That wasn’t in your request. You just asked for an amp that will give you that current.
I need to tighten the brief!
Hey, thanks for sharing. I do have a Cayin CS55 Tube Amp that I would like to do this with. Can you share me details of the Mundorf Resistor you used?
1 Like
What’s of primary importance is getting the right value and the power rating of the resistor. To figure out the value, you’ll just need to do a parallel resistance calculation (just use an online calculator) to determine what the effective impedance will be with your headphone’s impedance and the resistor to get to bring the impedance down to a more speaker amp friendly level (e.g. 8 ohms). The second is just to make sure your resistor can handle the power level (at least a few watts). Beyond that, the “quality” of the resistor shouldn’t be very important since this is not in the signal path. I only went with the mundforf just for the heck of it. In my specific case, those are 8.2 ohm resistors with up to 10w power handling. Again, this was for use with my Susvara which is 60 ohms.
1 Like
Long ago, Joe Grado designed a resistor setup to hook to a speaker amp to use the HP-1000. I’ll have to see if I can find a copy. Old receivers such as the Fisher 400 tube amp used the output of the power amp section to drive their headphone jack. They put a small resistor inline (IIRC 5 ohm) for a bit of protection.
Anybody tried accuphase e600 speaker output for focal utopia?
Is this ok? with -20db attenuator button on.
1 Like
People might find this thread helpful or at least post your questions here:
I’ve been listening to the Atrium and Susvara directly out of the speaker taps of the Parasound a21+ amp (300W/ch @8 ohm) but was curious if adding 8ohm resistors on the taps would be beneficial. Both cans sound fantastic without resistors but there’s a tiny bit of noise floor with the Atrium (sounds like white noise with music paused but is imperceivable while listening to music) while the Susvara is dead quiet.
I calculated effective resistance adding an 8ohm resister in parallel:
- Susvara + 8ohm = 7.06 ohm effective
- Atrium + 8ohm = 7.79 ohm effective
Questions:
- will adding the 8ohm 300W resistors improve the sound?
- will they lower the noise floor on the Atrium?
- how much power will each headphone potentially see? I estimate the current wattage as 37 and 9 for the Susvara and Atrium, respectively but I could be way off.
A few more tidbits of info, I have the input gain at the rear of the Parasound a21+ around 50% on each channel which allows me to set the Freya+ preamp volume around 12 o’clock.
3 Likes
I found a similar spec resistor but in a fairly attractive, heat-dissipating case.
Does anyone know how these will affect power to headphones when hooked up in parallel to speaker taps?
You don’t need a 300W resistor for a 300W amp, unless your going to max the volume out, and then the headphone will go first.
If you put an ~8 Ohm resistor across the speaker terminals (in parallel with the headphone), it just needs to be big enough to carry the current that will actually be there at volume levels your going to actually use. It’ll carry ~8x the current/power of the 64 Ohm headphone, but the voltage differential will be identical.
5-10W should be enough for anything your likely to plug in.
It won’t protect the headphone from being destroyed. The weak link in the circuit is still going to be the headphone driver coil.
Generally it’s not necessary for SS amps, they are relatively invariant to load, you would want to do it for a transformer coupled tube amp.
In both cases it will have some effect on the quality of the output, most people who’ve tried the Hifiman speaker tap box (which is just resistors in a box) vs direct output from a SS amp will tell you that. The quality of the resistor does matter, but you will have a problem sourcing very high quality resistors at 10W and higher.
2 Likes
Appreciate the response Polygonhell.
That makes sense about not needing 300W resistors since I’m not testing peak power or doing anything remotely that demanding so I’ll look for something closer to 10W.
Regarding noise floor which factors contribute to that the most? The Atrium has an impedance of 300 Ohms and a sensitivity of 96dB/mW. Maybe there’s no avoiding noise floor driving them out of a 300W speaker amp.
You could probably build a voltage divider, and it might help reduce the noise.
Practically speaking though there is very little reasons to try and run a headphone like the Atrium off speaker taps, unless we’re talking a very expensive 300W Amp, you’d almost certainly better results just getting a crap dedicated headphone amp, and honestly the Atrium deserves more than that.
There are better reasons to do it with low efficiency planars.
1 Like
I’ll look into voltage dividers. Thanks for the suggestion.
I have a few headphone amps that’ll work just fine with the Atrium but I wanted to experiment with the a21+ and it definitely sounds nice, albeit the minor noise floor. I may end up getting a dedicated headphone tube amp next year to drive both susvara and atrium.
I’ve been using the Hifiman HE6 adapter with my Marantz PM8004 to run my Senn 600, 800, HE6se V2 and LCD 2.2 ---- to great effect. I haven’t really noticed any “veil” over anything but I haven’t hooked these directly up to my speaker taps raw. I have noticed running these from the amp has really made them come alive though — especially the Senn 800. There’s everything the 800 has but “more” of it to great effect. More air, detail and punch on them. The HE6se V2 really drinks down the power too and they sound great off the amp.
2 Likes