Page 1
1M
Trainwreck Blues Express
Version A5a
12AX7
33k
1.41vdc
20uF
195vdc
1k5
100k
1uF
poly
B+5
290vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Bass
250kB
Middle
25kB
Volume
1MA
12AX7
1.84vdc
20uF
220vdc
2k7
B+5
290vdc
100k
1uF
poly
B+1
356vdc
(381vdc)
.001uF
418P
56k
12AX7
2.87vdc
10k
B+2
354vdc
(379vdc)
273vdc
B+3
339vdc
(363vdc)
100k
B+4
304vdc
B+4
304vdc
(326vdc)
.022uF
418P
1M
12AX7
63.1vdc
56k
B+5
290vdc
(311vdc)
276vdc
1k5
56k
B+3
339vdc
418P
.022uF
418P
.022uF
418P
This version uses a Triode switch to
smooth out the response (which is
very harsh in the Pentode mode).
220K
5K6
25uF
220K
5K6
EL84
2
130/5w
2
356vdc
3
B+2
12.0vdc
3
356vdc
7
355vdc
9
9
7
1k
5W
1k
5W
355vdc
Pentode
EL84
Triode
Switch
B+1
8 ohm
Black
120vac
Power
White
Power
Switch
2.0A SB
Fuse
KT-17620
336vac
4 - 1N4007
3 - 10v/ 5w
zeners
100R
100R
Hi-V
Sw
To filaments
100uF
350v
100uF
350v
1k/5W
220k
220k
20uF
450v
4k7
20uF
450v
18k2
20uF
450v
9k1
"This amp was built on the chassis of an
Electar Tube 30 amp, which is advertised
20uF
450v
as a 25 watt Class A amp."
Inspired by designs
from Ken Fischer
Rev.05-12-00
Page 2
12AX7
Mojo SP10L50
33k
Input
Trim
1MA
20uF
Trainwreck Blues Express
Version A5b
B+5
1k5
196vdc
1.42vdc
100k
1uF
poly
291vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
12AX7
100k
2k7
20uF
250pF
228vdc
1.89vdc
1uF
poly
B+4
300vdc
100k
.001uF
418P
12AX7
56k
2.81vdc
10k
250pF
270vdc
B+4
300vdc
100k
.022uF
418P
1M
100k
12AX7
1M
58.9vdc
56k
259vdc
1k5
56k
This revision reduced the signal level and
treble response in the preamp for a smoother
sound in both cathode and fixed bias modes.
The power supply was also revised for lower
B+3
318vdc
B+ voltages to the EL84 plates.
100pF
.022uF
418P
.022uF
418P
220K
5K6
25uF
220K
5K6
EL84
2
130/5w
2
336vdc
3
11.2vdc
3
336vdc
B+2
7
324vdc
9
1k
5W
B+1
1k
5W
9
324vdc
7
8 ohm
Speaker:
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
B+1
338vdc
(356vdc)
10k
1k/5W
220k
20uF
450v
220k
Bias
–12.5vdc
B+2
334vdc
(352vdc)
4k7
20uF
450v
B+3
318vdc
(339vdc)
9k1
20uF
450v
B+4
300vdc
(320vdc)
(310vdc)
9k1
20uF
450v
B+5
291vdc
EL84
"This amp was built on the chassis of an
Electar Tube 30 amp, which is advertised
as a 20 watt Class A amp. It sounds like
an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Cathode/Fixed bias switch
not shown on this schematic
Inspired by designs
from Ken Fischer
Rev.06-25-00
Page 3
22k
12AX7
47k
Input
Trim
1MA
20uF
Trainwreck Blues Express
Version A5c
B+5
1k5
196vdc
1.42vdc
100k
poly
1uF
291vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
12AX7
100k
2k7
20uF
250pF
228vdc
1.89vdc
1uF
poly
B+4
300vdc
100k
.001uF
418P
12AX7
56k
2.81vdc
10k
250pF
270vdc
B+4
300vdc
100k
.022uF
418P
12AX7
1M
58.9vdc
56k
259vdc
1k5
56k
B+3
318vdc
1200pF
mica
.022uF
418P
.022uF
418P
This variation uses a crossline 150k/1200pF
RC network after the PI coupling caps to
reduce the AC voltage on the EL84 grids
and to cut some of the highs.
