Bas Horneman said:
A job for Mr. Aikido? Pretty simple, selectable gain, low output impedence, non-exotic power supply (maybe even share the supply) - 6DJ8 version? Maybe a single 6DJ8 triode for the input side and 6GM8 for the follower?
Sheldon
planet10 said:
from schematic in this post
http://www.diyaudio.com/forums/showthread.php?postid=998055#post998055
I get it the input impedance is ~50 kOhm.
The minimal output current needed we get from:
Voltage input (for maximal output) / input impedance.
The input voltage needed in relation to input impedance will give the current that must be provided.
Very correct an amplifier is always an adapter
between a source and a load.
Knowing these values, as Bas Horneman and planet10 has put it
is essential!
Read more amplifier basics:
http://www.diyaudio.com/forums/showthread.php?postid=893062#post893062
lineup
Yes, the Aikido is also an excellent canditate...but with 4 tubes and a whole lot of resistors it is relatively difficult. But one could do a lot worse than buy John Broskie's boards and switched attenuators! http://www.tubecad.com
Even if one does not use the Aikido the switched attenuator kit over at tubecad is great to use with any tube preamp that is decided here.
Even if one does not use the Aikido the switched attenuator kit over at tubecad is great to use with any tube preamp that is decided here.
Only need three triodes per channel, as long as you're not doing a lot of tube swapping.
http://www.tubecad.com/2004/blog0013.htm
Sheldon
http://www.tubecad.com/2004/blog0013.htm
Sheldon
Bas Horneman said:
I use something similar for a DAC gain stage after a passive I/V.
http://www.ecp.cc/5687_module.html (I might even have an extra one of these boards laying around ...)
I also have a board showing up in the next few days for a 6n6p/6n30p based one of these that uses either LED or standard resistor biasing.
dsavitsk said:
6N30P ( 6n30pi )
is one tube i have read a lot about, and from what i have understood
it is a good preamp tube - with high current output drive capacity.
The link posted by dsavitsk shows us
this little fantastic BEAUTY
An externally hosted image should be here but it was not working when we last tested it.
is a great tube. But the 6n6p is virtually the same. However it still can be bought cheap because it's fame has not spread as much. But there are many tubes one could use. With the CCS being flexible you could use any tube you fancy.
PS...dsavitsk great little pcb! That way you can change a capacitor (or psu) in a New York minute!
Bas Horneman said:
Thanks. (sorry to thread crap) I have taken to doing everything modularly like this, so that project I can swap in and out one of 3 DAC boards, 5 different gain stages (several single ended, a srpp, and an opamp), a pile of power supplies, etc (not to mention swapping different coupling caps). I am also working on a headphone amp that is the same -- there are little boards that have a PCB mount socket but also a retaining ring. All the resistors/caps, etc and terminal blocks are on each board so it takes about 3 minutes to change the amp completely. I even picked up some bottlehead hole shrinkers so it can use both octal and noval tubes.
Fuling said:
ECC86
is about as low in NOISE you can get with tubes.
Has been used in 1.000 of low noise preamps for almost as long as existed.
And many Professional equipements and microphone amps use it!
A short explanation of the schematic:
The triode is of course the actual gain device, operating at 15V 2mA.
The plate is loaded with a 2SK170-based CCS
and direct coupled to a cascoded Jfet White follower.
Your circuit setup is interesting
and really deserves some try out!
Thanks very much, Fuling.
from
lineup
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.
I´m 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.
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.
I´m 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.
Direct coupling to the output stage was a major design goal, if I had to use a coupling cap I´d definitely choose a more potent tube and skip the White follower.
Bas Horneman said:
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/diytubegainclone/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/member.php?s=&action=getinfo&userid=4828
😎
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 ...?
But wouldnt it be posiible to simply use a low noise step-up transformer😕
Nah, maybe not eneough voltage ...?
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!
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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