[Hun7er]

  My new headphone amp set up:  Audio Note Conqueror Silver power amplifier, 6N7W drivers, ELROG 300B power tubes, VT244 rectifier, Blue Circle headphone adapter (resistive).
 

 
A tiny bit of noise (that disappears when playing music) due to high gain in system (Audio Note CD4.1x + DeHavilland UV3 + AN power amp),
but this set-up has a lovely sound, more to my liking than my dedicated Stratus headphone amp.  A lot has to do with power tubes.
 
 

 
Why did you like more than the Stratus ?

 

[Frihed89]

   
Why did you like more than the Stratus ?

First of all, the Stratus IS quieter, no doubt about that.  But the double C-Core OPTs in the Conqueror Silver + the ELROG 300B tubes help to give the music I listen to more presence, more weight, but still incredible smoothness, balance and tone to the instruments.  The bass is also more present with the 300B.  The Stratus just has a more ethereal sound to it, but is very well balanced.  With the Stratus, you are in heaven listening to recorded music; with the Conqueror you are close to real music, at least as close as  you can get with SET.  (An SET will perhaps never equal an amplifier with a transistor output stage in its faithfulness to the recorded version of the music.  This is largely because of the low distortion of this variety of SS amplifier in all harmonics and the abundance of second-order (pleasing) harmonics in SET amplifiers, as a rule.

 

[Frihed89]

  I can't see why one would use a transformer in the first place..

Because I would like to drop the output voltage and match the impedance and I hate what attenuation does to a signal.

 

[davidsh]

 
I can't see why one would use a transformer in the first place..

Because I would like to drop the output voltage and match the impedance and I hate what attenuation does to a signal.

Impedance can be matched reasonably with a L-pad style attenuator circuit. Transformers mess with the frequency response and phase which isn't ideal..

 

[Armaegis]

An L-pad just chops your output and can potentially present an ideal load to the amp, but rarely looks as nice from the headphone's perspective. On the plus side, resistors are cheap to implement.
 
A good transformer/autoformer shouldn't affect the frequency and phase response that much and will do a better job of providing impedance matching mojo, but good transformers are stupid expensive.

 

[davidsh]

From memory it seems to me that the added output impedance seen from headphone POV will be around 4-7 ohms depending on choice of resistors and the headphone impedance. Correct me if I'm wrong.

 

[Armaegis]

That's about right. For an OTL tube amp that already has a high output impedance, not a dealbreaker. For an amp with <1 ohm output impedance, that's a big difference.
 
Depends on your resistor configuration, types used, yadda yadda voodoo.
 
Or maybe we want to use transformers because we're all crazy.

 

[davidsh]

That's about right. For an OTL tube amp that already has a high output impedance, not a dealbreaker. For an amp with <1 ohm output impedance, that's a big difference.

Depends on your resistor configuration, types used, yadda yadda voodoo.

Or maybe we want to use transformers because we're all crazy.

That sums it up perfectly in my head..
I suppose we aren't going to use our speaker amps for multi driver armatures.. Or?
Really, the added impedance from the resistor network is completely redundant in 99% use cases in my opinion.

 

[Chris J]

From memory it seems to me that the added output impedance seen from headphone POV will be around 4-7 ohms depending on choice of resistors and the headphone impedance. Correct me if I'm wrong.

Hard to generalize.
You would have to look at the resistor network or the transformer.

 

[davidsh]

From memory it seems to me that the added output impedance seen from headphone POV will be around 4-7 ohms depending on choice of resistors and the headphone impedance. Correct me if I'm wrong.

Hard to generalize.
You would have to look at the resistor network or the transformer.

Yes, it is. But in the case of the resistors we did assume it was a L-pad configuration and I'd like to assume we want the speaker load around 8 ohms. In that case output impedance will vary from some 0.5~8 ohms in just about any use case.

 

[Chris J]

Yes, it is. But in the case of the resistors we did assume it was a L-pad configuration and I'd like to assume we want the speaker load around 8 ohms. In that case output impedance will vary from some 0.5~8 ohms in just about any use case.

