Leeds HIZ PRE User manual

L
L
E
EE ED DS S
P
P
R
RO O
A
A
U
UD DI IO O
H
HI IZ Z P PR RE E
A
A
C
CO OU US ST TI IC C
I
I
N
NS ST TR RU UM ME EN NT T
T
T
U
UB BE E
P
P
R
RE EA AM MP P
-
- E EQ Q - - A A
C
CT TI IV VE E
D
D. .I I. .
User’s manual

L
L
E
EE ED DS S
P
P
R
RO O
A
A
U
UD DI IO O
H
HI IZ Z P PR RE E
A
A
C
CO OU US ST TI IC C
I
I
N
NS ST TR RU UM ME EN NT T
T
T
U
UB BE E
P
P
R
RE EA AM MP P
-
- E EQ Q - - A A
C
CT TI IV VE E
D
D. .I I. .
User’s manual
Revision 1
2009, Leeds Technology LLC
All rights reserved.

HiZ Pre Limited Warranty
Leeds Pro Audio warrants this product to be free of defects in material and
workmanship for a period of three year from date of original retail purchase.
This warranty is enforceable only by the registered owner of the product
identified by the product serial number. To be protected by this warranty, the
purchaser must complete and return the enclosed warranty registration card
within 14 days of purchase or complete the on line at:
http://www.leedsproaudio.com/15101.html. During the warranty period, Leeds
Pro Audio shall at its sole and absolute option, either repair or replace, free of
charge, any product that proves to be defective on inspection by Leeds Pro
Audio or its authorized service representative. To obtain warranty service, the
purchaser must first email or write Leeds Pro Audio at the email or address
printed below to obtain a Return Authorization Number and instructions of
where to return the unit for service. All inquiries must be accompanied by a
description of the problem. All authorized returns must be sent to the Leeds
Pro Audio repair facility postage pre-paid, insured and properly packaged.
Leeds Pro Audio reserves the right to update any unit returned for repair.
Leeds Pro Audio reserves the right to change or improve the design of the
product at any time without prior notice. This warranty does not cover claims
for damage due to abuse, neglect, alteration or attempted repair by
unauthorized personnel, and is limited to failures arising during normal use
that are due to defects in material or workmanship in the product. Any implied
warranties, including implied warranties of merchantability and fitness for a
particular purpose, are limited in duration to the length of this limited warranty.
Some states do not allow limitations on how long an implied warranty lasts, so
the above limitation may not apply to you. In no event will Leeds Pro Audio be
liable for the incidental, consequential or other damages resulting from the
breach of any express or implied warranty, including, among other things,
damage to property, damage based on inconvenience or on loss of use of the
product, and, to the extent permitted by law, damages for personal injury.
Some states do not allow the exclusion of limitation of incidental or
consequential damages, so the above limitation or exclusion may not apply to
you. This warranty only applies to products sold and used in the United State
of America. For warranty information in all other countries please refer to your
local distributor.
Leeds Technology LLC
7053 Lake Island Drive
Lake Worth, FL 33467
[e-mail]
2009, Leeds Technology LLC. All rights reserved.

___________TABLE OF CONTENTS
1 Overview
1.1 Introduction 4
1.2 Features 5
2 Controls & Connections
2.1 Front Panel 6
2.2 Back Panel 7
2.3 Connection Diagram 8
3 Operation
3.1 Overview 9
3.2 Instrument Input 9
3.3 Clip Indicator 9
3.4 Equalizer 9
3.5 Output Level 10
3.6 Vacuum Tubes 10
3.7 Power Supply 11
3.8 Mounting Instructions 12
3.9 Interference 12
4 Technical
4.1 Audio Specifications 13
4.2 Input Specifications 13
4.3 Output Specifications 13
4.4 Power Specifications 13
4.5 Physical Specifications 13
5 Miscellaneous
5.1 Information 14
5.2 Notes 14
__________________ ______________________
3

1. OVERVIEW________________
1.1 Introduction
Thank you for purchasing the HiZ Pre Acoustic Instrument
Tube Preamp - EQ - Active D.I. The HiZ Pre is a vacuum tube
driven active direct box with a superb equalizer to craft your
sound. The ultra high input impedance preserves the full
bandwidth and bass response of a piezo element pick up. Our
negative feedback voltage amplifier design provides a very low
noise floor and wide bandwidth to ensure accurate
reproduction of your instrument’s timbre. The buffered outputs
allow you to simultaneously drive your mixer/console and
stage amplifier without loss of signal clarity. The road ready
rugged heavy gauge steel chassis is rack mountable for your
instrument case or studio rack. This pre-amp was designed
using state of the art components to provide a clean, yet warm
tube sound. Please contact us at [e-mail]
with your questions or comments regarding this product.
Leeds Pro Audio welcomes the comments of our customers.
We appreciate the support you have shown us through the
purchases of this product.
Please pay close attention to how you connect your HiZ Pre to
your system. Improper grounding is the most common cause
of noise problems found in studio or live sound systems. We
recommend you to read this manual to familiarize your self
with this product.
Enjoy your HiZ Pre
__________________ ______________________
4

