Amp/Preamp Asylum Looking for a new Amp or Preamp? If you're after tubes, post over here. |
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Got to a point where I might benefit from having a buffer amp in one rig I'm fooling with, so I was looking at those little tube preamps from eBay that run on a wall-wart power supply. Their main attraction is that are certainly cheaper than anything I can build myself. Then my old tube-design synapses started tingling...
They *can* work but there are critical design considerations. I think the performance potential of a miniature twin triode with 12-25V on the plate is pretty limited. Ultimately I was dissuaded by not wanting electrolytics in the signal chain, which this kind of rig would likely introduce. Unless maybe if it's a cathode follower... A cathode follower is very sensitive to input and output impedances (and power supply) so again, low probability of getting high performance potential.
Whatever the case, if you get one of these and the bias isn't adjustable, you can't "roll" tubes.
This article about the design of these is intelligible and points to the limitations of putting a very low voltage on the plate of a tube designed for at least 100V B+.
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Topic - Thinking of one of those little triode preamps from eBay? - mr.bear 12:48:25 12/03/16 (10)
- RE: Thinking of one of those little triode preamps from eBay? - niws 05:09:58 12/06/16 (0)
- RE: Thinking of one of those little triode preamps from eBay? - Greg Cz 11:19:57 12/05/16 (0)
- little triode preamps, buffers or headphone amp/buffer ? - Interstage Tranny 16:25:38 12/04/16 (3)
- modded or straight up? - Scholl 05:13:56 12/10/16 (2)
- Yes, even straight up... - Interstage Tranny 16:45:49 12/11/16 (1)
- RE: Yes, even straight up... - Scholl 04:25:55 12/16/16 (0)
- "the one rig Im fooling with" - Awe-d-o-file 20:33:26 12/03/16 (0)
- RE: Thinking of one of those little triode preamps from eBay? - ahendler 13:25:31 12/03/16 (2)
- I bought a $200 one. Worthless. Found a $4,500 preamp for $1,400. Worth it as a 'glorified' tube buffer... nt. - Smelly_Socks 14:13:34 12/03/16 (1)
- RE: I bought a $200 one. Worthless. Found a $4,500 preamp for $1,400. Worth it as a 'glorified' tube buffer... nt. - John Elison 16:27:19 12/03/16 (0)