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Various Tubes - $1 (alameda)
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Light use and working properly
TUNGSOL 7591A matched pair - $70
General Electric 7247 NOS - $25
Sylvania 12X4 - $15
Finally we have a 7591 tube that is a close replica of the original NOS tubes. If you have an old Fisher or Scott tube receiver, or other amplifier, the new reissue Tung-Sol 7591A power tube won't break the bank, and will keep them sounding great!
Strongly committed to quality manufacturing, Tung-Sol tubes have always been known for their reliability and great tone. Today's new production Tung-Sol tubes are constructed with the same commitment to quality and reliability. Tung-Sol tubes reflect the best in vintage Tung-Sol construction with unsurpassed tone and reliability.
The General Electric 7247 (often branded interchangeably with the 12DW7) is a vintage, 9-pin miniature dual-triode vacuum tube. It is a "hybrid" tube featuring two dissimilar triode sections in one glass envelope: half of the tube acts as a high-gain 12AX7, and the other half acts as a lower-gain 12AU7. [1, 2, 3, 4]Key Specifications & Layout
Section 1 (12AX7 equivalent): Designed for low-noise, high-gain, low-hum, and low-microphonics stages.
Section 2 (12AU7 equivalent): Designed for phase-inverter or cathode follower service.
Heater Voltage: Can be run in parallel (6.3V @ 0.3A) or series (12.6V @ 0.15A). [1]
Common Applications
Hi-Fi Audio: Widely used in vintage stereo gear, most notably in the driver section of the classic Dynaco ST-35 power amplifier.
Guitar Amplifiers: Popularly used in vintage and modern tube amps to tame harsh gain structures. Putting a 7247 into a 12AX7 socket reduces the gain in that specific stage, sweetening the tone and increasing clarity. [1, 2, 3]
Sourcing & ReplacementsBecause General Electric ceased production of these tubes decades ago, authentic GE 7247 tubes are now considered "New Old Stock" (NOS) and generally command a premium price on the secondary market (often ranging from $40 to $80+ depending on the condition and test scores). [1, 2, 3, 4]If you are looking to replace a GE 7247 in your equipment, it is completely compatible with modern-production 12DW7 or ECC832 tubes from manufacturers like JJ Electronic or Electro-Harmonix. [1, 2]
The Sylvania 12X4 is a 7-pin miniature, full-wave, indirectly-heated vacuum tube rectifier. It is primarily used in vintage auto radios, compact AC receivers, and classic tube preamplifiers (such as vintage PAS preamps) to convert AC into stable DC for high-voltage supply. [1, 2, 3, 4, 5]Quick Specs & Electrical Data [1]
Filament Voltage: \(12.6\text{ V}\)
Filament Current: \(300\text{ mA}\) (or \(0.3\text{ A}\))
Max Peak Inverse Plate Voltage (PIV): \(1250\text{ V}\)
Max Steady-State Peak Plate Current: \(245\text{ Ma}\) per plate
Max Average DC Output Current: \(70\text{ Ma}\)
Max Heater-Cathode Voltage: \(\pm 450\text{ V}\) (DC or peak) [1, 2, 3, 4]
Physical & Mechanical Specs
Bulb Style: T-5½ glass envelope
Base: Miniature button 7-pin (JEDEC E7-1)
Cathode Type: Coated unipotential (indirectly heated)