New 'phones or new amp?

W

Wanderer

New member
I have a Quickie rigged with older Specos as a headphone amp to drive my 600 ohm AKG 240m. Sounds just dandy on solo and small ensemble classical/jazz which is 85% of my listening. With large orchestra classical - Elgar, Poulenc, etc. - I do think I am hearing things get somewhat compressed.

Would more efficient phones, say Beyerdynamic 880 (600 ohm) be a possible solution? (I don't care for the Sennheiser 600/650  have heard finding them sorta "murky/romantic" sounding. Open to other suggestions)

..or would my time and effort be better spent with a Crack kit and the AKG 240m cans?

Thoughts?

       
 
The Quickie has a very low power output for headphones, 1mW in stock form as opposed to 50mW for standard headphone amps. That's about 17dB difference. It is a preamp, not a headphone amp, after all!

For that reason, I would expect higher efficiency phones to work better with it. Ideally, you'd like to see 102dB/mW rated sensitivity, with 96dB a practical limit. Should be loud enough for "normal listening," whatever that is.

The best you can do with the stock power supply would be to revise the operating point for maximum power rather than voltage, and use a choke load in place of the resistor load. That could give you as much as 6dB of boost - not a lot but should be clearly audible. Now we're talking 90dB-96dB minimum sensitivity.

Beyond that, you could raise the voltage. For another 6dB you could double the number of batteries (which would double the current so they last half as long). This quadruples the cost of batteries, so I don't consider it optimal, it just shows the sort of compromises available.

Crack, being current-limited, makes the most power into 600 ohm phones - around 200mW, which is 6dB above the reference. Smack can easily make 50mW into 600 ohms, and around 200mW into phones in its target range (16-250 ohms).
 
According to the manufacture's site the 240 monitors clock in at only 88 dB SPL/mW.

I have the PJCCS in the Quickie and that get the volumn up to just loud enouph for me. Had chokes wired in and that got the volumn useable but I prefer sound with the PJCCS.

New high impedance 'phones that top my old AKGs are about the price of a Crack kit, hence the dilemma.

 
 
Not technical input here but considering how you seem partial to your 240M's, seems that the most logical choice would be Crack rather than Beyers for the quickie.  I love my Beyers but I think your AKG's would probably benefit from the additional output of the Crack.  Certainly, it was designed with higher impedance cans in mind.  With my having the opportunity to purchase my 880's from a friend and also owning an older 600 ohm AKG, Crack was a logical choice and at the price, it was relatively low risk.  It is probably the best audio related decision I have made, atleast in the last dozen years. 
 
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