Solution Delivery Series 207d two channel tube mic And Instrument preamplier with 24-Bit 96kHz ADC Instruction Manual P/N 999-4260 Revision 1 Released 02/04/2005 Manufactured by Aphex Systems Ltd. 11068 Randall St. Sun Valley, CA 91352 USA S Y S T E M S Copyright 2004 Aphex Systems Ltd. All rights reserved. Produced by: Donn Werrbach. Creation tool: Adobe InDesign 2.
07d Dear Aphex Customer, instruction Manual A MESSAGE FROM THE PRESIDENT We are pleased to present the Model 207D Tube Microphone and Instrument Preamplifier with analog and digital outputs. This continues the commitment made in all the products in our Solution Delivery Series- high performance audio; extensive, useful and unique features; attractive and clean front panel design; and cost effective pricing.
2-ch tube mic preamp with adc 1.0 CONTROLS & INDICATORS PLUS QUICK 207d Table of Contents SETUP........................................................................ 4 2.0 INTRODUCTION 2.1 What Distinguishes the Model 207D..................................................................................... 2.2 What Does the Tube Add? .................................................................................................. 2.3 What Else Is So Special? .........................................
207d instruction Manual 1.0 Controls and Indicators with Quick Setup POWER ON When the unit is turned on, audio is not passed through to the output for a few moments while the tube warms up. During the warm-up time, the power indicator is yellow. When the power indicator turns green, the audio will pass through to the output. This protects you from heavy turn-on thumps. MICROPHONES You can use any type of balanced, low impedance microphone from dynamics to ribbons to condensers.
2-ch tube mic preamp with adc 207d Quick Setup OPERATING LEVEL This adapts the model 207D’s internal dynamic range to match either professional balanced equipment or semi-professional unbalanced equipment at the output. It controls both output jacks. Both jacks supply the same output level. Set as needed. DIGITAL AUDIO In external sync mode, the 207D locks up to frequencies between 32 and 96kHz.
207d instruction Manual 2.0 Introduction 2.1 WHAT DISTINGUISHES THE MODEL 207D There are certainly a lot of mic preamps available in the world. It seems that every audio equipment company has at least one model to offer. A study of currently available products shows that a large percentage use similar circuits based on one or two popular commercial i.c. chips. The basic design has been done by the chip maker and the chips do a competent job.
2-ch tube mic preamp with adc 207d Introduction tortion is so natural. The very slight tube distortion of the Model 207D comprises typically less than 0.02% of second order harmonics at average levels. What is even more interesting is that this curve follows the tube’s law as regards level, and furthermore, it responds to certain very subtle dynamic space-charge effects known only in tube amplifiers. Thus, the sound with an RPA can have a large and open feeling that is very natural and transparent. 2.
Page 8 HI-Z INSTRUMENT 1/4” PHONE INPUT XLR-3F MIC INPUT FET PREAMP MIC/INST AUTOSWITCH SWITCHED +48V PHANTOM POWER POLARITY MiCLiM™ LDR PAD LOW CUT FILTER 1/4” TRS PHONE INSERT JACK RPA DISCRETE TUBE AMPLIFIER FROM OTHER CHANNEL ONE CHANNEL SHOWN MiCLiM™ CONTROL GAIN DISCRETE NPN FRONT END 2.
207d 2-ch tube mic preamp with adc 3.0 Installation & Interfacing 3.1 INSTALLATION The Model 207D occupies a single rack space (45mm or 1-3/4 inches) of a standard EIA equipment rack. When rack mounting, use appropriate cushioned rack screws. Never restrict air flow through the device’s vents. When installing the units into a rack, distribute the units evenly. Otherwise, hazardous conditions may be created by an uneven weight distribution. Connect the unit only to a properly rated supply circuit.
