What's the best 78xx/79xx and B649/D669 replacement?

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smellygas said:
B649/D669 transistors in the output stage. Are there premium versions or equivalents that can drop in as well?

Matsushita A1535/C3944(A), for a close to equivalent SOA.
(on the other hand, the DC curve in a SOA graph has little bearing, and Hitachi was not willing to share more than just that single DC-line)

Humor me, why would anyone use B649/D669 as output devices of a headphone amp with opamp front end ?
I'd sooner pick a 600MHz straight as an arrow Sanyo A1536/C3951 pair than those Hitachi numbers.
British design by chance ?
 
Lumba Ogir said:
Jacco and Andrew,
the A1536/C3951 are video transistors and will unlikely sound good under heavy load. Sanyo uses the MBIT process in current amplifiers.

My thoughts are that much slower transistors are good enough for audio. Again, it will depend on the actual design and how well it handles Cob. (I assume the whole point of low-Cob transistors is to minimize HF rise in distortion?)

- keantoken
 
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