Valve Matching Update

We have recently built a new testing rig for matching valves. This enables us to test valves at real world voltages for more precise matching.

• 0 to 500 vdc Anode and Screen (regulated to 0.1%)

• 0 to -60 vdc bias (regulated to 0.01%)

• 0 - 10v heater (regulated to 0.01%)

All voltages are tightly regulated as you can see above.

Older valve testers like the AVO, Taylors and the like are good valve testers but the main problems with these types of tester is loading that takes place on the transformer(s) and also the lack of higher anode voltages seen in most guitar amplifiers. Because the voltages are not regulated the results are inconsistent although they will get you somewhere near the ballpark.

For instance, a decrease of 0.3v on the filament (heater) will decrease the anode current between 4 to 6% on average. That’s just one variable without taking into account other variables.

The line voltage from the socket can also deviate from 235vac at busy times (when the kettle goes on) to 245vac at quiet times. This can lead to approx 4% difference on the rectified dc voltages

Put all this into the pot and you can see how difficult it is to get consistently accurate and repeatable results.

With our old valve matcher we had to go to great lengths with the line voltage by using a voltage stabiliser (incidentally we now have one for sale, if anyone interested drop an email or give me a call) and other equipment to get consistent results. Judging from our customers it worked well, but our new matcher is pretty much plug and play which saves us a lot of time and headaches.