207d instruction Manual Installation & Interfacing TABLE 3-1 - INSERT “Y” CABLE PINOUTS Tip -SEND Ring - RETURN Sleeve - GND may both be used at the same time to feed separate equipment. Both jacks run at the same output level but are not fully isolated from each other. Shorting out the XLR will take down the 1/4 phone. However, shorting the 1/4 phone will not affect the XLR. You may safely plug a mono style (TS) 1/4” phone plug into the phone jack and take an unbalanced output.
2-ch tube mic preamp with adc 207d 4.0 Using the 207D FRONT PANEL VIEW 4.1 SPLIT INDEPENDENT PREAMP SECTIONS The Model 207D is a two channel unit. It contains two separate, independent, preamplifier channels. Each channel operates as a mic preamp or an instrument preamp. Plugging into the instrument jack automatically disables the mic input and substitutes the instrument input. 4.2 USING THE INSTRUMENT INPUT This input is designed to work with most standard instrument pickups, both active and passive.
207d instruction Manual Using the 207D interfering with the audio signal carried on the same wires. The industry standard phantom power source is positive 48 volts d.c. supplied to pins 2 and 3 through 48 V.D.C. SUPPLY + 6.81KΩ 1% 2 1 6.81KΩ 1% PREAMP 3 Figure 4-1 Phantom Powering precision low noise 6.81KΩ resistors. You may note from spec sheets that many mics rated for phantom power actually run at something less than 48 volts.
207d 2-ch tube mic preamp with adc Using the 207D 4.3.3 USING THE PAD An input pad is nothing more than a resistive attenuator that drops the level coming from the input jack. Its purpose is to give you a way of preventing overload of the preamp when incoming signals become excessive. Another purpose is to change the preamp’s mic input into a line input. In the 207D, we provided a pad of 20dB. That means when the pad is on, the net gain of the preamp is 20dB lower than normal.
207d instruction Manual Using the 207D closer to the peak ceiling. Although it is certainly possible to operate MicLim™ in that fashion, and often the effect will be desirable, we recommend the use of restraint. MicLim™ was designed to be fast and unobtrusive for protection against accidental overloading, especially with voices. You may find the fast speed of this limiter too aggressive for general purpose effect limiting. Your favorite studio compressor/limiters can still be put to good use.
2-ch tube mic preamp with adc 207d Using the 207D1 No matter how noble the intent, there is one dilemma that can thwart you in successfully bypassing the mic pre of some consoles. You must become aware of this problem in order to deal with it. We have been instructing you to connect the Model 207D to the LINE inputs of your console or other equipment, and NEVER connect it to a mic input.
207d instruction Manual Using the 207D their work. The low noise and highly detailed, open sound of the 207D delivers breathtaking results. All expert recordists know the techniques we’re about to show you. However, others may find them interesting to learn about. tronic matrix circuit processes both microphones and provides Left and Right channel outputs. This method vectorially extracts the left and right channels from the sum and difference signals (the middle cardioid and side figure 8 patterns).
2-ch tube mic preamp with adc 207d Stage Distance X 3X Figure 4-4 SPACED PAIR 3 to 1 TECHNIQUE Stage Cardioid Mics Figure 4-5 X-Y TECHNIQUE Figure 4-7 BINAURAL MIC Stage (Example: Neumann KU-100) Cardioid Mid Bi-Directional Sides Figure 4-6 M-S TECHNIQUE Aphex Systems Ltd.
207d instruction Manual 5.0 Warranty & Service 5.1 Limited Warranty PERIOD One year from date of purchase SCOPE All defects in workmanship and materials. The following are not covered: a. Voltage conversions b. Units on which the serial number has been defaced, modified, or removed c. Damage or deterioration: 1. Resulting from installation and/or removal of the unit. 2.
2-ch tube mic preamp with adc 207d 6.0 Specifications 6.
7d instruction Manual Specifications 6.2 ARCHITECTURAL SPECIFICATIONS Basic Description A two-channel electronic preamplifier for microphones and instruments comprising a transformerless balanced microphone input and a high impedance unbalanced Instrument input for each of the two channels. The preamplifier shall comprise a Reflected Plate Amplifier tube-type transformerless output stage.