EL84
7
336vdc
11.2vdc
B+2
324vdc
9
1k
5W
1k
5W
9
324vdc
7
Bias
–12.5v
150k
5K6
220K
220K
5K6
130/5w
2
3
3
2
336vdc
8 ohm
B+1
Speaker:
Ruby
SP10L50
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
B+1
338vdc
(356vdc)
10k
1k/5W
220k
220k
Bias
–12.5v
334vdc
(352vdc)
20uF
450v
B+2
4k7
20uF
450v
B+3
318vdc
(339vdc)
9k1
20uF
450v
B+4
300vdc
(320vdc)
(310vdc)
9k1
20uF
450v
B+5
291vdc
Fixed Bias
Switch
25uF
EL84
"This amp was fine-tuned for blues tones,
with a sparkling clean sound that gets more
aggressive when you crank up the volume.
It sounds like an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.07-30-00
Page 4
22k
12AX7
47k
Input
Trim
1MA
20uF
Trainwreck Blues Express
Version A5d
B+5
1k5
196vdc
1.42vdc
100k
poly
1uF
291vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
12AX7
100k
2k7
20uF
250pF
228vdc
1.89vdc
1uF
poly
B+4
300vdc
100k
.001uF
418P
12AX7
56k
2.81vdc
10k
250pF
270vdc
B+4
300vdc
100k
.022uF
418P
12AX7
1M
58.9vdc
56k
259vdc
1k5
56k
B+3
318vdc
100pF
This variation uses 150k ** grid load
resistors (instead of 220k) to reduce
the AC voltage on the EL84 grids.
.022uF
418P
.022uF
418P
Bias
–12.5v
10k
150K **
150K **
10k
130/5w
336vdc
2
3
3
2
336vdc
11.2vdc
EL84
7
9
B+2
9
7
324vdc
1k
5W
1k
5W
324vdc
8 ohm
B+1
Speaker:
Ruby
SP10L50
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
B+1
338vdc
(356vdc)
10k
1k/5W
220k
220k
Bias
–12.5v
334vdc
(352vdc)
20uF
450v
B+2
4k7
20uF
450v
B+3
318vdc
(339vdc)
9k1
20uF
450v
B+4
300vdc
(320vdc)
(310vdc)
9k1
20uF
450v
B+5
291vdc
Fixed Bias
Switch
25uF
EL84
"This amp was fine-tuned for blues tones,
with a sparkling clean sound that gets more
aggressive when you crank up the volume.
It sounds like an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.08-12-00
Page 5
22k
12AX7
47k
Input
Trim
1MA
20uF
Trainwreck Blues Express
Version A5e
1k5
196vdc
1.42vdc
100k
poly
1uF
B+5
291vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
12AX7
100k
2k7
20uF
250pF
228vdc
1.89vdc
1uF
poly
B+4
300vdc
100k
.001uF
418P
12AX7
56k
2.81vdc
10k
250pF
270vdc
B+4
300vdc
100k
.022uF
418P
12AX7
1M
58.9vdc
56k
259vdc
1k5
56k
B+3
318vdc
4 - 17V
zeners
.022uF
418P
This variation uses zeners across the
EL84 grid stoppers to limit the AC voltage
on the grids. The optional 100pF caps
across the 100k * resistors add an LPF
effect triggered by the signal level.
