Kenwood KAC-PS621 Bedienungsanleitung

B53-0140-00 (N)2704

POWER AMPLIFIER

KAC-PS621

KAC-X621

SERVICE MANUAL

VOLTFAN

CURRTEMP

POWER IN RESET LINE IN LINE OUTREMOTETO H/UID NUMBER

Screw set

(N99-1752-05)

Screw set

(N99-1577-15)

Heat sink

(F01-1752-01)

Accessory

(W01-1606-05)

Cover

(F07-1140-12): KAC-X621

(F07-1141-12): KAC-PS621

Screw

(N07-0003-08) Screw

(N09-4214-08)

Fuse (25A)

(F52-0014-05)

KAC-PS621/X621

BLOCK DIAGRAM

●PREAMPLIFIER UNIT (X08-4150-10)

Ref. No Application / Function Operation / Condition / Compatibility

IC1 Infrasonic filter

IC3 Tone and volume variable Controlled by microprocessor

IC4 6dB voltage amplification

IC5 HPF

LPF

IC6 Lch : 6dB voltage amplification

Rch : Signal 180 reverse and 6dB voltage amplification

IC7 LCD driver Controlled by microprocessor

●AUDIO UNIT (X09-5770-10)

Ref. No Application / Function Operation / Condition / Compatibility

IC1 Buffer

IC2 DC/DC converter

IC3 AMP communication buffer

COMPONENTS DESCRIPTION

IC1,10

ISO AMP

ISO AMP ISF

ISF HPF

HPF BUFFER

BUFFER

LPF

CONTROL

MUTE

AMP

CONTROL

AMP

POWER

AMP

POWER

AMP

IC1 IC5 IC4,6 IC3 Q101 Q107-135

OUT

OPERATION IFS FILTER SENSITIVITY AMP CONT

OUT-R

OUT-L

H/U COM

AMP COM

IC6

O.C. PROTE.

D.C. PROTE.

T.M. PROTE.

O.V. PROTE.

5V AVR

+15V AVR

-15V AVR

BATT

GND

P-CON

Q66

u-COM

Q61

Q62

FAN

DISP.

MO/ST ON/OFF HPF/OFF/LPF 5V-0.2V ON/OFF

6dB 12dB 24dB

DC/DC CONV.

KAC-PS621/X621

Ref. No Application / Function Operation / Condition / Compatibility

IC5 H/U communication buffer

IC6 Microprocessor

IC7 Reset IC

IC9 Current detection

IC10 Isolation amplifier

Q50 5V AVR

Q51~54 DC/DC output driver

Q55~60 DC/DC drive (Final)

Q61 +15V AVR

Q62,63 -15V AVR

Q64,65 DC/DC converter (IC2) ON/OFF Controlled by microprocessor

Q66,68 5V AVR

Q69 5V AVR ON/OFF

Q70,71 P-CON control

Q81 +15V AVR (Constant current)

Q91,92 DC/DC control

Q97 AMP communication stability power supply

Q101,102 Mute

Q103~112 A class first stage amplifier

Q113~118 A class 2nd stage amplifier

Q119,120 Final temperature compensation

Q121~124 Amplifier current detection (Current limiter)

Q125~132 Final driver

Q133~140 Final

Q141 Mute control

Q142~145 Shock noise prevention

Q146,147 AMP current detection

Q148,149 DC detection

Q249,250,263

ATT control Synchronized with temperature detection

Q301~307 H/U communication output driver

Q310 H/U communication ON/OFF

Q313 H/U communication output driver

Q341~344 H/U communication input driver

Q346 H/U communication output driver

Q347~349 AMP and H/U communication ON/OFF control

Q351,352 BATT voltage output

Q353~358 Fan stability power supply

Q403 LCD backlight LED control

Q404 LED control

Q601,602 DC/DC drive (Final)

