In the last century I bought a few thousand tubes and tested them with the computerized curve tracer Sofia by Audiomatica. The tubes I purchased were mostly direct heated triodes ( DHT ) and high transconductance noval. Over time I have kept only the most linear tubes and matched them. In the coming weeks a part of my collection will be on sale (among these DHTs such as UX201A, CX301A, 171A, 112A, CV1660, 3A/110A, AC/P4, 801A, 10Y, 801 RCA ceramic base, RE604 TFK globe, RE084, RE134, D3A Siemens, etc )
If you need information on the interpretation of the curves or enlargements of specific areas, just ask.
It should be noted that Sofia's software makes an error when measuring direct heated tubes.The cathode reference point is lifted up by half of the heater voltage; so, for example, when the filament is fed at 4 volts, all curves are actually measured at 2 volts less than nominal. The curve you see at -40 volts is actually at -42 volts. The higher the voltage of the filament, the greater the difference (especially with the family of 10Y/VT25/VT62/801A etc with a 7.5 volt filament the error is 3.75 volts) You can read about it on the dedicated page in Sofia by Audiomatica on the Jac music website.
Auction for one used tube Valvo AZ1 rectifier tube logo on top ( like TFK RGN1064 ) with big mesh plates. Strong emission, near 100%
In the next days I will add several matched pairs of Cunningham and RCA globe CX310A and UX201A
For any infos and for combined shipping, please ask. For shipping outside Europe, please ask for better prices