H A Ü P F E A R ©™
"Keeping The Tradition"

By
DaviSound




SOLD - 5-05

This listing describes our very first "DaviSheen" offering which was sold on eBay after a short posting on our "Unique Special Items" website area.

We will have other "DaviSheen" pieces available in the future when time permits.

The listing also spawned other interest and other custom preamp commissions.

WE WELCOME CUSTOM COMMISSIONS FOR SIMILAR VACUUM TUBE OFFERINGS, MADE-TO-ORDER, PER YOUR PREFERANCES, INCLUDING OUR LATEST SE TRIODE MPT-CIRCUIT BLOCKS!

Just send us an email letting us know what you would like in a preamp control center and we will submit a custom quote to all serious, qualified inquirors.

For reference, this piece is $3K price range.

Please review the following eBay description, which was written in narrative style, to hopefully provide an entertaining and informative read while, at the same time, fully describing this particular creation and all that went into it!

Thank you for your interest in DaviSound "DaviSheen" Audio!






Please scroll entire page for complete description.
The following index is provided for repeat viewing of specific sections.

LISTING INDEX:
BEGINNING | INVITATION TO BID | SPECIFICS | GAIN SETTINGS | DAVISIRKIT RESPONSE GRAPH
PANEL LAYOUT LEGEND | CIRCUIT DESCRIPTION | SPECIFICATIONS | SUMMARY





This listing announces a very unique, truly rare (because it is one-of-a-kind!) ...
Totally new (just recently completed) ...
Entirely hand-made, audiophile quality, stereo audio system control preamplifer.



I named this unit ... "HAÜPFEAR" ... in honor of my Paternal Grandmother
(her maiden name) and her family of craftsmen including my Great Grandfather ...
a German immigrant.
(NOTE: HAÜPFEAR is pronounced, authentically, "Hawph-ear" or traditionally, by us southern family members, as "Hop-fear")

I am not attempting to convey that it has a "German connection" other than that.

Although I do, also, recognize, honor and applaud the German tradition for audio excellence and, so, if it should bring that to mind in any way by its name, design and performance, then I will be honored in that regard, as well.

I am Hayne Davis, operator of DaviSound (DaviSound.com), and this handcrafted piece is my own creation, built especially to be introduced and offered herewith. I would like to describe this unusual preamp here, specifically, and explain why I believe it to be uniquely special.

Then, if you will indulge me, I would like to follow with some general information about DaviSound and our unusual audio design philosophy and fabrication technique that has distinguished us for over thirty years in select, professional audio circles.

I believe that you will find this documentation both informative and necessary to fully convey the integrity behind this piece and the long tradition for sonic excellence that supports it.

I implore you to, please, stay with me throughout the entire description presentation before forming a lasting impression of my work ... especially if I happen to mention something along the way that may normally be "scoffed at", or sometimes dismissed as "bad practice" in certain audiophile forums. If that seems to happen, then I assure you there is a very "sound", logical reason for it which will be brought to light as you read further!



The HAUPFEAR Preamplifier


" BOTTLE CRATE ? "

As you may surmise from the two center ports in the top and the faceplate, this is a total vacuum tube, active circuit design which is, unhesitantly designed to both facilitate, and showcase,
the "bottled beauty" of the twin triodes!

This stereo consolette employs just one, uniquely configured, tridode vacuum tube per channel as you will read about in detail herein.


If you know anything at all about DaviSound ... you will know that we have become rather well known in recent years for our exclusive, innovative solid wood, hand-sculpted cabinet enclosures.

You will note that this piece, like our professional processors ...
the DaviSound Tool Boxes, is fashioned entirely from wood.
In this "case" (pun optional), it is solid, 1/4 " reinforced, hand finished, Black Walnut.

Unfortunately, photographs NEVER seem to do justice to the real thing and just cannot convey the hand sculpted detail, and the natural wood beauty, anymore than all of the description herein can convey the audio performance. You just have to experience both, personally, to even begin to appreciate the unit aurally and visually!

But, digital photos and written descriptions are all that we can present here ...
so we will do the best we can.


Entirely built by me in every regard, from scratch by hand, The "HAÜPFEAR" is designed to have an aesthetically simple, rustic elegance of appearance to match the simple elegance of its sonic beauty!




The HAUPFEAR Preamplifier


Audio Professionals
have described DaviSound hand-made original items as ...
"FUNCTIONAL WORKS OF ART"

And function ... they DO!

We would be honored for you to bring this one-of-a-kind, exemplary piece ...
directly to your home from the DaviSound craft bench!




