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RCA

5751 RCA NOS Black Plates Halo Getter Matched Pair Tubes Made in USA

5751 RCA NOS Black Plates Halo Getter Matched Pair Tubes Made in USA

$297.00 AUD
$297.00 AUD
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5751 RCA NOS Black Plates Halo Getter Tubes Made in USA

AMPLITREX Tested – Ultra Low Noise & Microphonics – VERY STRONG - Vintage American RCA Production

Test Results:

Tube tested on AMPLITREX AT-1000 Tube Tester:

  • Test Conditions: Va = 250V ; Vg = -3V
  • 100% Average: Gm = 1200 ; Ia = 1.0 mA
  • Test Result: VERY STRONG

Tube 1:

  • Section 1: Gm = 1400 ; Ia = 1.2 mA
  • Section 2: Gm = 1300 ; Ia = 1.1 mA

Tube 2:

  • Section 1: Gm = 1300 ; Ia = 1.3 mA
  • Section 2: Gm = 1500 ; Ia = 1.6 mA
Additional Tests Performed:
  • Burn-in / Stability Test: 48h – OK
  • Microphonics: Very Low. Tested and confirmed for use in hi-fi equipment and guitar amplifiers, even in the most sensitive audio stages.
  • Noise: Low and well-controlled. Quiet operation in hi-fi environments and in musical amplifiers in the intended positions.
  • Balance: Good. The sections show a consistent balance, fully compatible with use in hi-fi environments and musical amplifiers, in all applications where absolute symmetry between sections is not required.
  • Emission Quality: Excellent – Very strong and stable emission, without fluctuations.
  • Short Circuits and GAS: Absent.

Description:

Important pair of 5751 RCA NOS of American production, characterized by the sought-after Black Plates and the classic Halo Getter. The internal structure of the two pieces is consistent, while the silkscreens show a different degree of preservation: one tube retains part of the original orange marking, while on the other the lettering has almost completely disappeared. The construction characteristics allow them to be indicatively attributed to production in the 1960s.

The tests performed with the Amplitrex AT-1000 highlight performance clearly superior to the nominal reference of 1200 µmhos. The four sections indeed measure between 1300 and 1500 µmhos, with anode currents between 1.1 and 1.6 mA. The transconductance averages of the two tubes are particularly close: 1350 and 1400 µmhos, with a variance of less than 4%, confirming excellent overall electrical consistency.

The internal balance is also good: Tube 1 measures 1400/1300 µmhos and 1.2/1.1 mA, while Tube 2 reaches 1300/1500 µmhos and 1.3/1.6 mA. This is not a selection with absolute symmetry between all sections, but rather two strong, stable units fully suitable for normal audio applications compatible with the 5751.

The 48-hour burn-in verified the stability of the parameters, with no fluctuations, short circuits, or gas presence. Particularly significant is the Ultra Low Noise & Microphonics selection: both tubes showed very contained noise and extremely low microphonics, qualities that are fundamental in the most delicate audio positions.

These characteristics make them particularly suitable for hi-fi preamplifiers, compatible phono stages, headphone amplifiers, and guitar amplifiers, even in V1 and high-sensitivity input stages. The 5751 offers a lower amplification factor than the 12AX7 and can be an interesting choice when more control, more headroom, and a less aggressive response are desired; compatibility must, however, be verified in relation to the circuit used.

In terms of sound, RCA Black Plates are appreciated for a full-bodied, musical, and natural reproduction, with a rich and well-articulated midrange, solid low frequencies, and a high end that is defined without being harsh. In hi-fi systems, they promote depth, tonal coherence, and fatigue-free listening; in guitar amplifiers, they offer dynamic response, control, and excellent articulation, preserving the instrument's character.

A high-level offering for those looking for two 5751 RCA NOS Made in USA tubes, with Black Plates, Halo Getter, emission above reference, and a particularly rigorous selection for noise and microphonics: two authentic vintage tubes, tested individually and ready for use even in the most sensitive audio stages.

Condition:

  • Condition: NOS - New Old Stock - Tested and functional - Supplied in our custom box for optimal protection. 
  • Functionality: Perfectly operational.
  • Cosmetic condition: Adequate – One tube with lettering partially faded or poorly legible, one tube with lettering completely absent. General appearance shows obvious signs of age. See photos for details.
  • Manufacturing Code: RCA Radio Corporation of America production, Camden, N. J. - Code undecipherable. Production indicatively attributable to the 1960s based on construction features.

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Terms of Sale & Safety

Sales Terms & Product Safety

Each vacuum tube is carefully selected, tested, and verified in our laboratory before shipment. Where stated in the listing, test results, matching data, and declared characteristics refer to measurements performed using the specified test equipment and operating conditions.

Sound descriptions are provided for guidance only and reflect the characteristics generally associated with that particular tube type. Personal sound preferences, tube rolling, or perceived differences between audio systems do not constitute a product defect.

Before installation, please verify the tube’s electrical and mechanical compatibility with your equipment and follow the manufacturer’s instructions.

New production and NOS tubes are shipped with a tamper-evident security seal and internal technical documentation to ensure traceability of the product’s condition at the time of shipment.

Product Safety (GPSR)

Vacuum tubes are electronic components intended exclusively for use in compatible equipment and must be installed in accordance with the equipment manufacturer’s instructions.

Due to their historical or vintage nature, certain technical specifications may be based on original datasheets or equivalent technical documentation when documentation from the specific manufacturer is unavailable.

Use only with suitable equipment. Keep out of reach of children.

Shipping & Returns

Shipping & Returns

We ship worldwide using carefully selected express carriers and protective packaging specifically designed for vacuum tubes.

If you change your mind, you may exercise your right of withdrawal within 14 days of delivery, where applicable under the relevant consumer protection laws. The product must be returned complete with its original packaging and accessories, in the same commercial condition in which it was received. Return shipping costs are the responsibility of the customer.

Every returned item undergoes a technical inspection. Installation, use, tube rolling, or any other handling may reduce the product’s commercial value and may affect the refund amount, in accordance with applicable law.

If you believe the product has a lack of conformity, our laboratory will carry out the necessary inspections and apply the remedies provided by the applicable consumer protection legislation.

For further details, Customers are invited to consult the “Terms and Conditions” and “Refund Policy” sections of our website, or to contact us before placing an order.

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