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Aphex

Thermionics

- Division of Aphex Systems Ltd.

Model 1100 MkII Mic Preamp - Owner’s Manual

the transmission characteristics.

Maximum Brute Force cable length depends
on several factors, but you probably shouldn’t
attempt distances greater than 4 feet.

NOTE ON CONVERTING TO A

MATCHED LINE:

because of the

1100  MkII’s  automatic  input  level
adaptation,  you  can  convert  a  brute
forced  clock  source  into  a  workable
matched  line  by  inserting  an  in-line
75

Ω

, 10dB pad

at the sending

end of the cable

, and then install-

ing a 75

Ω

termination adapter at

the receiving end. This may reduce
or eliminate jitter problems when the
word clock distribution cable is of
appreciable length.

Typical 75

Ω

Attenuator

Last Unit In Line

Ω

Terminator

Tee

Figure 5

End-of-Line Termination

Page 10-3

Содержание 1100 MkII

Страница 1: ...duced without permission AphexThermionics Division of Aphex Systems Ltd Manual designed and written by Donn Werrbach 02 03 Creation tool Adobe InDesign 1 5 for Windows Printed in U S A Model 1100 MkII Dual Class A Discrete Tube Microphone Preamplifier with Integrated 24 Bit 192kHz A D Converter Document No 999 4200 ...

Страница 2: ...protection against electric shock do not remove the cover No user serviceable parts inside WARNING This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to Part 15 of the FCC Rules These limits are designed to provide reason able protection against harmful interference when the equipment is operated in a commercial environment This equipment gener...

Страница 3: ...nately these cases are greatly offset by the phenomenal word of mouth praise and promo tion we have received for the RPA products from their actual owners over the years Since the original patent was filed we have dis covered new ways to create many useful circuits with RPA principles that would be impossible to realize with conventional tube circuitry For example the Model 1100 MkII Mic Preamp in...

Страница 4: ...2 Preamp Gain 13 MicLim Detector 14 Reflected Plate Amplifier Output Stage 15 Headroom Meter 16 24 Bit A D Converter 17 AES EBU Output 18 Line Output Page A 4 Block Diagram 1 2 4 5 6 12 3 15 16 9 8 10 11 13 17 18 14 7 19 20 10 LoCafTM Low Cut Cancellation Filter 19 700Hz Tone Generator 20 Tone Relay 21 21 Return Jack 22 22 Send Jack 23 23 Impedance Compensator 24 24 S PDIF and TOSLINK Digital Outp...

Страница 5: ...tching and high attenuation The patented Reflected Plate Amplifier output stage adds 3dB of gain to the front end yielding the specified gain range of 21 to 65dB Because of graduated power rails the front end clip point matches the output stage clip point very closely Therefore metering the output of the front end accurately displays the headroom of the total system Also connecting the A D convert...

Страница 6: ...nding Using MicLim Interfacing Cables Installation Instructions Service Warranty Specifications Tube Topics White Paper More Gain No pain Page A 6 Contents Aphex Thermionics The Story A 2 Block Diagram A 3 Introduction A 4 Appendix A Word Clock Wiring 2 3 4 5 6 7 8 9 10 ...

Страница 7: ...t the output calibration trim and possibly the rear panel output normal switch to get a 0dB indication on the VU meter of an analog recorder or console This assures you will get 20dB of recording headroom along with the lowest possible noise The tone is also useful for calibrating the drive to an external A D converter 1 4 Phantom This button turns on and off the 48 volt phantom power to the micro...

Страница 8: ...selected then word clock is taken from the rear panel BNC clock input jack The 1100 MkII will go into a hunt mode until it finds the word clock parameters and locks on The frequency indicator lights DO NOT come on to tell you the locked frequency These lights are reserved to indicate clock frequencies during internal sync only If external clock is not pres ent then the 1100 MkII will continue hunt...

Страница 9: ...o oxidize including these points of contact When that happens metal oxide point contact diodes are created that rectify the audio signal causing distortion The extremely minute current from a microphone signal cannot break down these diodes and eventually the diode effect grows worse and worse until it is plainly audible We chose to avoid the problem alto gether albeit at a higher cost by using se...

Страница 10: ...larity Normal Reverse 5 16 Tone 20dB reference level 700Hz 6 17 Phantom Power 48V On Off 7 18 Mute On Off 8 19 MicLim On Off 9 20 Line Output Calibrate 3 Turns 0 to 12dB 10 21 Headroom Meter 0 to 50dB indicated 11 22 Clip Limit LED Flashes to indicate clip or MicLim action 23 Internal External Sync Clock Source 24 A D Converter Indicators Internal External Locked 25 Clock Rate 44 1 48 88 2 96 and ...

