Bonjour à tous j'aurais besoin de vos compétences, j'ai acheter chez tubeampdoctor deux 12AX7 TUNGSOL et le test qui a été fait donne ces resultats:
Tungsol 1 :
0,7 mA / 1,6 gm
0,6 mA / 1,3 gm
Tungsol 2 :
0,9 mA / 1,6 gm
0,8 mA / 1,7 gm
Protocole de test : Ua = 250v, Ug = -2v pour l'émission exprimée en mA, et variation d’Ug pour déterminer la pente exprimée en mA/V.
Valeurs attendues pour les 2 triodes : 1,2 mA / 1,6 mA/V
tester avec
radioelecsuite au résultat je contact le SAV, il me repond ça:
"For the preamp tubes we let them run like in a real amp with cathode biasing which values that are common for real life tube amps. (e.g. 1k cathode, 100k plate, 300V B+)
The current through the tube is hence regulated by the tube itself (cathode biasing). What is important in these applications is the amplification or gain.
On testers like the AT1000 You have always a fixed bias system. As far as I have seen, a fixed bias is never used in real life for 12AX7´s!
The data on which the AT1000 refers to a datasheets for a typical tube. The spread is not considered!
Just have a look at the official datasheet of a Philips 12AX7. Second Page, Anode current. Nominal is 1.2mA. Official spread is 0.75-1.75mA. That means a tube with 0.75mA would have only 62.5% Emission.
And that is truly OK according to the datasheet!
Or Just look at power tubes. Their range of spread is much wider. So Your good-bad statement depends on the value You record to the tester! You surely have seen power tubes which have 25mA idling, others have 50mA. Does that mean the 25´s have only 50% emission? Not really…
Just compare the delivered RT080 tubes in a real amplifier to other brands which have on the AT1000 a good statement and You will realize that both will have the correct gain and performance!"
Pour moi c'est du foutage de gueule car au vu des résultats et même si le testeur utilisé n'est pas un monstre de precision je considère qu'acheter des tubes avec ces valeurs, c'est comme acheter une voiture avec le mauvais moteur dedans.
merci