DaviSound
Hand-crafted Precision Professional Audio Components
are utilized in elite professional recording studios around the world.

We are pleased to create our pro audio tools
for some of the most discriminating, high profile ...
veteran music and media professionals working today!

You can read user comments
from a few of these distinguished users on our website.


Limited and Single Edition ...
Unique ... High-End Home Audio Components
Are handcrafted only by commission or ...
At RARE Opportunity ...
Specifically created for a limited auction such as this!

Not only are these individually styled items often sought after for their
impeccable audio quality ...
They are also desired for their future appreciation value ...
as a collectible investment ...
As well as for their unusual aesthetic appeal
as unique furnishings for the home environment!







The cabinetry for this unique design is hand crafted, rubbed Black Walnut ...
including the control panel highlighted by WHITE LED, switchable accent lighting ...
large, vintage style bakelite knobs ...
and multi-colored LED status indicators.


The UNIQUE Haupfear Consolette


The UNIQUE Haupfear Consolette


You will note that, aside from the main nameplate ...
"HAÜPFEAR" features NO panel nomenclature or lettering of any kind.
This is a unqiue design consideration and characteristic of DaviSound pieces such as this one.
We have found that such a control panel contributes greatly to aesthetics while adding mystique.

The panel and controls are logically laid out and largely self explanatory in function.
A printed legend is provided so that the operator may become familiar with the various controls but, after only a few hours of use, the operation of the unit becomes entirely second nature to the owner while deliberately appearing esoteric to the casual observer.







SPECIFICS


This is basically a six stereo input, two channel, five stereo output, audio control center.

But, aside from it's unique aesthetic appeal, this consolette also features some very esoteric functional features as well!



Some of these can best be presented, at a glance, by a simple, signal flow diagram:


This preamplifier was designed for versatilty and a measure of control seldom seen with so-called, "high-end" designs.


Rather than use the traditional rotary switch method of selecting inputs, the "HAUPFEAR" utilizes a bank of double-pole, double-throw mini-toggle switches mounted at the top center of the control panel with which to select any of the FIVE, rear stereo inputs from their gold plated RCA jacks.


All RCA Input and Output jacks are, of course, GOLD Plated
for maximum conductivity and corrosion resistance.


There is also a single, front-panel convenience jack per channel, also with an
adjacent in/out switch.



You will note that this switching system allows for a measure of "MIXING", or more accurately, combining, by a properly designed matching network of low noise, metal film resistors.

Coming from first a broadcast and, then later, a recording studio background, I never understood the flawed logic of purposely avoiding a mix feature in a multi-source preamp because of some misplaced reasoning. In fact, I originally considered a full mixer design for this unit incorporating both individual level controls as well as "balance" controls for each input!

One of those "purist" "scoffers", you say? Well there is no reason for it to be, that's for sure!

I maintain that a properly designed, and matched, combining network will have no effect on signal purity other than, possibly, very subtle level changes due to the slight variations in loading when switching multiple sources in/out. This, of course, the whole point of having individual "gain" controls for compensation!

Furthermore, since the unit is NOT intended primarily for use with the combining feature, each combining resistor is totally OUT of the circuit when any input toggle switch is in the "down/out" position.

Our "old-school" hand wiring techiniques and layout, employing braided, twisted pairs, insure that there are NO effects, or artifacts, caused by the wiring from this input arrangement.


In reality, one may very likely never use the "mix" feature, especially for more than two sources at a time, but it is there just in case. Otherwise, the operator simply switches the input toggles on/off in succession, one at a time,
as may be desired.

While on this topic, it is worthwhile considering just why we need/use a preamp in any event now that high line level digital sources are the norm. I also find it amusing that I now hear discussions about "passive" "preamplifiers" ...
an oxymoron if I ever heard of one!

Assuming one could cope with about 6 dB overall through-loss, I could just have easily designed and offered a truly PASSIVE control center to be used ahead of one's power amplifier. I would have, of course, in that case called it a "passive controller" and NOT a "passive preamplifier".

But, even with the high levels of CD players and other similar sources available nowadays, it is still nice to actually have a true GAIN option when desired. In this instance, I chose to have our gain, about 15 dB per channel, provided by a uniquely configured triode vacuum tube per channel! This is plenty of drive and control to properly match the needs of ANY power amplifier!

And, while on this subject of the "INS AND OUTS" of this unit, though it should go without saying to any enthusiast who may be considering such a preamp, we will say it anyway. The inputs to "Haupfear" will accomodate virtually any line level audio source such as CD player, DVD player, MP3 player, computer audio line output, analog tape deck, TV audio, receiver, home theatre processor ... WHATEVER.

