[IDEA] Hybrid amplifier: tube + class D - Printable Version +- Moode Forum (https://moodeaudio.org/forum) +-- Forum: Audiophile (https://moodeaudio.org/forum/forumdisplay.php?fid=32) +--- Forum: Audio gear (https://moodeaudio.org/forum/forumdisplay.php?fid=10) +--- Thread: [IDEA] Hybrid amplifier: tube + class D (/showthread.php?tid=3302)

Hybrid amplifier: tube + class D - STUDI - 12-27-2020 My hybtrid tube preamp + class D power stage prototype amplifier. First step: volume potentiometer with switch, switch power by relay, DIP switch to configure oscillator frequency of power stage.  Major changes in next version: no DIP switches, oscillator set to 1.2MHz, dealy muting and no power switch because capacitors with low ESR can stick the contacts together. Minor changes: increased load on the anode voltage converter to reduce the noise level. The appearance of the first (prototype) version:   Final schematic (for the next versions): Inductors: MSS1210 - 10uH: L1-L4, 1.5mH: L5 MSS1278 - 330uH: L6 MSS7348 - 680uH: L7, 1mH: L8 All inductors manufactured by Coilcraft Capacitors types: MKS2: C3, C4, C9-C12 0805 size, X7R: C31, C32, C41-C43, C44, C46, C48, C49, C54, C55 1206 size, X7R: C13-C16, C52, C57, C58 1812 size, X7R: C21-C24  0805 size, C0G: C1, C2, C5, C6, C17, C29, C30, C39, C40 1206 size, C0G: C17-C20, C25-C28 hybrid (OSCON): C7, C8, C45, C47, C51, C53 standard aluminium: C33-C38, C50, C56, C59 Capacitors voltages: C5, C6, C56, C57, C58: 100V C7, C8, C9, C10, C51: 63V C3, C4, C11, C12, C20-C32, C39-C43, C46, C48-C50, C54-C56: 50V C33, C34, C35, C36, C37, C38, C59: 35V C47: 25V C44: 16V C45: 10V Resistors: Mini-MELF 0204: R1-R16 MELF 0207: R17-R20 1206 0.5W: R30 0805 0.125W - all others Resistors tollerance: 1% all Mini-MELF, MELF and R31, R32, R34, R35 5% all others Electron tubes: V1, V2, metal-ceramic (nuvistor) triodes, mu=32, gm=11.5mA/V - 6S51N or 6S51N-V (russian products). V3, subminiature magic eye DM70 Layout of PCB top side: bottom side: PCB dimensions: 147mm * 98mm Preamplifier stages, typical voltage stages on triodes. Cathode resistors unblocked. The achieved gain of the degree is approximately 14 times. Magic eye controlled by two voltage doublers with a common output condenser. Both rectifiers are supplied directly from the positive output terminals. No regulation, for full control of the 22.5 - 24 V voltage generator, the "exclamation mark" is completely extinguished. IC2 - a buck converter that powers lamp glow. Set the VR1 potentiometer to 6.3V at TP1 point. IC3 - a boost converter for 47V anode voltage for tube preamplifiers and 70V voltage supplying the magic eye. The R33 resistor adds an additional load to the converter, reducing the noise level. T1 - automatic mute after failure detected by TPA3116 system. T2, RL1 - mute after turning on the power, eliminating two crackles in the loudspeakers, the first after switching on the voltage and the second when the preamplifier tubes are already emission. RE: Hydrid amplifier: tube + class D. - STUDI - 12-27-2020 Design assumptions: Sensitivity is sufficient for commercial level (-10dBV / 316mVrms). Output power: 2 * 32W/8Ω at 24V supply Bandwith -0.5dB: better than 20Hz-20kHz Bandwith -3dB: better than 10Hz-45kHz  Measurement: Software: RMAA 6.4.5 on Windows 10 x64 Audio interface: Focusrite Scarlett 2i2 2gen. Load: real speaker sets Supply: industrial power supply 24V/100W, manufacruter: Delta Results for full undistorted power Noise RMS: L: -85.6dB R: -84.2dB Noise RMS (A): L: -86.9dB R: -85.5dB Noise peak valuse: L: -71.8dBFS R: -70.1dBFS DC offset: L: 0.00% R: 0.00% THD: L: 0.366% R: 0.387% THD+noise: L: 0.367% R: 0.387% THD+noise (A): L: 0.483% R: 0.509% IMD+N: L: 0.407%, R: 0.356% IMD+N (A): L: 0.251%, R: 0.271% IMD+N (swept freq): 5kHz: L: 0.422%, R: 0.450% 10kHz: L: 0.226%, R: 0.240% 15kHz: L: 0.175%, R: 0.184% Crosstalk 100Hz: L->R: -58.6dB, R->L: -65.1dB 1kHz:  L->R: -66.1dB, R->L: -67.3dB 10kHz: L->R: -62.6dB, R->L: -51.8dB Noise level: THD: IMD: Results for ~-12dB level Noise RMS: L: -73.0dB R: -72.6dB Noise RMS (A): L: -74.5dB R: -73.8dB Noise peak valuse: L: -58..4dBFS R: -48.8dBFS DC offset: L: 0.00% R: 0.00% THD: L: 0.103% R: 0.111% THD+noise: L: 0.112% R: 0.120% THD+noise (A): L: 0.138% R: 0.149% IMD+N: L: 0.123%, R: 0.114% IMD+N (A): L: 0.079%, R: 0.089% IMD+N (swept freq): 5kHz: L: 0.120%, R: 0.128% 10kHz: L: 0.083%, R: 0.126% 15kHz: L: 0.080%, R: 0.083% Crosstalk 100Hz: L->R: -62.9dB, R->L: -67.7dB 1kHz:  L->R: -68.7dB, R->L: -66.1dB 10kHz: L->R: -65.6dB, R->L: -51.4dB Noise level: THD: IMD: Note: The distance from the right speaker system to the tubes during measurements is less than 50 cm, from the left one about 80 cm. Please note that the microphone of the tubes affects the crosstalk. The DC voltages of the SPICE simulation match better than 10% with the measurements of the assembled prototype. *$ .SUBCKT 6S51N  1 2 3 ; P G C (Triode) 21 May 2004 by GaLeX + PARAMS: MU=54.72  EX=1.248  KG1=123.5  KP=99.63  + KVB=300.0  VCT=0.00 RGI=1500 + CCG=4.2P  CGP=1.8P CCP=2.5P E1 7 0 VALUE= +{V(1,3)/KP*LOG(1+EXP(KP*(1/MU+(V(2,3)+VCT)/SQRT(KVB+V(1,3)*V(1,3)))))} RE1 7 0 1G G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1} RCP 1 3 1G    ; C1 2 3 {CCG}  ; C2 2 1 {CGP}  ; C3 1 3 {CCP}  ; D3 5 3 DX     ; R1 2 5 {RGI}  ;      .MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N) .ENDS RE: Hydrid amplifier: tube + class D. - STUDI - 12-27-2020 In action: https://files.fm/down.php?i=znh8ub82e