Note: Add 100pF caps across
100k * resistors for LPF effect
.022uF
418P
Bias
–12.5v
100k *
100k *
10k
150k
150k
10k
130/5w
EL84
7
336vdc
324vdc
3
11.2vdc
3
336vdc
B+2
9
1k
5W
B+1
1k
5W
9
324vdc
7
8 ohm
Speaker:
Ruby
SP10L50
2
2
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
B+1
338vdc
(356vdc)
10k
1k/5W
220k
220k
Bias
–12.5v
334vdc
(352vdc)
20uF
450v
B+2
4k7
20uF
450v
B+3
318vdc
(339vdc)
9k1
20uF
450v
B+4
300vdc
(320vdc)
(310vdc)
9k1
20uF
450v
B+5
291vdc
Fixed Bias
Switch
25uF
EL84
"This amp was fine-tuned for blues tones,
with a sparkling clean sound that gets more
aggressive when you crank up the volume.
It sounds like an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.08-18-00
Page 6
22k
12AX7
47k
Input
Trim
1MA
20uF
Trainwreck Blues Express
Version A5f
1k5
196vdc
1.42vdc
100k
1uF
poly
B+5
291vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
12AX7
100k
2k7
20uF
250pF
228vdc
1.89vdc
B+4
300vdc
1uF
poly
B+1
338vdc
(356vdc)
100k
.001uF
418P
12AX7
56k
334vdc
(352vdc)
2.81vdc
10k
B+2
250pF
270vdc
B+3
318vdc
(339vdc)
B+4
300vdc
100k
.022uF
B+4
300vdc
(320vdc)
418P
12AX7
58.9vdc
1M
B+5
291vdc
(310vdc)
56k
B+3
318vdc
56k
.022uF
259vdc
1k5
418P
4 - 17.0V
zeners **
.022uF
418P
** For a more subtle
effect use 20V zeners.
This variation adds a switch to the zener
limiting circuit from version A5e. In the
center position the zeners are removed
from the circuit and in the up position the
100k resistors are bypassed with 100pF
mica caps for an LPF effect.
EL84
25uF
336vdc
2
2
9
3
B+2
11.2vdc
3
9
336vdc
EL84
Zener Limiter
Switch
4 - 100K
resistors
2 - 100pF
mica caps
Bias
–12.5v
Fixed Bias
Switch
10k
150k
150k
10k
130/5w
7
7
324vdc
1k
5W
1k
5W
324vdc
8 ohm
B+1
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
10k
1k/5W
220k
220k
–12.5v
20uF
450v
Bias
4k7
20uF
450v
9k1
20uF
450v
9k1
20uF
450v
"This amp was fine-tuned for blues tones,
with a sparkling clean sound that gets more
aggressive when you crank up the volume.
It sounds like an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.08-19-00
Page 7
22k
12AX7
47k
Input
Trim
1MA
20uF
Trainwreck Blues Express
Version A5g
1k5
196vdc
1.42vdc
100k
1uF
poly
B+5
291vdc
100k
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
12AX7
100k
2k7
20uF
250pF
228vdc
1.89vdc
B+4
300vdc
1uF
poly
B+1
338vdc
(356vdc)
100k
.001uF
418P
12AX7
56k
334vdc
(352vdc)
2.81vdc
10k
B+2
250pF
270vdc
B+3
318vdc
(339vdc)
B+4
300vdc
100k
.022uF
B+4
300vdc
(320vdc)
418P
12AX7
58.9vdc
1M
B+5
291vdc
(310vdc)
56k
B+3
318vdc
56k
.022uF
259vdc
1k5
418P
100k
100pF
4 - 17.0V
zeners **
.022uF
418P
** For a more subtle
effect use 20V zeners.
This variation adds two 27k resistors in
series with the zener limiting circuit to
make the effect more subtle. The EL84
grid stoppers were also returned to the
earlier value of 5k6 to restore some of
the chiminess to the clean sounds.
EL84
25uF
336vdc
2
2
9
3
B+2
11.2vdc
3
9
336vdc
EL84
Zener Limiter
Switch
27K
2-100k
27K
Bias
–12.5v
Fixed Bias
100k
100pF
Switch
5k6
150k
150k
5k6
130/5w
7
7
324vdc
1k
5W
1k
5W
324vdc
8 ohm
B+1
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
10k
1k/5W
220k
220k
–12.5v
20uF
450v
Bias
4k7
20uF
450v
9k1
20uF
450v
9k1
20uF
450v
"This amp was fine-tuned for blues tones,
with a sparkling clean sound that gets more
aggressive when you crank up the volume.
