Headphone into Preamp out?

[leebert]

I'm downsizing my audio system and thinking about converting to a high quality headphone system. One of the thing's I'd like to do is plug headphones into the output of my preamp (which doesn't have a headphone jack) and use that as a headphone amp.

Has anyone done this, or know if this can be done?

My quick impression says it's just converting the headphone jack into R&L RCA male plugs. Right? Wrong? Complications?

Your input is valued.

Lee

 

[rickcr42]

Quote:

My quick impression says it's just converting the headphone jack into R&L RCA male plugs. Right? Wrong? Complications?

Yes.....no....um........maybe

totally depends on the preamp and not a universal answer

1-What is the output current/voltage capability of you preamp output ?
2-is it a DC stage or does it have capacitor coupling meant to be used into a high impedance ?
3-do you have multiple outputs and is there a means to "mute" the line output while using the preamp with headphones.having "output 2" active with "output 1" mutrdc? If not you will need another means to interupt the signal to the rest of you system

Bottom line is to just try it with your headphones.It will do no damage and may save you a couple of bucks.worst case if it is marginal it can be a stop gap solution until you are able to obtain a true headphone amp

 

[JaZZ]

The two factors deciding on headphone-driving capability are the presence of (low-value) coupling capacitors (bad for low-frequency extension) and the output impedance (should be below 120 ohm for a 300-ohm headphone). I wouldn't seriously consider low-impedance headphones, as the output impedance most likely will be too high to drive them adequately.
.

 

[leebert]

Thanks guys. The preamp is Audio Electronic's AE-3 DJH. It has 20db of voltage gain, no caps in the signal path, and the output impedance is 560ohms.

Again, ideally I'd like to have Cardas (or one of the other aftermarket cable guys) bake a RCA version of their Sen650 cable, but I don't know if this is possible (no response from Cardas or another reseller on that question). I've discovered there's a 'Y-adaptor' that would do the trick, but I'm not crazy about adding a kludge into an otherwise high quality playback chain.

Lee

 

[JaZZ]

Quote:

Originally Posted by leebert The preamp is Audio Electronic's AE-3 DJH. It has 20db of voltage gain, no caps in the signal path, and the output impedance is 560ohms. Again, ideally I'd like to have Cardas (or one of the other aftermarket cable guys) bake a RCA version of their Sen650 cable, but I don't know if this is possible (no response from Cardas or another reseller on that question). I've discovered there's a 'Y-adaptor' that would do the trick, but I'm not crazy about adding a kludge into an otherwise high quality playback chain.

No need to worry about quality issues with the adapter -- the 560 ohm disqualify its pre-outs from driving headphones anyway. Sorry!
.

 

[leebert]

Jazz,

Thanks for that info. Next question: is the impedance due to the RCA jacks? There are no components between the 6SN7 output pins and the jacks. Therefore, could I purchase a Neutrik jack, install it, and convert it that way?

As you might be able to tell, I'm quite fond of this little preamp, and would like to find a way to make it work. If I can't, I suppose I could go the microZOTL route....

Thanks again,

Lee

 

[rickcr42]

Quote:

Thanks for that info. Next question: is the impedance due to the RCA jacks? There are no components between the 6SN7 output pins and the jacks. Therefore, could I purchase a Neutrik jack, install it, and convert it that way?

Sounds like it is a combination SE Triode Gain Stage/Se Cathode Follower amp (one half of the dual triode for each stage) and no way there is nothing between the CF and the output jacks ! There must be a capacitor there to block DC so that is the limting factor on the output and would need to be increased in size thus lowering the output impedance assuming enough room inside the chassis.Considering how expensive and how large goo coupling caps can be this is always an area where a manufacturer will use the smallest value they can get away with and still have good bass response.
Possibly realistic would be getting it down enough to drive 300 ohm cans but not really not suited for lower impedances without a coupling/matching transformer.
Again you could try it and at worst you would have reduced bass and limited drive but hurt nothing

 

[leebert]

Rick(cr?)

Thanks for the push-back; you're right about the circuit; I was way too hastey in assessing it. After speaking with Audio Electronic Supply, it turns out they charge $525 to modify the unit, so it appears to be way more involved than simply adding a jack (which they have done for Audio Addict for ~$200).

Anyway, I'm inclined to go Berning MicroZOTL now, thanks to your input.

Best,

Lee

 

[rickcr42]

Quote:

Rick(cr?)

Rick works.The "cr" is just the first two letter of my last name.

Quote:

After speaking with Audio Electronic Supply, it turns out they charge $525 to modify the unit, so it appears to be way more involved than simply adding a jack (which they have done for Audio Addict for ~$200).

for the price most likely a total redesign of the output stage or it is made into a "WOT" preamp (With Ooutput Ttransformer).A simple cap upgrade with jack no matter how high in quality would not approach that price I think.

Quote:

Anyway, I'm inclined to go Berning MicroZOTL now

a damn fine amp that can pull double-duty as a speaker amp within its 2 Watt limitations.Usually not a problem for nearfield monitoring at the desk top no matter how insensitive the speakers are.

Quote:

thanks to your input

My pleasure lee

Rick

 

[ursdiego]

Posted into the wrong thread, sorry...
However, here is a new one about roughly the same topic, for those interested:
http://www.head-fi.org/t/571386/headphone-power-amp-or-how-to-connect-cans-to-a-regulated-preamp-output-in-casu-dnm-primus-preamp#post_7747800