COMPONENTS DESCRIPTION

KAC-PS621/X621

AMP_SCL LX_REQ_M

LX_REQ_S

LX_DATA_M

LX_DATA_S

LX_CLK

LX_RST

HU_BU

AD-I

AD-V

TEMP1

TEMP2

TEMP3

TEMP4

TEMP5

TEMP6

COMM-SW

D-PWER

POWER-ON

5VSW

V_DOWN

PCON

LX_CON

L_DATA_L

L_DATA_A

L_CLK

L_CE

FAN1

FAN2

AMP_SDA

AUDIO_SCL

AUDIO_SDA

AUDIO_MUTE

E2P_SCL

E2P_SDA

LCD-ILL

WHITE-LED

MUTE1

MUTE2

DIP-SW1

DIP-SW2

DIP-SW3

DIP-SW4

MODEL1

MODEL2

DC-DET

D-CUR

AB-CUR

ATT1

ATT2

ATT3

AMP µ-com

784224YGC117

Audio control

AMP communication I/F LX BUS I/F

Display data monitor

Power supply control

LCD driver I/F

Fan control

Destination, AMP ID

Protection control

Illumination control

Mute control

E2PROM I2C

communication

●MICROPROCESSOR : 784224YGC117 (X09 : IC6)

◊Block Digram

◊Terminal Function

Pin No. Pin Name I/O Function Processing Operation Description

1~3 TEMP4~TEMP6 I Temperature detection 4~6

4AVSS - GND

5L_CE O CE output to LCD driver H : LCD driver CE

6 LX_REQ_S O Data transmit request to H/U H : OFF, L : ON

7AVREF1 - DA reference voltage

8L_DATA_L I Data input from LCD driver

9L_DATA_A O Data output to LCD driver

10 L_CLK O CLK output to LCD driver

11 LX_DATA_M I Data input from H/U

12 LX_DATA_S O Data output to H/U

13 LX_CLK I CLK input from H/U

14 LX_BU I LX BUS communication, H/U connect detection H : Not connect (Except master amplifier), L : Connect

15 NC O Not used

16 SDA_AMP I/O Data input/output AMP communication

17 NC O Not used

MICROCOMPUTER’STERMINAL DESCRIPTION

KAC-PS621/X621

Pin No. Pin Name I/O Function Processing Operation Description

18 SCL_AMP I/O CLK input/output AMP communication

19 AUDIO_SCL I/O CLK input/output with audio chip

20 AUDIO_SDA I/O Data input/output with audio chip

21 AUDIO_MUTE O Mute output to audio chip H : Mute OFF, L : Mute ON

22 E2P_SCL I/O CLK input/output with E2PROM

23 E2P_SDA I/O Data input/output with E2PROM

24 NC O Not used

25~28

DIP-SW1~DIP-SW4

IAMP address setting

29 MODEL1 I Model setting 1

30 MODEL2 I Model setting 2

31,32 NC O Not used

33 VSS1 - GND

34~37 NC O Not used

38 LCD-ILL O LCD backlight switch H : ON, L : OFF

39 WHITE-LED O Triangle illumination switch H : ON, L : OFF

40 NC O Not used

41~43 ATT1~ATT3 O Output attenuate due to rise in temperature 1~3 H : Attenuate, L : Not attenuate

44,45 NC O Not used

46 COMM-SW O Communication IC power switch H : ON, L : OFF

47~50 NC O Not used

51 D-PWER O D class amplifier power supply control H : ON, L : OFF (2ch/4ch L fixed)

52 DC-DET I Speaker output DC voltage detection H : Normal, L : Abnormal

53 NC O Not used

54 POWER-ON O Amplifier power supply control H : ON (D/AB class), L : OFF

55 5VSW O 5VSW H : OFF, L : ON

56 MUTE1 O Amplifier section input stage mute control H :OFF, L :ON

57 MUTE2 O Driver stage pop-noise mute control H : OFF, L : ON

58 FAN1 O Fan rotation control H : Operate, L :Stop

59 FAN2 O Fan speed control H : Low speed, L :High speed

60 RESET - Hard reset H : Normal, L : Reset

61 PCON I Amplifier power control H : OFF, L : ON

62 LX_CON I LX-BUS communication control H : OFF, L : ON

63 LX_REQ_M I Data receive request from H/U H : ON, L : OFF

64 NC O Not used

65 V_DOWN I Momentary power down detection H : ON (Power down detection), L : OFF (L fixed)

66 NC O Not used

67 VSS0 - GND

68 VD1 - VDD

69 X2 - Main clock input 1

70 X1 - Main clock input 2

MICROCOMPUTER’STERMINAL DESCRIPTION

KAC-PS621/X621

◊LogicTable

1) Destination

The destination in AMP does not mean the sales regions but

specific models.

