#166816  by Incaroads77
 Wed Jan 29, 2020 10:32 am
I recently upgraded the cathode bypass caps in a Fender preamp clone I built to tantalum 150d series Spragues. They have a super bright top end (not in a good way) and some burn-in time is needed. It seems these are the standard bypass caps in the AB763 for Jer tone and i wanna give them a chance. What methods do you guys use for burning in components on a fresh amp? I currently have pink noise running to the input with a power amp and speakers connected (its essential for there to be a load on the preamp while its on right?) I have the bass down, treble up, volume up on the settings. Curious to see what the most common method is.
 #167659  by claytushaywood
 Sun Jul 19, 2020 4:22 am
It’s crazy how much a capacitor composition in the cathode bypass positions changes the sound of those preamps!

I actuallly ended up changing the metal film plate resistors to high end Takman 1/2w carbon films. (Best of both worlds really). And used a polystyrene 250pf treble cap instead of silver mica. That tamed the harshness a bit. But yeh. High action also helps so you’re not getting any sort of buzz with that super bright jerry setup.

I’m super interested in your diy preamp. Would you mind sharing some pics? Or how you went about the transformers, enclosure, reverb, circuit board- I really wanna build my own or gas t someone to build me a rack mountable tube preamp with tube driven spring reverb and a small power amp on board- like a one watt single ended tube or a solid state 10-20watter.