Страница 11: ...or the chassis of other equipment for example To meet legal requirements we have not pro vided a means to lift the power cord ground from the chassis If you determine it is necessary to lift the power cord ground you must use a ground lift adapter on the power plug You will not be able to lift the power cord ground from inside the chassis 2 3 AES EBU Digital Audio Output Preamplifier channels 1 2 ...

Страница 12: ...g in internal clock mode the Clock Out jack is discon nected from Clock In and instead is connected to the unit s internal clock source Thus any Model 1100 MkII operating in internal clock mode can serve as a master clock source when required The internal clock is derived from a low jitter crystal oscillator and is fully competent as a master clock 2 4 3 Local Clock Mastering In the absence of a s...

Страница 13: ...per level into your gear when the Model 1100 MkII s Head room Meter is peaking within the proper range To learn about the Headroom Meter look in sec tion 1 of this manual 2 5 3 Mic Input This is where you plug in the microphone Pins 2 and 3 are phantom powered when the phantom power is turned on by the front panel button There is little more to say about this jack The input phase is matched to the...

Страница 14: ...allowances It may run hotter if you are pushing the MicLim heavily You should use the input gain controls of your outboard equipment to match this level rather than turn down the preamp gain The return audio level should be adjusted on the outboard equipment to match the send level The front panel Headroom Meter indicates the level at the Return This is also the A D converter feedpoint so the mete...

Страница 15: ... showing a conventional line driver where there are two output amplifiers to drive the balanced line in counter phase through two equal resistors The only real difference between the counter phase driver of figure 2 8 and the impedance balanced driver of figure 2 7 is that to make up for a zero signal on one wire the impedance balanced driver must double the voltage output to the signal wire In ot...

Страница 16: ...ssis Ground Lug Digital Audio AES EBU 24 Bit Digital Audio Output Channel 1 LEFT Channel 2 RIGHT Sample Rates 44 1 48 96 192 KHz S PDIF and OPTICAL digital audio outputs Word Clock I O Jacks W C passes directly through in external mode Output is from internal generator in internal mode Analog Audio Output level noninal 0dBVu switch Provides 4dBu or 10dBV nominal reference level Impedance balanced ...

Страница 17: ... under severe con ditions That s because there is typically at least 16dB of limiting headroom afforded to any microphone of 150 ohms or higher Effectively that means that with MicLim you get 16dB more preamp headroom before distortion 3 2 How MicLim Works in Detail This discussion is especially for the technically astute reader The rest of you can skip this until later or forever if you re not re...

Страница 18: ...e are no special rules about making MicLim work for you The concept is simple run the preamp gain at a point where the peaks indicated on the Headroom Meter only reach the MicLim threshold infrequently or unexpectedly It may be evident to the astute that if one delib erately increased the preamp gain until peaks frequently limit one could obtain a very dense output level by bringing the average si...

Страница 19: ...R to XLR above 4 4 XLR to Phone Unbalanced The preferred method to make an unbalanced cable is shown below Note the use of balanced wire This technique improves hum rejection over standard single conductor shielded wire The method for using single conductor shielded wire is shown below You should use high grade shielded wire to assure the lowest hum pickup 4 5 Grounding Practices Over the years th...

Страница 20: ...onsumer operat ing levels by providing a normal level switch on the back panel 4 9 Mute Function Wiring The rear panel mute jack accepts either a mono or stereo phone jack Refer to section 2 on Back Panel Features for wiring diagrams and instruc tions for use 4 10 Insert Jacks The 1100 MkII s rear panel send and return jacks are intended to allow you to insert a compres sor or other processing dev...

Страница 21: ... not stack units directly on top of one another Use some type of blocking to leave at least an inch of airspace between units 5 7 Safety Considerations To minimize the risk of shock or fire do not expose the unit to moisture Allow adequate ventilation for cooling Do not open the chassis cover there are no user serviceable parts inside Installation should be performed only by qualified individuals ...

Страница 22: ...y through your audio wiring The best way to stop these prob lems is to reassign the power distribution panel so all outlets in the same room are from the same power phase If that is not possible then you should consider placing suitable power isolation transformers in your room to isolate the equip ment power from the house wiring When possible you can plan the house wiring to include insulated gr...

