DIY Front End 2022

Ya I wouldn't sweat a teeny tiny bit of rolloff like that graph in the article. That's like tenths of a db there in your area of concern..

Another quick thing.. C1 is really optional if you can be certain that anything feeding this circuit does not have DC on it. A greenhorn might be better off leaving it in place as a safety blanket. If a source has DC offset, the individual that designed it should be drawn and quartered because that's not acceptable in my world.
 
You can skip the RC on the rails. But I think capacitance on the output of the regs is still recommended.

Somehow the store FE '22 boards get by without compensation caps. Be sure you check for stability on your new pcb, it may oscillate with a different, less optimized layout.
 
Last edited:
15mA is a good ball park number. The actual number may be a bit higher or a bit lower.

R11 and R12 form a voltage divider for the unipolar power supply option, to equally divide the voltage between the two capacitors. It is not needed if the power supply is bipolar, although it can be left in place.
 
I have wired the pre as balanced input,single output and with a 36v single supply.I am getting a slightly variable static sound at all times that increases with volume control. It is on both channels. Is this transistors failing? Appreciate any suggestions to cure this problem.
 
Does it work - does it play music? Or does it only output static?

Have you double checked component placements, wiring, and solder joints? Bad solder joints can result in noise.

Post some clear, focused pictures. Include shots of the overall construction and closeups.
 
I'm stuffing resistors into a bunch of boards, (V0 and V1) and came across an ambiguity (at least in my eyes). Guidance on setting the gain is clear here:
The balanced input version assumes R1=R2 and R3=R4, and the gain is set by R3/R1. Unity
gain is achieved by R1=R3. You can run the input unbalanced/single-ended with arbitrary
resistor values and by attaching the -IN to ground.
But I'm not sure what to do with R4. I've selected 30k for R3 and will be using a 48VDC positive supply with single-ended input. Should R4=R3 as directed above with balanced input, or use 100k as shown on the schematic since I will be using single-ended input?

TIA, Skip
 
For unity gain and SE input, I would go R1=R2=R3=R4=10k

Connect -IN to GND

For something other than unity gain, keep things real simple and just do R1=R2, R3=R4 as specified, balanced or not. As a more advanced move with just an SE input, you can use R3 to set the input impedance, and R1 forms an RF input filter along with the combined capacitance of the input jfets (2x Q1). For further confusion, I still keep the ratio the same from R1,R3 and R2,R4 in my current setup.
 
Last edited: