headphone level to line level conversion

[zephonic]

My Yammie P85's only outputs are headphone 1/4" which I have connected to my audio interface with an insert (stereo jack to two mono jack) cable. However, levels aren't hot enough. Isn't there a device that converts headphone output levels to line output levels (-10)? And what about impedance conversion? That necessary or do I misunderstand?

 

 

[ITGITC]

OK.

 

You need a preamp. Go out from the preamp to your audio interface.

 

I'm guessing here, but I would think a good example would be to send the output of the P85 through two direct boxes - one for the left, one for the right. That would take care of any impedance problems (although I'm not certain that this is a big deal).

 

From the direct boxes, run a mic cable to the mic inputs of a small mixer. Pan one channel left, the other right.

 

From the output of the mixer, run a cable to your audio interface.

 

Or you may be able simply to run a cable from the headphone output jack to the left and right line inputs of the mixer. You'll have to try it to see if that gives you enough gain. I just don't know for sure.

 

I don't know of a low-noise all-in-one device that will do this.

 

But there could be something out there that I'm not familiar with.

 

Good luck.

 

Tom

 

 

[Bill Heins]

http://www.sweetwater.com/expert-center/techtips/d--10/26/2000

 

Just a little info for you

 

Bill

[Byrdman]

Impedance does not matter. The headphone out is designed to drive a low impedance so feeding a high impedance instead will be fine.

 

However, -10dbV is about .3V. Pro line level is +4dbV, which is roughly 1.6V. A typical headphone out has to be able to supply somewhere around 80mW into say 300 Ohms. Some AKG headphones are 600 Ohms, but I know some consumer headphone outs won't drive those to any sort of level so lets stick to 300 Ohm. That requires a voltage output of about 5V. Even if your headphone output is way wimpy it should be able to drive even pro levels reasonably well. It should have no trouble with consumer levels.

 

The wimpiest imaginable would be something like 20mW into 8 Ohms. That is still 0.4V, which is still more than consumer line level.

 

So something odd seems to be going on here and adding a pre-amp may not help. I would check those inputs with some other pieces of gear, especially if you have something with real line level outs to do it with.

 

 

[ITGITC]

I would check those inputs with some other pieces of gear, especially if you have something with real line level outs to do it with.

 

 

Agreed.

 

I forgot that Kurzweil recommends you use the headphone output of the PC2X when using unbalanced cables/connections. I use it all the time. Other headphone outputs may introduce some noise into the signal. This one doesn't.

 

Try plugging in a set of 'phones rated at 300 ohms and let us know if it's loud enough. Otherwise, there may be something going on with your interface. What brand/model izzit anyway?

 

 

[zephonic]

Thanks all for your insights. I use a Focusrite Saffire LE, but use the 2 preamps for mics and guitar, so the P85 is connected to the line ins (these have no gain pots). I'll have to fork out for an extra preamp, I guess.

 

[JeffLearman]

What Byrdman sez -- something's wrong if your headphone outputs won't drive your line inputs. Either the headphone outputs are terribly wimpy or the line inputs are broken, and you need to find out which.

 

If the line inputs aren't working right, a preamp won't help you, because it only amplifies the input up to line level, which is much lower than what your headphone outputs should be driving.

 

If the headphone outputs aren't working right, a preamp might do the job, but you might also get lots of noise.

 

So, better to find out what's broken and fix it, than to add a part that you (a) shouldn't need, (b) isn't the right tool for the job, © only has a 50% chance of helping, and (d) even if it does help, might not work very well.

 

Finally, do you know *which* kind of direct box or preamp to get? There are several different kinds for different purposes. But none of them are made for this purpose. (The best bet would be the kind also called "instrument preamp" or "high-impedance mic preamp".)

 

Hopefully, you just have a bad cable. Be sure to rule that out first!