Likewise, the low impedance outputs will drive any variety of loads such as, of course, your power amplifier of choice, a recording unit digital and/or analog, computer audio line input and, virtually, anything else of the proper load impedance (10 Kohms or above) that you may want to bridge across the output divide network at any output jack.

And, of course, the newly modified version of "Haupfear" offers PASSIVE RIAA equalized phono preamplification now normalled through at the channel 5 inputs.





The extra gain buffering also allows for another very useful feature which is a totaly transparent, "either / or" function that we have included. It is a very gentle EQ "pre-set" which we call the "DaviSirkit". This feature provides for,
at least, some tonal enhancement at the flick of a switch when/if it may ever be desired. If not ...
simply never switch it in!

I assure all "purists" that the "DS" pre-set EQ ...
has absolutley no affect on the circuitry, or the audio signal, when not switched in!

The DaviSirkit provides a mild, (+7 dB Maximum) shelving, hi / lo boost curve
very similar to traditional "loudness" equalization.
It is accomplished, in this instance, with passive R/C nets ...
composed of polypropylene film/foil capacitors ...
and non-inductive, low-noise, close-tolerance resistors.


It is, in actuallity, a broad dip filter that, when used in conjunction with a few dB of tube gain
from the gain control, provides the HI /LO shelving "boost" effect.



OTHER FEATURES INCLUDE ...


You will note the unusual power switch bank to the right face of the control panel. There are three vertically in-line mini-toggles with three adjacent, associated, staggered LED indicators.

The lower most switch is the main AC power switch.

The second, middle switch is the DC powered, "Filament" switch for the tubes which energizes the tubes to "warm-up", or "stand-by", condition.

The final, top-most toggle controls the plate voltage and it is interlocked with the filament switch so that it can not be turned on unless the filament switch is on.

We utilize the familiar, instinctive "Traffic Light" indicator sequence with the bottom, "idle" indicator being RED ... the middle "warmup" (heater voltage) indicator YELLOW ...
and the top most "on" (Plate voltage) indicator GREEN.

We are amongst those who still believe it desirable, even with low power, small signal tubes, to switch power to the heaters for a minute or so prior to switching on the high voltage to the plates.

This system requires you to follow that 1-2-3 power-up procedure.

Continually switching high voltage to cold tube plates could, possibly, cause cathode stripping.

By the way, we also recommend that the unit be shut down by the same method - in reverse order.

Furthermore, it may be worth mentioning that despite the advice to the contrary by some of today's "expert" dealers, we are of the "old pro school" that believes tube gear should best be left on consistently,
twenty-four hours a day, for maximum lifespan and lowest noise, consistent electrical performance over time.

In the "old days", large studio complexes would even "cook" new tubes, in specially designed equipment with
"burn-in" sockets, for extended time periods before retubing gear and the studio equipment was, subsequently,
NEVER powered down!

So, you might want to consider, at the very least, minimizing the on/off cycles of your own gear!


Just as two, separate L/R input jacks are provided for auxillary front panel access, two output jacks are also provided on the front panel, one for each channel. In addition, there is a headphone switch which operates "either/or" routing the main outputs to their normal distribution networks and subsequent rear panel Gold plated RCA jacks, or to the front panel 1/4" T-R-S headphone jack.

Since there is no discreet headphone amplifier, there can be no simultaneous feed to both the normal outputs and headphones. However, this method does allow for monitoring the outputs, albeit at very reduced, low volume, with lightweight, medium impedance headphones, direct from the tubes, when desired for testing purposes. It will be explained how this low impedance drive is possible from an OTL circuit, when circuit topology is covered shortly!

ALSO SEE *TUBE NOTE* BELOW


The associated level controls are separate, one for each channel, and are highest studio quality, sealed, conductive-plastic potentiometers guaranteed for over a million, smooth, noise-free rotations.



The HAUPFEAR Preamplifier


Light Therapy?

Among the unique features of "HAÜPFEAR", are the rotatable,
white LED accent lamps as pictured above.

These feature tight-focused, white LED spot lighting mounted in penlight housings attached to ball-in-socket swivel mounts at the top ends of the control panel. This allows ambient lighting to highlight the control panel under dim lighting conditions and provides a very appealing aesthetic effect, along with the warm glow of the tubes and the LED indicator lighting.

These lights may be rotated to virtually ANY position thus accenting and illuminating any part of the panel, or adjacent surroundings, to the degree desired.



The HAUPFEAR Preamplifier

Just as the preamplifier offers the front panel tube ports for both viewing and ventilation purposes, the top cover provides similar, 1 1/2" diameter ports directly above each tube. This allows for air flow as well as easy viewing of the tops of the tubes.

