I understand, but my question is why not build an amplifier that provides 350 V RMS directly? For safety, because there aren't many designs for such amplifiers around, some other reason? (Just being curious.)
1) It never crossed my mind to do that. But 2) mostly because these headphones are no longer made, and if I screw the capsules up, I'm SOL.... and, they sound quite good as they are.
Lehman black Cube Linear
https://aliexpress.ru/item/33028799...eb201602_,searchweb201603_&sku_id=67199735925
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That's an interesting one, OldDIY. As are the ones based on Beyerdynamic A1 headphone amplifier also:
CIRMECH base on Beyerdynamic A1 headphone amplifier MC33078 BD139 BD140 architecture With headphone protect ALPS potentiometer|headphone amplifier|beyerdynamic a1 headphone amplifierbeyerdynamic a1 - AliExpress
but how will they handle 20 Ohms...
CIRMECH base on Beyerdynamic A1 headphone amplifier MC33078 BD139 BD140 architecture With headphone protect ALPS potentiometer|headphone amplifier|beyerdynamic a1 headphone amplifierbeyerdynamic a1 - AliExpress
but how will they handle 20 Ohms...
Id probably recommend the circuit in post #18, but perhaps with MJE15032/3 transistors instead of the BD139/140.
Probably not...
I made some output line drivers like these for a recording console back in the 90's and they worked really well, but they only had to drive a bit over a volt into 150 Ohms.
I made some output line drivers like these for a recording console back in the 90's and they worked really well, but they only had to drive a bit over a volt into 150 Ohms.
DIY: single ended class A running at <1A.
Otherwise you'll not get the best out of your headphones.
Circuits with op-amps and complex NFB loops...won't sound as good.
Otherwise you'll not get the best out of your headphones.
Circuits with op-amps and complex NFB loops...won't sound as good.
# 5 Class A on two transistors with a 20 ohm resistor load. The second could be BJT Darlington or Shiklai (or Mosfet).
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Use a power transformer whose two secondaries each deliver 18VAC (RMS). That'll get you plus and minus 23V supply rails for the amp, but call it plus and minus 20V to account for low-AC-mains conditions and to account for trafo output sag when load current is high. 20V rails will give you at least 14 watts RMS into an 8 ohm load.
Now just build a bog standard "Blameless" class-AB power amp using thru hole, discrete transistors, following Douglas Self's textbook exactly. Done.
Now just build a bog standard "Blameless" class-AB power amp using thru hole, discrete transistors, following Douglas Self's textbook exactly. Done.
