Can I hook up a headphone amp to my integrated?

I took a look at the descriptions and specs on the GS-X, WA7 (although only the Fireflies version seems to be listed currently, that version including a DAC), and the LCD-3.

The GS-X seems quite promising, although I have no knowledge of its sonic quality. And, yes, it provides all of the functionality you would require, so you wouldn’t need a switchbox or splitters or y-adapters. You would connect the Manley to its RCA input, and you could connect the CD player to its XLR input via a simple RCA-to-XLR adapter. You could then connect its preamp output to the pre-in of the LM (which would utilize the LM just as a power amp), or alternatively you could connect its loop output to a line-in on the LM (choosing between those alternatives based on whichever sounds best). With the first alternative, though, you would have to have the headphone amp powered up in order to listen via speakers; I’m not certain but I suspect that wouldn’t be necessary with the second alternative (i.e., using the loop output).

The WA7 Fireflies doesn’t provide that kind of functionality, as you realize. And I’d also have some concern that its output power rating is spec’d at 1 watt into 32 ohms, which **might** mean that it can only deliver significantly less than 1 watt into the 110 ohm impedance of the LCD-3, for which amplifier power of 1 to 4 watts is recommended as being optimal.

Good luck. Regards,
-- Al

It also has 1 preamp line out....

I only have the three line in and one pre-in?

It appears that the second statement is correct, but not the first, and the only outputs provided by the amp are its speaker-level outputs.

Therefore the possible approaches are:

1)Connect the amp outputs to some sort of a speaker-level switchbox that would route them to either the speakers or to some sort of a speaker-level to line-level converter that would in turn connect to the headphone amp. Not sure how practical this approach would be, or how good the results would be.

2)Same as approach 1, except without the speaker-level to line-level converter but with a headphone amp that can accept speaker-level inputs. Not sure if such a thing exists, and at best this approach would severely limit your choice of headphone amps.

3)Choose a headphone amp that provides only a single line-level input. Obtain a line-level switchbox that would select between your phono stage and your CD player, and connect the output of the switchbox to a line-in of the integrated amp and also to the input of the headphone amp. Given the fairly high input impedance of the integrated amp (measured by Stereophile as 59K or more for the LM-518IA, at various frequencies), a headphone amp having an input impedance of 47K or more would be preferable in this case, especially if your phono stage or CD player has an output impedance of more than a few hundred ohms.

Line-level switchboxes that would be suitable include the DB Systems DBP-2JAU/5 ($110), with which you would need a pair of y-adapters or splitters to connect its output to the two destinations, and the Decware ZSB ($359), which provides two sets of outputs.

This approach should work reasonably well, as long as the two source components do not have unusually high output impedances and as long as cable lengths are not unusually long.

4)Choose a headphone amp that can accept two sets of inputs, and use splitters or y-adapters to connect the phono stage and the CD player to both the headphone amp and the integrated amp. A headphone amp having an input impedance of 47K or more would be preferable in this case, especially if your phono stage or CD player has an output impedance of more than a few hundred ohms.

This approach should also work reasonably well, as long as the two source components do not have unusually high output impedances and as long as cable lengths are not unusually long.

Good luck. Regards,
-- Al

Good! The Manley has very low output impedance, and while the output impedance of the 6005 doesn’t appear to be specified I would expect it to also be fairly low. The 6005 appears to have a built-in headphone amp, BTW, and provides a headphone jack, but of course that wouldn’t make it possible to listen to records via headphones, and its sonic quality is unknown.

Yes, approaches 3 and 4 certainly make the most sense among those I listed. The choice of headphone amp would probably be driven primarily by the type of headphones you choose, as well as by how much you want to spend. I have no particular suggestions to offer, assuming you are interested in conventional dynamic headphones, as in my case I use an older pair of Stax electrostatic headphones. Those require a special purpose amplifier suitable for driving electrostatics, which is also made by Stax in my case. And Stax or other electrostatic headphones tend to be quite expensive these days.

Yes, using the LM just as a power amp (connecting to its "pre-in"), with a separate preamp driving both the LM and the headphone amp (and preferably providing a "tape output" that would be used to drive the headphone amp) is certainly a viable approach. But of course it would be more expensive than approaches 3 and 4 (unless you can find a headphone amp that would provide such a preamp function itself), and it would result in sonics that may or may not be either better or worse than those approaches.

Good luck. Regards,
-- Al

Both the WA2 and the WA22 have very high 100K input impedances, so in that respect they would be good candidates for approaches 3 and 4 that I had defined. As you’ve most likely seen, the WA2 also provides switching among multiple unbalanced sources, so it would be suitable for approach 4 (no switchbox). I’m not sure that the WA22 would be suitable for approach 4, because it’s not clear if the selection it provides between its unbalanced input and its balanced input keeps those inputs fully independent (i.e., conceivably it may connect the signal on the RCA input directly to one of the two signal pins on the XLR connector, and just ground the other signal pin on the XLR connector when the RCA input is selected. Meaning that the unit may have been designed with the expectation that only one of the inputs would be connected).

Also, you would not be taking full advantage of the WA22’s balanced configuration, since your sources just provide unbalanced outputs. Unless, that is, you used a suitably chosen Jensen transformer (approximately $300) to convert the output of one of your sources (presumably phono) to a true balanced signal pair.

The one slight reservation I have about the WA2 is that the specs in its manual indicate that its power capability into 120 ohms (that being close to the 110 ohm impedance of the LCD-3) is 550 mw (0.55 watts), which falls short of the 1 to 4 watt rating that is stated as being "optimal" for the LCD-3. Although that isn’t a big shortfall, as 550 mw amounts to only about 2.6 db less than 1 watt. But it could conceivably be an issue on material having particularly wide dynamic range, such as some well engineered classical symphonic recordings. The WA22 is fine in that respect, btw (1600 mw into 120 ohms).

Hope that helps. Regards,
-- Al

Someone at work told me I could get a splitter and put on my phono stage output and run one set of interconnects to the integrated amp, and another to a headphone amp. Sounds like that might work, but not sure how much that might degrade the overall sound?

Yes, Mike, that was my approach no. 4, with splitters on the outputs of both the CD player and the phono stage. Given that both of those components have low output impedances, and given that both your integrated amp and the WA2 have very high input impedances, and given that the lengths of the cables that would be involved are not unusually long, I suspect it won’t degrade the sound at all.

My belief has long been that the bad rap splitters and y-adapters sometimes seem to get is not due to the splitters or y-adapters themselves, but in most cases to impedance issues and cable driving issues. In other words, to the inability of the component whose output is being split to drive both sets of cables and both destination components with good results. Neither of those factors will be a problem in this case.

Also, I would recommend this particular splitter.

Good luck. Regards,
-- Al

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

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