The following are the models. When reset is released, it is

checked only once.

Model name MODEL1 (29pin) MODEL2 (30pin)

KAC-PS811D/X811D Low Low

KAC-PS521/X521 Low High

KAC-PS621/X621 High Low

KAC-PS541/X541 High High

Pin No. Pin Name I/O Function Processing Operation Description

71 TEST - Flash ROM writing

72 XT2 - Not used

73 XT1 - Not used

74 VDD0 - VDD

75 AVDD - VDD

76 AD-I I First current detection (for display)

77 AD-V I BU voltage detection (for display)

78~80 TEMP1~TEMP3 I Temperature detection 1~3

MICROCOMPUTER’STERMINAL DESCRIPTION

2) AMP ID

AMP ID is checked only ohce at the time reset is released or

when the microcomputer is released from the low consump-

tion mode.

When set to AMP ID 8/9 no remote control is possible.

AMP ID DIP-SW1 DIP-SW2 DIP-SW3 DIP-SW4

(25pin) (26pin) (27pin) (28pin)

0High High High High

1Low High High High

2High Low High High

3Low Low High High

4High High Low High

5Low High Low High

6High Low Low High

7Low Low Low High

8High High High Low

9Low High High Low

3) Fan speed

Operation FAN1 (58pin) FAN2 (59pin)

Stop Low High/Low

Low speed High High

High speed High Low

KAC-PS621/X621

CIRCUIT DESCRIPTION

AD-I

D309 (2/2)

IC9 (1/2)

IC9

AMP RECT

MPU AD-PORT

OUTPUT VOLTAGE

DETECTION

LEVEL

10u35

270

10K

15K

0.01 0.01

10K 1

13K

470

10K

Q301

Q303

Q305

Q307

to H/U

H/U GND

CONSTANT

CURRENT AMP

GND

from

MPU

3421

47 47

REQC

H/U-GND

100K

12K

1.5K

20K

IC3

J4 D302

D301

to OTHER AMP

RECEIVE

TRANSMISSON

to MPU

TRANSMISSON

RECEIVE

BOTH DIRECTION

BUFFER

4.3K

270

11 8

10u25

10K

1.8K

VCCSX

GND

TX TY

RY 6

CLK

DATA

No. Item Alignment Point Method Align For Note Fig.

1IDEL CURRENT VR1 (Lch) Connect a DC voltmeter between 2.5mV After Power on PC board

VR2 (Rch) check land A, B. 2 minutes (X09-577)

ADJUSTMENT

●Current detection circuit

Amplify and rectify potential differences at

two points in the primary-side current circuit

and send it to the AD-port of the MPU and

obtain data for displaying current value.

●Constant current output circuit

Remove troubles caused by the potential

differences between the constant current

output and the GND, so that the GND po-

tential differences between the H/U and the

AMP is not overlapped in the AMP to H/U

communication.

●I2C buffer

Using an IC for I2C communication, be-

tween-AMP communication is conducted so

that there will be no trouble from GND po-

tential differences.

KAC-PS621/X621

ABCDE

PC BOARD (COMPONENT SIDE VIEW)

R17

R55

R23

R24

C48

R78

R79 R69

R70

C49

C38

R34

R38 R18

R56

R110

R31

R29

C23

C35

C34

R45

R46

C33 R41

R42

R43

R44

C28

R25

R26

C21 R27

R28

C75

C27

R32

C22 C24

R30

R72

C74

R52

R74

R76

C73

R73

R77

R111

R109

R112

R107

R108

R104

R115

R106

R105

R101

R102

R103

C101 C102

C103

R114

C104

R11

R12

R21

R19

C29

C37

C30

R20

R10

C41

C42

C43

C44

C45

C40

C13

R22

R16

R14

R15

R33

C65

C12

R63

R64

C66

R65

C63

R39

R40

C64

R66

C11

C107

122

114

14 8

16 1

33 48

200Hz50Hz

5V 200mV

124

50Hz

200Hz

R13

R116

C105

C61

C10

C15

C16

C17

C18

C19

C20

C25

C26

C31

C32

C39

C67 C68

R117

LOW PASS

STMONO

OFFON

ON OFF

LPFOFF

INPUT SENS

HPF

HI PASS

ANP CONT I.S.F

503C 503C 103A

VR1

VR3 VR2

CN1

CN2

ED1

WH2

IC6

IC5

IC7

IC4

IC3

IC1

PREAMPLIFIER UNIT X08-4150-10 (J76-0010-12)

Refer to the schematic diagram for the values of resistors and capacitors.

