Simple Headphone Output to tube Preamp - ideas?

[DoubleAA]

Hello all,
I've searched and can't find an answer (that I understand) for what I want to do. I have a tube preamp (a grounded grid based on Bruce Rozenblit's design) that uses 3 12au7s. The output impedance is 200 ohms. I would like to add a simple headphone output - it doesn't need to be world class high end (or even tube based), but should give a clean, pure faithful reproduction of the sound. A small circuit would be best.

The headphones I want to drive ar 32 ohms, though I may change those in the future. Can someone suggest a simple design I could drop in? I'm guessing this would be something that would piggyback off of the (single ended) outputs, but the whole impedence matching thing is where I have my concerns.

Thanks in advance for any help on this.

Aaron

[jcx]

http://headwize.com/projects/index.htm

[DoubleAA]

Right - I was looking exactly at those. But in terms of hooking up to my pre, is the input for any of these (for example) just the single ended RCA outputs? Do I have to be concerned with any impedance (mis)matching?

I know this is going to pretty simple conceptually, I just don't want to screw anything up. It is only recently that I've had a need for listening via headphones and, since I have space in my pre chassis, thought it would make sense to add an additional output there.

Thanks!

Aaron

[oshifis]

I have exactly the same problem. I intend to use BUF634T or similar opamp buffer. The output voltage swing of my tube preamplifier is more than enough for driving the headphones, so I need just current driving and low impedance output. My problem is that I have +12V non-regulated only, and I wanted to avoid input/output coupling capacitors. Any ideas?

[jcx]

audio signal interfaces are usally not matched impedance

typically the source output is expected to be low Z (0 to ~1K Ohm) and the input to the next device is usually >10K Ohms


audio signal caps can be fine and the "simplest" way to get AC gnd in a single supply amp, non-polar/bipolar Al electrolytics are the best for the larger values required to keep headphone output Rload*C corner frequency <<20 Hz - otherwise you need some sort of active supply splitter circuit

[danzup]

Originally Posted by jcx

audio signal interfaces are usually not matched impedance

typically the source output is expected to be low Z (0 to ~1K Ohm) and the input to the next device is usually >10K Ohms


audio signal caps can be fine and the "simplest" way to get AC gnd in a single supply amp, non-polar/bipolar Al electrolytic are the best for the larger values required to keep headphone output Rload*C corner frequency <<20 Hz - otherwise you need some sort of active supply splitter circuit

Quite right !
This is the basics of audio .
So do connect the headphone amplifier without any concern regarding impedance .
- a typically input is expected at around 10K
- a typically output is expected at around 600ohmi