OK, then I see what you are getting at and I agree. I was thinking of all those vintage receivers with 220 Ohm resistors in the headphone jack.....:eek:

We'll ignore those wonky vintage receivers.
Then if you are using (for example) a 2 and a 6 Ohm resistor, then from the headphone's POV, the output impedance will be less than 2 Ohms.

Then, by extension, why bother with the expense of a transformer to "impedance match"?

Unless, of course, you are trying to use a low impedance headphone with a vacuum tube OTL amp. In this case, a transformer would be useful, or why not just buy a vacuum tube amp with output transformer already designed in?

 

[davidsh]

Besides, perhaps someone can explain to me how to calculate and understand the output impedance seen by the phone in the L pad configuration. I do know the formula from robrobinette's site, yet can't quite grasp why he calculates it as though all the resistors were in parallel.

 

[Chris J]

Besides, perhaps someone can explain to me how to calculate and understand the output impedance seen by the phone in the L pad configuration. I do know the formula from robrobinette's site, yet can't quite grasp why he calculates it as though all the resistors were in parallel.

To make real long story real short:
Because that is how the headphones see the resistance, because that mathematically describes how the headphones are damped if we want to calculate the effective damping factor applied to the headphones.

 

[jdcarlson]

I have done it with a McIntosh MC2205 and Sennheiser 600s with balanced cabling. I am feeding the MC2205 with an MS750 running through an MX118. I also have some high resolution digital takes from live tapes (192K - 24bit) that I play from a separate hard drive through a USB DAC to the MX118.
I have a resistor network connected to the amp (10 ohms, 400 watt wire wound for each channel), but do not use it when listening to the headphones - it is just there for when I turn off the headphones to keep a load on the amp (I know - many say you don't need a load on a solid state machine - but I am the "belt and suspenders" type).
I am running the 600s off of the 8 ohm tap.
I realize that there is a terrible impedance mismatch - but it does not degrade the sound to my ear.
I like the increased detail - i.e., I can hear the individual instruments.
I listen mostly to acoustic jazz or classical - and it works great for me.
In "an earlier life" I spent quite a bit of time "in the orchestra pit" with a small orchestra (50 pieces). Part of the time playing, mostly as conductor. Always supervising the recording. I have learned what to listen for in live acoustic music.
Even going back to some of the original tapes we made (35 years ago) it is amazing how much detail I can now hear - even with my 70 year old ears. I recognize more from the tapes than I remember from the performances.
We were using 12 mics for 50 instruments. The woodwinds and strings got a lot of mic coverage. Sax a little less. Brass almost none. None for percussion, electric guitar, organ. The hardest to get placement dialed in was suspending two mics over an open grand piano.
Anyway - the MC2205 / balanced Sennheiser 600s is a great combination to my ears.
BUT - I have to watch to volume - when the needle gets to 0.02 watts, I have to turn it down!
At least - I know the amp is NOT stressed. It barely running above idle, so distortion from the amp is negligible. Any distortion has to come from the impedance mismatch, the cables, or the headphones.
In all fairness - I have not sampled the HD800s with a dedicated amp - so I really cannot say how my setup would compare.
But - my experience is - as long as you have balanced cable connections - do not be afraid. Just do not try to get the volume too high. (I learned that the hard way with some STAX heaphones about 15 years ago - yes - one can destroy the drivers with too much volume!)
Thanks,
Jim

 

[Wildcatsare1]

For those that need a resistor box for a tube amp, I have moved to SS so I will be listing it on the F/S Thread after Christmas.

I am now using my Lyr 2 with '75 Voskhods as a pre-amp (my Audible Illusions M3 is too big), too either a Belles One or B & K 125.2 red. II. Charleston Cables UOCC Balanced to Draug 2 HE560 or Vanquish Alpha Dogs. I truly don't understand why people mess with underpowered, overpriced Specality HP Amps?!?

Edit: PM if you are interested in the HiFiman Adapter Box.