X08-4150-10

Ref. No. Address

IC1 2D

IC3 6D

IC4 6D

IC5 6C

IC6 6D

IC7 4B

KAC-PS621/X621

JIHGF

PC BOARD (FOIL SIDE VIEW)

TP183

TP42

TP35

TP5

TP4

TP15

TP8

TP19

TP1

TP2

TP3

TP6

TP7

TP9

TP10

TP11

TP12 TP13

TP14

TP16

TP17

TP18

TP20

TP21

TP22

TP23

TP25

TP27

TP28

TP29

TP30

TP31

TP32

TP36

TP37

TP38

TP39

TP40

TP41

TP43

TP44

TP45

TP46

TP47 TP48

TP49 TP50

TP51 TP52

TP53

TP54

TP55

TP56

TP59

TP60

TP61

TP62

TP63

TP64

TP65

TP66

TP67

TP68

TP69

TP70

TP71

TP72

TP73

TP74

TP75

TP76

TP78

TP88

TP89

TP90

TP91

TP92

TP93

TP94 TP98

TP99

TP100

TP101

TP102

TP103

TP104

TP105

TP106

TP107

TP108

TP109

TP110

TP111

TP112

TP113

TP114

TP115

TP116

TP117

TP118

TP119

TP120

TP121

TP122

TP123

TP124

TP125

TP126

TP127

TP128 TP129

TP130

TP132

TP180

TP181

TP182

TP189

TP186

TP188

TP185

TP184

TP187

TP192

TP193

PEAMPLIFIER UNIT X08-4150-10 (J76-0010-12)

Refer to the schematic diagram for the values of resistors and capacitors.

KAC-PS621/X621

KLMNO

Q250

Q97

D354

D2D3

D312

D352

D353

Q354

Q351

Q352

Q357

D351

Q353

Q102

Q101

Q347

D301

D317

D302

Q349

Q348

D315

Q346

Q313

Q50

Q306 Q304

Q302

D316

D307

Q301

D311

Q303

D308

D303

Q310

Q307

Q305

D55 Q69

Q68

Q355

Q249

D257

Q147

D133

Q112 Q111

D313

D306

D314

Q341

Q344

Q343

Q342

Q263

Q148

Q149

Q141

D310 D132

Q63

Q145

Q144

D260

D131

D344

D103

D305

D304

D343 D341 D342

Q71

D70

Q70

Q62

Q356

Q358

D59

Q66

D108

Q61

D60

D71

D105

D106 D107

D109

D110

D111

D112

D114

D115

D116

D117

D118

D128

D130

Q103

Q104

Q105

Q106

Q107

Q108

Q109

Q110

Q113

Q114

Q115

Q116

Q117

Q118

Q120

Q122

Q123

Q124

Q125

Q126

Q127

Q128

Q129

Q130

Q131

Q132

Q134 Q136 Q137

Q138

Q140

Q146

Q403

Q404

Q142

Q143

Q81

CN10

IC10 IC1

IC7

IC8

IC5

IC6

IC3

AUDIO UNIT X09-5770-10 A/2 (J76-0007-01)

