Elvic KA-100 Combo
Nothing to do with the Sixties or even the Seventies. This one came from Elvic Electronics in Essex in the late Eighties - early Nineties. Haven't seen one before, so it had to come apart.
It has one 15" speaker, a high frequency horn with crossover, plus an extra piezo horn in the bottom right hand corner that's a later addition. The output measures 64watts rms at clipping into its own 8ohm cabinet from a mosfet power stage.
After a lot of searching, nothing came up about it on the internet, so any information about the spec would be appreciated. Presumably 'KA' stands for Keyboard Amplifier. I'm told it works well for bass too.
Cabinet dimensions:
595mm wide x 315mm deep x 575mm high
measured across the corner protectors.
Weight: 27kg
Front Panel
Channels 1 to 3:
High gain input
Low gain input
Gain
Treble and Bass
Reverb level
Channel 4:
High gain input
Five pin, 180deg DIN socket for Tape in / out
Treble and Bass
Reverb level
(The 'tape out' signal comes after the master volume control - something to watch if you're recording a live gig)
Master Volume
Master Reverb
Reverb Footswitch
Power on indicator
The knobs are missing their pointer caps but this is what they would have looked like.
They're 1/4" D shaft, 19mm at the base with a recess to cover the nuts. Best guess is Cliff K11s. Not readily available.
Rear Panel
IEC fused mains inlet (2amps A/S)
Illuminated mains on / off rocker switch
2 x speaker outlets
Slave output
Effects Send and Return
General Assembly
Above:
Front panel assembly.
Left:
Rear panel assembly. The mains transformer is screwed into the cabinet on the other end of the six way connector on the left.
Below:
Accutronics 8AB3C1B reverb tank.
Everything's generally well made but the mechanical designer must have been in a really bad mood that day.
To get the front panel assembly or the mains transformer out you have to remove the speaker and unsolder it's very short leads. It can be left attached if you're feeling lucky.
That gives access to the reverb tank phono connectors and the transformer fixings.
The wires to the crossover have to be unsoldered from the power amp board to get the back panel off.
Speakers
A really nice 15inch Fane speaker with a cast basket:
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Basket marked 153267 / 8 - 49 - 89
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Cone marked 55
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Impedance 8ohms
Presumably from 1989. That would tie in with the 1988 date codes on the op-amps.
HT351F multicellular horn tweeter:
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Crossover 3KHz
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Impedance 8ohms
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Power 30watts
HP35K High Pass Filter:
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Cut-off 5kHz
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Power 300W
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Impedance 8 ohms
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Attenuation 16db
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:
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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.
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Open the file and use the print menu to make a hard copy or save as a pdf.
Power Amplifier Schematic
Measured rms power output with a continuous 1kHz sine wave was 72watts into 4ohms and 64watts into 8ohms at clipping. That doesn't tie up with the KA 100 name but it clips symmetrically and appears to be working properly.
Minimum load impedance is 4ohms. Plugging into the rear panel speaker jacks doesn't disconnect the internal 8ohm system meaning that any extension speakers must be greater than 8ohms in total.
Power Amplifier Component Layout
Channels 1, 2 and 3 Preamp Schematic
Every pot in the amplifier is a 10K linear. They're stamped '10K A' but that doesn't indicate Audio (log) in this case.
Tape Input Channel and Master Volume Section Schematic
Channel 1, 2 and 3 Input Board Component Layout
Tone Control Board Component Layout
Tape Input Board Component Layout
Master Volume Board Component Layout
