Preamp · Dual triode
5751
Ruggedized dual triode with lower gain than a 12AX7; sometimes chosen to tame preamp gain.
Base: 9-pin miniature (noval)
- Specs checked against a cited datasheet
- No replacement verified yet
Where to buy 5751
- ReverbNo affiliate relationshipSearch 5751 on ReverbOpens reverb.com search results
Online marketplace for new and used music gear, including vacuum tubes.
- Apos Audio isn't listed: its site search didn't return a 5751 when we checked on Nov 4, 2026.
Each button opens that retailer's own search for 5751. We don't see their prices or stock.
Before you buy, check that the listing names 5751. A listing that mentions another tube name isn't necessarily the same type. Affiliate disclosure
Specifications
Checked against the manufacturer's datasheet. Source: General Electric GL-5751 data sheet ETX-245A, pp. 1–2 (dated 6-52) · checked Nov 5, 2026
From the datasheet: GE describes the GL-5751 as a high-mu twin triode built to resist vibration, for industrial and other uses that need dependable operation under rigorous conditions. GE notes its heater draws slightly more current than conventional tubes of this type.
Manufacturer's published ratings from the datasheet above, under the conditions shown. Another manufacturer's tube of the same type may be rated differently; check the datasheet for the tube you have.
| Heater | 6.3 V, 0.350 A (parallel) / 12.6 V, 0.175 A (series) |
|---|---|
| Max plate voltage | 300 V (design-center); 330 V (absolute) |
| Max plate dissipation | 1.0 W each section (design-center); 1.1 W (absolute) |
| Max negative grid voltage | 50 V (design-center); 55 V (absolute) |
| Max heater-cathode voltage | 90 V peak (design-center); 100 V peak (absolute) |
| Operating point | Class A, each section: 250 V plate, −3 V grid |
| Amplification factor | 70 |
| Plate resistance | 58,000 Ω |
| Transconductance | 1,200 µmhos |
| Plate current | 1.0 mA |
What these figures mean
- Heater (series / parallel):
- the voltage and current the heater needs. A center-tapped heater can run from a 12.6 V supply (halves in series) or a 6.3 V supply (halves in parallel) (GE 12AX7 data sheet ET-T509B, p. 1).
- Max ratings, design-center:
- limits for a typical tube of the type that equipment should not exceed under normal conditions (GE 12AY7 data sheet, p. 1).
- Max ratings, absolute:
- limits that supply variation, component tolerances and control settings combined must not push past (GE 12AU7-A data sheet ET-T880A, p. 2).
- Operating point:
- the plate and grid voltages at which the figures below it were measured. They describe the tube there, not in any particular amplifier.
- Amplification factor (µ):
- how much the plate voltage varies in relation to the grid (input) voltage (US Navy NEETS Module 6).
- Transconductance:
- how much the plate current varies with the grid (input) voltage (US Navy NEETS Module 6). 1,000 µmhos is 1 mA per volt.
- Plate resistance:
- plate-voltage change divided by plate-current change at a fixed grid voltage; it equals µ divided by transconductance (Lessons in Electric Circuits, “Tube Parameters”).
- Plate current:
- the current each section draws at the operating point shown.
These figures alone don't show whether one tube can replace another; heater, pin connections and ratings must suit your amplifier.
Common uses
- guitar preamp
- hi-fi preamp