General description:
All resistors are standard metal film 250mW except: R1/3/4/7, these are 2W metal film, and the 0.22ohm beeing 5W. Around R7 is wounded a 0.6mm isolated (enamelled) copper wire forming the output coil. (~12 windings) For c19 i used 470uf/16v, all other electrolytics 63v. The 10/100/330pF should be mica-caps. The 100nf and 47nf is recommended to be Wima MKS2 (or better), also for C1 i suggest Wima MKS2, 4.7uf is enough. For Trimpot i use a Piher. The MPSA18 can be substituted by BC550C, for all other parts i do not recommend changes, especially the feedback network (r29/30) should be kept unchanged, feedback compensation is very delicate for this circuit ! Be careful when substituting the MPSA18 with BC550C, the pinout is reversed between these 2 transistors !!! The bias is adjusted via the trimpot (R22). Recommended bias is 55ma, resulting in 12mv across a single 0.22ohms or 24mv across both 0.22ohms. Connect a DMM to the upper wires of these resistors and adjust trimpot until DMM reads wanted voltage.
Features:
THD: ~0.005% (measured) sim'd: 0.002%
Power into 8ohm: 60 watts
Power into 4ohm: 100 watts
Gain: 32dB (~1:40) full output at 0.7v input (0.5v rms)
Feedback: 57dB
GainBandWidth: ~400Mhz
Slewrate: ~20v/us (symetrical)
Supply voltage: +/- 36v
Biasing: 55ma, ~12mv across a single 0.22 ohm
Measurings:The measuring setup itself is far from perfect, but gives a good idea !
Frequency response: 3.2hz to 145khz (-1db) using 4.7uf input cap
Phaseshift at 10khz: <3°
More will follow !
Circuit Diagram:
 |
| 100w audio amplifier circuit diagram |
Layout Diagram:
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| 100w audio amplifier layout diagram |
Partlist:
Device
|
Qty
|
Value
|
Notes
|
Q1,Q2
|
2
|
MPSA18
|
can be substituted by BC550C (pins reversed !)
|
Q7,Q8
|
2
|
BC546B
|
or maybe 2n5551 (pins reversed !)
|
Q3,Q9
|
2
|
2N5551
|
OnSemi/Fairchild/Philips
|
Q4,Q5,Q12
|
3
|
2N5401
|
OnSemi/Fairchild/Philips
|
T1
|
1
|
BD139
|
or bd135, bd135-16
|
U$5
|
1
|
MJE15030
|
OnSemi
|
U$6
|
1
|
MJE15031
|
OnSemi
|
U$3
|
1
|
MJL3281A
|
OnSemi
|
U$4
|
1
|
MJL1302A
|
OnSemi
|
Device
|
Qty
|
Value
|
Notes
|
C14
|
1
|
10pF (has been 22pF)
|
Mica
|
C2,C7
|
2
|
100pF
|
Mica
|
C3,C4
|
2
|
330pF
|
Mica
|
C18
|
1
|
47nF
|
Wima MKS2
|
C5, C6, C10, C11, C16, C17, C20
|
7
|
100nF
|
Wima MKS2
|
C1
|
1
|
10uF (4.7uF also fits)
|
Wima MKS2
|
C8,C9
|
2
|
100uF
|
Electrolytic 63v (at least 40v)
|
C19
|
1
|
470uF
|
Electrolytic 16v
|
C12,C13
|
2
|
1000uF
|
Electrolytic 63v (at least 40v)
|
Device
|
Qty
|
Value
|
Notes
|
R27,R28
|
2
|
0R22
|
5Watts
|
R1, R3
|
2
|
1R2
|
2Watts metal film
|
R4
|
1
|
4R7
|
2Watts metal film
|
R7
|
1
|
10
|
2Watts metal film
|
R2
|
1
|
10
|
250mW metal film
|
R8, R9
|
2
|
22
|
250mW metal film
|
R31, R32
|
2
|
47 (have been 22)
|
250mW metal film
|
R26
|
1
|
33
|
250mW metal film
|
R10
|
1
|
68
|
250mW metal film
|
R15,R17
|
2
|
150
|
250mW metal film
|
R11
|
1
|
220
|
250mW metal film
|
R24,R30
|
2
|
499 (or 500)
|
250mW metal film
|
R5,R6
|
2
|
680
|
250mW metal film
|
R13,R23
|
2
|
2k
|
250mW metal film
|
R12,R14,R29
|
3
|
22k
|
250mW metal film
|
R18,R20
|
2
|
47k
|
250mW metal film
|
R22
|
1
|
1k pot
|
Piher, small (470ohm might be better)
|
Device
|
Qty
|
Value
|
Notes
|
F1,F2
|
2
|
2.5T Fuse
|
Slow blow
|
F1,F2
|
2
|
---
|
Fuse holder
|
L1
|
1
|
---
|
0.6mm isolated (enamelled) copper wire wounded around R7 forming the output coil.
|
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