which creates two possible causes for concern:

1)1/4 inch headphone jacks are not exactly the most robust connectors in my experience, and I would have some concern that eventually frequent plugging and unplugging would loosen the grip of their contacts.

2)As you may be aware, tube amps having output transformers, or at least such amps that are used to power speakers, should not be operated without a speaker or equivalent load connected, particularly when a signal is going through the amp. Otherwise damage to both the output transformer and the output tubes can occur, as a result of what is called "inductive kickback." I’m wondering if the same thing could occur with the WA6-SE when it is operated with a signal going through it but without the headphones being plugged in, since the WA6-SE utilizes an output transformer to drive the headphone jacks. Perhaps it isn’t a concern in this case because of the much lower power capability of the WA6-SE compared to most tube amps that are intended to drive speakers, or because of the relatively high impedances the WA6-SE is designed to drive, but I’m uncertain. And perhaps it isn’t entirely coincidental that nearly all of the headphone amps described at the Woo site as providing pre-outs in their standard configurations are the OTL models, which of course do not have output transformers.

With approach no. 4, of course, those issues would be avoided since the headphone amp could be turned off whenever you aren’t listening via the headphones.

As I say, you may want to present those questions to Woo, before deciding to spend the extra money to have the pre-outs added.

Regards,
-- Al