Since the cover is too far above the sockets for easy finger access ...
whenever cold tube swaps might be desired for experimentation, or for replacement ...
the top cover must then be completely removed.



        Dimensions are: Faceplate 19" x 6 3/4"         Cabinet - 17" (width) x 10" (depth) x 6" (height)

We regret that the lighting and color balance in the photos abvove is not entirely accurate and does not convey the richer BROWNISH color of the Black Walnut.
The color rendition is somewhat more accurate in the photos of the panel lighting closeups shown previously.

The unit includes four one-inch diameter rubber cushioned feet mounted on the bottom.



THE NEW, COPPER-BACKED, 1/4" THICK WALNUT CIRCUIT BOARD FOR THE STEREO PHONO STAGE

The phono stage, added since original completion in April, is a classic passive RIAA EQ, "sandwich" ...
with gain distributed amongst two triode stages for both optimal headroom and S/N.
The first triode is the input buffer for each stereo channel...
and the second tube serves as the EQ buffer for each channel.




A NEW ANGLE "UNCOVERED"

Another photograph of the unit, with a different camera from the last photo shoot,
allowing a little closer to the true color representation of the black walnut cabinet.
It also better displays the gentle, tilted slope of the front control panel.



CIRCUITRY AND SPECIFICATIONS

And speaking of tubes ...
I know that all readers, by now, must be quite anxious to find out about the circuit topology...
and the tubes which are utilized.

With a name like "HAÜPFEAR" ...
you, no doubt, expect the use of Telefunken smooth plates, or similar.

As a matter of fact, we did consider using Telefunken 12AX7s for this design but a matched pair was not readily available at the time of completion and testing (But ... be sure and see the "Tube Note" included below!).

We did find a set of Brand New (NOS) 5751 tubes with near identically matched specs! For those who may not know, 5751s were originally introduced by GE in 1948 (coincidentally, the same year I was "introduced" so we are the same age!) for "aircraft, industrial and control" (ARINC) designated applications for the military.

While often seen in "hi-tech", state-of-the-art medical equipment of the day, such as one of the first, successful ECG machines, these tightly held, military specs tubes were very expensive to produce and were therefore considered much too "pricey" for general purpose audio use in those days.

However, they are, essentially, just very rugged 12AX7s with extra mica spacers, sturdier frames and extra parameter control maintained during manufacture, including must-pass tests for extremely
low internal vibration and microphony.

The heaters run slightly hotter, drawing a bit more current and they inherently offer reduced distortion over a 12AX7. Otherwise, they are essentially the same as a 7025 version of a 12AX7. With their linear characteristics, they happen to be ideal for the particular circuit topology that we chose for our preamp!

And, just as I can attest that this is an unusually VERY quiet tube preamp design overall ...
I can also assure you that the matched 5751s offer very low noise performance indeed! Your audio will "jump out" to you from a background of "velvety silence"! The recent noise tests with these tubes actually far surpass the published specs herein!



"Re-Inventing The Wheel"

I have an odd characteristic (actually MANY "odd" characteristics according to my wife!) of consistently attempting to "re-invent the wheel". I am noted for going off for days on "brain-storming/brain-bruising" sessions figuring out "new ideas", honestly and creatively ...
only to find out later that somebody else had already figured it out before I did!

Such was the case, to some degree, with the circuit I came up with that I felt may make a unique,
"ideal tube preamplifier" gain block!

I think that for me personally, as a designer/builder, the chief appeal of, and continuing fascination for, vacuum tube audio, (nostalgia aside) is, again that phrase, "elegant simplicity" as I have often seen it called. Those audio enthusiasts familiar with the DaviSound ... "DaviSimple" ... philosophy know that we aspire toward the most efficient, least cluttered circuit topologies we can devise for ALL of our designs!

I have had quite a bit of past experience with vacuum tube design and application but my most extensive past experience, and my expertise, is, admittedly, with making solid state circuitry "jump through hoops".

So, when I began my latest "brainstorming" efforts, scribbling various circuits on paper, trying to come up with what I thought would be a fairly original idea for a two stage, reasonably low impedance, high-drive tube line amplifier circuit, I was naturally drawing on my experience and knowledge base of solid state circuit design.

I had never actually employed direct coupled, two-stage triode circuits in operation before but wanted to try and implement the concept in this design if I could. I started with the same design I use in our DaviSound "MP-4" discreet transistor, Class-A, "MasterPiece" circuit block module. And, while, of course, they are not always directly interchangable, I began sketching out triode tube configurations with plates, grids and cathodes in place of collectors, bases and emitters or drains, gates and sources.

