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Old 3rd November 2009, 08:22 AM   #41
Calvin is online now Calvin  Germany
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Hi,

interstage trannies are probabely the easiest and best way of drive....at least its technically elegant ;-).
What were Your reasons for a bridge design instead of the often to find CCS-loaded common cathode stage?

jauu
Calvin
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Old 3rd November 2009, 01:26 PM   #42
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Quote:
Originally Posted by Calvin View Post
Hi,

interstage trannies are probabely the easiest and best way of drive....at least its technically elegant ;-).
What were Your reasons for a bridge design instead of the often to find CCS-loaded common cathode stage?

jauu
Calvin
Decent x_former with isolation working voltage of 3...5 kV primary to secondary in not the easiest by my experience.
What CSS is made of? MOSFET's or pentode/tetrode?
Well... Radiotron Handbook says that pentode loaded triode stage is still a triode stage...
Then the question would be: Where to get floating 200-300V supply for second grid?
Beveridge circuit uses beam tetrodes with floating zeners.
Triode mu follower will make power supply voltage even more dangerous
Alex
Frustration while building tube circlotron's driving stage inclines me towards transformer...
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Old 3rd November 2009, 04:05 PM   #43
Calvin is online now Calvin  Germany
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Hi,

*lol* can feel with You regarding cyclotron´s driver stage. My boss still dreams of such an amp as DD for ESLs and I still try to get him off that idea.
My favourite at the moment would be a SIC-JFET or Triode stage, loaded with a CCS (fixed current or maybe even output voltage controlled).
The CCS could be made of a depletion mode SIC-JFET or MOSFET and cascoded decices to allow for the specified voltage range. I´d prefer heaterless devices for the ´high sided-CCS´ to omit with problems of the power supplies of the heater.

jauu
Calvin
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Old 4th November 2009, 04:15 AM   #44
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Quote:
Originally Posted by Calvin View Post
Hi,

*lol* can feel with You regarding cyclotron´s driver stage. My boss still dreams of such an amp as DD for ESLs and I still try to get him off that idea.
My favourite at the moment would be a SIC-JFET or Triode stage, loaded with a CCS (fixed current or maybe even output voltage controlled).
The CCS could be made of a depletion mode SIC-JFET or MOSFET and cascoded decices to allow for the specified voltage range. I´d prefer heaterless devices for the ´high sided-CCS´ to omit with problems of the power supplies of the heater.

jauu
Calvin
Shall not it be considered as tube "infidelity" or cheating with transistors
In regard to Circlotron - this one is not intended for driving ESL. Even then
+/- 450V of driving voltage required. No appropriate AF tubes were found,
transmitter and sweep only... Floating heater is not that bad in respect to
floating second grid supply for tetrodes - (I hope my english would be adequate)
galette or disk or vertical sectioned transformer will do it just fine.
Alex
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Old 4th November 2009, 06:40 AM   #45
Calvin is online now Calvin  Germany
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Hi,

I´m not very dogmatic about parts. I do prefer certain types like JFETs, but I try to find and use that device that is most suitable for the task. Transistors are easy to use for CCS and achieve better results. So why should I worry about a suitable Pentode and their associated circuitry when a depletionmode MOSFET (or a cascode formed with it) does the same even better and with less harrasment?? The ´real´ amplyfying device could still be a Triode
KR-Audio has already prototyped and tested a new 4kV Triode for us and as soon as time allows I think I´ll be at it, or one of the SIC-JFETs.

jauu
Calvin
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Old 4th November 2009, 08:26 AM   #46
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Quote:
Originally Posted by Calvin View Post
Hi,

I´m not very dogmatic about parts. I do prefer certain types like JFETs, but I try to find and use that device that is most suitable for the task. Transistors are easy to use for CCS and achieve better results. So why should I worry about a suitable Pentode and their associated circuitry when a depletionmode MOSFET (or a cascode formed with it) does the same even better and with less harrasment?? The ´real´ amplyfying device could still be a Triode
KR-Audio has already prototyped and tested a new 4kV Triode for us and as soon as time allows I think I´ll be at it, or one of the SIC-JFETs.

jauu
Calvin
Thanks,
nice link.
The tubes I've got are transmitter tetrodes rated @ 10kV, DC.
Pretty linear in triode connection. I do feel inappropriate to go into
details before amp is built and tested.
FETs are known for very non-linear output capacitance which seems to
be very relevant for a capacitive load.
Alex
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Old 4th November 2009, 02:18 PM   #47
Face is offline Face  United States
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Wolfcott tube amps with adjustable damping are made specifically for Electrostats. the Presence Tube Amplifiers
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Old 4th November 2009, 02:52 PM   #48
hreith is offline hreith  Germany
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innoxx audio
...are made specifically for Electrostats
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Old 4th November 2009, 03:24 PM   #49
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Quote:
Originally Posted by hreith View Post
innoxx audio
...are made specifically for Electrostats
Sure,
any ideas on topology used?
All I could find were spare parts (sic.!) tubeE tubeP tubeG
Does not this smell like consumables
http://www.innoxx.com/deutsch/download/sparepart_8.pdf
Fill the amplifier with the fresh tubes before starting...
Most interesting that higher voltage one requires only two tubes,
very reasonably priced...

Alex
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Old 4th November 2009, 05:24 PM   #50
Calvin is online now Calvin  Germany
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Hi,

Face...we are talking high voltage direkt drive here.....which renders the Wolfcotts OT.

I like the optics of the Innoxx and the use of a µC to control functions and biassing, but they are somehow ´items in between´ as they are no universally usable ESL-amps. You should be beware of and stay within the limitations. The output voltage range is a bit low to drive (segmented) fullrange panels and their current capabilties are a bit low to drive non segmented panels of middle or large size. This leaves segmented hybrid panels and small non segmented hybrid panels as best fitting candidates.
Tubes look like EL/PL519... nice tube, easy to source, attractively priced.

If we want to achieve full power bandwidth of just 20kHz sine(!) we need:
Ipeak[mA]: 62.8 x C[nF] x Vpp[kV] .
Lets assume a non segmented panel of 1nF and rather low voltage needs of 3kVpp (1.06kVrms). Power supply voltage will be app 1.8-2kV. The amp must be able to drive a peak current of ~190mA into the load to fulfill the above stated requirement.
Now segmenting reduces the capacitive load, but such panels typically need more drive voltage, say 200pF and 7kVpp (power supply app. 4kV). Ipeak is then 88mA. Large fullrangers are even more demanding.

jauu
Calvin

Last edited by Calvin; 4th November 2009 at 05:28 PM.
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