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so I wanna try to use amp sims on logic pro with a real cab. I have a laptop with an apogee one audio interface. My idea was to plug the guitar to apogee, then apogee to logic and finally, connect the apogee's headphone output to an amp's Effects Loop return (in order to use the power amp in the amp) and then the amp is connected to a cab. Apogee's headphone output is 1/8", will a regular 1/8" male to 1/4" female adapter work, using a regular guitar cable to connect to the power amp?

Thanks

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It may work, but it's a risky proposition. Headphone outputs generally have a low impedance (0.5 - 50 Ohms) and relatively high level signal (5-20 dBu). Apogee One nomimal specifications state a 14dBu output without indication of impedance.

Generally an effects return is a "line level" input, it expects (depending on the specific equipment) anywhere from -10 dBv ("consumer line level") to +4dBU ("professional line level"). So rather less "potent" signal than the Apogee's headphone output. So depending on the specific characteristics of your amp you may be able to drive it by means of the effects return, provided you keep rather low the output volume from the Apogee. If you turn it too high you almost for sure are going to saturate the amp, and damage may even be possible.

Also, due to impedance mismatching you may also loose signal quality, namely (I think) high frequencies content. Headphones typically have an input impedance of a few dozens to a few hundred ohms, so the output of the Apogee (not specified) may be optimized for that. But that's less probably a problem, as line level inputs have typically an input impedance of around 10 kΩ or more and any source with a LOWER output impedance will probably be fine.

In summary, for the price of jack adapter (~1$/€ in eBay) I say it's worth a try, but being EXTREMELY carefull controlling the output volume of the Apogee (starting from 0, increase VERY slowly and see what happens).

Also perhaps worth trying is using the lineout from the PC's motherboard. I know the audio quality may be not as good as the Apogee's, but the signal level is probably better adapted to feed the amp. Even if you only have a single "line/headphones" output in the PC, typically these output drivers are built to compromise between several types of load (headphones, recorder inputs, etc.) and respond in a more flexible way to the load applied to them than an optimized headphones output. For that, you would need to route audio in the PC to the motherboard audio output. This brings in another host of possible difficulties, but apparently from the Apogee description, the bundled software would facilitate that, as well as avoid internal latency.

  • I am not well versed enough in electronics to know if all that technical stuff you said is correct. I am willing to upvote if for no other reason than you made a valiant effort to answer the question. However I am hopeful that someone with more knowledge of these type things will weigh in with a comment to your answer or a new answer. But I certainly want to commend you on taking time to post an answer and hope you will continue to participate on Stack Exchange. – Rockin Cowboy Apr 5 '16 at 18:55
  • Thank you very much for your extremely detailed yet easy to understand answer. I read the apogee one's manual and found this: Select an output operating characteristic in the Audio Output Source menu: Select Stereo when connecting ONE to headphones, powered speakers, a mixing console or a home stereo; Select Amp when connecting ONE to an instrument amplifier. Maybe, by selecting Amp as the output, i can get the 'line level' you mentioned, thus not damaging the amp. – tsuo euoy Apr 6 '16 at 1:00
  • Thanks Rocking Cowboy for the encouragement, I fully subscribe your concern and encourage peer review as way of ensuring qualified answers. – José David Apr 6 '16 at 10:32
  • Tsuo, that's good news. The Amp option will probably give what is called "instrument level" (the type of signal coming what of an electric guitar), which is a weaker signal even than line level. This option will probably work best with the input (not effects return) of the amp. As per the manual description option "Stereo" will probably work ok too with the effects return. Any way with these options I'm pretty sure that you'll find a working solution, just be careful initially with the output volume. – José David Apr 6 '16 at 10:45

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