paranoidandroid
Active member
- Joined
- Jun 3, 2004
- Messages
- 38
Hey there, i'm putting together a bastard version of the hamptone preamp from Tape-op and i've been having some problems! The main difference is that i'm using an altec 1588C as the input transfo, this provides 34 db of gain running at 18v and also puts out at 600ohms, and then a 15356A 600:600 bridging transfo for balanced output. Between the transfo's i have the two stages just like in the article. My problem is that the darlington in the second stage is overheating, it's not an MPSA14 but it is in a 220 package so it should definetly not be on the verge of melting like it is. I've changed the 10Mohm resistor at the source to 10K. I'm using 2n5089's as the bipolars and closely matched 2n5457's that bias slightly above 12v. I have 100K's in place of the 47Ks to the bipolars but the voltage drop across the 100ohm resistors to ground is still well above 4v(PRR said it should be at 4 or under) until i raise the values to around 220K which seems pretty high. This is kinda my first real experiment off the beaten track so i have no idea what could be going on. Thanks for reading all this!