It wasn't long before I actually came up with my own "original" ... so I thought ... version of an unusual looking circuit that I subsequently learned had already been devised, even pattented ... just a "little while ago" ...
a little while ago back in 1943, no less!

Then, after being initially put-off a bit, I was both surprised and simultaneously elated to discover that a few of today's high-end designers are already using this circuit, or their tweaked version of it, in somewhat the same way that I intended!

The general circuit topology that I am referring to is known as SRPP. This translates to ...
"Shunt Regulated Push Pull" configuration. At least that is the most commonly accepted name of the circuit!

It seems that SRPP was the only designation listed for the circuit by the originator and everyone else has since just guessed exactly what SRPP refers to! Some think it is ...
"SERIES Regulated Push Pull", while some few say ...
"Series Reflex Push Pull".

Personally, based on the way it functions , as well as the terminology that was used in the forties ("reflex"), I tend to go along with the latter designation- "Series Reflex Push pull". But there were shunt voltage regulators based upon similar cascade structure so who is to say for sure where, exactly, the SRPP designation comes from or what it refers to. In any event, it is basically just a variation on the old "totem pole", bootstrapped, cathode follower layout with a few "twists" applied. In my case, I have even employed another subtle "twist", or two, (actually just a few well-chosen/placed resistors) to further balance the circuit and enhance performance!

Now, I have have had some correspondence relating to this topology that I need to address here and, thereby, clarify some misconceptions. Since our first listing, several "passionate", audiophiles have written to tell me that I should consider something besides an SRPP styled circuit for my new "tube gain block" for this or that reason. As is, more often than not, the case in such "biased" situations, each of these was basing a conclusion on wrong information in all of these communiques!

First of all, the circuit DOES , indeed, function in TRUE CLASS-A ! In fact, that is the only way this circuit CAN function ... it depends upon Class-A bias in order to work at all!

Secondly, yes I know it really is "push-pull" and, unlike some, I do NOT consider that a bad thing when properly applied. But, in fact, I do think that this unique circuit arrangement might offer the "best of both worlds" and that fact may lead to, yet, another name designation for it by some users ...
that being "SINGLE-ENDED REGULATED PUSH-PULL" (oxymoron time again?)!

Thirdly, yes, it truly does indeed act as its own "phase-splitter" for push-pull function and, although no curative, overall negative AC voltage feedback is utilized, it also seems to have a "magic" distortion-reducing arrangement by about a factor of 10 (based, I suspect, upon the 180' out-of phase, constant-current, cancelling effect)!
Some "simple" little circuit, indeed!

So, while there seems to be much misinformation out there about this, obviously, very misunderstood circuit topology, and I don't pretend to have all the answers to solving its mystery, I can say, based on my testing and experience to date, I believe it to be the most unique, all around tube circuit topology I have come across! Since there is no overall negative voltage feedback, there still can be plenty of "tube sound" although the measured distortion is lower than expected at nominal output levels and loading.

It DOES offer the ideal audio transfer characteristics of high input impedance, very low output impedance and excellent linearity with fairly high output drive capability. All of the parameters, of course, being governed precisely by the particular tube utilized. Some of the most common tubes seen in various spin-offs of this technique include the, low-gain, 12AU7 and its close cousin, the ubiquitous, high-gain, 12AX7!


Our particular "SuperSirkit" here operates in Class A with no externally applied global AC feedback!


Now, what we have learned is, the Sylvania, JAN (joint Army Navy) military grade 5751s we are utilizing herein, perform exceptionally well in this circuit and exhibit superb audio characteristics right out of the chute!

Our uniquely configured version of the SRPP circuit is already superb for audio, as mentioned, with the "upper half" of the tube acting as the direct-coupled cathode follower output stage while simultaneously serving as a constant current, plate load for the voltage gain, "lower half" configuration. That, aided by the extra linearity of the 5751 employed in this application, makes for an almost unbelievably low distortion tube amplifier!

So ... that's our topology ... almost public domain "textbook" but with a couple of our own little improvement "tweaks" and a great pair of tubes!


The new owner of the "HAÜPFEAR" can feel free to experiment and try other 9 pin, dual triode equivalents in the circuit, including those beloved Telefunkens, and see what his/her own ears reveal. That is, of course, half the fun of owning a tube amp!


* TUBE NOTE *

Substituting a pair of higher current, high-drive 12AT7s in this preamp design (in the main tube board) will actually yield listenable headphone levels from the headphone jack, direct from the tubes ...
if medium to high impedance (non-loading) phones are utilized!