Страница 23: ...ce agencies by contacting Aphex Systems by phone fax or on the Internet 6 2 Warranty Claims All warranty claims must be presented to the Aphex factory customer support department or to an authorized dealer distributor or agency for processing Unauthorized repairs and modifica tions to the unit may void the warranty at the sole discretion of Aphex Systems Qualification for warranty service will be ...

Страница 24: ...s required WHAT WE WILL PAY FOR We will pay for all labor and material expenses for covered items We will pay return shipping charges if the repairs are covered by the warranty LIMITATION OF WARRANTY No warranty is made either expressed or implied as to the merchantability and fitness for any particu lar purpose Any and all warranties are limited to the duration of the warranty stated above EXCLUS...

Страница 25: ...se Gain 65dB input shorted BW 100Hz to 22KHz EIN 135dBu THD Output level 15dBu 0 09 output level 4dBu 0 05 IMD Output level 15dBu 0 12 output level 4dBu 0 08 DIM Below noise floor at all possible measurement levels Slew Rate 22V uSec Analog Dynamic Range 97dB to 101dB depending upon preamp gain setting Analog Output Noise 70dBu to 74dBu depending upon preamp gain setting Analog Signal To Noise Rat...

Страница 26: ... Off 30 36 44 53 63 77 92 111 134 162 195 Hz Line Output Calibration each channel 3 Turn precision potentiometer 0 to 12dB range 20dB Pad each channel on off Polarity each channel positive negative Tone each channel on off Phantom each channel on off Mute each channel on off MicLim each channel on off Clock Source Internal External Internal Rate 44 1 48 88 2 96 192 KHz Power on off Rear Panel Cont...

Страница 27: ...types because of their low noise rugged construction and low microphonics They are readily available in pre mium quality from new old stock and not very popular for audio equipment making their con tinuing supply well assured Bear in mind as already stated the difference between tubes will be sonically very subtle not as great as heard when substituting tube types in other equipment using conventi...

Страница 28: ...that the Aphex patented Reflected Plate Amplifier takes full advantage of thermionic tube amplification at a relatively low plate volt age and current With the RPA the plate voltage is held essentially constant while the low plate current is extracted reflected and magnified by a linear current mirror It is the reflected plate cur rent that generates the output voltage The tube runs much cooler ye...

Страница 29: ...er will be overloaded due to an unexpected increase in input level but the nominal output level will con sequently be very low That low output level will have to be boosted in a following gain stage This how ever shifts the problem of overload distortion to the following stage That is why it is quite common to see a compressor or a limiter in between the preamplifier and the following stage The pr...

Страница 30: ...headroom in the low cut range as compared to conven tional techniques Additionally the added low frequency headroom eliminates the need for the MicLim to trigger earlier than necessary from excessive low frequency energy c Drift Stabilized A D Converter Conventional analog to digital converters utilize high pass filters in the digital domain to block any DC generated in the conversion process or a...

Страница 31: ...g an open circuit mutes the preamplifier while a closed circuit un mutes This facilitates the convenient use of mute controls such as floor mat switches step on to un mute and musician s footswitches j Internal Switchmode Low Noise Power Supply One of the technology improvements comprising the model 1100 MkII is a highly efficient switchmode linear hybrid power supply Switchmode design is used to ...

Страница 32: ...er having a very low output impedance and high output current drive The maximum output level of 27dBu meets the needs of any professional application Matched impedance balancing assures peak performance whether driving balanced or unbalanced lines A rear panel switch is assigned to insert a 12dB low impedance pad into the output line for systems based on IHF semi pro operating levels Rear panel XL...

Страница 33: ...ially at high fre quencies When the cable exceeds a certain length depending on the cable s quality cable equalization may be required to recover addi tional bandwith Nevertheless a general rule is that matched transmission lines will always have better bandwidth and less jitter than unmatched lines of equal length It should be noted from figure 1 that when a matching line driver is not loaded by ...

Страница 34: ...ly unmatched transmission lines as best as one can and then rely on brute force clocking to hold it all together With brute force clocking 4 5Vp p clock pulses are fed out from a low impedance line driver with no intention of impedance matching the coaxial cable Daisy chaining is not usually pos sible because the magnitude of jitter rapidly rises Very short cable runs are necessary Every piece of ...

Страница 35: ...E because of the 1100 MkII s automatic input level adaptation you can convert a brute forced clock source into a workable matched line by inserting an in line 75Ω 10dB pad at the sending end of the cable and then install ing a 75Ω termination adapter at the receiving end This may reduce or eliminate jitter problems when the word clock distribution cable is of appreciable length Typical 75Ω Attenua...

Страница 36: ...Notes Model 1100 MkII Mic Preamp Owner s Manual ...

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