Röhren KT120 KT150 SE amp

Here are the Circuit diagrams for single ended amplifierer with: 300B, EML300B-Mesh, EML300B-XLS, EML1605, KT120
Post Reply
J. Leven
Posts: 191
Joined: Fri Jan 13, 2012 12:27 pm

Röhren KT120 KT150 SE amp

Post by J. Leven »

Im Bild sind 3 Röhren die für SE KT120 amps in Frage kommen,
die KT120 links und KT150 in der Mitte,sind hervorragend geignet für die bisher von mir veröffentlichen KT120 SE Schaltungen,
die Rechte KT150 mit 28 mA war dafür völlig unbrauchbar, die Verzerrungswerte
waren doppelt so hoch :? .

In Kürze gibt es eine neuere Schaltung wo beide Röhren eingesetzt werden können,
bis auf die 28 mA Type, die hier unbrauchbar ist bzw entspricht gar nicht den KT88 Typen.
Ich empfehle ,dass die KT120-KT150 sich für die Verwendung im SE amp im dem Parameterbereich der beiden linken Röhren bewegen sollten,
oder anders ausgedrückt, weit weg von den Parametern der 28mA Type.
Meine Vermutung für die doppelten Verzerrungswerte (28 er Type)ist , dass der Innenwiederstand erheblich abweicht bzw höher ist,
da die Verzerrungen sehr gleichmässig über die Frequenz und mit ansteigender Leistung verteilt waren .

Laut Aussage von BTB habe ich die KT150-28mA Röhre in 2013 gekauft
und diese Werte entprechen nicht mehr der aktuellen Produktion .

Die andere KT150 müsste von 2017 sein, woher die KT120 stammen kann ich nicht mehr sagen,
das Schild sieht aus wie Hersteller - Platinum Matched Paar


J.Leven
Attachments
DSCN1293.jpg
DSCN1293.jpg (80.6 KiB) Viewed 10659 times

User avatar
Admin19
Site Admin
Posts: 77
Joined: Sun Dec 11, 2011 1:55 pm

Re: Röhren KT120 KT150 SE amp

Post by Admin19 »

The problem is, as is so often, that certain dealers select but do not want to say how or what. And if "a special method" that is undesirable for me. Just test normally, that's good enough. Now you have such problems here that a tube only draws 28mA, and the first question I would have would of course be about the test conditions.

But if, like here, the test conditions are kept secret, you cannot check whether the tube is already OK when it is was delivered. Because under the same conditions, whatever they were, they must bring the same results.

The very noble USA brand names should not hide the fact that these tubes come from the Russian plant in Saratov, where vacuum errors occur, regardless of brand names. Their cheap Sovtek or Standard EHX were no better or worse than the expensive gold versions. This hardly expressed itself immediately after delivery, only that these batches were always below average for the anode current. This can and may be so, and by itself does not mean a problem. Only after storage, they got worse. Up to the complete loss of vacuum, after the guarantee period.

If the anode current is lower due to mechanical tolerance, the transconductance should be higher, bcause mechanical deviations cause exactly THAT. If both values ​​are considerably lower, you should convince yourself otherwise that the cathode is OK, like test if the tube can deliver maximum output power.

The test conditions should also be relevant. Which in my opinion is not the case at 28mA for such a heavy tube. It only becomes realistic above 25 watts and 100mA. The tube should survive 15 minutes under maximum conditions without changing the parameters. However, the label burns darker, and this is generally perceived by end customers as "suspect". Although personally I ind it desirable if I can see that a performance test has been made.

The sticker on the left tube shows at least 100mA current and Gm = 9500. This is the sticker from New Sensor in New York. Such tubes are computer tested, and sold by them 10% more expensive than tubes directly from Saratov.

Post Reply