So, that being the case, we will INCLUDE, AT NO EXTRA CHARGE ...
a selected pair of genuine Telefunken 12AT7 tubes for the new owner ...
inside the box, at shipment!


The "Uniqueness" Continues ...

The HAUPFEAR Tube Circuit Board

Our 5751s are mounted on a unique, hardwood circuit board whose hand-wired, hand-soldered, surface mounted support components are securely surrounded by thermal epoxy. The 9 pin tube socket is, itself, epoxy mounted to the board and its silver-soldered pin connectors are also encased in a rigid, protective covering of thermally conductive epoxy!

NOTE:
All electrical connections within DaviSound "DaviSheen" preamps ...
including all internal to HAÜPFEAR ...
are first soundly, mechanically formed ...
and then SILVER soldered!

(This unit utilized almost an ounce of silver solder)


The HAUPFEAR Tube Circuit Board


The discreet circuit boards are, in turn, mounted to the cabinet bottom with a sandwiched layer of double- sided copper ground plane between the boards and the Walnut floor.

Whether or not you have the West German Telefunkens installed in this particular model, the "HAÜPFEAR" can boast another "theme" component from the "Motherland" ... the inclusion of ROE, high quality, low ESR, "European style" high voltage electrolytic decoupling capacitors of West German manufacture used consistently throughout.

Three such 1,000 uF caps are seriesed, to triple their voltage rating, for a resulting capacitance of about 300 uF. These banks are, in every instance, by-passed over-all by high quality,
.68 uF 400V film/foil signal capacitors.


You will note one such decoupling R/C network at the B+ entrance to each tube. The caps are recess mounted in countersunk holes, again encased in thermal epoxy for stability. As a result of this method, each tube, in effect, has it's own isolated supply! Our decoupling arrangement has ultra low impedance at audio and allows ultimate dynamic range.




The HAUPFEAR Power Supply

The power supply board is made of yet another section of discreet Black Walnut. It mounts two separate, high quality Toroid, transformers feeding a high voltage, full-wave bridge rectifier for the stable, high voltage B+ circuitry exclusively and a third transformer for the separate heaters and lamps supply.

The resulting DC is filtered on the main board by an RC net previously described and, in turn, by the individual decoupling nets on the tube board.

"HAÜPFEAR" utilizes RC filtered DC for the filament supplies.

The entire supply is fed from a fused, EMI filtered, IEC connector with detachable AC cord.






The HAUPFEAR Preamplifier

The Haupfear Consolette about midway during construction and prior to supply board installation.





The HAUPFEAR Preamplifier

Another interior view of The Haupfear Consolette upon completion.











Electrical Measurements


  • Gain +15dB into 10 Kohm load
  • Input Impedance ~ 10 Kohms
  • Output Impedance ~ 150 ohms
  • Bandwidth (-3dB) 2.12 Hz to 66 kHz
  • Combined Distortions < 0.08% at 1kHz, 1.2 Vrms into 10 Kohms
  • THD almost entirely second harmonic
  • Odd order and all upper harmonics near nil
  • SNR - Main Inputs to output > 87 dB unweighted
  • SNR - Phono Inputs to output > 76 dB unweighted
  • Output to input phase Inverted at center pins







  • Haupfear Highlights in a "Wal NUT SHELL"
    An outline of features covered in description

  • Tubes - 2 Sylvania -JAN - NOS - 5751; 2 Telefunken 12AT7 (spare/option);
    2 New/Matched Sovtek 7025/12AX7WA (Phono)

  • Coupling/By-Pass Capacitors - Film/Foil

  • Signal Shaping Capacitors - Polypropylene Film

  • Resistors - 1% Metal Film

  • Filter Capacitors-Main - Roe Low ESR Electrolytic
    Phono Board - 2 High Voltage computer grade - 390 uF/400V each

  • Inputs - 12 discreet Gold Plated RCA 6 per channel

  • Outputs - 10 discreet Gold Plated RCA 5 per channel

  • Individual Toggle Switch Input Routing

  • Precision Passive combining/ dividing networks

  • Three Toggle Switch Turn-On
    Sequence System

  • 3-Way Red, Yellow, Green LED Indicator panel lights

  • 270' Rotatable White LED Accent Utility Panel Lighting
    Separately Switched

  • Large, brushed metal, cabinet handles

  • AC supply - 1 amp AGC fused power input to IEC filter conditioner receptacle
    Detachable AC three prong power cord

  • Power Supply Transformers - 3, 1.5 amp Toroid

  • Power-on warmup time approximately 15 sec.
    Power-down Bleeder resistor supply discharge
    approximately 2 volt/sec.

