That'll be tough. HD650s are not hard to drive current wise, yet insensitive enough to not make every last bit of noise heard. It seems the CK² III isn't super low noise, but distortion is low and its current drive capability is ample.
Do you hear any hiss from the amp? Which position is the volume pot typically in? I imagine one could still tweak it a little with a 10k pot and lower-noise supply - but wouldn't expect any miracles.
An O2 is always handy to have around, but it may very well sound just the same as the CK² III with HD650s (assuming you have chosen gain wisely). The difference with some SE535s or somesuch could be quite pronounced though (particularly in noise level).
Don't even think about this tube OTL stuff unless you're aiming for a massive downgrade. Some people like decidedly imperfect amplifiers, but it's not exactly an efficient way of getting the sound you want.
Hi, opc's 'The Wire' SE-SE headphone amp is worth considering also. To me, the HD-650's sound very good driven by an O2, but I note an even greater clarity of detail with The Wire.
The best I have heard hd580, hd650 and hd800 sound is with a DHT headphone amp. There is a thread with ongoing development/discussion here: http://www.diyaudio.com/forums/tubes-valves/228625-all-dht-set-headphone-amp.html
well there may be (quite a few) amplifiers "audibly indistiniguishable" from "a wire with gain"
but many may choose "conceptual art" or even accept, seek out "euphonic" distortion of the signal
with the HD650 300 Ohm load and 98 dB/mW sensitivity only +/-12 V, 40 mA are required to reach 120 dB SPL - in fact that much power will bottom out the voice coil at lower frequencies
the Vswing is within many monolithic op amp's capabilities, some can also provide the current without strain
but many may choose "conceptual art" or even accept, seek out "euphonic" distortion of the signal
with the HD650 300 Ohm load and 98 dB/mW sensitivity only +/-12 V, 40 mA are required to reach 120 dB SPL - in fact that much power will bottom out the voice coil at lower frequencies
the Vswing is within many monolithic op amp's capabilities, some can also provide the current without strain
the O2 site goes to great detail why one might believe it is good enough to be audibly indistinguishable from "perfect" in the accuracy, lack of distortion, flat frequency response "wire with gain" direction
other projects go further in low noise, distortion - perhaps without justification - but rather because it is currently technologically easy to greatly exceed some of the known or suspected human hearing limits
others choose to follow audiophile gurus, formulas like "no feedback", "simple circuits", vacuum tubes, in circuits from half a century ago...
these concepts "stories", including beliefs about "wire with gain" accurate amps do have effects on human perception of audio independant of their actual technical performance - and some do cause clearly audible objective signal differences
other projects go further in low noise, distortion - perhaps without justification - but rather because it is currently technologically easy to greatly exceed some of the known or suspected human hearing limits
others choose to follow audiophile gurus, formulas like "no feedback", "simple circuits", vacuum tubes, in circuits from half a century ago...
these concepts "stories", including beliefs about "wire with gain" accurate amps do have effects on human perception of audio independant of their actual technical performance - and some do cause clearly audible objective signal differences
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I find this somewhat reminiscent of Douglas Adam's 'HHGTTG' - in the use of 'ultimate' as in 'the ultimate question of life, the universe and everything'. In the original, they built a computer to answer this without really knowing what that question was.
So is 'ultimate' meant in terms of today's industry standard suite of measurements, or in listening pleasure?
composite op amp circuits can beat that - I couldn't see any 1 kHz IMD product in one of my multiloop circuits with 10+11 kHz 1:1 with test signal fundamental removal arrangement and 30 dB amp ~ -160 dB resolution floor with 100 s averaging - did have to replace NP0 caps with polystyrene
so basically unmearurable distortion from active parts is possible - then care in passives part selection and layout of course
another big question is "ultimate" analog volume control - $50 Noble pot, $100+ stepped attenuator, $300+ TVC, $400 Penny Giles oil filled pot - or LDR, PGA - what do you believe, how much do want to spend for it
so basically unmearurable distortion from active parts is possible - then care in passives part selection and layout of course
another big question is "ultimate" analog volume control - $50 Noble pot, $100+ stepped attenuator, $300+ TVC, $400 Penny Giles oil filled pot - or LDR, PGA - what do you believe, how much do want to spend for it
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Depends on the loading. In this case result was achieved driving 2Vrms onto 15Ohm. With lighter loads, something like 51Ohms it goes down to levels mentioned by you.
And yeah, that was composite too
Again, it is not a question of the level itself. It is just a demonstration how easy it is these days.
And yeah, that was composite too
Again, it is not a question of the level itself. It is just a demonstration how easy it is these days.
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Have you thought about looking for some new headphones?
I'm not saying that the HD650 is a bad choice, or that I've got any better suggestions, but there might just be something a bit more fun and musical out there.
It certainly is a lot easier to change the sound of your system this way, than by changing the amplifier.
A vote for OTL DHTs
I'm driving my HD600s with a Bottlehead Crack w/Mullard CV4003 driver, vintage RCA 6080 power triode, PEC 50k pot and Dayton film caps bypassed w/Russian FT-1 0.047 teflon caps, and it sounds like a million bucks, even before the Speedball CCCS upgrade. Great sound for not a lot of money.
I'm driving my HD600s with a Bottlehead Crack w/Mullard CV4003 driver, vintage RCA 6080 power triode, PEC 50k pot and Dayton film caps bypassed w/Russian FT-1 0.047 teflon caps, and it sounds like a million bucks, even before the Speedball CCCS upgrade. Great sound for not a lot of money.
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