[jpelg]

*** Caution: DIY idiot. Pls forgive in advance ***

I assume it's possible, given the proper connections, to drive a headphone directly from the RCA outputs of a preamp? What are the pitfalls here? What difference does it make if the cans are low vs. high-impedance?

Any & all info appreciated here. TIA.

 

[JahJahBinks]

Preamp out circuitry might not be able to supply the proper voltage and current level that the load (your headphones) require. Most of the time what will happen is that the preamp out doesn't have enough voltage headroom to make the headphones sound loud. In this case you get a good but soft sound. Occasionally you may ran into a case with very low impedance cans that they don't saturate in voltage but they draw more current than what the source can supply, then it's very possible the output protection (overcurrent limiting feature) of the preamp circuit output is activated (if it has such feature), and you get a degraded sound with lots of distortion. However even if you don't get a distorted sound it doesn't mean you are not pushing it to the limit, the only way to be 100% sure is to study the circuit diagram and do your calculation, of course that's not viable. The bottom line is preamp out is designed to drive high impedance load. DIY amps such as PPA has input impedance of about 1mega ohm (and it's resistive), that's significantly larger than any headphone impedance. Also headphones impedance (mostly inductive) varies with frequency, which is something preamp out hates to see.

Low impedance cans require more current than high impedance cans.

 

[jpelg]

Thanks, JJB.

So low-impedance (ex. Grado) cans present a more difficult load to the preamp due to their current-draw requirements? And that is worse than a hi-impedance can (think AKG K240M) that, while requiring more voltage & may not sound great or loud, presents a load closer to the input impedance of an amp device? Overall not a good idea either way, right?

So what does something like a Szekeres circuit do in between that changes things so much (in a good way) using low-impedance drivers like Grados?

 

[McFortner]

I was thinking along the same lines. I was wondering about using my preamp to drive my Total BitHead. Since I was not 100% sure and only had the TBH for a week, I emailed HeadRoom about it and this was their reply:

Hello Michael,

Thanks for your inquiry.... No such thing as a stupid question here at
HeadRoom!

Provided that the turntable pre-amp provides a TRUE direct line-level
analog output, hooking it up to the amp's analog line-in should not
present any problems whatsoever and should, in fact, offer the same type
of sonic benefits as the Total BitHead would deliver from any other
audio source!

Please feel free to reply if any further questions or concerns pop up!


Cheers,

www.headphone.com

Jorge Cervera
Sales Manager / Staff Writer
HeadRoom Corporation

Really nice guys there at HeadRoom. So I hooked up my Technics SL-BD2 to my Pyle Pro PP-999 preamp into my TBH and it worked fine. My son and I listened to some old Jazz LPs together. You won't have the equalization functions like you would on a home stereo system, but it will work. In fact, if you had an equalizer you could add that between the preamp and the amp to adjust the sound.

Anyway, this gives me something to listen to when the wife has the computer until I can get all my LPs copied over to MP3s.

Hope this helps.

Michael

 

[jpelg]

Quote:

Originally Posted by McFortner I was thinking along the same lines.

Errr...not quite: Quote:

Originally Posted by jpelg to drive a headphone directly from the RCA outputs of a preamp

No (additional) amp involved. I'm still learning what each stage of the audio chain provides the next, and ultimately to the output devices. Was wondering what the preamp outputs would provide directly to the headphones. My brain is old, and it hurts

.

But I'm glad your setup is working out for you and your son. Sounds like an enjoyable listen!

 

[BTV]

Hi jpelg! In the case of low impedance headphones you will have higher frieqency for lowcut filter (headphones R and DC blocking C are involved).

Personally I think that you can connect 600 Ohms and get not so big bass reduction. But the volume will not be too high.

 

[bozebuttons]

Didn't work when we hooked up the balanced GS1000s to Jahns Melos preamp xlr outs at the NYC summer meet.Sounded like crap.

 

[JahJahBinks]

Quote:

Originally Posted by jpelg Thanks, JJB. So low-impedance (ex. Grado) cans present a more difficult load to the preamp due to their current-draw requirements? And that is worse than a hi-impedance can (think AKG K240M) that, while requiring more voltage & may not sound great or loud, presents a load closer to the input impedance of an amp device? Overall not a good idea either way, right? So what does something like a Szekeres circuit do in between that changes things so much (in a good way) using low-impedance drivers like Grados?

Besides voltage and current, preamp out is not designed to be connected to an inductive load, so it's not a good idea.

Szekeres circuit can provide more current, it's like a current buffer IC.

 

[Jahn]

Quote:

Originally Posted by bozebuttons Didn't work when we hooked up the balanced GS1000s to Jahns Melos preamp xlr outs at the NYC summer meet.Sounded like crap.

Bingo! Nastiest sounding thin nasally dribble of sound evar. Lineout to Headphone, bad. Line signal to beefy tube amp hybrid to headphone out, GOOD.

 

[audiomagnate]

Here's a real world example. The headphone jack on my SAE Mark XXX preamp gets the exact same signal that goes to the main outs, and my low impedance cans have no bass and exaggerated treble. Turning the bass all the way up and the treble all the way down makes them almost listenable, so the juice is there, it's just an impedance mismatch. Many higher end preamps have a real headphone amp but this one doesn't. Very high impedance cans like the old Sennheiser HD414s at 1800 ohms can work with pre outs. I wonder why they even bothered to put a headphone jack on it.  

 

[jjthorn]

I have never used high quality headphones, have always listened to Speakers.
 
I am considering using my Pre-Amp to drive new headphones which I have yet to purchase.
 
Preamp Spec
Output Impedance – 2 Ohms (open loop).
Amps – 10 (upgrade available to approximately 40 Amps).
Maximum Output Voltage – 10 Volts.
 
Would best quality RCA connectors to Preamp provide better sound quality compared to a TRS jack?
 
The Preamp is not balanced, the headphone cable would be connected to the Left and Right amplifier RCA outlets.
 
I will obviously listen to headphones before I purchase, if possible through my Preamp and DAC.
 
I was considering purchasing the Either Flows or Focal Utopia headphones, if acceptable I would use the headphone with the Preamp for a while and perhaps purchase a headphone amp if required after I can judge the merits of the headphones.
 
Is anyone using a Preamp to drive high end headphones?