Probably because of limiting the power dissipation of each transistorI`m interested to know the VAS of the Harman Kardon powers amplifiers.Why has two transistors in paralllel? Q417-421 and Q419-423.
#3 is correct. Smaller devices, sharing the current, will have lower parasitic capacitances and be faster. This has profound impact on the sound quality.
Modern devices like the 2SC3423 will run higher currents - up to 15mA with ease - so two devices may no longer be needed.
Hugh
Modern devices like the 2SC3423 will run higher currents - up to 15mA with ease - so two devices may no longer be needed.
Hugh
If just so, then why use a parallel pair in the Vas and a higher power device with nearly identical specs as driver ?
http://www.diyaudio.com/forums/solid-state/98631-bjts-vas-stages.html#post1165309
(= $6000 msrp Class A amp)
Vas : 2SA1145/2SC2705
Driver : 2SA1360/2SC3423
http://www.toshiba.com/taec/components2/Datasheet_Sync//66/7580.pdf
http://www.toshiba.com/taec/components2/Datasheet_Sync/66/7540.pdf
http://www.diyaudio.com/forums/solid-state/98631-bjts-vas-stages.html#post1165309
(= $6000 msrp Class A amp)
Vas : 2SA1145/2SC2705
Driver : 2SA1360/2SC3423
http://www.toshiba.com/taec/components2/Datasheet_Sync//66/7580.pdf
http://www.toshiba.com/taec/components2/Datasheet_Sync/66/7540.pdf
If you use an EF to drive the VAS, you will pick up about 2dB lower H2 and 15dB lower H3 with no change to other artefacts at +20dBU and 1KHz. For very large output stages, a buffer on the VAS is a good idea too.
For domestic amps, I've never found any benefit with a buffer after the VAS.
Jacco,
Bloody good question.....
Cheers,
Hugh
For domestic amps, I've never found any benefit with a buffer after the VAS.
Jacco,
Bloody good question.....
Cheers,
Hugh
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