2-ch tube mic preamp with adc 207d 7.0 Appendices Appendix A: Balanced and Unbalanced Lines and Operating Levels Interfacing all types of equipment with balanced and unbalanced lines and can sometimes be troublesome. First you have to somehow connect balanced to unbalanced and then you have to deal with different levels. This tutorial will teach you about the principles of balanced and unbalanced lines, wiring standards, and how to effectively interface them.
207d instruction Manual Appendices Your balanced input stage looks at the two wires and detects only the potential (voltage) difference between them. Anything that is the same on the two wires (for all practical purposes as seen measuring from ground) is called a common mode signal and is cancelled out by the differential amplifier. Figure 1 illustrates how the hum is induced into both wires equally and therefore is cancelled out.
2-ch tube mic preamp with adc straight through you! No matter what you do, you may not be able to prevent some of your equipment from generating ground currents. The most likely culprits are digital products because they use switching power supplies that require heavy line filters to prevent conducted EMI from going out of the box. Filters so employed very often take the ground leakage current right up to the UL safety limits.
207d instruction Manual Appendices Avoid Transformers The use of balancing transformers is an option, but you will invariably lose audio quality due to transformer limitations. Try everything else first. Appendix C: Proper Wiring Techniques A true balanced line should be used wherever your equipment allows. Use “twisted pair” shielded cable. For unbalanced wiring you should use high grade, low capacitance shielded wire for best results.
2-ch tube mic preamp with adc 207d Appendices TABLE 1 - BALANCED & UNBALANCED CONNECTOR WIRING STANDARDS 3-Pin XLR 1/4” TRS Phone Standard Wiring Convention (Balanced) Pin-1 Sleeve Ground/Shield (Earth, Screen) Pin-2 Tip Positive (Signal, High, Hot) Pin-3 Ring Negative (Signal Reference, Return, Low, Common) 1/4” TS Phone RCA Standard Wiring Convention (Unbalanced) Tip Center Pin Positive (Signal) Sleeve Shell Ground/Shield (Signal Reference/Return) lines as low impedance and unbalanc
207d instruction Manual Appendices transformerless balanced, usually called “active balanced”. Transformer balanced outputs are becoming outdated because of their high cost and their sonic limitations. However, they can still be found on a lot of older equipment. Within the transformerless class, there are several types of circuits that are used by different manufacturers.
2-ch tube mic preamp with adc 207d Appendices PART 2: BALANCED OUT to UNBALANCED IN Voltage Balanced Outputs (Used on the 207) It was mentioned that there are several types of balanced output stages in use today. The following diagrams show you how to properly unbalance each type of output. If you follow these instructions, you should have no problems. SIMPLIFIED SCHEMATIC Unbalancing loses half the output level. You lose 6dB of gain.
207d instruction Manual Appendices PART 3: UNBALANCED to UNBALANCED Standard Cable (Guitar Cord) Mono (TS) Phone Plug Mono (TS) Phone Plug PART 4: UNBALANCED OUT to BALANCED IN Standard Method Mono (TS) Phone Plug Enhanced Method (Pseudo Balanced) Advantage: Reduced Hum and Noise Pickup Stereo (TRS) Phone Plug (Guitar cord of Part 3 above usualy works just as well) Mono (TS) Phone Plug Stereo (TRS) Phone Plug Not Used Male XLR Male XLR Mono (TS) Phone Plug Mono (TS) Phone Plug Not Used PART 5:
2-ch tube mic preamp with adc 207d Patent Notice This product is protected under one or more of the following Aphex patents. 4,578,648 4,633,501 4,843,626 4,939,471 5,115,471 5,155,769 5,334,947 5,359,665 5,422,602 5,424,488 5,450,034 5,463,695 5,483,600 5,485,077 5,612,612 5,737,432 5,848,167 5,896,458 5,898,395 5,930,374 6,266,423 Aphex Systems Ltd.
207d Page 30 instruction Manual Aphex Systems Ltd.
