Sylvania 5881/6L6WGB Matched Quad NOS NIB

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Sylvania 5881/6L6WGB Matched Quad NOS NIB

The Sylvania-made 5881 / 6L6WGB is one of the toughest and most musical American power tubes ever built.

Manufactured by Sylvania and RCA branded during the golden age of American tube production, these ruggedized 5881s were designed for reliability, stability, and long service life. Originally developed for military and industrial applications, the 6L6WGB became a favorite in guitar amplifiers and hi-fi equipment thanks to its smooth breakup, tight low end, and warm American character.

The 5881 helped power some of the most legendary American amplifiers ever made, including the tweed Fender Bassman 5F6-A, early Fender Twin models, and the famous Ampeg Portaflex B-15. Its balanced tone, durability, and musical compression made it a defining tube of 1950s American amplification.

Compared to larger 6L6GC types, the 5881/6L6WGB typically delivers slightly earlier breakup and compression, making it especially loved in vintage Fender-style amplifiers where touch sensitivity and warmth matter most. In hi-fi systems, they offer a smooth, balanced presentation with excellent clarity and natural dynamics.

These particular tubes were manufactured by Sylvania and rebranded for RCA, something that was extremely common during the tube era. Many of the best American tube companies sourced tubes from one another while maintaining strict quality standards.

This matched quad has been carefully tested and matched for strong, balanced performance and is ideal for stereo hi-fi amplifiers or larger guitar amplifiers requiring four matched output tubes.

Every tube is thoroughly tested, matched, verified for proper operating function, and backed by the Fuzz Audio one-year guarantee.

Tested. Matched. Guaranteed.

Need help deciding what tubes are best for you?

Use our plate cheat sheet and vacuum tube buyers guide to determine which tubes are best for you. Likewise, you are welcome to reach out to us directly at Support@FuzzAudio.com or by using our chat located on our shop page if you have further questions.

NOS vs. ANOS vs. Test NOS

These designations are strictly used to describe the cosmetic condition of our tubes. All tubes we sell test identically, come with 100% life and are guaranteed to work in your device!

If you are picky about owning an original box or wanting a specific logo please reach out to us before purchasing.

  1. NOS (New Old Stock) Tubes- are 100% brand new vintage tubes in mint cosmetic condition with show zero signs of use. You should expect a legible logo and clean straight pins. An original box is not guaranteed. 
  2. ANOS Tubes- otherwise known as “almost new old stock” tubes are basically new, but may show slight signs of use in cosmetic condition, such as a missing logo or slightly bent pins. An original box is possible but unlikely. 
  3. Test NOS Tubes- are used but still operating to specification with 100% life. These tubes are equal in function to NOS valves, yet they cost considerably less because they have cosmetic blemishes. If you plan to disappear your tubes into the back of an amplifier or do not care what the tubes look like, then this is cost effective choice. Blemishes and cosmetic imperfections do not affect tone…

Logos: Vintage tubes have a wide variety of logos printed on them. It is not uncommon to see a Mullard made tube with an RCA or GE logo, or a GE made tube with a Mullard logo. Your tube may come with a logo such are Heath Kit, Baldwin, Fisher, Hammond, Magnavox, Fender, Gibson, Silvertone, etc. but the true manufacturer of that tube will be correct to your order. If you are looking for a specific logo please reach out before purchase.

Testing Standards

Testing Standards

At Fuzz Audio:

  • We match all tubes for free!
  • All vintage tubes are guaranteed for one year.
  • All tubes are tested on a calibrated Hickok 539C, Amplitrex, Maxi-Matcher, or other industry standard tube analyzers.
  • Preamp tubes are matched by gain and mutual conductance (Gm)
  • Power tubes matched by mA and Gm
  • All tubes tested for microphonics and are guaranteed to work in your application.
  • If you require SUPER LOW noise tubes, please reach out. We will most likely meet your requirements for free.
  • Do not hesitate to reach out if you have any questions or concerns, we are here for you.

We guarantee NOS test scores, clean pins, tight matches, and ultimately that they work in your application or YOUR MONEY BACK!

Tubes in photos represent the tube you will receive. Getter construction or logo may differ. Logo may be partially missing or cleaned off. You may or may not receive a box. Tube type, manufacture, and NOS test quality will NOT change. If logos and original boxes are a deal breaker- please reach out before purchase we are always happy to accommodate.

Shipping details

1. General
Subject to stock availability. We try to maintain accurate stock counts on our
website but from time-to-time there may be a stock discrepancy and we will not
be able to fulfill all your items at time of purchase. In this instance, we will
fulfill the available products to you, and contact you about whether you would
prefer to await restocking of the backordered item or if you would prefer for us
to process a refund.

2. Shipping Costs
Shipping costs are calculated during checkout based on weight, dimensions and
destination of the items in the order. Payment for shipping will be collected
with the purchase.
This price will be the final price for shipping cost to the customer.

3. Returns
3.1 Return Due To Change Of Mind
Fuzz Audio will happily accept returns due to change of mind as long as a
request to return is received by us within 30 days of receipt of item and are
returned to us in original packaging, unused and in resellable condition.
Return shipping will be paid at the customers expense and will be required to
arrange their own shipping.
Once returns are received and accepted, refunds will be processed to store
credit for a future purchase. We will notify you once this has been completed
through email.
(Fuzz Audio) will refund the value of the goods returned but will NOT refund the
value of any shipping paid.

3.2 Warranty Returns
Fuzz Audio will happily honor any valid warranty claims, provided a claim is
submitted within 90 days of receipt of items.
Customers will be required to pre-pay the return shipping, however we will
reimburse you upon successful warranty claim.
Upon return receipt of items for warranty claim, you can expect Fuzz Audio to
process your warranty claim within 7 days.
Once warranty claim is confirmed, you will receive the choice of:
(a) refund to your payment method
(b) a refund in store credit
(c) a replacement item sent to you (if stock is available)

4. Delivery Terms
4.1 Transit Time Domestically
In general, domestic shipments are in transit for 2 - 10 days. We ship packages Tuesday-Thursday so plan accordingly. 

4.2 Transit time Internationally
Generally, orders shipped internationally are in transit for 4 - 22 days. This
varies greatly depending on the courier you have selected. We are able to offer
a more specific estimate when you are choosing your courier at checkout.