Burns Sonic Solid State Amplifiers
Including Baldwin Burns and Baldwin versions
The Sonics. Burns' move into more affordable alternatives to the Orbit series.
For 'Vibrato' read 'Tremolo'
Originally offered as the 'Burns' Sonic 20, 30 and 50, the range was updated after the Baldwin takeover and reissued as the 'Baldwin Burns' Sonic 25, 35 and 55. The new cabinet designs were more in line with Baldwin's own American equipment, although the circuitry stayed British.
These newer versions were updated yet again, badged simply as 'Baldwin' and featuring new circuitry and revised panel layouts. If the badges are missing (not unusual) the quick giveaway is the position of the mains switch. 'Baldwin Burns' units have the switch in the back of the cabinet and 'Baldwin' units have it on the front panel.
The Baldwins all offered an extra five watts because -
"Baldwin-Burns engineering experience and know-how have 'Power Boosted' the Sonic range of amplifiers...without sacrifice to tonal purity and quality components."
So now we know.
They also offered a range of colours for the cabinet covering:-
Saddle Tan
Jay Blue
Gold
Charcoal Grey
Silver Jet Black
Cardinal Red
Sage Green
Tangerine
Honey
White.
Somebody must have collected them all ! Photographs appreciated.
Testing:-
Power ratings quoted as 'British' will be rms at some crazy distortion level. The Sonic 30 below made a continuous twenty five watts at clipping.
Speaker loads were either three or six ohms depending on the model.
Noisy? Yes, after fifty years they often are, but it's nothing that can't be fixed. Whether the cost is justified is another discussion.
Expect to find the footswitch and control knob inserts missing and the celluloid control panel overlay buckled. Makes you wonder who's got all the footswitches stashed away doesn't it?
Still working on this page. Things added as they turn up.
IMPORTANT: These drawings and notes are provided for interest only and are not guaranteed to be accurate. Use at your own risk and discretion. The equipment shown contains lethal voltages and should only be worked on by people with suitable training and experience. Schematics and layouts are typical but will vary.
PRINTING
Wix (bless 'em 😖) have changed their image format - again - to avif just to make them awkward to print. Unless you want to buy a converter, the easiest way to make a hard copy is:
-
Left click when the magnifying glass icon appears and wait for the picture to clear.
(On a touch screen, tap on the image). This will display a higher res file. -
Right click and 'save image as' to somewhere as an avif file.
(On a touch screen, touch and hold down to view the menu) -
Upload the saved file to your Google Drive.
-
Open the file and use the print menu to make a hard copy or save as a pdf.
Burns Sonic 20
Catalogue No. 546
Advertised Power Output: 20watts (British)
Size:
Weight:
Speakers: 2 x 10"
CONTROLS
Channel 1:
Input x 1
Volume, Treble, Vibrato Intensity, Vibrato Speed.
Power On/Off Switch
Channel 2:
Treble, Volume.
Input x 1
Captive Vibrato Footswitch in the back of the cabinet.
Baldwin Burns Sonic 25
Catalogue Number 601
Baldwin Burns Control Panel
Baldwin Control Panel
Catalogue Description
Power Output: 25watts (British Rating) at less than 10% distortion
Loudspeakers: Two 10inch, reinforced construction
Mains Supply: 200-250 volts, 40-60 cps, no adjustment required
(100-125 volts to order)
Size : -
Weight: -
Channel 1:
-
Input: High impedance, 200k ohms
-
Controls (Baldwin Burns): Volume, Bass, Treble, Vibrato Intensity and Speed
-
Controls (Baldwin ): Volume, Treble, Vibrato Intensity and Speed
Channel 2:
-
Input: High impedance 200k ohms
-
Controls: Volume and Treble
General (Baldwin Burns):
-
Captive vibrato footswitch in the back of the cabinet
-
Power On/Off switch in the back of the cabinet
General (Baldwin):
-
Captive vibrato footswitch in the back of the cabinet
-
Power on/off switch on the front panel
Burns Sonic 30
Catalogue No. 544
Advertised Power Output: 30watts (British)
The measured output was 25watts rms at clipping into 6ohms
(See the speaker rating)
Size: 23"w x 19"h x 91/8"d
Weight: 30Ib (13.7kg)
Speakers: 1 x 12" (Orbital (Fane), Model 122/14, 6ohms, 22watts)
CONTROLS
Channel 1:
Inputs x 2
Volume, Bass, Treble, Vibrato Intensity, Vibrato Speed.
