"DaviSuper" TB-10 Preamplifier
"On-Line Manual" - Applications Data
Like the TB-1, the TB-10 is offered EXCLUSIVELY in a handcrafted Solid Oak "WG" style cabinet occupying 3 rack spaces (3U). The unit offers two large, lighted VU meters toward the center of the cabinet.
NOTE:
The actual VU meter styling may vary from photo since the specific meters used in the prototype TB-10 are no longer manufactured and our reserve stock is now depleted. Meters will be similar Modutec units with a face approximately 2 1/2 inches wide by 2 inches high.
Rack handles may very slightly also since the stainless steel handles for the prototype in the photo were custom made by the client as a contribution for his own amplifier ( he operates a steel fabrication company ). Normal rack handles for the TB-10 are the large wooden variety as shown on the TB-1 cabinet photos on our website. Metal handles similar to those shown here are also available as are identical copies of the ones shown, on special order, for an extra fee.
This dual preamplifier package is, in reallity a FOUR CHANNEL unit offering TWO DaviSound "MIC-ALL" microphone amplifiers and TWO instrument preamps. The layout is grouped in pairs with a channel one mic and instrument amp to the left side of the unit with a second identical pair on the right side. The left and right VU meters may be switch selected to monitor the output of either respective amplifier.
The center toggle switch not marked on the above layout, is the main AC power switch.
The VU Meters employ two mini-toggle switches located directly below the meter face. The first switch, mounted horizontially selects either the INSTRUMENT signal when switched toward the center of the unit in the direction of the instrument inputs, or when switched toward the outer side of the unit, the MICROPHONE signal level is monitored.
The vertical switch selects a reading of +4 dBu when up and -10dBu when in the down position.
The microphone input in each channel offers a front panel XLR input connector (extra parallel rear panel connectors are available as a custom option for an extra fee) and the MIC-ALL active gain control.The adjacent horizontal mounted mini toggle switch is the PHASE REVERSE switch with left/right toggle operation, and the vertically mounted on/off switch below it is the PHANTOM POWER on/off switch with up/down operation. A green LED indicates phantom power on/off.
The left/right phase reverse action of the respective phase switches is all relative of course but the RIGHT toggle position corresponds with input pins 2 & 3 to output pins 2 & 3, whereas the LEFT position reverses the polarity of input pins 2 & 3.
Approximate gain control settings for the MIC-ALL microphone preamps, as determined by the white pointer position on the control knob, are as follows:
The INSTRUMENT INPUTS offer approximately 18dB LESS GAIN at each similar position of their controls.
A very unique design for an instrument amp was incorporated into the TB-10!
Due to the rather crowded conditions of four front panel inputs along with the proximity of the higher impedance instrument inputs to the VU meters and their corresponding susceptibility to hum pickup, instead of the typical UNBALANCED instrument inputs found on most preamps, the TB-10 employs a special impedance/gain adjusted version of the MIC-ALL amplifier block in its DIFFERENTIAL configuration.
This arrangement offers the extremely large low frequency Common Mode Rejection Ratio inherent to the MIC-ALL amplifier design (around 100 dB) and this results in extremely quiet instrument input operation with extremely high immunity to hum pickup!
The TB-10 employs four, separate MP-2 modules for all functions thereby allowing the four channels to all be used simultaneously.
As can be seen, the REAR PANEL is as simple as it gets with a pair of outputs for each channel.
The AC power cord IEC EMI FILTER RECEPTACLE and FUSE HOLDER are at the far left of the panel. .
The XLR output is 100 ohms "quasi-balanced" as per DaviSound Tool Box standards with PIN 2 HI and PIN 3 LO. For balanced operation, shields are ground and should be connected at ONE END only.
For unbalanced operation from the XLR outputs, use only PIN 2 (IGNORE PIN 3) and the shield which, for unbalanced use, should be connected to connectors at both ends of the cable.
The 1/4 inch jacks are for the instrument outputs and are standard tip/ring/sleeve balanced line-level feeds at 100 ohms output impedance. These can also drive unbalanced inputs on succeeding stages if desired by simply ignoring the ring connection (plugging in a standard mono 1/4" plug).
NOTE- XLR outputs for the instrument channels may be substituted if desired as a user option. Also, original TB-10s utilized Tip / Sleeve 1/4" jacks for the instrument inputs.
Inputs now, also, utilize T-R-S jacks to offer additional instrument cable wiring options when mating with the differential inputs.
