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Arthur Loesch 1.1 Control Preamplifier

1.1 Control Preamplifier
 
Considered by many to be classics of the high-end tube revival, for the past 20 years Arthur Loesch (pronounced "Lesh," like the Grateful Dead's Phil Lesh) Phono Preamplifiers were occasionally produced on a one-off basis by builders like J.C. Morrison, Herb Reichert, and John Baier. For a while, they were made by John Wiesner under the Loesch & Wiesner brand.
 
For this ultimate edition, Dr. Loesch revisited the RIAA phono spec and recalculated all of the restoration points, regrouping them in a unique pattern to optimize their placement in the signal path. Using a wide range of passive parts, many of which were unavailable in earlier versions, the end result is a complete restatement of the Loesch circuit and represents the last word in phono reproduction.
 
Rated "Class A" by Stereophile
 
In the October, 2010, and April, 2011, issues of Stereophile, the Full-Function Phono Preamplifier was rated "Class A," it's highest level of approval. Class A is defined as the "Best attainable sound for a component of its kind, almost without practical considerations; ' the least musical compromise.' " Of his time with the unit, writer Art Dudley said that "the 1.1 produces the voices and instruments of good stereo recordings with believable scale and physicality."
 
Featured Component in Bound-For-Sound
 
The Full Function Phono Preamplifier is the subject of a two-part article in the December, 2009, and March, 2011, issues of the Bound For Sound Report.
 
Click here to download the full review. (Requires Adobe Reader.)

 
1.1 Control Preamplifier Back

 
Read more about:
 
The Sound The Circuit The Tubes The Power Supply Full Specs Prices

 
The Sound
 
In voicing both the phono and line sections, unamplified music, recorded in a live environment, rather than in a studio, was used as the primary reference. The result is a natural, well-balanced sound, with nothing added or subtracted. If the details are on the disk (or disc) and the rest of the audio system is on a par, you will easily hear nuances that were previously hidden. These include those unique, low-level cues which distinguish individual recording spaces from one another. The lack of a sonic signature produces a sound that's notable for its natural bass, glare-free treble, and rich, detailed midrange. Add to these assets an uncanny degree of clarity, plus "air," and you can follow every individual instrument or voice with ease. When integrated with equipment of comparable quality, the audio system simply disappears, leaving you alone with the performers, themselves. Now the only question to ask is this — are they playing in your space or are you listening in theirs?
 
The Circuit
 
Amplifying the audio signal in three gain stages, the Phono circuit is suitable for any cartridge with an output of 0.25mV (or lower) to 2.5mV, moving coil or moving magnet. In some systems, lower output cartridges (less than 0.8mV) may benefit from the optional Nuvistor head amp.
 
Left and right channels are built on a pair of identical boards, mounted side-by-side for true dual-mono operation. Cartridge loading is infinitely variable via fixed-value plug-in resistors, located on the PC Board next to the phono input.
 
Phono Load Detail

Optional RCA sockets can be added on the back panel for listeners who prefer external plug-ins.
 
An Active Line stage is included as a buffer to smooth out the edginess often associated with CDs. Aurally, this seems to fill in the gaps between the pits and helps to render the music as if it were eminating from an analog source, rather than a digital one.
 
A pair of Passive Line inputs, which bypass the gain circuitry and go directly to the dual-mono volume controls, are available for high output sources, such as an FM tuner. When only using these inputs, the preamp's power supply can be turned off to save on tube life.
 
Preamplifier Signal Path

A new feature is the adjustable bias control. By changing the bias (plate voltage) of the first stage tube (5842/417A), listeners can tailor the sound to match their system in a range from High Bias (Warm), Medium Bias (Neutral), or Low Bias (Cool).
 
Audio Circuit Signal Paths

Each stage is built with its own optimal blend of parts, many of which are normally considered to be upgrades. These include VCap Teflon® capacitors, "naked" Vishay Resistors, WBT NextGen RCA sockets, and extra soft temper, pure silver wire. Hand-selected and precisely matched low-noise NOS (new old stock) American and British tubes, culled from an extensive in-house inventory, are standard.
 
 
1.1 Control Preamplifier
 
NOS Tubes
1st Stage 2nd Stage 3rd Stage
Raytheon 5842
Western Electric 417A
RCA 6GK5 Tung Sol 5687

Tubes in Bold Face are supplied. Those in Light Face can be substituted.

 
The 1201B+ Power Supply
 
Based on a design originally developed for military and laboratory test equipment, the 1201B+ Power Supply is a separate tube regulated unit that's been updated and optimized for high-end audio. User adjustable for 120V or 240V worldwide operation, it's housed in a chassis that's completely separate from the audio section in order to provide optimum shielding for low noise operation. An illuminated meter and 10-turn trimpot allow the user to precisely adjust the output voltage, while circuit breakers mounted on the front panel do away with fuses. The power supply is connected to the audio stage by a heavy duty umbilical which is available in lengths from 2 feet (0.6 meters) to 8 feet (2.4 meters). In addition, a second power supply can be added at any time for complete dual-mono operation. This has the advantage of increasing overall dynamics and bass response, especially in phono mode. An IEC inlet allows the use of an upgraded AC power cord on each supply.
 
 
Arthur Loesch 1201B+ Power Supplies
Click here or on the photo for complete power supply information and specs.
 
