Yes,I I have the swing to drive it full output,but some say you need lot
of current to drive the Mosfets,e.x http://www.diyaudio.com/forums/showthread.php?s=&threadid=84361&perpage=10&pagenumber=4
That´s why I thought of a bigger trafo.
Ryssen said:
Yes,I I have the swing to drive it full output,but some say you need lot
of current to drive the Mosfets,e.x http://www.diyaudio.com/forums/showthread.php?s=&threadid=84361&perpage=10&pagenumber=4
That´s why I thought of a bigger trafo.
Keep this one if you like it, and build a new one with a bigger current using fatter tube. For example, 12L6 (or 50L6) in triode mode. And a new power transformer. I use pairs 12J5 (5MA, 120V) + 12L6 (50 MA, 120V) to drive 500W / 2 Ohm hybrid amp, I like the sound.
Ryssen said:
How are the tubes connected?Both tubes as voltageamplifiers?500w class A?
Yes, both tubes as voltage amplifiers. Each is loaded by a corresponding CCS, directly coupled with a voltage shift (I use bipolar anode power supply), and with a feedback from the 2'nd anode to the 1'st catode.
No, just A+B
A couple of things you can try
Instead of a tube load the ccs with a 2K resistor to ground, the voltage accross the resistor will tell you what your CCS is set to for current. 20mA would be 40V, 30mA would be 60V and so on...If the CCS is delivering sufficent current you can use a resistor on the cathode to ground rather than an LED, start at 90 ohm and you can decrease from there.
Ryssen said:I have been bussy with this SEWA hybrid thing
An externally hosted image should be here but it was not working when we last tested it.
It´s a 6c45 CCS stage:
An externally hosted image should be here but it was not working when we last tested it.
It seems to be working fine through my junkspeakers,the only problem now is that i found out (Thanks Fuling)the supply for the tubes are a bit weak.I can use 15ma/tube but if I go higher I only get hum,will order a bigger trafo wich I use backwards on the SEWA supply,and try it out on my better speakers.
An externally hosted image should be here but it was not working when we last tested it.
cheers.
Instead of a tube load the ccs with a 2K resistor to ground, the voltage accross the resistor will tell you what your CCS is set to for current. 20mA would be 40V, 30mA would be 60V and so on...If the CCS is delivering sufficent current you can use a resistor on the cathode to ground rather than an LED, start at 90 ohm and you can decrease from there.
Nope,I can´t get more than 15-17mA even with resistors.
Locking at the Plate characteristics of 6c45 at -1,7v that I get with this Led,and 140-145v I cant get more than 15mA from the tube.Is 150v the max voltage for 6c45?At 155v -1,5v I get 30ma,I have some IR Leds that give 1,5v.And at bout 170v -1,7v I get 30mA,if it´s safe to use the tube at 170V?As you can se I like to use Leds..
I have ordered a larger trafo to try.
Locking at the Plate characteristics of 6c45 at -1,7v that I get with this Led,and 140-145v I cant get more than 15mA from the tube.Is 150v the max voltage for 6c45?At 155v -1,5v I get 30ma,I have some IR Leds that give 1,5v.And at bout 170v -1,7v I get 30mA,if it´s safe to use the tube at 170V?As you can se I like to use Leds..
I have ordered a larger trafo to try.
If you reduced the bias point to say 1V, then you would set the conditions for lowing the plate voltage whilst maintaining the current through the tube (the CCS will consume more voltage). This is "having more headroom" for a given current, which is what you want. Unfortunately I think you will have to give up on the use of LED for bias purposes.
It depends whether you can live with just 1V of bias.
Shoog
It depends whether you can live with just 1V of bias.
Shoog
Ryssen said:
I think that´s the case,already tried with 1,2v bias the trafo can´t keep up the voltage..Gonna try this bigger trafo I ordered.
But don't expect significant quality improvement.
To charge a capacitance of 1 Farad during 1 Second to 1 volt we need 1 Ampere (I love the Metric system!).
Suppose, your FET has 3000 pF input capacitance. Suppose, you have about 0.5 voltage swing s-g to fight against the capacitance (actually much less).
Minimal current is 2*(10^4)*2*3(10^-9)0.5=6*(10^-5) Amperes, i.e. 0.01 mA. If you have 10 Ma, it means you have 1000 times more, or you have already enough current for a swing 500V s-g.
It means, neither CD, nor MP3 can give you such a quality signal so you can measure differences on the high end of your band.
Ryssen said:Well,I´ve heard some say the 6C45 "needs" at least 30mA to sound it´s best,so who knows.
They were right. Better use another tube.
An externally hosted image should be here but it was not working when we last tested it.
CCS with 6C45
I think you need to raise b+ to about 220V and lower the resistance on the CCS (10E in Series w/470E) and you should be on your way. As far as an LED goes, I can't help you much there. I think you got it right that you are too low a voltage on the CCS that feeds the tube, THe 6C45 sounds fine to me at 18-20mA, but it will handle more current if that is your wish.
I think you need to raise b+ to about 220V and lower the resistance on the CCS (10E in Series w/470E) and you should be on your way. As far as an LED goes, I can't help you much there. I think you got it right that you are too low a voltage on the CCS that feeds the tube, THe 6C45 sounds fine to me at 18-20mA, but it will handle more current if that is your wish.
The new bigger one,lets hope it can keep up the power..
An externally hosted image should be here but it was not working when we last tested it.
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