LaChapell Audio 503 500 Series EQ User Manual
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Stated below are a few areas that you must take the time to read before you install and use your 583. You as the
owner/user are responsible for completely understanding how to operate this device safely and properly.
UNPACKING:
Inspect thoroughly. Although we take extreme care at final assembly and packing, things can
happen during transit. It is very important that you contact LaChapell Audio if there is anything broken or
damaged upon receipt of package. Shipping is always insured and we will do our absolute best to satisfy any
legitimate claim as long as it is made within 7 days of receipt. Included in every package should be: (1) prelimi-
nary operating manual, (1) packet of mounting screws, (1) registration card. It is a good idea for you to retain the
packaging (box & foam case) in case there is a need to return the unit for service or repair at a later date.
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SERVICE/REPAIR:
With the exception of tube replacement (see below) the user should NOT
attempt to service this unit in any way, due to the risk of electrical shock and the presents of lethal
voltages inside the 583 while powered. Only LaChapell Audio personnel are to perform maintenance
and service activities. The user should also take note that excessive ‘swapping’ of tubes will Introduce
undue wear on the tube socket. It is therefore recommended that tube replacement be performed only
when necessary and by technically competent individuals.
Tube replacement: Turn power supply off and remove 583 from the chassis, wait five minutes to allow
the vacuum tube to cool before attempting to remove it. Using your fingers, apply a slight
circular/rotating motion as you pull it away from the socket. It is important to replace the tube with the
same type. When a replacement tube is installed double check that you’ve inserted the correct tubes
into the 583’s tube socket BEFORE powering up.
NOTE:
The 583’s standard tube is the EH 12AX7. However, there are many different ECC83/12AX7
variants that are virtually identical and can be used in either 583 module. These include: ECC803, E83CC,
CV4004, 6057, M8137, C492, 7025 and the 5751 (you will notice a slight drop in gain when using the
5751).
WARNING: Warrantee may be void if tubes other than those listed above have been used at
any time.
PRODUCT SUMMARY (583E, 583S):
The LaChapell Audio 583 series modules feature single-ended vacuum tube
preamplifiers designed for use in the “500 series” format. The microphone input configuration is based on the 992EG
and consists of an input transformer with a turns ratio of 1:10 and one ECC83/12AX7 vacuum tube. The instrument
input stage is transformer-less with the signal essentially going strait to the grid of the tube. The output stage utilizes
premium Burr-Brown and THAT Corporation line drivers along with an 80% nickel alloy core transformer to generate
a balanced line-level output signal. The model 583E features an ultra-clean transformer-less three-band EQ section
with fully sweeping frequency controls and cut/boost settings of +/- 8dB... t
he EQ can run as an integrated EQ
(serving the preamplifier) or separate as its own autonomous module apart from the preamplifier.
PRODUCT SUMMARY (503):
The LaChapell Audio 503 is a 3-band transformer-less EQ based on the EQ section of
the 583E pre/EQ. The 503 feature additional cut/boost range of +/12dB, 2-position high-pass and 2-position low-pass
filters along with a gain trim stage of +/- 6dB.
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