New Tubes

[adrianywu]

If the tubes are indeed 11 years old, I am not surprised that they died. The way they wrote the 1 and 9 is very typically French. I have seen this with all the French people I know.

 

[DasguteOhr]

Hi Adrian, these are the original EH matched pair selected by Jadis for my amp. These died suddenly. And there are 2 sets of measurements in each tube. Would you know what these are, like plate voltage, etc?

View attachment 87970

11.15 or 10.40 is the static slope is defined as a measure of the amplification of the tube for a certain point on the characteristic curve, which lies in the approximately linear characteristic curve, as S = ?IA / ?UG in mA / V
grid voltage and anode current determine the gain pic exsample

 

[jadis]

129.4 is probably the plate current in mA. B3 probably marks the position of the tube on the amp. Don't know what 11.15 means, but the date of manufacture is sometimes indicated by year and week. Therefore, this could mean 15th week of 2011 (since the other is 10.40, probably 40th week of 2010).

Thanks Adrian. A3 and B3 indeed are the tube socket positions posted in their manual.

 

[jadis]

11.15 or 10.40 is the static slope is defined as a measure of the amplification of the tube for a certain point on the characteristic curve, which lies in the approximately linear characteristic curve, as S = ?IA / ?UG in mA / V
grid voltage and anode current determine the gain pic exsampleView attachment 87973

Thanks for your inputs, Stephan.

 

[jadis]

So much tech specs for a tube amp. LOL I'm a tube gear and tube lover but never got into the tech specs part of it. I let my trusted source do all the matching . Power tubes for me , I decided not to invest in the NOS variety because they do not really last that long. I feel the the old ARC amp with individual pots per tube is the best in finding new tube replacements. Jadis indeed uses push pull for each pair. Long ago I thought they has some electrical thing to regulated their so called auto bias system.

 

[DasguteOhr]

Thanks for your inputs, Stephan.

my pleasure, "S" not so important in a pushpull amplifier design, because you hear the sum of all tubes in chanel in fixed bias pushpull amps there are often symmetry potentiometers to compensate for the perfect.
a set amplifier it is important that both channels amplify equally loudly.

 

[jadis]

An update on the pair of failed tubes in my Jadis PA100 amp. I had the 2 tubes tested and one of them is really dead while the other is quite strong (all the way to the end of the green good area). So apparently, when 1 tube dies, the amp's circuit has a way to 'kill' its partnered push-pull tube, thats' what I figured. I have 2 brand new Psvane K88 replacing the stock EH tube pair in the meantime (just to make it work) while I ordered 2 pairs of brand new EH KT88s matched pairs. 1 pair as reserves. I'll test them when they arrived in a week.