K&K Audio / Lundahl Transformers

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Which Lundahl line out for bass preamp?

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Posted on May 10, 2016 at 13:39:15
andy evans
Audiophile

Posts: 4382
Joined: October 20, 2000
 I'm a bass player and thinking to make a small tube preamp. Just one 12AX7 could do it, but the second stage would need an output transformer if it were to feed something like a digital amp stage. Second stage like first stage is a typical 12AX7 one - 100K plate resistor, 1.5K bypassed cathode resistor.

What would you guys suggest from the Lundahl range? Give me a few options.

 

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RE: Which Lundahl line out for bass preamp?, posted on May 10, 2016 at 14:55:16
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 That's a tough application for a transformer due to the high plate impedance of a 12AX7 in grounded cathode connection. The bass register will suffer the most, ironically, right where it will sonically hurt the most. I couldn't recommend any transformer I know of for that job. Whether it's parafeed or series feed, you would need to have a plate impedance closer to 20K to make a full bandwidth output stage. Of course, you could build a two stage 12AX7 amplifier with global feedback to drive the transformer....like much of the 70s tube gear (without the transformer, of course!).

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: Which Lundahl line out for bass preamp?, posted on May 11, 2016 at 10:11:39
drsx
Audiophile

Posts: 369
Location: around
Joined: September 11, 2005



You can also add a source follower and drive just about any transformer with ease.

 

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