If you're like me, what drew you to the Pearl2 was the adjustable gain in the 'opamp' style 2nd stage. You could adjust the gain to fit the different output levels of cartridges. Unfortunately that's what also kept me from starting!
Dual supply, picking gain resistors, choosing compensation caps, 'instability' ... some people seemed to be having trouble ...
We'll here's an easy way to get started and have the rest of the circuit working before tackling the 2nd stage. There are no cuts to the PCB and the only 'damage' is the gentle bending (use 2 needlenose!) of 1 outer leg on 1 precious JFET.
The powersupply simplicity of the of the Pearl2 and the 2nd stage simplicity of the Pearl1! Ladies and gentlemen, a hybrid ... the Pearl1.5!
The full board
The normal 1st stage
Ah, now the Pearl1.5 second stage!
From a bunch of angles so you can see what's going on:
Here's the circuit of the second stage from the Pearl1
View attachment pass pearl1 phono.pdf
Instead of using the unobtainium dual 389FET, I used two 170s in parallel with 10 ohm to gnd like in the 1st stage.
So, from the top you have:
1) 1k going from the bottom of R6 to the top of Q5
2) ztx450 in Q5 (facing the opposite way) with it's top leg going to the top of Q4
3) bridge from the middle of Q4 to the top of R26
4) bridge from the top of C7 to the bottom of C7
5) 10k from the top of Q2 to the bottom of R15
6) 10k from the top of R14 to the bottom of R25
7) 170FET in Q10 (facing the opposite way) with a bridge from the middle of Q10 to the top of R27
8) 170FET in Q11 (facing the opposite way) with its top pin bent to the top of Q10
9) 10ohm from the top of R28 to the bottom of R14
10) 10ohm from the top of R29 to the bottom of R14
11) bridge from top of R17 to bottom of R17
12) regular C8, C13 (output caps! Needed because the output is at half the supply voltage ~ 12V ***note polarity*** silmic2 bypass with Panasonic P polypro) and R18 (output resistor)
Ta Da! It's playing now! I was too excited and I just hooked it up! (I know, I know unsafe but I ... just ... woohoo!)
I'll come back and do some measurements but that second stage should be about in the middle of the voltage swing ...
I've been having the time of my life finding little gems in the used vinyl section for $1!
You've got no excuses! Go for it!!!
The Pearl is awesome!
Cheers,
Jeff
Dual supply, picking gain resistors, choosing compensation caps, 'instability' ... some people seemed to be having trouble ...
We'll here's an easy way to get started and have the rest of the circuit working before tackling the 2nd stage. There are no cuts to the PCB and the only 'damage' is the gentle bending (use 2 needlenose!) of 1 outer leg on 1 precious JFET.
The powersupply simplicity of the of the Pearl2 and the 2nd stage simplicity of the Pearl1! Ladies and gentlemen, a hybrid ... the Pearl1.5!
The full board
The normal 1st stage
Ah, now the Pearl1.5 second stage!
From a bunch of angles so you can see what's going on:
Here's the circuit of the second stage from the Pearl1
View attachment pass pearl1 phono.pdf
Instead of using the unobtainium dual 389FET, I used two 170s in parallel with 10 ohm to gnd like in the 1st stage.
So, from the top you have:
1) 1k going from the bottom of R6 to the top of Q5
2) ztx450 in Q5 (facing the opposite way) with it's top leg going to the top of Q4
3) bridge from the middle of Q4 to the top of R26
4) bridge from the top of C7 to the bottom of C7
5) 10k from the top of Q2 to the bottom of R15
6) 10k from the top of R14 to the bottom of R25
7) 170FET in Q10 (facing the opposite way) with a bridge from the middle of Q10 to the top of R27
8) 170FET in Q11 (facing the opposite way) with its top pin bent to the top of Q10
9) 10ohm from the top of R28 to the bottom of R14
10) 10ohm from the top of R29 to the bottom of R14
11) bridge from top of R17 to bottom of R17
12) regular C8, C13 (output caps! Needed because the output is at half the supply voltage ~ 12V ***note polarity*** silmic2 bypass with Panasonic P polypro) and R18 (output resistor)
Ta Da! It's playing now! I was too excited and I just hooked it up!
(I know, I know unsafe but I ... just ... woohoo!)
I'll come back and do some measurements but that second stage should be about in the middle of the voltage swing ...
I've been having the time of my life finding little gems in the used vinyl section for $1!
You've got no excuses! Go for it!!!
The Pearl is awesome!
Cheers,
Jeff
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