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Series 200 Mono Amplifiers

Series 200 Mono Amplifier

Single-Ended 300B, 3-Stage Amplifier

Series 200 Mono Amplifiers
In the 1970s, influential Franco-Japanese audio designer Jean Hiraga declared the 300B to be "the tube of the century." During his teen years in Montreal, Dr. Arthur Loesch (pronounced "Lesh," like the Grateful Dead's Phil Lesh) studied French and later read Hiraga's original articles in Revue du Son, Revue L'Audiophile, and Nouvelle Revue du Son. In the 1980s, calling on his background as a research scientist in physics and mathematics, Dr. Loesch developed his own Single Ended triode (SET) circuit and became a major figure in its revival for home audio in North America.
In the early 2000s, working in both Dr. Loesch's basement "audio cave" in Guilderland, NY, and our own dedicated testing room in nearby Troy, NY, we collaborated for over a year to optimize his circuit using the most advanced components available. The result was the Series 300 Mono Amplifier.
Building on the strength of the original design, we've modified the drivers, input tubes, and output transformers to produce a more robust, yet economical unit -- the Series 200 Mono Amplifier.
The Sound
The Series 200 amps further optimize the sound of the 300B. Highs are clean and detailed; the midrange rich and vibrant; the bass solid and resonant. Sound staging is wide, deep, and three-dimensional. Overall, there's a presentation that's unusual in an all-tube design. These amplifiers produce music with the impact of a live performance, sailing through the most difficult recordings as they lift the last veil between you and the stage.
We spent hundreds of hours voicing the circuit using matched pairs of 1940s vintage Western Electric 300B's as a reference, so that every internal component compliments each other and none distracts from the overall sound. Onboard iron includes ISO (formerly Tango) output transformers, custom built Heyboer power transformers, and vinatge American filter chokes.
AC vs. DC Filament Supplies
Unlike most modern tubed amps, Loesch designs feature AC on the power tubes' filament supplies (heaters), rather than DC. Although DC on the filaments is inherently quieter, it forces the tubes to have different bias readings on each filament. This variation in the left and right filaments results in unequal plate current across the tubes and compromises their linearity. The net result is the introduction of distortion that does not exist with AC. Subjectively, AC on the filaments makes the sound more realistic.
While AC on the filaments is often criticized for amplifying the 60Hz (or 50Hz) line frequency (characterized by a faint background hum), the Series 300 amps filter out the hum by incorporating a line frequency filter just ahead of the heaters. The result is that the AC heated filaments are just as quiet as those heated by DC without DC's inherent distortion.
Features include:
  • Pure Class A Performance
  • ISO (Tango) Output Transformers (Single SET or Push Pull)
  • Hashimoto Output Transformers (Parallel SET)
  • Choke Input after the rectifier
  • ASC Polypropylene in Oil filter capacitors
  • Jupiter Copper Foil, Paper and Oil coupling caps
  • Zero Negative Feedback
  • AC heated filament supplies
  • Secondary filter that eliminates the line hum often associated with AC filament supplies
  • Teflon® insulated, pure silver wire throughout the audio signal path.
  • Teflon® insulated, silver-plated copper wire throughout the power supply.
  • Teflon® Tube Sockets, made in Italy
  • Caddock MS Series Power Resistors
  • WBT RCA Top Line input sockets and Economy binding posts
  • Furutech 15A IEC Teflon® Power Inlet
  • WBT RCA Top Line input sockets
  • WBT Binding Posts
Upgrades (at additional cost) include:
  • Duelund or Audio Note Silver Foil coupling caps
  • WBT NextGen Ag Pure Silver binding posts
  • 100K Mono volume controls (your choice of types)
Recommended Premium Tube Sets:
  • Emission Labs Classic or Mesh Plate 300B, Takatsuki TA-300B, Western Electric 300B
  • RCA 5U4GB or Emissional Labs 5U4 (with the EML or Takatsuki 300B)
  • Silvertone Mesh Plate 37 (in the 3-Stage design)
  • Raytheon 6J5WGT or G.E.C. 6J5 (in the 3-Stage design)
  • Western Electric 417A (replaces the 37 and 6J5 in the 2-Stage design)

SpecificationsSeries 200 Mono Amplifiers
ImpedanceInput = 100K Ohms
Output = 8 Ohms, plus other taps dependent on the output transformer installed
Rectifier5U4, 5U4GB (shown)
Output (Power)300B (Emission Labs Classic shown)
PowerClass A
Plate Voltage350V, optimized for the EML 300B Mesh.
On request, this can be increased for other 300B power tubes
Plate Dissipation22 Watts, optimized for the EML 300B Mesh.
On request, this can be increased for other 300B power tubes
Power Output8 Watts
81W @ 0.75A per Mono Amplifier
Power Supply 
AC Mains Input120V/60Hz for use in North America
240V/50Hz or dual voltage available on request.
Size16.75" Wide x 12.0" Deep x 10.0" High
(425mm Wide x 305mm Deep x 254mm High)
Net Weight35 lbs. (15.9 kg) each, 70 lbs. (31.8 kg) per pair
Shipping Weight42 lbs. (19 kg) each, 84 lbs. [38 kg] per pair
PricesPlus shipping from Saratoga Springs, NY 12866, USA
Amplifiers OnlyBeginning at $7,000 per pair, without tubes, depending on the final configuration
Premium Tube SetsPrices vary with the market
FabricationHand-made in Troy, NY 12180, USA
Warranty10 years, transferable, on parts and labor. 90 days on vacuum tubes. Unauthorized parts substitution or circuit modification(s) may void the warranty.
AvailabilityContingent on your requirements. The exact configuration may differ from the ones illustrated.

Series 200 Mono Amplifier
Single-Ended 300B, 3-Stage Amplifier shown with WBT NextGen Ag Pure Silver binding posts

OrderingBecause of the numerous choices and variables, we don't have a shopping cart. Instead we encourage you to telling us exactly what you need and where you are located (US state or country). We usually respond within 24 hours (often sooner) and will try to provide an exact quote, including shipping.
PaymentWe accept payment via MasterCard, Visa, and Discover directly through our secure server form, as well as PayPal.
Shipping & HandlingShipping from the workshop in Troy, NY 12180, USA is additional. The actual cost depends on the total weight, carrier, and destination.
AvailabilityA pair of amplifiers takes 40 hours to build. They are made to order, by hand, in our workshop in Troy, New York, USA. Lead time is typically 6 to 10 weeks from order to shipment, subject to parts availability and work orders ahead of yours.

Tempo Electric LLC
PO Box 770
Saratoga Springs, NY 12866-0770
+01 (518) 542-7004

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