by EWBrown » Fri May 27, 2005 7:34 am
I have built the BottleHead "SEX" amp, uses 6DN7 spud tubes as a 2WPC SET amp. It is also set up as a headphone amp, the phone jack is the standard 1/4 in dia 3 conductor type. The 8 ohm speaker outputs are connected through 120 ohm 1/2 watt resistor for each channel. It sounds great with Sennheiser HD-600s! Itr is a good idea to load the 8 ohm speaker outputs with 8 or 10 ohm 2W resistors.
This 120 ohm resistors-in-series method is pretty much of an industry standard, for feeding phones with a power amp. This works well with 'phones between 32 and 300 ohms impedance. If anything this helps to preserve one's hearing...
I've seen the HeadWize site, and have printed out the schematics and parts list. I'm planning eventually to build one up, using a 6080 rather than a 6AS7 (identical specs) just because I have several 6080s, and only one 6AS7, and that one is rather "questionable" shape.
I've played around with LM380 and 386 IC headphone amps in the past, and was really underwhelmend by their poor sound... Tubes are the way to go.
After listening through $15 CD player grade 'phones, the Senns are a real awakening! Antique Sound Labs and others have latched onto the tube headphone amp market already, their units sell between $400 and 800, for relatively simple circuitry. The fancier ones have a line stage and 3 or 4 source selector switch.
/ed B in NH
Real Radios Glow in the Dark