Post by myles on Jul 19, 2006 11:54:54 GMT -7
This area will be continually updated with the latest test resuts on current vacuum tube production.
These tests will be done at RCA / GE book spec and compare the results to the NOS standards of the past.
The data sheets produced by virtually all the tube companies currently take the old published data targets and sheets and replicate them.
Groove Tubes will test all of the current offerings as time permits and publish the results, for better or worse. As new runs of each tube are received we will publish the updated information so we can all see if things are getting better, worse, or staying the same.
There is a very wide range of specs in today's tubes. Most fall far short of specs from the 1950s - 1970s. One aspect of GT offerings is that the gold series of tubes must fall within a narrow range. This means a lot of tubes are rejected. Current reject rates are generally over 50% from all vendors.
The tubes listed here were not tested or put through any selection process. These are straight from the vendor. Most vendors pack tubes 100 per box in the case of preamp tubes. Preamp tubes are the most critical in your amplifier. A tube that is low on current output, gain, transconductance, etc., will not let the amp perform at it's best level. Typical preamp tubes which are bulk factory untested samples and not selected typically can be 50% down in one or more of these factors.
Output tubes will have the mid range tubes in a given shipment as the test samples. An example of this in RCA book spec is that a 6L6 at 250 plate volts and 250 screen volts with a -14 volt bias should produce 72mA as the expected design spec.
By publishing these test results it is hoped that the consumer and industry will all work together so the tube makers will have better manufacturing methods and utilize tighter QA procedures.
If you have a tube or tubes that you wish to have tested please contact GT and ask for Myles Rose.
Note - curves were not posted in this post.
These tests will be done at RCA / GE book spec and compare the results to the NOS standards of the past.
The data sheets produced by virtually all the tube companies currently take the old published data targets and sheets and replicate them.
Groove Tubes will test all of the current offerings as time permits and publish the results, for better or worse. As new runs of each tube are received we will publish the updated information so we can all see if things are getting better, worse, or staying the same.
There is a very wide range of specs in today's tubes. Most fall far short of specs from the 1950s - 1970s. One aspect of GT offerings is that the gold series of tubes must fall within a narrow range. This means a lot of tubes are rejected. Current reject rates are generally over 50% from all vendors.
The tubes listed here were not tested or put through any selection process. These are straight from the vendor. Most vendors pack tubes 100 per box in the case of preamp tubes. Preamp tubes are the most critical in your amplifier. A tube that is low on current output, gain, transconductance, etc., will not let the amp perform at it's best level. Typical preamp tubes which are bulk factory untested samples and not selected typically can be 50% down in one or more of these factors.
Output tubes will have the mid range tubes in a given shipment as the test samples. An example of this in RCA book spec is that a 6L6 at 250 plate volts and 250 screen volts with a -14 volt bias should produce 72mA as the expected design spec.
By publishing these test results it is hoped that the consumer and industry will all work together so the tube makers will have better manufacturing methods and utilize tighter QA procedures.
If you have a tube or tubes that you wish to have tested please contact GT and ask for Myles Rose.
Note - curves were not posted in this post.