It sounds like an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.08-25-00
Page 8
12AX7WB
Input
Trim
1MA
22k
Sovtek
47k
1k5
20uF
The Blues Express
Version A5h
B+5
185vdc
1.49vdc
100k
1uF
poly
285vdc
100k
0.22uF
poly
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
Sovtek
12AX7WB
100k
2k7
20uF
250pF
209vdc
1.99vdc
B+5
285vdc
1uF
poly
B+1
344vdc
(364vdc)
100k
.001uF
418P
56k
250pF
Sovtek
12AX7LPS
270vdc
2.94vdc
10k
B+2
B+3
319vdc
333vdc
(351vdc)
(337vdc)
B+4
300vdc
100k
B+4
301vdc
(318vdc)
12AX7LPS
.022uF
418P
20.8vdc
1M
B+5
285vdc
(301vdc)
Sovtek
56k
261vdc
57.8vdc
1k5
56.1vdc
56k
This is the final version of the Blues Express
amp. The zener limiting circuit was removed
and a modified cross-line MV was installed
in its place. The bias/grid load resistors were
returned to their original value of 220k.
The 2nd stage supply was rewired to B+5
B+3
318vdc
instead of B+4 and the 0.22uF/630v poly cap
from B+5 to ground was drawn in.
2
10.89vdc
2
25uF
344vdc
3
B+2
3
344vdc
270k
.022uF
418P
.022uF
418P
0.22uF
Bias
–12.5v
Fixed Bias
MV
1MA
Switch
5k6
220k
220k
5k6
130/5w
9
9
7
7
330vdc
1k
5W
1k
5W
330vdc
EL84
8 ohm
B+1
Speaker:
Jensen
P10-Q
EL84
Black
120vac
Power
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Hi-V
Sw
Bias Adj
10kB
10k
1k/5W
220k
220k
Bias
–12.5v
20uF
450v
4k7
20uF
450v
9k1
20uF
450v
9k1
20uF
450v
"This amp was fine-tuned for blues tones,
with a sparkling clean sound that gets more
aggressive when you crank up the volume.
It sounds like an old BF amp on Viagra..."
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.11-13-00
Page 9
12AX7WB
Input
Trim
1MA
22k
Sovtek
47k
1k5
20uF
Blues Express Plus
Version A8a
B+5
.047uF
209vdc
1.99vdc
(351vdc)
100k
100k
1uF
poly
B+2
333vdc
285vdc
.0068uF
715P
Fat Switch
B+3
319vdc
(337vdc)
.0016uF
180k
715P
B+4
301vdc
(318vdc)
12AX7LPS
185vdc
1.49vdc
100k
1uF
poly
B+5
285vdc
100k
0.22uF
poly
50pF
mica
.022uF
418P
.022uF
418P
Treble
1MA
Volume
Bass
250kB
Middle
25kB
1MA
Smooth Switch
22M
100k
Sovtek
12AX7WB
(364vdc)
22M
20uF
B+1
344vdc
2k7
Sovtek
82k
B+5
285vdc
(301vdc)
270vdc
2.94vdc
10k
B+4
300vdc
100k
.022uF
418P
1M
Sovtek
12AX7LPS
261vdc
20.8vdc
57.8vdc
1k5
56.1vdc
56k
The Blues Express Plus adds a "Fat" switch to allow
for more Marshall-ish sounds by using a switchable
.0068uF coupling cap after the second stage. In
the other modes this cap is run in series through a
.0016uF cap which results in a net capacitance
of 1295pF. A center-off DPDT switch was used
to toggle the grid load of the 3rd stage from 56k
B+3
318vdc
to 82k in the two "blues" modes, while dropping
to 45k to cut the gain a bit in the "Fat" mode.
