Tube Data Report Sample (pdf)


Tube Test Order Form (pdf)


Vacuum Tube Testing & Matching

Tube Testing, Matching, and Ordering Information (Order Form Above)

Standard Test    $4 per tube    No minimum order  

All tubes are screened for shorts, gas, and heater-to-cathode leakage (unless it’s a directly heated tube), and then tested for emissions and transconductance (Gm) on an Amplitrex AT1000 (in some cases on a Triplett 3444).  Measurements are compared to published standards and/or Amplitrex database for emissions and transconductance.  This includes diode tubes (like 6AL5 and 6T8) if they have a triode, pentode, or tetrode section.  Diode sections are measured for Forward and Reverse Current.  Full-Wave rectifier tubes (like 5U4, 5Y3, GZ34) are measured for Peak Forward and Reverse Voltage drops for both sections. (These tubes have no standard measurements for emissions or transconductance, as they do not amplify.)  All tubes are tested in Fixed Bias mode, which is our default and the mode we consider most valid in general. See the Bias Page for details.  We can test in Auto Bias if you indicate that on the order form.

Standard Test Results You Receive (except Diodes and Rectifiers. See above.) 

· Emissions New Spec and Actual (New Spec per RCA RC-30 or manufacturer data)

· Gm New Spec and Actual (New Spec per RCA RC-30 or manufacturer data)

· Gm Actual as % of New

Ratings Scale (Based on Gm % of New)

This is our scale and somewhat abitrary.  We tend to reject most tubes under 70% of new, although some knowledgeable industry sources use 50% as the lower limit of acceptability for Good.

69% and below = Reject

70%-74% = Good

75%-84% = Very Good

85% and higher = As New  

Optional Tests and Services

Noise / Microphonics   $2 per tube

Most critical for preamplifier tubes, this test requires additional setup time and is a subjective one to detect and rate noise and microphonics.  Ratings are Very Low, Low, Moderate, and Excessive.  Separate results for noise and microphonics.

Tube Data Report  $2 per tube

This is a more detailed and extensive test data report for users who require it.  There is an observations/notations section, and the report includes general manufacturers’ specifications and your tube's results compared to the specifications.  A sample report link is at the top of this page.

Tube Matching  $5 per pair

We can test your tube pairs/quads and rate their degree of matching.  This has a cost of $5 per tube pair in addition to the Standard Test.  Generally, single-section tubes can be matched to each other, and dual-section tubes can have their sections matched (and thus establish matching parameters for a second and subsequent dual-section tube).  Tubes can be matched for emissions or Gm.  Matched preamp tubes can improve amplifier performance.  Power output tubes can benefit, too, with better power output and lower distortion, especially if the amplifier does not have DC and AC balance controls.  Our tests will tell you if your tubes are matched for emissions or Gm by section (for dual-section tubes), to each other (single-section tubes).  Generally, a good match is when emissions are good and within 10% of each other and within 5% for Gm or better.  Included is a data sheet showing the results and matching data for each pair.

Directions for Sending Your Tubes

Please fill out the PDF form (click on link at top), and include it with your tubes.  Send via a trackable service, insured, as we cannot be responsible for tubes lost in transit to us.  Please do not use envelopes unless you first wrap tubes in bubble wrap and then an outer corrugated/cardboard shield.  Best to use a small box and wrap tubes in small bubble wrap, and then provide cushioning all around with crumpled wrapping paper or newspaper.  

Ordering, Invoicing, and Return Shipping

We’ll test your tubes, usually the same day we receive them, and have them back on their way to you the following business day.  We accept Paypal and most credit cards via PayPal 

(a PayPal account is not required) and will send you an invoice prior to return shipping.  We use USPS First Class Package Service.  It's trackable, with delivery six days per week.  Best of all, ours is $4 flat rate to the lower 48 states, whether it's one tube or 10!  If you prefer another shipping service (USPS, UPS, or FedEx only), indicate on the form.  Those services will be billed at actual cost.  


Sorry, we prefer not to test any tubes that are not identifiable from the manufacturer’s markings on the tube.  If the tube is a common one, we normally waive this rule.  You can send photos first if you want.  We don’t want to smoke your tube or our equipment.

We use long-established test procedures and trusted equipment to test your tubes (and ours) safely.  Our liability is limited to replacement of your tube in the unlikely event that we damage it.  Western Glow Tube Service is not liable for any indirect or consequential damages arising out of testing your tubes.  In no event shall our liability exceed the replacement cost of your tube, once we establish and agree that we damaged it.  Hasn’t happened yet.

Our testing services generally focus on tubes from about 1950 and later guitar and bass amplifiers, audio amplifiers (separates and integrated), and AM/FM or FM tuners, stereo or mono.  We also test old radio and short-wave radio tubes from about 1940 and later.  Please contact us by email first ( if you need testing of old (prior to 1940) radio or other tubes, especially uncommon ones.  We will confirm if we can test.