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Old 6th April 2013, 07:17 PM   #1
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Default KT120: When does it starts to sing ?

I have exchanged my EL34 with the KT120 for testing purposes. Both run at 350V@55mA. For the EL34, a good operating Point as 350*0,55=19,25 Watt. For the KT120 I guess not optimal.

Ths question is if playing with the bias (easy) or the voltage (difficult), will Change the Sound in what way.

Currently the KT120 has a very good Body, a very good depth, but at the same time it Sound like a liitle curtain or minimal fog is between you and the musicians. While the EL34 is mor like you can touch them. The EL34 is nevertheless a Little less good organizes interms of who stands where, both left-right and front-back.

Does anyone have made the comparison and can share your experience ?

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Old 7th April 2013, 01:56 PM   #2
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What transformer are you using Raa?? If the outputs are 5kRaa or higher, give the Russian 6P3S and 6P3S-E a try, better suited to 350V, but back off the bias. The 6P3S-E wafer base sound great and are low cost. The down side is that they cannot drive low impedance transformers, they run out of steam. For 4.3kRaa iron I use 6550 or Kt88's, I would recommend the Kt120's for 1.9Kraa applications with decent B+ 400 to 450V and run the heaters at 6.3V or a little hotter do not exceed the 6.9 limit. . A major design concern is over the input miller capacitance, the grid 1 capacitance difference between the EL34 and Kt120 are about double, 15pf to 29pf... The KT120s have to be driven to overcome that. The best substitute for EL34's that I like are the Svetlana 6550=C= tubes, best clarity and sound stage, better sound with less feedback needed.
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Old 7th April 2013, 03:12 PM   #3
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I am running 4 el34 or kt120 in pushpull per channel. This is driving them with a 6922 with 10Ma. Raa is 2k7...
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Old 7th April 2013, 03:41 PM   #4
roline is offline roline  United States
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For a driver I prefer the 6N6PI but at a heater current cost of 900ma. 30ma current capability if needed. What is the heater voltage, how did you match the tubes?
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Old 7th April 2013, 06:34 PM   #5
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Hmmmmm, I like the 12BH7 as well a lot, but I have a 6H6 here as well...with which voltage/ current are you using it ? What is your plate and cathode resistor value ?

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Old 7th April 2013, 07:37 PM   #6
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The problem with all 6L6 - like tubes is, they would start singing when anodes start melting.
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