PERFORMANCE -
Performance "DaviSpecs" Specifications
Unless specifically stated otherwise in individual descriptions ...
and for all Tool Boxes which employ our "MP-2 MasterPiece" circuit module, which is nicknamed the "Mic-All", for the complete signal chain gain block, the electrical specifications are as follows:
ALL amplifiers feature ruler flat frequency response ...
with -3dB points at 1.6 HZ and 35 KHz (maximum gain). There is a slightly variable HF bandwidth increase as gain is actively decreased to unity or below
(flat to 70KHz at unity).
This is because an active filtering configuration is employed to intentionally rolloff extreme high frequency response to minimize RF / EMI out of band interference, noise contribution, and intermodulation distortions.
Combined distortions specifications are where the DaviSound "MIC-ALL" amplifiers REALLY outperform most all others anywhere! There is virtually NO measurable distortion at any level or frequency until maximum gain settings are utilized. Even then, the measurements are near the residuals of the test instruments and barely detectable at the frequency extremes- (.008% at 20 KHZ, +55dB gain)!
Under more reallistic gain settings, amplifier distortion is even lower (example: typically .001%, 1KHZ, 40dB gain ... immeasurable at gain settings below 40 db [theoretically, mathematically indicated better than .0008%] )!
This performance characteristic is responsible for claim after claim from virtually ALL awe inspired users that our amp is the "cleanest" they have ever heard!
One of the most crucial parameters in microphone signal handling is HEADROOM. The MIC-ALL amps are relatively unsurpassed in this regard with signal handling capability right up near +32 dBU before clipping! We acheive this with our House IC and thermal protection which allows a much higher power supply voltage than most conventional designs. This provides a full 8 to 10 dB more headroom than many other professional designs on the market today!
Keep in mind, that output level offered by an output boosted stage does NOT always correspond to system headroom throughout! Some other units boast an output of +36 dB, or more, that do NOT offer that headroom throughout their chain. DaviSound specs are through chain, input to output.
EIN Unweighted -122dB 100 ohms
Noise 20Hz to 20KHz Unweighted - 98dB
Actual internal impedance is 2KOhms, differentially balanced for optimum voltage transfer of all low impedance professional microphones from 50 ohms impedance to 600 ohms impedance.
Actual output impedance is 100 ohms (47 ohms unbalanced) and the high current "Mic-All" output stages will drive virtually any line load from 600 ohms to high impedance bridging with no increase in distortion or any other loading effect!
ELECTRICAL SPECIFICATIONS FOR DAVISOUND HOUSE IC USED IN "MIC-ALL" MP-2 "MasterPiece" Modules |
The inherent specifications of the House IC itself are actually further enhanced in our actual audio application by our circuit design techniques within the MP-2 module!
One such technique ... which we believe has so much to do with the exceptional, noticable "accuracy of detail" comment that we hear so often from users in regard to the performance of our amplifiers ... is a unique inter-stage direct coupling/biasing scheme which forces the amplifier into near full Class-A operation. Any extra heat generated in this process is harmlessly dissapated in the thermally conductive epoxy ecasement of the sealed MP-2 module!
This, combined with the, overload proof, fully variable, active gain technique, produces results as close as you can get to a truly "distortionless" amplifier!
Generally speaking, in regard to most performance specifications, DaviSound Tool Boxes perform better than any of the state-of-the-art equipment that is currently available to test them! This is why we say they offer the quality reference by which to judge all others.
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NOTE:
While the MIC-ALL AMP in theTB-10 offers up to near 60 dB of gain, keep in mind, as can be seen from the chart below, that such extreme settings are very seldom needed! Typical maximum studio mic preamp gain requirements are around 40 dB or less on the average.
Some interesting observations in regard to actual microphone output levels and, thus, resulting amplification requirements -
Here is an enlightening study, done some time ago, and published in Audio Amateur Magazine on several occasions (original- Russell Hamm - JAES 21:4 [May, 1973] ) in regard to audio signal levels measured direct FROM MICROPHONES.
Please note that the measured levels we are talking about here are STRAIGHT out of the microphones themselves with NO additional amplification!
This will surprise most all but the most experienced, veteran recording engineers since, in some cases as will be shown, you would not only NOT need ANY mic preamplification but might even need gain reduction in order to avoid clipping at LINE INPUT LEVEL!