W368

R113

C11

W404

C12

R23

R16

R15

R21

R442

R22

R350

W372

W396

R19

R20

W403

R102 R101

W346 W390

W384

W386 R355

R354

C353

W385

R351

R352

R478

W371

R115

R104

R103

W382

C152W387

R224

C154

R222

R116

W388

W375

R250

R221

C151

R223

C153

W348

W360

R307

R303

C303

R306

W352

W359 W392

R311

W355

W351

R317

R315 W393

W349

W391

W345

C313 R308

R314

R312

W335

R326

R325

W395 W394

R324

C307

W339

R310

R241

C343

W342

R329 W341

R328

R79

C71

R77

W400

R52

W336

R360

C402

R459

R278

R277

R249

C603

C602

C406

W343

R195

R196

C142

R193

C65

R190

W383

R112

C106

W380

W379

R118

W373

R117

R203W377

W376

C105

R111

R142 R148

C128

W362

TH3

R140

C126

W354

W361

R67

C314

R272

R263

R269

R266

W327

R83

R192

R191

R177

R176

R175

R174 W316

C66

R70

R69

R92

C62

R183

R181

R186

R185

R141

C127

R182

R187

R188

R180

R178

R179

R110

W334

R339

C454

R476

R475

W366

R453

R481

C13

C14

R18

R17

R211

R212

R13

C21

R10

R14 R12

R11

W370

W369

C457

W389

R426

R425

R353

R450

R477

R482

W374

R402

C456

R356

R357

W381

R114

R429

R460

W347

R304

W402

C354

C305

R309

R349

W364

R348

W363

C453

R422

R421

C452

W365

R313

R458

R76

C302

C304

W344

R347

C311

C312

R338

R316 W337

W338

R323

R341

R86

W340

R74

R434

R479

R452

R451

R480

R454

R443 R455

R444

C451 W356

R433

C404

C405

W405

R483

R432

R423

R424

W350

R428

R427

R430

R431

R401 R80

R81

R194

R108

R189

R144

W357

W358 W353

R85

W401

R337

R336

R344

W330

R342

R84

R82

R199

R198

R197

R200

R107

W331

W332 R109

W321

R441

W399

W322

W329R93W324

R147

W323

W319

W398

R184

W217

W218

W101

W226

W214

C64

C138

W83

C257

W85

C401

C63

C109

W145

C147

W119

W68

C61

C67

C76

C103

C104

C111

C112

C137

C139

C140

C143

W107

C260

C301

C308

C349

C350

C351

C352

C358

C403

C70

W96

W200

W227

W87

R105

R106

W220

W45

W61

W62

C15 C16

C19

C101

C102

C107

C108

C115

C116

C117

C118

C119

C120

C122

C123

C124

C129

C130

C131

C132

C133

C134

C135

C136

C141

W75

W259

W203

W129

W63

W72

W197

R119

R120

R121

R122

R123

R124

R125

R126

R127

R128

R129

R130

R131

R132

R134

R136

R138

R145

R146

R152

R154

R156

R158

R160

R161

R162

R163

R164

R166

R168

R169

R170

R172

R173

R301

R302

R318

R319

R320

R321

R322

R334 R335

R345

W168

W219

W70

W41

W46

W44

W50

W48

W199

W187

W149

W260

W102

W176

W74

W142

W141

W192

W130

W110

W123

W57

W139

W53

W52

W49

W51

W47

W43

W73

W76

W77

W58

C17

W71

W177

W147

W91

W150

W173

W162

W160

W161

W159

W163 W137

W138

W67

W231

W124

W122

W104

W133

W171

W164

W180

W184

W153

W167

W165

W97

W135

W144

W172

W185

W175

W181

W78

W230

W131

W148

C69

W202

W90

W84

W81

W82

W134

W86

W66

W89

W65

W179

W194

W198

W195

W174

W191

W190

W92

W166

W158

W109

W64

W59

W60

W111

W125

W169

W114

W55

W106

W121

W196

W157

W178

W201

121

222

W193 W189

W188 W186

W154

W182

W152

W146

W140

W132

W112

W126

W127

W99

W105 W94

W98

W95

W108

W88

W118

W115

W155

W100

W54

W56

W143

W136

W80

W116

W151

W79

W183

W204

W232

C74

W229

W113

W42

W128

C18

W228

EB EB

34 1

EB EB EB EB E B

EB EB

BE BE BE

BE BE

BEBE

BE BE

BEBEBE BE

BEBE

DATA

CLK

+15V

-15V

+5V

Rch

TP1

TP4

TP6

TP7

TP12

TP10

TP22

TP21

TP20

TP19

TP18

TP16

TP15 TP14

TP11

TP2

TP24

TP26

TP27

TP28 TP29

TP30

TP31

TP32

TP33 TP34

TP35

TP37

TP38

TP39

TP36

TP25

TP40

I-GND

L-IN

R-IN

GND

GND GND

RESET

GND

TEST

Vdd

DA-S

CLK

TP5

TP23

TP3

I-GND

DC voltmeter

2.5mV

VR2

PC BOARD (FOIL SIDEVIEW)

