Discrete All-Transistor RIAA-Equalized MM Phono Preamplifier 2.

[@jim9930]

Looks like ~2nv/rt Hz or the equivalent noise of 200 ohm resistor. Perfect transistor matching with five 1845's should be around 1.4nv (3dB better or ~150r). ie The two quietest ones are doing all the heavy lifting, higher Hfe, lower Vbe. Nice project! It would be interesting to try MPSA06 or 2N4403 (PNP)... Also, your at the equivalent noise of two paralleled LM4562's 👍 {below vinyl surface noise}

[@buildaudioamps]

Thanks!

[@jim9930]

@@buildaudioamps So I did try a single 2N4403 (30r emitter resistor, R21 in your circuit) and found the noise to be 3.1nV / rt Hz at 1ma. I didn't bother to reverse engineer the values in your preamp; but it shouldn't be too hard to modify the board for PNP's and the emitter current for the 5 parallel 1845's / RIAA filter Z's (flip the caps and change the sex of the other transistors). Built a two stage 2N4403, 2N3904 with a gain of 100 just to measure the noise and distortion with 10uv input. ~.01% thd at 100uv rising to .1% at 1vrms output (9v battery)

[@buildaudioamps]

@@jim9930 Thank you for the info!

[@robertkovar8710]

switching DC-DC XL6009 (400kHz) for phono is act of brutality, :) you need low noise power supply - linear (capacitive multiplier or shunt )

[@buildaudioamps]

Please refer to the schematic diagram. Test results showed otherwise. Thanks.

[@joancarlescanadas5123]

Totalmente de acuerdo; es un circuito elevador de tensión que, usa señal de conmutación y produce ruido ; se deben usar una power supply convencional con transformador separador, estabilitzador y filtros bobinados o bancos de baterias de 1,5V en serie, hasta obtener los 32V de trabajo. Piensenlo!

[@robertkovar8710]

for maximalist LT3042, preregulation LM317

[@buildaudioamps]

@@joancarlescanadas5123 My reference power amplifier is an Icepower 1000ASP, shop.icepoweraudio.com/wp-content/uploads/2023/02/ICEpower1000ASP_Datasheet_1_7.pdf. It does not have a transformer, but is an audiophile professional high quality power amplifier. Thanks.

[@saanjayray]

Nice one

[@buildaudioamps]

Thanks