1975 Dobro Ampliphonic Mandolin
Imagine a world without
electrically amplified instruments. In order to be heard by a large audience,
you’d need the loudest acoustic instruments you could get – probably a trumpet
or a banjo. It’s not surprising, then, that brass instruments and banjos were
the backbones of countless bands in the 1920s and 1930s. Guitars just couldn’t
keep up; even the biggest, loudest archtops were often drowned out in the
cacophony that emanated from bandstands. Today, the seemingly natural solution
is to connect a guitar to a loudspeaker. This is done using a pickup of one kind
or another (or occasionally a microphone) to transmit an electrical signal to an
amplifier whose speaker cone turns the signal back into sound waves. Before this
innovation was sufficiently refined for public consumption, however, an
intermediate step was proposed: put a loudspeaker
inside a guitar and transfer the
energy directly from the strings to the speaker cone.
This was the idea created by George Beauchamp and John
Dopyera in 1927: the resonator guitar. The resonator itself is a thin aluminum
cone that acts as a loudspeaker. The energy of the strings is transferred
through the bridge to the cone, causing it to vibrate. This invention was the
raison d’être of the National String Instrument Company, founded in 1927. The
first National designs used a tricone setup: three smaller cones in an offset
arrangement connected by a T-shaped bridge. This did indeed create an
extraordinarily loud guitar with incredible sustain, but it had one major
drawback: it was expensive.
John Dopyera soon split from National (which his brothers
Rudy and Emil continued to run) to form the Dobro Manufacturing Company in 1928.
Dobro created a more affordable resonator system with a single large cone. The
bridge contacted the cone at the center and also at the edges via eight legs –
hence the appellation “spider” bridge. The spider design created a different
tone from the tricone, a more nasal sound that has become the standard for all
resonators used in bluegrass music. National created its own single-cone design
in response (called a “biscuit” bridge) which has become one of the signature
sounds of early blues recordings.
The two companies merged in 1935 to form the
National-Dobro Corporation. Note that none of the company names explicitly
referenced guitars; they all built mandolins and ukuleles as well. National
built biscuit-bridged mandolins with metal bodies, while Dobro built
spider-bridge mandolins with wood bodies; the tones of each are very different.
The National instruments were generally more sturdily built, and are more highly
regarded by collectors today. However, the Dobro instruments have their fans as
well. Rudy and Emil Dopyera formed the Original Musical Instrument Company (OMI)
in 1970 to continue building National and Dobro-style guitars, and in 1975 they
started building mandolins as well.
The newer mandolins used a spider-bridge system like the
original 1930s Dobro designs, but they were built to much higher standards of
quality, sound and playability. The new mandolins were built with mahogany
bodies; there were a few mahogany Dobro mandolins built in the 1930s, but most
were birch. The bodies were redesigned to be much deeper, giving the instrument
a huge, warm voice that contrasts pleasantly with the recent biscuit-cone
mandolins by National Resophonic. As with guitars, the spider-bridge mandolins
have longer sustain and more compressed dynamics than their biscuit-bridge
cousins. One major upgrade to the new instruments was an adjustable truss rod
that counteracts the neck’s tendency to bow under string tension.
My mandolin, built in 1975, was one of the first
reissues. The model was known as the Ampliphonic, but it was changed to the
original Model 15 designation by 1978. Mine has minor wear but is in excellent
condition overall; the neck has been reset and some minor work done to alleviate
a kick-up in the fretboard over the body, but otherwise it’s all original. Dobro
continued to build mandolins until 1995, shortly after OMI was acquired by
Gibson. The newer mandolins fetch a considerably lower price than the originals,
but given the improvements in sound and playability, I’m happy with the one I
have. It’s one of my favorite instruments, and people who hear it are often
amazed both by its unique appearance and the warm torrent of sound that emanates
from its small body.