X09-5770-10

Ref. No. Address

IC1 5L

IC2 5S

IC3 5M

IC5 5N

IC6 4M

IC7 4L

Ref. No. Address

IC9 4P

IC10 5K

Q50 5M

Q51 4S

Q52 5S

Q53 4S

Ref. No. Address

Q54 4S

Q55 3S

Q56 3S

Q57 4S

Q58 4S

Q59 5S

Ref. No. Address

Q60 4S

Q61 2N

Q62 2O

Q63 2N

Q64 5S

Q65 5T

Ref.No. Address

Q66 5N

Q68 5M

Q69 5M

Q70 6O

Q71 6O

Q81 3N

Ref.No. Address

Q91 4S

Q92 4S

Q97 5L

Q101 3L

Q102 3L

Q103 3L

Ref.No. Address

Q104 3L

Q105 3L

Q106 3K

Q107 3L

Q108 3L

Q109 3L

Ref. No. Address

Q110 3K

Q111 3L

Q112 3L

Q113 4N

Q114 4N

Q115 4N

Ref. No. Address

Q116 4N

Q117 4O

Q118 4N

Q119 2P

Q120 2M

Q121 2Q

Ref. No. Address

Q122 2M

Q123 2O

Q124 2L

Q125 3O

Q126 3M

Q127 3O

Dieses Handbuch passt für folgende Modelle

Inhaltsverzeichnis

Andere Kenwood Verstärker Handbücher

Kenwood

Kenwood KAC-6402 Bedienungsanleitung

Kenwood

Kenwood KA-501 Bedienungsanleitung

Kenwood

Kenwood KC-991 Bedienungsanleitung

Kenwood

Kenwood KAC-9020 Bedienungsanleitung

Kenwood

Kenwood BASIC M1D Bedienungsanleitung

Kenwood

Kenwood KAC-PS100 Bedienungsanleitung

Kenwood

Kenwood KA-1100D Bedienungsanleitung

Kenwood

Kenwood KAC-Q74 Bedienungsanleitung

Kenwood

Kenwood KAC-1021 Bedienungsanleitung

Kenwood

Kenwood KAC-714 Bedienungsanleitung

Kenwood

Kenwood NEXEDGE KAS-10 Bedienungsanleitung

Kenwood

Kenwood KAC-6201 Bedienungsanleitung

Kenwood

Kenwood KAC-X301T Bedienungsanleitung

Kenwood

Kenwood KA-95 Bedienungsanleitung

Kenwood

Kenwood KAC-X811D Bedienungsanleitung

Kenwood

Kenwood KAC-720 Bedienungsanleitung

Kenwood

Kenwood RA-54 Bedienungsanleitung

Kenwood

Kenwood KA-892 Bedienungsanleitung

Kenwood

Kenwood KAC-644 Bedienungsanleitung

Kenwood

Kenwood KAC-322 Bedienungsanleitung

Kenwood

Kenwood X501-1 Bedienungsanleitung

Kenwood

Kenwood KA-907 Bedienungsanleitung

Kenwood

Kenwood KAC-M1804 Bedienungsanleitung

Kenwood

Kenwood KAC-5202 Bedienungsanleitung

Beliebte Verstärker Handbücher anderer Marken

ASTRO

ASTRO HVO V40 P Bedienungsanleitung

Marantz

Marantz SUPERSCOPE BLA-545 Montageanleitung

NAD

NAD CI980 Bedienungsanleitung

Technics

Technics SE-CH770 Bedienungsanleitung

Harman Kardon

Harman Kardon HK6300 Bedienungsanleitung

NAD

NAD T975 Bedienungsanleitung

McIntosh

McIntosh MA6850 Bedienungsanleitung

Electro-Harmonix

Electro-Harmonix ENGLISH MUFF’N Bedienungsanleitung

Viatron

Viatron Autrix Bedienungsanleitung

GME

GME GA9800 Bedienungsanleitung

Atlas

Atlas CP700 Bedienungsanleitung

Roland

Roland KC-1000 Bedienungsanleitung

Pyle

Pyle PFMRA350BW Bedienungsanleitung

Advantage

Advantage S-250 Bedienungsanleitung

IRT Electronics

IRT Electronics DVA-3007 Bedienungsanleitung

Dimavery

Dimavery BA-100 Series Bedienungsanleitung

Sony

Sony XM-S400D Bedienungsanleitung

Schertler

Schertler ROY X Bedienungsanleitung