Why the ad hominem affront? I'd like to see a technical reply from you to this matter.
Technically it does produce this change. What I was saying is what if the distortion is already below audibility.. then you would not see an improvement.
I'm thinking that we agree that there isn't a 'current drive' mechanism at play, per se? That this is about what we can do with distortion..
There is no need to measure them with a microphone. EQ (for the direct comparisons discussed here) is best applied according to the drive signal, measurable at the headphone input.
How about distortion? You need microphone to see if there is reduction in distortion.
Unless you want to keep it virtual like ASR. Those just measure, never listen.
If distortion is already low enough to be audible? Lower distortion but not audible? Maybe what produces those distortions are more audible than the measurements indicate? 
That's the question, isn't it. There is always going to be some distortion, so you may be right, at least up to a point. At what point does reducing distortion even matter? I myself don't think we are there yet.
Have you heard about 'resistor drive' where you add an 8R resistor (makes the amp 1/4 powerful) and that would make it 2:1 - and they say that they can hear the difference. Haven't tried to put that resistor in parallel. They should have tried it.
But maybe you are suggesting they are imagining that they are hearing a difference? And that the measured improvement is largely irrelevant because the distortion is low enough as it is?
That's the question, isn't it. There is always going to be some distortion, so you may be right, at least up to a point. At what point does reducing distortion even matter? I myself don't think we are there yet.
Have you heard about 'resistor drive' where you add an 8R resistor (makes the amp 1/4 powerful) and that would make it 2:1 - and they say that they can hear the difference. Haven't tried to put that resistor in parallel. They should have tried it.
But maybe you are suggesting they are imagining that they are hearing a difference? And that the measured improvement is largely irrelevant because the distortion is low enough as it is?
Others here: There is an alternative to current drive that those with Sennheiser headphones can try:
Most headphone amplifiers can drive 16 Ohm headphones.
Sennheiser like the HD650 etc are 300 Ohm.
So how how putting a 22R-33R on the output of the amplifier (that load should offer no problem), one across each channel. And now listen to see if there is an improvement. I won't affect the frequency response.
Most headphone amplifiers can drive 16 Ohm headphones.
Sennheiser like the HD650 etc are 300 Ohm.
So how how putting a 22R-33R on the output of the amplifier (that load should offer no problem), one across each channel. And now listen to see if there is an improvement. I won't affect the frequency response.
Yes. You basically measure the impulse response under current drive without any correction, at the amp output with the phones in place. Then you invert that IR (in the frequency domain) and have the correction kernel which you stuff into a convolver, processing the input signal.
Personally, I don't think current drive for headphones will do much but of course there might be surprises.
No data from Wattsman
My viewpoint is purely subjective listening. I have been listening to the HD 600 for almost 20 years on basically the same headphones amp (micro ZOTL). but a month or so ago I bought a new inexpensive DAC (SMSL-SU1 ) which led me to disassembling my old DAC units(K&K RAKK DAC) which has a transformers(LL1674)output circuit board in 1to8 configuration.I decided to hook them up directly to SU1 output then to HD600,astonishingly it had enough volume to sound correct for me , a much improved base response, clarity that I’ve never heard before, all instruments seem to be more spaced out than before. l’m just looking for new avenues for headphone amp and I have a quantity of LM3875 chips. Below is a photo of new listening rig , passive headphone amp?
My viewpoint is purely subjective listening. I have been listening to the HD 600 for almost 20 years on basically the same headphones amp (micro ZOTL). but a month or so ago I bought a new inexpensive DAC (SMSL-SU1 ) which led me to disassembling my old DAC units(K&K RAKK DAC) which has a transformers(LL1674)output circuit board in 1to8 configuration.I decided to hook them up directly to SU1 output then to HD600,astonishingly it had enough volume to sound correct for me , a much improved base response, clarity that I’ve never heard before, all instruments seem to be more spaced out than before. l’m just looking for new avenues for headphone amp and I have a quantity of LM3875 chips. Below is a photo of new listening rig , passive headphone amp?
The DAC SMSL SU1 DAC has what output? I suspect it has ICs to buffer and filter the AKM DAC.
Transformers can be used on the outputs of the AKM DACs, but generally that would be 1:1 and for line level. I have done this and really good results. But headphones? That's different. Maybe set the the LL1674 as 4:1 step up rather than down. Will be DAC be able to drive headphones via step-up? Just thinking aloud though. The AKM DAC has a 32bit volume control, I believe. In the Oppo 203 with AKM DAC it worked nicely. Again, just thinking out loud. Are you using the AKM DAC's volume control?
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The primary are wired in parallel at one, the secondary are wired in series 4+4 . The secondary have a parallel resistor, which is 1500ohms.I measured at the resistance with the headphones plugged in which is 208ohms.The output impedance of SU-1 is 47ohms. below is a photograph of how the transformers are wired.