  • DC Heater Supply
  • Gain- Phono stage - 40 dB; Main stage - 15 dB (variable)

  • Phono Input matched for MM cartridge
    Adaptable to MC on request

  • Switches - Miniature Toggle

  • Potentiometers - Low noise, precision, Conductive Plastic

  • Stereo 1/4 inch headphone jack

  • Interconnections -Ultra Low Capacitance/Low Noise
    Belden Twisted Pair Ribbon

  • 14 Gauge, Reinforced Grounds where bussed

  • Braided RF Grade Ground Strap at Phono Inputs

  • Double Sided Copper Ground Plane Shields

  • Hand Sculpted/ Hand Rubbed Natural Black-Walnut Cabinet -
    Penetrating Tung Oil Hard Finish

  • Top/Front Tube Ports

  • 1 inch diameter by 1/2 inch thick, cushioned, rubber feet

  • Hand-wired, Hard-wired, Silver-Soldered

  • 48 Hour Burn-In Full Audio Proof Of Performance

  • Custom Owner's Manual Applications Notes

  • Printed Certification



  • The following segment by DaviSound associate engineer, O.T. Hudson

    DaviSound has been custom fabricating hand-made, top quality signal chain audio components for almost two and one half decades. Many of the things you read about that are heralded as "innovative" by various manufacturers in today's marketplace, DaviSound has been aware of .... and utilizing .... all this time.

    Hayne Davis "wrote the book" (quite literally - Davisound TECH REPORTS ©1986/2000) on audio power supply design and capacitor relationships, along with special grounding techniques, and has always practiced what some are just now advocating .... such as multi-tier filter capacitor banks .... signal quality
    by-pass capacitors throughout .... and decoupled, isolated supplies for each stage.

    Likewise, truly unique grounding and construction techniques, many of which are exclusive to DaviSound in this day and age, also contribute to the unique audio clarity that distinguishes all DaviSound creations.

    Another DaviSound tradition has been to use hand-picked, matched, selected
    over-rated components and carefully, and skillfully, hand-solder them using tedious assembly techniques that are rapidly becoming a lost art amongst today's engineering society.

    Interconnecting hard-wiring employs exclusive Twisted Pair Belden Ribbon Cable with alternating pairs configured as ground shields between the signal pairs
    (based upon a technique taught by the late, great audio engineer ...
    Norman Crowhurst!).

    Other "DaviSecrets" amongst these utilized from day one by DaviSound, but only recently being boasted about elsewhere, are to keep circuit impedances comparatively low throughout the internal chain and to keep the signal path as simple and as uncluttered as possible with a minimum of active, and reactive, components all properly positioned and laid out with respect to each other.

    I assure you this is a "living example" of the "perfect marriage" of "yesterday/today", handcrafted, audio engineering!

    I am pleased to contribute my endorsement of Hayne's personal work on this one!





    H A Ü P F E A R






    A CLOSING, PERSONAL MESSAGE FROM THE CREATOR OF THIS UNIT ...
    HAYNE DAVIS, Director, DaviSound




    With this listing you are NOT dealing with a volume retailer or distributor but, instead, you are dealing directly with me, the designer and the fabricator!

    I will be happy to answer any and all questions before and after the sale and your purchase will be backed by the integrity of DaviSound!


    I personally hand-sign, and date, the interior cabinet of each piece I create, upon completion, just prior to cabinet enclosure. I assume sole responsibility for it's proof of performance.

    This is not a "vintage" piece because it is a brand new hand-made unit ...
    hand-made by me, personally.

    But it is intended for a "vintage" owner ... "vintage" meaning "been around quite a few blocks ... quite a few times" ... like me.

    That's why it may be listed in a "vintage" category where I am most likely to find that appreciative owner who still cherishes the ultimate ANALOG signal chain combined with "old fashioned, hands-on control".

    If you could be the one to bring this unique piece home, this most likely means that, also like me, you are disgusted to the point of being almost sickened by many of today's so-called "state-af-the-art", manufactured audio offerings.

    However ... if your priorities in a preamp include "remote control" and the inherent coloration and distortion that comes with it ... a clutter of white, cliche'd screenprint labeling on a look-alike black anodized surface ... miniaturized cookie cutter circuit boards ... "chick" overpricing and nonsensical descriptive hype .... a reassuring, flowery, trendy review in an audio "fashion" magazine ... then this listing is not for you.