____________________OVERVIEW
1. Features
The following is a summary of your HiZ Pre features:
Ultra-high input impedance input stage
The ultra high input impedance provides a very low noise floor
and preserves the full bandwidth and bass response of a piezo
element pick up.
12AX7 vacuum tube for warm harmonically rich sound
Our negative feedback voltage amplifier design provides a
very low noise floor and wide bandwidth to ensure accurate
reproduction of your instrument’s timbre.
2 band Baxandall type shelving equalizer
The shelving equalizer enables ultra clean +/- 20 dB boost or
cuts of treble and bass frequencies.
Balanced XLR output, Unbalanced ¼” buffered output
The buffered output allows you to simultaneously drive a stage
amplifier and a balanced XLR input on your console or mixer
without loss of signal quality.
Rugged Road Ready Construction
The HiZ Pre is constructed of heavy duty 16 gauge steel. The
chassis is finished in a scratch resistant, textured powder
coating designed to combine an elegant look that withstands
the wear and tear of a working musician. The HiZ Pre is rack
mountable for your instrument case or studio rack.
__________________ ______________________
5

2. CONTROLS & CONNECTIONS
.1 Front Panel
Hi Z input – High impedance input matched to piezo electric
elements such as under saddle and soundboard transducers.
Bass – Sets low frequency shelving equalizer gain to +/- 20dB.
Treble – Sets high frequency shelving equalizer gain to +/-
20dB.
Clip – Monitors the instrument input and indicates if the input is
being driven with a signal that is too hot. The clip indicator has
been finely tuned to illuminate when the input signal level
reaches an amplitude that may cause an increase in harmonic
distortion of the output of the HiZ Pre.
Volume – Sets the output level. Ideally
Power – Power switch and indicator.
__________________ ______________________
6

_____CONTROLS & CONNECTIONS
.1 Rear Panel
Unbalanced output – Buffered ¼ inch output to drive a monitor
or stage amplifier. The buffer allows both the 1/4 and XLR
outputs to be used simultaneously without loading down the
output stage of the HiZ Pre. Cable Wiring:
TIP SIGNAL (+)
SLEEVE GROUND (-)
Balanced Output – XLR output to couple to a console or mixer.
Use this for highest quality sound and for long cable runs
(through a stage snake for example). Cable Wiring:
PIN 1 GROUND
PIN 2 SIGNAL (+)
PIN 3 SIGNAL (-)
Power Jack – Connect the 16VAC, 1000mA wall transformer.
__________________ ______________________
7

CONTROLS & CONNECTIONS_____
.3 Connection Diagram
__________________ ______________________
8
HiZ Input
XLR
balanced
output
¼” Un-
balanced
output
HiZ Pre
A
A
C
CO OU US ST TI IC C
I
I
N
NS ST TR RU UM ME EN NT T
Tube Preamp - EQ - Active D.I.
Mixer /
Console
Amplifier
Power
Supply
Guitar
w/ piezo
pickup
16VAC
1000mA

3. OPERATION_______________
3.1 Overview
In summary, ensure you do not overdrive the HiZ Pre input.
EQ and maximize the HiZ Pre Volume while minimizing the
input level on the mixer, console, or amplifier.
3. Instrument Input
The instrument input is designed to accommodate a ¼” tip and
sleeve plug from instruments such as acoustic electric guitars
and basses. This instrument input is an ultra high impedance
amplifier designed to allow the full frequency bandwidth of an
acoustic piezo element instrument pickup to be realized. Care
should be taken not to overdrive this input with instruments
that have their own preamplifiers. Ideally, the HiZ Pre is to be
connected directly to the piezo pickup.
3.3 Clip Indicator
This is particularly useful for instruments which have an
integral battery powered pre-amplifier. Turn the pre-amplifier
gain to a level when the clip light momentarily blinks when the
guitar is strummed just a bit louder than the musician’s playing
style. This will optimize the signal strength entering the HiZ
Pre, allowing the user to not overdrive the HiZ input.
3.4 Equalizer
The shelving equalizer is controlled with the Treble and Bass
knobs to boost or cut high and/or low frequencies +/-20dB.
The “0” at the 12 o’clock position is flat or 0dB gain.
________________ _________________________
9

