Hello Peeps...
I was wondering what types of transistor peeps have used in their easy face builds. A 2n3906 seems to be the most common for Q1 & I've got a couple of AC128, OC71 etc for Q2. Any thoughts on what 'sounds best' so to speak. Also, are there any common problems I should be on the lookout for ?? Just getting back in to building after becoming a Dad for the first time & I don't seem to have the time (or patience) for Olympic sized debugging :)
Thanks in advance.
i like 2n3906 for Q1. i have tried others but i forget.
for Q2, gain of around 125 using Rg's method sounds great to me, but anything from 90 to low 100s works pretty well also.
if Q2 isn't too hot, to get a better match, try gus smalley's trick of reducing Q1 gain with a 100 or 200 ohm R to ground at Q1 emitter. or a 500 ohm trimmer to check it out.
I've built my easy face with a 2n3096 at Q1 and an ac128 with a hfe of about 120 at Q2. I wasn't getting any effected signal, so I ran my APC through it and got the audio probe out. Basically, the signal starts to degrade heavily as soon as I get to the output of the 100k pre-gain pot. I swapped out the pot and the wires connecting it just in case. Same problem. The signal has disappeared altogether by the time I get to the input caps.
I've tested it with my voltmeter and I'm getting readings at both transistors. I've also checked all connections & solder points.
Hmmm. I'm devoid of ideas.
don't know if that is a typo, but you need a 2n3906, not 2n3096
Hahaha. It was a typo.
After more investigation, it seems the signal is being lost somewhere at Q2. I've tried different transistors there & it's the same with each one. I can hear a faint crackle when I turn the 10k bias pot & the 'noise' rises when I turn the volume pot
i've checked the layout so many times my head hurts. I may just rebuild it tomorrow.
i laugh at the time i've spent debugging, sometimes i could have built the thing 3 to 5 times over in the time i spent debugging.
i keep telling myself that the debugging is forcing me to learn something, WTF was it again?
Quote from: 1878 on July 28, 2012, 01:17:35 PM
i've checked the layout so many times my head hurts.
have you checked the voltages once?
Yuppity.
Everything was fine apart from the volume pot. Swapped it out & it's all working fine. I like/love it !! I'm gonna mess with transistors this weekend & see what fits best.
Thanks Joe !!