Quad RFT EF86 Tubes Tested Strong – Solid Shield Pentodes (Vintage GDR)
Unlock the authentic vintage tone of the Cold War era with this Quad RFT EF86 Tubes. Manufactured in the former German Democratic Republic (GDR), these pentodes are highly regarded by technicians and audiophiles for their exceptional reliability and neutral, detailed sound character.
Condition and Testing (Honest Assessment):
This set consists of four authentic vintage tubes. While they are housed in period-correct RFT boxes, the differing production codes printed on the glass (301003, 102005, 807038, 547325) indicate they are from different manufacturing batches.
However, performance is paramount. As shown in the gallery, each unit has been rigorously tested on a Kyoritsu K-119 Tube Tester. All four tubes show emission levels well into the “GOOD” (green) zone, ensuring plenty of headroom and a long life ahead. They are sold as a functionally matched set based on electrical performance rather than date codes.
Technical Construction – The “Solid Shield” Advantage:
Unlike early Mullard “mesh plate” tubes which can be fragile and prone to ringing (microphonics) in loud environments, these Quad RFT EF86 Tubes utilize a Solid Internal Shield (grey stamped metal structure).
Why this matters: The solid structure minimizes internal vibration. This makes the RFT EF86 the preferred choice for combo guitar amplifiers (like the VOX AC15/AC30) where the tubes sit directly next to vibrating speakers.
Sonic Signature:
RFT tubes are known for a “no-nonsense” sound. They offer a tight bottom end, a very rich midrange, and a smooth top end that is not harsh. They are fantastic for taming bright amplifiers or adding body to hi-fi preamps.
Ideal Applications:
Guitar Amplifiers: VOX AC30 Heritage, Matchless DC-30, Dr. Z Z-28, 65 Amps.
Hi-Fi Audio: Quad II Monoblocks, Leak Stereo 20, Radford preamps.
Studio Microphones: Neumann U67 (as a robust alternative to the EF806S).
Technical Specifications:
Type: AF Pentode (Low Noise).
Base: B9A (Noval).
Filament: 6.3V / 0.2A.
Origin: GDR (East Germany) – Erfurt/Míhlhausen Works.
Equivalents: 6267, Z729, CV2901, 6F22.
Technical Datasheet Summary
| Parameter | Value |
| Heater Voltage (Vf) | 6.3 V |
| Heater Current (If) | 0.2 A |
| Anode Voltage (Va) | 250 V (Max) |
| Anode Dissipation (Pa) | 1.0 W |
| Screen Voltage (Vg2) | 140 V |
| Transconductance (S) | 2.2 mA/V |
| Amplification Factor (µ) | 185 (approx) |
Frequently Asked Questions (FAQ)
Q: Are these Quad RFT EF86 Tubes brand new (NOS)?
A: Due to the mixed batch codes, we sell them as “Vintage Tested Strong.” While they measure as new on our equipment, the history is unknown. The boxes are vintage RFT but may not be the original ones issued with these specific tubes.
Q: Why do the codes on the glass differ?
A: The codes (e.g., 301003 vs 807038) represent different production dates or factory lines in East Germany. While cosmetically different, they share the same internal construction and have been tested to ensure they function correctly as a set.
Q: Will this Quad RFT EF86 Tubes set work in my VOX AC30?
A: Yes. In fact, the RFT construction is often preferred for the AC30 because the solid metal shield is less likely to rattle or squeal (microphonics) compared to mesh-plate tubes when the amp is played loudly.
Q: What is the equivalent American type for this tube?
A: The American designation for the EF86 is 6267. You can use these RFT tubes in any device calling for an EF86, 6267, or Z729.