    On the other hand, if you are that one, special, owner I am seeking for my preamp who senses what I am saying here, who will take the time to go to the DaviSound.com website and study , and thereby subsequently appreciate, our audio electronics design/fabrication methods that we have provided for the elite of the pro audio industry for so long ... then please thoroughly consider
    my offering herewith.

    It is for the true, seasoned audio enthusiast who has been around long enough to know unique, esoteric quality when he/she hears it and, yet, who has the good common sense to appreciate, and recognize, just what techniques and methods cause it to happen as opposed to those which have nothing
    to do with it.


    With DaviSound there is no "suggested retail" since everything we build ...
    we sell directly to the customer.

    Normally we work for a waiting list of clients who commission select,
    made-to-order pieces. This one is my own commission and offered here prefabricated and ready to ship. Such an opportunity does not come often!

    This is a piece that I have, personally, wanted to build and offer for some time and, I assure you, it is the ONLY such audio preamplifier in the world! Certainly, that fact qualifies it as a true collector's item along with offering the very finest in a vacuum tube audio control center of its kind.

    You can be sure that my gear is fairly priced regardless of what it may be. If the price is significant, this is for valid reasons, namely the time and labor intensive, meticulous, "old-fashioned" hard work totalling many, many hours of fabrication time and reflecting many more hours of prior design and research.

    Our prices are NOT the result of a "purchased reputation", or based upon gullible exploitation of the fad inclined, as are some others.

    Furthermore, DaviSound audio creations are made for the individualist who wants to wrap his/her hands and fingers around some larger sized knobs attached to smooth, solid controls mounted on genunine hand-constructed ...
    hand- finished panels which are designed for aesthetic beauty, and unique character as opposed to assembly line convenience.

    Our utilization of hand crafted, solid wooden cabinetry and discreet hardware componentry offers a fine quality piece for your home that is seldom, if ever, seen in today's audio world anywhere besides DaviSound! It should be a family treasure for years to come.

    On the inside, our unique handwired, point-to-point, circuit laying techniques are truly most unique to us and are at the heart of what gives DaviSound audio signal chains the laboratory reference quality by which to judge all others ...
    quality we are known for prevalent in all of our critical, pro studio preamplifiers!

    Whether you have never before tried tube circuitry, or you are a seasoned veteran, I am convinced that you, too, will "fall in love" with the "bottled beauty" that the new "DaviSheen" designs provide including the unique topology used here in the first, original "HAUPFEAR"!







    These ready-made audiophile offerings are, inherently, VERY rare
    since our pro audio commitments only allow for limited opportunities ...
    and because the design/fabrication time investment is significant and irrecoverable.

    So, when we say,"RARE" and "LIMITED EDITION" ...
    we mean that in the strictest sense!

    We do not know just when we may be able to present
    another prefabricated version of ...

    HAÜPFEAR






  • This unit presented herewith is guaranteed to be free of electrical defects and to meet the specifications as described. We will repair the unit, under lifetime warranty, for the original owner, subject to the terms and conditions set forth on the "Current Price Lists" Terms-Policies-
    information page published on the DaviSound.com website.

  • Tubes and cosmetics are excluded from the lifetime warranty.

  • While we believe it should go without saying to anyone considering this item, we still publish the following disclaimer herewith:
    There are exposed, potentially LETHAL , High Voltages inside this unit. Remove top cover ONLY with all power switched OFF and detachable AC cord removed! DaviSound can not and will not be held liable for any application or misapplication of this unit after purchase!

  • An owner's applications manual will be provided detailing operation and handling of the unit and further describing a recommended power-down, capacitor discharge procedure for tube removal.

  • While we believe we have provided ample information herewith to establish our credentials and to allow you to make your purchase...
    We urge that you further investigate the integrity of DaviSound.com by visiting our website.

  • Only serious, qualified buyers are solicited.
    Please email any questions regarding any uncertainties BEFORE you bid/buy!

  • Be totally committed to the purchase before you bid/buy.
    All sales of DaviSound handcrafted items are firm and final.


    WE SINCERELY THANK YOU FOR READING
    AND FOR YOUR THOUGHTFUL, INVESTMENT CONSIDERATION!






  • DaviSound
    "DaviSheen"
    Bottled Beauty


    The above phrase and all designations herein ...
    are copyrighted trade names of DaviSound by DaviSound ©™ 2005, ALL RIGHTS RESERVED!



    LISTING INDEX:
    BEGINNING | INVITATION TO BID | SPECIFICS | GAIN SETTINGS | DAVISIRKIT RESPONSE GRAPH
    PANEL LAYOUT LEGEND | CIRCUIT DESCRIPTION | SPECIFICATIONS | SUMMARY










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