Iron Age Audioworks 500 Series User manual
User’s Manual
Mic Preamp QP5
©2019 by IronAgeAudioworks
Thank you for your purchase of an Iron Age Mic Pre (QP5). Iron Age Audioworks is a small
team of engineers and designers and we truly appreciate your business. We hope you enjoy
using this as much as we enjoyed making it.
Safety
Safety with audio equipment is normally a matter of common sense, but we want to make sure
you get the best use out of your equipment. So please, use common sense including...
●Use typical practices for using electrical and audio equipment.
●Don’t clean this with water or use it around water.
●Any ventilation openings in the case need to remain open.
●Don’t use this around anything that’s hot (such as a radiator or space heater).
●Don’t use a cut or damaged power cord, and keep the cord from getting pinched or
stepped on.
●Don’t service a box unless you’re a qualified technician.
Power
The unit is powered by the 500 series chassis it is mounted in. It complies with VPR standards,
and can also be used with supplies up to +/-24V.
©2020 by IronAgeAudioworks 1
Overview
The Iron Age 500 series mic preamp was designed as a utility front end solution. The mic
preamp is the most important part of your signal chain, and this preamp gives the detail and
depth your signal deserves.
Each QP5 features an all-discrete, transformer balanced input and output mic pre with a
flexible and powerful topology that offers up to 80 dB of gain! The QP5 uses the same
preamplifier as our QPP rack mount units, packed with additional useful features. The unit uses
a Jensen input transformer and a custom-wound steel core Cinemag output transformer,
selectable for 1:2 or 1:3 ratio. The first op amp works as a preamplifier, with adjustable gain of
up to 40 dB. We took the rumble filter from our CS1 channel strip, followed by the same
discrete transistor buffer we use in the CS1 and the V2 equalizer. A second op amp is fed by a
trim control, and a “high gain” switch adds 12 dB more if needed. A bank of -20 dB pad,
polarity, and 48V phantom power switches round out the feature set.
As with all Iron Age products, the QPP uses the M2 discrete operational amplifier, designed
and built by us.
Block Diagram
Through the IAA Custom Shop we also offer a variety of input transformers, output
transformers, and op amps. Whether you're looking for clean and clear, warm and smooth, or
edgy and rock and roll, this preamp can do what you need.
Reach out to us to whiteboard your idea!
©2020 by IronAgeAudioworks 2
Controls
The GAIN knob adjusts the gain of the operational amplifier.
The OUT knob attenuates the signal before the output stage. For
maximum headroom the OUT should be set fully clockwise.
The OUT HI/LO switch increases the gain provided by the output
amplifier by 12 dB.
The POL button inverts the signal being set to the primary side of the
output transformer, changing the polarity of the output signal by 180
degrees.
The RATIO button changes the ratio of the output transformer from 1:2 to
1:3 when depressed. This increases the overall gain by 3.5 dB and
decreases the output impedance seen by the op amp, causing a pleasant
change in tone.
The FILTER button engages a 50 Hz, 12 dB per octave slope high pass
filter. This is followed by a discrete three-transistor buffer.
The +48 button provides phantom power to the microphone.
The PAD button engages a -20 dB pad with a characteristic impedance
of approximately 2300 ohms.
Inputs and Outputs
The input uses a Jensen mic input transformer to receive a nominal -80 dBu balanced input via
the 500 series pinout.
The output is a nominal +4 dBu transformer balanced line output using a Cinemag output
transformer via the 500 series pinout.
Chassis
The Iron Age QP5 is a VPR compliant 500 series module.
©2020 by IronAgeAudioworks 3
Technical Specifications
Gain Range 28 - 80 dB
Maximum Input Level -3.5 dBu
Maximum Output Level +29 dBu
Input Impedance 2300 Ohms, transformer balanced
Output Impedance <75 Ohms, transformer balanced
Frequency Response +0.1, -0.75 dB 20Hz-20kHz
Actual Measured Noise -107 dBA typical
THD @ +15 dBu output 0.002% typical
Power Consumption <120 mA
©2020 by IronAgeAudioworks 4
Warranty
We warrant this product to be free from defects of materials and workmanship for a period of
one (1) year from the date of purchase. We will remedy any defect identified within this period
by repairing or replacing the product at our option. It will be your responsibility to pay for
shipping the product to us, and if the product is determined to be defective, our responsibility
to pay for shipping the product back to you.
LIMITATIONS AND EXCLUSIONS. This warranty, and any other express or implied warranty,
does not apply to any product which has been improperly installed, subjected to usage for
which the product was not designed, misused or abused, damaged during shipping, or which
has been altered or modified in any way. This warranty is extended to the original purchaser
only. THIS EXPRESS, LIMITED WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES,
EXPRESS OR IMPLIED, TO THE EXTENT ALLOWED UNDER APPLICABLE STATE LAW. IN NO
EVENT SHALL IRON AGE AUDIOWORKS BE LIABLE FOR ANY SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OF THIS PRODUCT.
If you suspect a defect in this product, please contact us to discuss the problem (it is possible
that a suspected defect could be quickly remedied or due to improper usage).
Contact us with any issues, to say hi, or share the music you’ve made. We love this gear and
want you to love it too.
©2020 by IronAgeAudioworks 5
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