B+2
9
9
7
330vdc
1k
5W
1k
5W
330vdc
7
EL84
0.033uF
630v
EL84
0.022uF
630v
B+1
10k
10W
Conjunctive
Filter Switch
8 ohm
Speaker:
Jensen
P10-Q
56k
.022uF
270k
.022uF
418P
418P
0.22uF
Bias
–12.5v
1MA
5k6
MV
150k
150k
5k6
130/5w
Fixed Bias
Switch
344vdc
2
3
10.89vdc
3
2
344vdc
25uF
120vac
Power
Black
White
Power
Switch
1.5A SB
Fuse
KT-17620
336vac
5 - 10v / 5w
100R
470R / 1W
4 - 1N4007
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Bias Adj
10kB
1k/5W
220k
220k
Hi-V Switch
–12.5v
10k
Bias
20uF
450v
The switchable conjunctive filter was used to smooth
9k1
4k7
9k1
out the response of the amp, making the 250pF caps
across the 2nd and 3rd plate resistors unnecessary.
20uF
450v
20uF
450v
20uF
450v
With the .022uF and .033uF caps in series the net
capacitance is .0132uF.
The Smooth switch is a local feedback loop between
the plate and grid of the 2nd stage. The traditional
value of 22M allows for a compressed sound while
the alternate value of 44M has a more subtle effect.
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.05-03-01
Page 10
Sovtek
12AX7WB
1M
1k5
20uF
185vdc
1.49vdc
Blues Express Plus
Version A9b
B+5
209vdc
1.99vdc
100k
1uF
poly
285vdc
.01uF
418P
Cut
50kB
10k
.01uF
418P
B+1
344vdc
(364vdc)
.005uF
418P
2200pF
1kV
1k/5W
100k
1uF
poly
B+5
285vdc
100k
0.22uF
poly
50pF
1kV
.022uF
418P
.022uF
418P
Black
Treble
1MA
Bass
250kB
Middle
25kB
Power
Switch
Volume
1MA
Bright Switch
500pF
1kV
(2 - 4M7)
KT-17620
336vac
120pF
1kV
820R
20uF
4 - 1N4007
Sovtek
12AX7WB
2k7
Sovtek
12AX7LPS
56k
B+2
333vdc
(351vdc)
(337vdc)
4k7
50pF
270vdc
2.94vdc
10k
B+3
319vdc
9k1
B+4
300vdc
B+4
301vdc
(318vdc)
100k
.022uF
418P
9k1
1M
285vdc
(301vdc)
Sovtek
12AX7LPS
20.8vdc
56k
B+5
261vdc
57.8vdc
1k5
56.1vdc
56k
B+3
318vdc
270k
.022uF
418P
The Blues Express Plus is a radical reworking of the
Blues Express chassis along the lines of more
traditional Trainwreck designs. The conjunctive filter
is the key to getting a smooth response from this
preamp with the output section using the stock Electar
Tube 30 OT; without the conjunctive filter the sound
would be extremely brittle and harsh.
EL84
7
10.89vdc
25uF
344vdc
330vdc
9
2
2
3
3
344vdc
B+2
1k
5W
1k
5W
9
330vdc
7
EL84
0.02uF
630v
0.02uF
630v
B+1
10k
10W
Conjunctive
Filter Switch
8 ohm
.022uF
418P
0.22uF
–12.5v
Fixed Bias
Switch
Bias
MV
1MA
5k6
150k
150k
5k6
130/5w
Speaker:
Jensen
P10-Q
120vac
Power
White
1.5A SB
Fuse
5 - 10v / 5w
100R
470R / 1W
zeners
To
Fils
20-0-20vac
100uF
100v
100uF
350v
100uF
350v
Bias Adj
10kB
220k
220k
Hi-V Switch
Bias
–12.5v
10k
20uF
450v
20uF
450v
20uF
450v
20uF
450v
The Cut control may be either a trim pot or a front
panel control and allows you to shape the sound
from the preamp much like the Cut control on an
AC-30. You may need to increase the value of the
10k fixed resistor if you get oscillations or nasty
sounds at lower settings of the control.
Revisions from Versions 2 & 5
shown in RED
Inspired by designs
from Ken Fischer
Rev.05-06-01
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