High Quality Vacuum Tube Headphone Amplifier

Theres no transformer in output, it only need coupling capacitor in the signal path is the output cap. A relay circuit was used to provide muting and a time delay was used to keep the output muted during warm-up in order to protect the headphones from the high voltages that would otherwise be present at the output of the amplifier.

A separate chassis was used for the power supply to keep noise levels as low as possible. Selection of input tubes (6SN7s) for low noise is important in order to realize the full capability of this circuit. Since I already have a regulated source of 12 volts DC, I intend to modify this amplifier in the future to use 12SX7s.

The power supply is a fairly conventional design using a 6550a as a series pass regulator and a zener string to set the operating voltage.

The amplifier circuit is a 6SN7 run in grounded cathode mode and is self-biased using an un-bypassed cathode resistor. The input stage is direct coupled to a 6CA7 that is used as a cathode follower. The output from the 6CA7 is coupled to the headphones using a 47uF capacitor, providing extended bass response. The output capacitors are bypassed with 1uf and .01uF polystyrene capacitors. An Alps 'Black Beauty' volume control is used to help preserver sonics and easily allows adjustment at low gain levels with adequate tracking between the two channels.

A switchable cross-feed circuit is present at the input of the amplifier to be used to help correct imaging problems, if desired.

source : kevin.kevino.org

Schematic of Hadphone Amplifier

Power Supply of Headphone Amplifier

Super Headphone Amplifier

Output Illustration

Spec. of Super Headphone Amp.

Output (in Class A) :
160mW at 8  Ohm
600mW at 30 Ohm
120mW at 600 Ohm

Distortion :
Less Than 0.01% at Normal Outout

Schematic

PCB1

PCB2

Parts List :

Reslstor :
R1,R1',R4,R5,R18,R18' = 1 k
R2.R2',R9,R9',R17,R17' = 22 k
R3,R6 = 27 k
R7,R7' = 220 k
R8,R8',R19,R19' =2k2
R10,R10',R13,R13' = 4k7
R14,R14',R20,R20' = 330 Ohm
R15,R15' = 3k3
R16,R16' = 1k5
R21,R21',R23,R23' = 820 Ohm
R22,R22',R24,R24' = 1 Ohm/1 W Carbon
P1,P2 = 50 k(47 k) Trimpot
P3,P3' = 2k5 (2k2] Trimpot
PAPA' = 10 k Trimpot

Capasitor :
C1,C1',C6,C6' = 22 p/10 V
C2,C3 = 47 uF/4 V
C4,C4' = 220 uF/4 V
C5,C5' = 33 p
C7,C7',C8,C8’ = 100 n

Semi Conductor :
T1...T5,T3',T4',T5'.T10,T11,T11',T12,T12' = BC 550C
T6...T9,T6'...T9',T14,T14' = BC 560C
T13,T13' = BD 139
T15,T15' = BD 140

Other Parts :
F1,F1' =  500 mA Fuse with socket
headsink for T13,T13',T15,T15'

Portable Headphone Amplifier

Here I present a very simple and impressive headset company Schedule using NE5534/2 . Moreover to the IC NE5534/2, the routine uses only few non-active components and can easily generate a lot of sound from even the most worthless headphones and there will be no deal for the fantastic.

The 5534/2 is a low-distortion, low-noise program, having also the automobile capabilities low-impedance a lot to a finish present shift while maintaining low shape disturbances. Furthermore, it is absolutely result short-circuit proof. Therefore, this routine was used with just one 5532 brand creating a number of songs, inverting amplifiers, having an ac acquire of about 3.5 and able to provide up to 3.6V peak-to-peak into a 32 Ohm finish (corresponding to 50mW RMS) at less than 0.025% complete harmonic shape disturbances (1kHz & 10kHz).

Schematic

Parts List :
P1 = 22K
R1 = 18K
R2 = 68K
R3 = 68K
R4 = 68K
R5 = 18K
R6 = 68K
C1 = 4.7uF/25v
C2 = 4.7uF/25v
C3 = 22pF
C4 = 220uF/25v
C5 = 220uF/25v
C6 = 4.7uF/25v
C7 = 22pF
C8 = 220uF/25v
J1 = 3.5mm Stereo Jack
B1 = 9V Alkaline Battery
IC1 = NE5532 or NE5534
SW1 = SPST Toggle Switch

Class A Headphone Amplifier

The headphone firm was a simple routine to design. This is due to the fact that neither the fill features nor the strength demands in the result is very difficult to obtain because the earphones are generally having a 50 ohm and higher fill impedance up to 600 ohms. For the regular result, it will only require 1 V to 2 V RMS at highest possible. A category A level of firm is recommended because only low strength is necessary on this routine. Frequently, category A amps include a continuous present transistor linked from result to adverse strength and a pushed transistor linked from result to good strength. The continuous prejudice present runs immediately from the good provide to the adverse provide in the lack of feedback indication. This will result with no result present but with several capabilities absorbed.

