Hey everyone.
Looking for your thoughts on an OP for KT120 Triode connection. Right now I'm using B+ 550V, fixed bias, 61mA as the idle point. The load is (questionable, the speakers are 8R nominal, 4R minimal, so I designed for 6R) 4k:6R.
Sounds fine, but I was discouraged by the lack of a fixed bias triode connected PP amp data on the (GEC) datasheet. They only give info for cathode bias. The grid resistance is 51k as per the datasheet.
Looking for your thoughts on an OP for KT120 Triode connection. Right now I'm using B+ 550V, fixed bias, 61mA as the idle point. The load is (questionable, the speakers are 8R nominal, 4R minimal, so I designed for 6R) 4k:6R.
Sounds fine, but I was discouraged by the lack of a fixed bias triode connected PP amp data on the (GEC) datasheet. They only give info for cathode bias. The grid resistance is 51k as per the datasheet.
I hope the KT120 is more linear, when triode wired, than it is in pentode mode. I've seen the pentode plate curves and they are distressingly non-linear. 😡 
Here's the sheet with the triode curves... http://www.tungsol.com/specs/kt120-tung-sol-specs-curves.pdf
It will surely be better than tetrode connection.
It will surely be better than tetrode connection.
Why you use the KT120 in triode?
I believe that with a right schematic and OT trafo you can reach a very good results in pentode mode
this is one of the amp I made:
P-P with EL34/KT120
look at the tests.
the sound is very fine as my friends say to me
Walter
I believe that with a right schematic and OT trafo you can reach a very good results in pentode mode
this is one of the amp I made:
P-P with EL34/KT120
look at the tests.
the sound is very fine as my friends say to me
Walter
Get the Hammond 1650N from here:
Hammond Push-Pull Tube Output Transformers - (1608 - 1620, 1645 & 1650 Series)
Would be my recommendation.
10K square wave from Hammond 1650N driven with push-pull triode connected KT120's
At ~550V you should get 45 watts out.
Hammond Push-Pull Tube Output Transformers - (1608 - 1620, 1645 & 1650 Series)
Would be my recommendation.
10K square wave from Hammond 1650N driven with push-pull triode connected KT120's
At ~550V you should get 45 watts out.
Attachments
I'm using a pair of those for a KT88 UL amp, but in this amp I'm using Triad VPT18-13800 Toroidal power transformers. I have been running it in tetrode, but prefer the lower Zout of the triode connection.
My 2 cents are> Ask to a guitarist that use KT120, if he said it overdrive very well it dont are linear for audio hi-fi.I hope the KT120 is more linear, when triode wired, than it is in pentode mode. I've seen the pentode plate curves and they are distressingly non-linear. 😡
The 120/150 price is very similar, so in terms of power and appearance the 120 was obsoleted by the 150.
Good looking is important to sell equipment, remains to know the reliability and time life.
?-If someone could inform us the KT150 usual timelife I would appreciated?
Good looking is important to sell equipment, remains to know the reliability and time life.
?-If someone could inform us the KT150 usual timelife I would appreciated?
I used lot of KT150 and 120
I found in the past some issue with stability of bias current. In three or four case I have ask to supplier to replace the tubes
The last 10 pcs seeme to be better after around 30 hrs of running
Mybe the quality is better now from two years ago, I think.
In my opinion the 150 is the best tetrode available now
Walter
I found in the past some issue with stability of bias current. In three or four case I have ask to supplier to replace the tubes
The last 10 pcs seeme to be better after around 30 hrs of running
Mybe the quality is better now from two years ago, I think.
In my opinion the 150 is the best tetrode available now
Walter
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