 
Specifications1.1 Control Preamplifier
Net Gain
  • +60dB Phono (6GK5) or
  • +48dB Phono (6C4)
  • +14dB Active Line Stage
InputsWBT NextGen RCA Sockets:
  • Phono In Direct
  • Phono In Via Step-Up Transformer (optional)
  • Phono Load Via External RCA Plugs (optional)
  • Active Line
  • 2 X Passive Line
OutputsWBT NextGen RCA Sockets:
  • 2 X Main Out
    Use the second, parallel outputs for bi-amplifying, with an external headphone amplifier, or to bridge both channels into mono output (special interconnect required)
  • Record Out (bypasses the volume controls)
Furutech XLR adapter:
  • Main Out
Volume/Balance
  • Dual-Mono Ladder Attenuators or
  • Slagle Autoformers
Selector Switch4 Inputs + Mute
Frequency Response20Hz - 50KHz
Phono Input ImpedanceInfinitely variable via plug-in resistors, internal or external
Default = 47K Ohms (supplied)
Phono Output ImpedanceZout = 3K3 Ohms (typical)
Recommended Amplifier Input ImpedanceZin = 100K Ohms (typical)
Total Harmonic DistortionNo more than 0.1%
IM DistortionNo more than 0.1%
Signal-to-Noise RatioBetter than 87dB
PhaseNon-Inverting
External Ground ConnectorsEarth Ground (AC Earth) and
Common Ground (AC Neutral)
Signal GroundSwitchable via locking toggle:
  • Signal to Earth (Default) or
  • Signal Float
AC Mains Input120V @ 60Hz or 240V @ 50Hz, user switchable
On request, the power supply can be wired for 100V, 110V, or 220V at no extra charge.
Dimensions16.75" Wide x 16.0" Deep x 4.5" High, including feet, excluding power supplies
(425mm Wide x 406mm Deep x 114mm High)
Net WeightAudio Stage: 15 lbs. (6.8 kg)
Power Supply: 25 lbs. (11.3 kg) each
Shipping WeightAudio Stage: 22 lbs. (10.0 kg)
Power Supply: 29 lbs. (13.2 kg) each

All features, parts, and specifications are subject to change without notice.
 
In addition, the Control Preamplifier can be purchased as the stand-alone 1.1 Phono Stage, omitting the Line Stage, Selector switch, and Volume/Balance controls.

 
Prices, Basic UnitPlus shipping from Saratoga Springs, New York 12866, USA
1.1 Control Preamplifier with Single Power Supply$7,100
Includes the RIAA Phono Circuit, 1 Active Line circuit, 2 Passive Line Inputs, and Dual-Mono Volume/Balance Controls. This is a complete unit, ready to play.
Options and Upgrades:Want to max out the Loesch circuit design? On a 1-100 scale, the following options will push the basic unit (above) from a 95 to a 100. Most of the improvement comes from the additional power supply, which will raise performance to a 98. To reach 100, add the Western Electric 417A, V-Caps in the Active Line Stage, and the CS custom power cords.
Add a Second Power Supply+$2,500 for full Dual-Mono operation.
Audio stages are pre-wired for Dual-Mono power supplies and do not have to be returned for this upgrade.
Upgrade the 1st Stage Tubes to WE417A+$250/Matched Pair of extra quiet NOS Western Electric 417A tubes
Purchase additional Phono Load Resistors+$32/1% pair of TX2352 ("Naked" Vishay) resistors in any value from 1 Ohm to 200,000 Ohms, including fractional values
Upgrade the Line Stage Capacitors+$400
Substitute VCap TFTF Teflon output capacitors for the more economical REL AudioCap RT Polystyrene capacitors
Upgrade the RCA SocketsUpgrade the WBT NextGen Cu Copper sockets to WBT NextGen Ag Fine Silver sockets. +$44/Pair
 
There are seven pairs on the Phono Stage. Installing the Step-Up Transformers adds an eighth pair of jacks. The silver sockets are recommended for listeners who use silver wire interconnects and speaker cables.
Upgrade the Power CordUpgrade the standard 14 Gauge shielded power cord to our 12 Gauge double-Teflon® insulated, CS Power Cord, featuring WattGate Audio Grade terminations.
+$250/6 feet, +$10 each additional foot, per power supply
CustomizationAdd different inputs, curves, or other custom features.
Quotations on request.
Replacement Tube Sets
  • (3) Pairs of Precisely Matched Preamplifier Tubes
    NOS Raytheon 5842, RCA 6GK5, Tung Sol 5687: $120 per set of 6
     
  • (5) Power Supply Tubes
    NOS American and Europrean Brands, as available: $60 per set of 5
Replacement Batteries(2) AA Alkaline Batteries + (2) 2/3A Lithium Batteries: $20 per set of 4
Warranty
  • 10 Years (transferable) on all parts and labor, with the exception of
  • 90 Days on tubes
Unauthorized parts substitution may void Warranty
AvailabilityNow ! All units are built to order by hand in our workshop in Troy, New York, USA. Lead time is typically 4-6 weeks from order to shipment depending on the individual configuration.

 
joseph@tempoelectric.com to arrange for an audition at our Troy, New York, listening room or for an in-home audition. Certain restrictions apply.
 

Tempo Electric LLC
PO Box 770
Saratoga Springs, NY 12866-0770
USA
(518) 542-7004

The best time to reach us by telephone is 10AM-6PM, US Eastern Time.
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