Headphones question

Posted by: Chris L on 16 January 2002

I've searched the forum archive, and couldn't find an answer to this, so here goes:

I read in the old Naim manual that it's possible to drive high impedance headphones direct from the pre-amp (well, the signal connection on the PSU, really). It gives 600 ohm as the required impedance.

Now, I have a pair of 'phones that I'd like to try out, but they are rated at 250 ohms.

Any ideas what would be the likely results of trying these: i.e. volume might be a bit sensitive, sound might be a bit off, "don't do it, it's a bad idea", etc?

Thanks,

Chris L

Posted on: 16 January 2002 by Martin Payne

I have a pair of Grados (SR60?) which produce almost no bass when driven this way from the 52PS.

Don't know if this is an impedance issue.

cheers, Martin

Posted on: 16 January 2002 by Chris L

Thanks, Martin.

I can't be certain, but that sounds to me like an impedance related problem.

Ah, well. I guess I just have to save for a Headline!

Chris L

Posted on: 16 January 2002 by Martin M

All Grado headphones are a 32 ohm load. I'd expect the 52 (and most headphone amps) to wilt under such a stern load. As for the 250 ohm headphones, try plugging them into the power amp output and keep the volume low.

Posted on: 16 January 2002 by Martin Payne

quote:
Originally posted by Martin M:
All Grado headphones are a 32 ohm load. I'd expect the 52 (and most headphone amps) to wilt under such a stern load.

Ah, thanks. That explains it.

They're basically used on walkmans, or occaisionally via 'phone socket on a Nak tape deck. I'm not a great fan of headphones.

cheers, Martin

Posted on: 17 January 2002 by bam

The max voltage swing of a Naim pre is 24V, so you could get 12^2/500=0.3W to your phones in theory. This should not damage the pre-amp although the sound quality may degrade at higher volumes.

If you want to connect the phones to your amplifiers speaker outputs I'd put some resistors in the way to decrease the volume. You could damage your headphones and your hearing if you make a mistake with the pre-amp volume setting.

With 250-ohm headphones try a 100-ohm in series and a 10-ohm in parallel with the phones. The 100-ohm should be rated at 10W and the 10-ohm at 1W. The trouble with this method is that you have to keep disconnecting the speaker cables and this is a pain. A dedicated headphone amp is more convenient.

Posted on: 17 January 2002 by Chris L

quote:
The trouble with this method is that you have to keep disconnecting the speaker cables and this is a pain

That's why I was asking about power the 'phones from the pre-amp. I have an old 12S and a currently unused SNAPS which I figured I could press into service, taking the signal off the tape outlet on my main system.

I plan to try the 'phones this way, provided RS get their on-line ordering sorted out. But I don't hold out a great deal of hope.

Chris L

Posted on: 17 January 2002 by Gavin B

Is a pretty cheap way of adding a headphone amp if this all fails. It's only around £100 and sounds good.

Posted on: 17 January 2002 by Chris Metcalfe

I've successfully driven Sennheiser HD600s from a NAP250, if that's any help.

Posted on: 17 January 2002 by Matthew T

Lobo,

I recently got a pair of HD600 for £100 from richer sounds, mention a What Hifi ad. This was instead of a 3 year old pair of Sennheisers HD565 Ovation (£150), no real contest, even on a £120 discman!

I have run both sets of headphones out of the power amp, bit noisy but wow!

cheers

Matthew

Posted on: 17 January 2002 by Mike Hanson

I had purchased a Headline and SNAPS2 before I learned that I could feed headphones directly from the pre-amp. I tried driving both my Sennheiser HD300 and AKG 250DF (?) with my 82/Super: They seemed a touch thin, but basically acceptable. Because I very rarely listen to headphones, it seemed like an acceptable solution.

At that stage, I intended to sell the Headline, and possibly the SNAPS. Fortunately, I never got around to it, because my 52 sounds quite awful driving either set as well as the 82. They are pinched, harsh and grating! In comparison, the Headline/SNAPS sounds full, rich, warm and balanced. I have no idea why this is so.

Although I still don't listen to headphones much on my main system, the Headline/SNAPS has taken up residence in my secondary system, which is part of my home studio. In that situation headphones are much more of a necessity. I also drive a set from the recorder itself (a Roland VS-880), as well as an old Yamaha integrated amp that I have kicking around. I may eventually get a dedicated headphone amp that can drive these things without so many bits and bobs lying about, but for now it works fine.

-=> Mike Hanson <=-

[This message was edited by Mike Hanson on THURSDAY 17 January 2002 at 16:04.]

Posted on: 18 January 2002 by JohanR

I meadured the output from my NAC 82 connected to AKG K200 Headphones. The headphones has a DC resistans of 97 Ohms according to my multimeter. With a 400 Hz sinus the 82 clipped at about .95 Volts (on a very old B&K meter). Not much, thats slightly above 10:30 on the pre volume with input from a CDS II, its loud enough for me, but only just so.
I forgot to measure the output from the pre without the headphones connected, but I'm shure it's considerably more!
Will hopefully try with a friends Sennheiser 600 that is speced to have 600 Ohms impepance. Will keep you posted...

/JohanR

Posted on: 18 January 2002 by Chris L

Well, after Radio Spares got their ordering sorted out, I ordered the in-line jack socket, and butchered a SNAIC that had a kaput din plug.

So, tape ouput on 32.5->12S tuner -> SNAPS -> headphones.

And, it works. lacks a little in the bass compared to the full system, but still nice to listen to. Clipping starts at around three o'clock on the volume, and 12 o'clock gives a good listening level.

So that's with BeyerDynamic DT511 'phones, 250 ohm.

This'll work nicely, until I decide on a permanant solution, which could be: a Headline, or a Rega Ear (or other "budget" dedicated headphone amp), or add my NAP140 (currently in my office sysem) to the 12S and use a "Can Opener", which some of you may remember, or, lastly, move house!

All this to avoid annoying the neighbours.

Chris L

Posted on: 18 January 2002 by JohanR

Chris L wrote:

All this to avoid annoying the neighbours

If you let them in to your apartment after installing all the extra boxes for headphoning, I suppose they will get so annoyed that they will move. "Oh, no our neighbour is a naimaholic!"

Posted on: 31 January 2002 by JohanR

As I threatened earlier I'm coming back after trying the Sennheiser HD 600:s.
The DC-resistance was 298 Ohms. Strangely enough the 82 clipped att the same volume setting, I had expected it to be higher with a higher impedance load. As there sensitivity was slightly lower one got even less volume.
With my Round Earth hat on they sounded much better then the AKG 200:s, more open, clearer bass, silky treble (and bla bla). But I think they PRaT:ed worse, so they are a no for me.

The conclusion is that I should get a headphone amp and start the search for better cans from there.

/JohanR