Help with phono preamplifier selection

[Panelhead]

I just finished a PassDIY Pearl and need just a little more gain. Maybe 20dB or so. I am using an AN UK transformer to get it up to about the same level as the disc player and tuner. But would love to do it with active amplification. Do any posters have a simple circuit suitable as a moving coil amplifier.
I have single rail supplies, very quiet and around 20v available to power either a transistor or opamp. Looking for warm, full bodied, fast, dynamic, and quiet. Not asking for much.
The MM input is close to the jacks, the leads could be pretty short on both ends. Currently the unit is very quiet even with the transformer.

George

[analog_sa]

Try 2 parallel 2sk170; drain - 1.2k, source - each 33R, whatever loading resistor suits you at the gate, 2.2uF output cap. Plays fine with 300uV carts and with NiMH batteries, tantalum resistors and MIT RTX output caps better to my ears than any transformer i've tried

[Panelhead]

Originally posted by analog_sa
Try 2 parallel 2sk170; drain - 1.2k, source - each 33R, whatever loading resistor suits you at the gate, 2.2uF output cap. Plays fine with 300uV carts and with NiMH batteries, tantalum resistors and MIT RTX output caps better to my ears than any transformer i've tried

Thanks, I will breadboard one up and give it a try. What voltage battery do you use? The input stage in my phono has a well filtered supply putting out 11 volts. Can this be used instead of the battery?

George

[analog_sa]

I use 16v but 11v should be fine. Choose a value for Rd which will give you approx half the supply on the drain. Such low level amps with near zero PSRR are extremely sensitive to power supply quality - that's why i use batteries

[Panelhead]

Originally posted by analog_sa
Try 2 parallel 2sk170; drain - 1.2k, source - each 33R, whatever loading resistor suits you at the gate, 2.2uF output cap. Plays fine with 300uV carts and with NiMH batteries, tantalum resistors and MIT RTX output caps better to my ears than any transformer i've tried

I am about to put this together. It is very close to the input stage of the Pearl. I have purchased 2SK170 transistors from MCM several times. They are not listed as GR, BL, or V. But looking at the transistors they are the GR and BL classification.
The Pearl uses the BL type and the IDSS runs 2 - 3 ma with 11 volts Drain to Source. Is there an advantage to using the GR at the low current levels?

George

[Panelhead]

Originally posted by analog_sa
Try 2 parallel 2sk170; drain - 1.2k, source - each 33R, whatever loading resistor suits you at the gate, 2.2uF output cap. Plays fine with 300uV carts and with NiMH batteries, tantalum resistors and MIT RTX output caps better to my ears than any transformer i've tried

I am about to put this together. It is very close to the input stage of the Pearl. I have purchased 2SK170 transistors from MCM several times. They are not listed as GR, BL, or V. But looking at the transistors they are the GR and BL classification.
The Pearl uses the BL type and the IDSS runs 2 - 3 ma with 11 volts Drain to Source. Is there an advantage to using the GR at the low current levels?

George

[john curl]

This is complicated. Normally use the highest current to get the lowest noise. If you HAVE to starve the fets, then the GR parts may work best, but the BL parts are actually better operating at nominally higher currents. Run at high current, if possible.

[Jocko Homo]

Keep the operating voltage down if noise is important. I would use under 15 volts.

Jocko