Peak Mic levels 0dB ref to 0dBu=.775 volts
INSTRUMENT Distance in inches Neumann U-87 RCA-77DX EV-666
(Typical condenser) (Ribbon) (Dynamic)
Bass Drum 6 0 -9 -4
Large Tom Tom 12 -1 -9 -5
Small Tom Tom 12 -1 -7 -1
Piano (single note) 6 -25 -38 -32
Cow Bell 12 -10 -29 -15
Loud Yell 4 0 Not Tested -10
Notice that a loud yell (or similar loud vocal musical note!) into a typical condenser mic can produce an unamplified output of 0 dBU which is .775 volts rms or about 2.2 volts peak to peak!
On the other hand, it is not uncommon to encounter, say with a "whispery" female vocalist into a ribbon mic, even as close as three inches, signals as low as -50 dBU or about 7 millivolts!
So, a microphone preamp has to, quite literally, deal with one extreme to another.
The MIC-ALL preamp can, as structured in the TB-10, typically output +28 dBu with some headroom.
However, if set for a gain of, say, 40 dB...it can be seem from the above examples that it would easily overload and distort with many of the microphone signals shown!
At that setting, a loud yell or vocal extreme into a condenser mic at about six inches could cause the amp to try and pass a +40dBu signal ...obviously at LEAST 12 dB past the clipping point!
Obviously, the higher you raise your
"0 VU" operating level, the LOWER your headroom before the clipping stage!
That is the point of the INFINITELY VARIABLE GAIN CONTROL that allows you to continually "dial-in" just the right amount of gain for your incoming microphone signal!
GENERAL -
The rack cabinet itself is made from hand sculptured SOLID OAK, natural wood. As of spring 2001, we have opted for lustrous, hard penetrating oil finishes for the cabinetry as this provides added protection for the wood and, unlike other oil finishes, it is relatively maintenance free. Simply wipe it with a soft dry cloth to restore lustre. The front and rear panels are treated with extra coatings of acrylics for added protection.
WG Models, such as the TB-10, are entirely made of wood! The front panel as well as the rest of the cabinet are ALL solid oak (unless other exotic woods have been utilized by client arrangement/preferance). Like all natural things, every piece of wood has its own, distinct character and "personality". This makes EACH AND EVERY "WG" model unique unto itself which enhances the aesthetic value of the piece and the actual appreciative monetary value as well!
Keep in mind that as part of this wood "character" it is impossible to find/utilize a "PERFECT" piece of wood. This means there may be slight imperfections, or variations, in terms of grain pattern, color uniformity, and skew. However, any such natural variations in our selected pieces are very minor and are the very thing that gives wood its charm and "character" appeal!
There are NO user servicable parts inside. DaviSound Tool Boxes are fashioned from our "Master Pieces" modules which employ hand-laid circuitry, silicon embedded into plastic cased modules. In the unlikely event that service should ever be required, simply contact us for return authorization and we will replace the defective module(s).
While never having been enforced, it has always been original DaviSound policy to void warranties if the cover is removed! However, certainly be advised that ANY internal tampering or unauthorized repair or modification attempts void all warranties!
DaviSound products are carefully assembled BY HAND, one piece at a time from start to finish,
in prototype assembly fashion, with extreme care and attention. They are designed to perform
from now on with no trouble.
However, there are always "real world" imperfections that can not be anticipated or accounted for no matter HOW careful one might be in fabrication. For example, we don't make the ICs and we don't wind the power transformers and these things can fail at times. Ours seldom do, due to extensive testing and pre shipment "burn-in" periods, but if you should ever have a problem, you are protected for as long as you own the equipment, as the original owner.
Simply carefully repack the unit in the original packing, ship it back to us (after notification) to
DaviSound, 1504 Sunset Ave., Newberry, SC 29108 803-276-0639
and we will repair and reship at no charge to you whatever!
Thank you for your purchase and use of a DaviSound Tool Box!
And, we also thank you for allowing us to go these "extra lengths" within YOUR operating manual to elaborate in accordance with our "mission" in publishing these on-line manuals. It is all part of an ongoing effort to provide as much educational material as possible from this website in the sincere belief that ...
The more one truly KNOWS about audio electronics, the more one can truly appreciate the DaviSound methods!
We thank all of you who ALREADY know all of this covered herein for your indulgence as we present it for those who do not!
Please let us hear from you regarding your application of our unit and feel free to contact us with any questions or comments throughout the future!
We also hope that you will consider ALL of the DaviSound Tool Box models for your rack!
THANK YOU and GOOD LUCK!