OPERATION____________________
3.5 Output Level
For ideal signal-to-noise ratio (clean signal with lowest noise),
it is recommended that the output level of the HiZ Pre is set as
high as possible without overdriving the mixer, console, or
amplifier while keeping the input level on the mixer, console, or
amplifier at a minimum.
3.6 Vacuum Tubes
The HiZ Pre comes supplied with a 12AX7 vacuum tube. Tube
life and performance are affected by how often a tube is used
and by how hard the tube is driven when in use. Signs of wear
may be exhibited by poor performance or by the tube
becoming “microphonic”. Periodic replacement of vacuum
tubes is recommended. The time between the suggested
replacement varies greatly with the amount of the nature of
use of the vacuum tube. A good rule to follow: If you notice
deterioration in sound quality, then it’s time to change the tube.
Tube replacement can be accomplished by following these
steps:
1. Unplug the unit from the electrical outlet
2. Remove the (3) knobs on the front panel by loosening (not
removing) the screws on the side of each knob
3. Remove the (3) nuts and washers from the potentiometers
(posts under knobs)
4. Remove the plastic nut on the front panel input jack
5. Remove the (8) screws which attach the front/top to the
chassis.
__________________ ______________________
10

____________________OPERATION
6. Carefully slide the front panel / top cover forward away
from the rear chassis.
7. Gently remove the vacuum tube. Care should be taken to
properly align the pins on the tube to the corresponding
holes in the receptacle. Make sure the tube is completely
seated in the receptacle.
8. Re-assemble the unit using steps 6-1 in reverse order,
Care must be taken to align the LEDs, power switch, and
potentiometer posts in the front panel holes.
Experiment! Your HiZ Pre can accept the 12AT7 and 12AU7
vacuum tubes. Try swapping out the 12AX7 for one of these
lower gain tubes to experiment and customize your sound.
Vacuum tubes do not have an infinite life span, and must be
periodically replaced. Primary causes of tube failure are:
1. Mechanical failure – bumps, excessive vibration, and
mishandling of the HiZ Pre unit can cause the vacuum
tube to fail. Care must be taken to mount the unit in a
vibration free environment, and avoid hard bumps or
knocks when transporting the unit.
2. Aging – Tube aging occurs as the unit is in use. Be careful
to not leave any tube driven device powered on
indefinitely. Use the power switch to power down the unit
to preserve tube life.
3.7 Power Supply
The HiZ Pre is accompanied by a 16VAC, 1000mA external
wall transformer. To ensure safe proper operation, do not use
any other wall transformer other than the unit provided.
__________________ ______________________
11

OPERATION____________________
3.8 Mounting Instructions
The HiZ Pre can be rack mounted, or operated as a stand-
alone unit.
Stand-alone Use: The HiZ Pre comes with (4) rubber shock
mount vibration dampers or “feet”. Please attach the rubber
feet to the bottom side of the HiZ Pre when using in a stand-
alone configuration.
Rack Mount Use: A rack mount kit is available from
authorized distributors.
The kit includes:
1. 1 Each, 2U Rack Mount plate (holds two HiZ Pre units)
2. 5 Each: Mounting screws
3. 4 Each: Rack nut clips, screws, and washers
Use the kit to mount the HiZ Pre into a studio rack or travel
case.
3.9 Interference
Care must be taken when operating the HiZ Pre in
environments susceptible to radio or magnetic interference.
Using the HiZ Pre in close proximity to computer CPU’s, power
supplies, or other electrical devices may introduce undesired
audio artifacts such as buzzing or hum into the output signal of
the HiZ Pre. Please operate the HiZ Pre to insure no electrical
interference occurs.
__________________ ______________________
12

4. TECHNICAL________________
4.1 Audio Specifications
Bandwidth 30–18k Hz +/- 1dB
Dynamic Range 80 dB
THD (-10dBu, 1kHz input) <1%
Noise Floor -75 dBµ
4. Input Specifications
Impedance, Unbalanced ¼” TS 10 MΩ
Peak Input Level -10 dBµ
4.3 Output Specifications
Impedance, Balanced XLR 100 Ω
Output Level, Balanced XLR -10 dBµ
Impedance, Unbalanced ¼” TS 100 Ω
Output Level, Unbalanced ¼” TS -10 dBµ
4.3 Equalizer Specifications
Maximum Boost/Cut +/- 20 dB
Shelving slope 20 dB/Dec
Shelving center frequency 1 kHz
4.4 Power Specifications
Input 16VAC, 1000mA
Power 5.8 VA
4.5 Physical Specifications
Net Weight 2.84 Lbs.
Dimensions 3.375“ H X 8.000“ W X 5.250“ D
Leeds Pro Audio reserves the right to change specification at
any time without notification.
__________________ ______________________
13

5. MISCELLANEOUS___________
5.1 Information
Please record information for your HiZ Pre for future reference.
Model Name / Number: ___________________________
Serial Number: _________________________________
Date of Purchase: _______________________________
Place Of Purchase: ______________________________
5. Notes
__________________ ______________________
14