Power On/Off Switch
Channel 2:
Treble, Volume.
Input x 1
Captive Vibrato Footswitch in the back of the cabinet.
Burns Sonic 30 Schematic
Left click to enlarge (see printing instructions above).
Burns Sonic 30 Wiring Layout
Left click to enlarge (see printing instructions above).
Spot the earth loop.
NOTES:
This particular chassis had a non-working vibrato and a permanent, very loud rushing noise. These are test results for the transistors using a Peak DCA55
The vibrato oscillator TR1 was u/s and TR6 was causing the noise. If the silicon Bush ss325s are causing problems they can be replaced with BC327s. AC128s work fine in the oscillator at a quarter of the price of 213s.
RIGHT:
After nearly sixty years, there can be a large amount of crossover distortion. This can be cured by increasing the base bias voltages slightly with a series resistor in each of the driver transformer secondary windings. In this case it needed an extra 0.5ohms. Check for thermal runaway afterwards though.
IMPORTANT: There should be an M5 or 2BA fibre washer between each of the mounting pillars and the bottom of the circuit board. There's a potential short circuit, track to ground, in one place. The other washers are there to keep the board level.
Baldwin Burns Sonic 35
Catalogue Number 602
Baldwin Burns Control Panel
Baldwin Control Panel
Catalogue Description
Power Output: 35watts (British Rating) at less than 10% distortion
Loudspeaker: 12 inch heavy duty, 6 ohms impedance
Mains Supply: 200-250 volts, 40-60 cps, no adjustment required
(100-125 volts to order)
Size: 25"w x 20"h x 10"d
Weight: 35Ib (16kg)
Channel 1:
-
Input: Two high impedance, 200k ohms
-
Controls (Baldwin Burns): Volume, Bass Middle Treble, Vibrato Intensity and Speed
-
Controls (Baldwin): Volume, Bass, Treble, Vibrato Intensity and Speed
Channel 2:
-
Input: High impedance 200k ohms
-
Controls: Volume and Treble
General (Baldwin Burns):
-
Captive vibrato footswitch in the back of the cabinet
-
Power On/Off switch in the back of the cabinet
General (Baldwin):
-
Captive vibrato footswitch in the back of the cabinet
-
Power on/off switch on the front panel
Baldwin Burns Sonic 35 Schematic
NB: The component numbers are for convenience only. Factory numbers not available at the time of writing.
Left click to enlarge (see printing instructions above).
Baldwin Burns Sonic 35 Component Layout
Left click to enlarge (see printing instructions above).
Burns Sonic 50
Catalogue No. 545
Advertised Power Output: 50watts (British)
Size:
Weight:
Speakers: 2 x 12"
CONTROLS
Channel 1:
Inputs x 2
Volume, Bass, Treble, Vibrato Intensity, Vibrato Speed, Vibrato Footswitch Socket.
Power On/Off Switch.
Channel 2:
Treble, Bass, Volume
Inputs x 2
Baldwin Burns Sonic 55
Catalogue number 603
Baldwin Burns Control Panel
Baldwin Control Panel
Catalogue Description
Power Output: 55watts (British Rating) at less than 10% distortion
Loudspeakers: Two 12 inch heavy duty, 6 ohms each
Mains Supply: 200-250 volts, 40-60 cps, no adjustment required
(100-125 volts to order)
Size: -
Weight: -
Channel 1:
-
Inputs: Two high impedance, 200k ohms
-
Controls (Baldwin Burns): Volume, Bass, Treble, Vibrato Intensity and Speed, Vibrato Footswitch socket, three way tone selector switch
-
Controls (Baldwin): Volume, Bass, Treble, Vibrato Intensity and Speed, three way tone selector switch
Channel 2:
-
Inputs: Two high impedance, 200k ohms
-
Controls: Volume, Bass and Treble
General (Baldwin Burns):
-
1/4" jack socket for the vibrato footswitch on the front panel
-
Power On/Off switch in the back of the cabinet
General (Baldwin):
-
Captive vibrato footswitch in the back of the cabinet
-
Power on/off switch on the front panel