In this routine, the transistors Q5 and Q6 should be ranked at 100 mA each, to be able to work as category A firm properly. A strength result of 1.5 H is created from the 15 V strength. A small heatsink is necessary though for each transistor. The sound feedback indication is specific by a 10K ohm logarithmic potentiometer RV1 while the result DC balanced out current for 0 V is specific by the slimmer TR1. Two tour will be required however, if it is suitable for music program.

                                                                                    Component List :

R1-4= 1.2Kohm
R2-3= 3.9Kohm
R5=100Kohm
R6-10= 10Kohm
R7-9= 2.2Kohm
R8= 150 ohm
R11-13= 6R8 ohm
R12= 4.7 ohm R14=68Kohm
RV1= 10Kohm Log. pot.
TR1= 10Kohm Trimmer
 

C1= 4.7uF 63V MKT
C2-7= 100uF 25V

C3-5= 100nF 100V MKT
C4-6= 100uF 16V
C8-10= 470uF 25V
C9-11= 100nF 100V ceramic
Q1-3= BC184
Q2-4= BC214
Q5= BD136 or BD538
Q6= BD135 or BD537
All resistors are 1/4W 1%

Noise reduction class-D headphone driver amplifier

The NE58633 is a noise reduction stereo Class D Bridge-Tied Load (BTL) helmet driver amplifier. Each channel has a Class D driver's helmet BTL amplifier, a electret microphone preamplifier for low noise, noise reduction circuit and returned to the music amplifier input.

NE58633 is the battery voltage from 0.9 V to 1.7 V, the chip employs on-chip DC-DC boost converter and the internal reference voltage Vref which is filtered and country of origin of noise removal. It is a mute control, and plop, and then click a reduction circuit. The amplifier gain of the microphone and amplifier of the filter is fixed with external resistors. Differential architecture provides better noise immunity.

The NE58633 is able to drive through a 800 mVrms 16 Ω or 32 Ω load and offers Electrostatic discharge (ESD) protection and short circuit. Available in 32-pin HVQFN32 (5 mm x 5 mm x 0.85 mm) package for high density of small and layout is ideal for noise-reduction headsets and audio teaching aids.

Caracteristic of NE58633

- Low current consumption of 4.4 mA

- 0.9 V to 1.7 V battery operating voltage range

- 1 % THD+N at VO = 1 VM driving 16 Ω with a battery voltage of 1.5 V

- 10 % THD+N at 800 mVrms output voltage driving 16 Ω and 32 Ω loads with a battery voltage of 1.5 V

- Output noise voltage with noise reduction circuit typically 31 mVrms for Gv(cl) = 25 dB

- On-chip mute function

- Plop and click reduction circuitry

- Class-D BTL differential output configuration

- Electret microphone noise reduction polarization amplifier with external gain adjustment using resistors

- Music and filter amplifier with external gain adjustment using resistors

- DC-to-DC converter circuitry (3 V output) with 2.5 mA (typical) load current

- Internal voltage reference pinned out for noise decoupling

- Available in HVQFN32 package

Block Diagram

 

Pin Out

Schematic Aplication

HI-FI Stereo Headphone Amplifier

 

 Features:

High performance - low noise and distortion

High and low impedance drives

High output power (up to 200mW;? At 8 and 32?)

Dual connectors for headphones - can drive two pairs!
Works with any power amp or line level audio

 

Measured performance:

Frequency Response ........................................................................... flat from 10Hz to 20kHz (see charts)
Nominal ....................................................................................... 200mW into 8? and 32?, 85mW at 600?
Max. output (current or voltage limited )........................ 575mW into 8?, 700mW into 32?, 130mW at 600?
Harmonic Distortion ...................................................................... Typically 0.0005% (600? Load) 0.001%

                                                                                                        (32? Load) and 0.005% (8? Charge)
Signal to Noise (weighted ).................................... -130 DB (600?),-120dB (32?) And 111dB (8?) For the 

                                                                                                                          output   power of 100mW.
Crosstalk ...................................................................... better than-68 dB from 20 Hz to 20 kHz at 100m? 

                                                                                                                            output power (see charts)
Input Impedance .................................... ~ 47k? | | 47pF
Output ..................... ~ 5?