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Old 5th September 2006, 09:21 PM   #31
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Another added advantage is the low voltage b+ one can use!
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Old 5th September 2006, 09:22 PM   #32
Fuling is online now Fuling  Sweden
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Thanks for shown interest!

The circuit is under evaluation, but initial testings indicates that it is perfectly capable of driving an IRFP260-based follower to 50kHz without loss of gain.
My PSU is not quite up to the task, and either the cathode resistor or the 175R reistor in the CCS must be made adjustable to set the operation point for max linear output swing.

Im definitely going to make something out of this some day when I have the time, there are plenty of more important projects in the pipeline right now.
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Old 5th September 2006, 09:24 PM   #33
Fuling is online now Fuling  Sweden
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Another added advantage is the low voltage b+ one can use!
Direct coupling to the output stage was a major design goal, if I had to use a coupling cap Id definitely choose a more potent tube and skip the White follower.
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Old 5th September 2006, 09:43 PM   #34
lineup is offline lineup  Sweden
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Quote:
Originally posted by Bas Horneman
Another added advantage is the low voltage b+ one can use!
Yes, this is great advantage for making a preamp for SEWA.
Same thinking as I had, Bas Horneman.

Here is another wellknown HYBRID project:
http://www.customanalogue.com/diytub...lone/index.htm

with the diyaudio topic of:
Tube with Power IC Output Stage - JLTi

This is a Tube preamp + a Chip Amp output power amp
= Hybrid between tube and transistors.
By this diyAudio.com member:
Joe Rasmussen
http://www.diyaudio.com/forums/membe...fo&userid=4828

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Old 5th September 2006, 10:11 PM   #35
tinitus is offline tinitus  Europe
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Excuse me fore being a bit ignorant and off topic......

But wouldnt it be posiible to simply use a low noise step-up transformer

Nah, maybe not eneough voltage ...?
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Old 5th September 2006, 11:00 PM   #36
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by tinitus
Excuse me fore being a bit ignorant and off topic......

But wouldnt it be posiible to simply use a low noise step-up transformer

Nah, maybe not eneough voltage ...?

you mean-xformer instead preamp?

then you forgot impedance issues
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Old 5th September 2006, 11:51 PM   #37
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Default I must agree with BAS a triode with a CCS

Bas Horneman has the right idea, a triode with a CCS on top. I have built this circuit to drive the grid of a 300B, should handle that MOSFET's without any issues.
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Old 6th September 2006, 11:56 AM   #38
Ryssen is offline Ryssen  Sweden
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should handle that MOSFET's without any issues.
Even the capacistanse of the Mosfets?Some say it wont,thats why I decided to go for a CF..
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Old 6th September 2006, 12:06 PM   #39
Fuling is online now Fuling  Sweden
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A CCS-loaded 6C45 would have about 1kohm output impedance, which might me a bit high.

The same tube with a 3:1 stepdown transformer on the output would probably be much better suited for the job!
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Old 6th September 2006, 12:29 PM   #40
Mad_K is offline Mad_K  Norway
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What is the problem with 1K out Z?

You'd be bandwith limited to about 600KHz...
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