Well, the two halves are in parallel.
So the two devices have the similar 100 ohm load in parallel but both amplified, so nelson gives: 'Drain load resistors R6 plus R7 divided by R5' = 200/100 =2. (Stupid me would think late at night that parallel gives 50 ohms
). Point is: they are 'used as unity gain DC level shifters', thus the DC shifts and the amplification is (roughly) 1 (being unity) but in fact a little bit higher. Output goes same way to give 15x. 2x15=30! Presto.
Well, the two halves are in parallel.
So the two devices have the similar 100 ohm load in parallel but both amplified, so nelson gives: 'Drain load resistors R6 plus R7 divided by R5' = 200/100 =2. (Stupid me would think late at night that parallel gives 50 ohms
I think you have it correct I changed R5 to 50 ohms and the output was about unity.
Good.
Thinking about it again:
I should have added: the 100 ohms R5 gets twice the current from both Q1 and Q2, , this way the 'degeneration or feedback' gets twice as high a voltage; this is equal to that on both R6 and R7.
I'm sure ZM is a better explainer, but I understand he is now out burning a lot of money
albert
Thinking about it again:
I should have added: the 100 ohms R5 gets twice the current from both Q1 and Q2, , this way the 'degeneration or feedback' gets twice as high a voltage; this is equal to that on both R6 and R7.
I'm sure ZM is a better explainer, but I understand he is now out burning a lot of money
albert
after I could manage k2 to zero with the left channel, I did not succeed with the next channel, curious behavior, turning P3 around and around
btw it was not complicated or dangerous..... watching the two multimeters of bias and offset
I could not get k2 down, and when I got k2 down a little k4 was growing ,he,he.
normally both are correlated .....
I changed the output pair of Toshibas, no change. I suppose the mismatched j-Fets are the culprit....
interesting journey....
btw it was not complicated or dangerous..... watching the two multimeters of bias and offset
I could not get k2 down, and when I got k2 down a little k4 was growing
,he,he.normally both are correlated .....
I changed the output pair of Toshibas, no change. I suppose the mismatched j-Fets are the culprit....
interesting journey....
BA-3 Testing
I also did some distortion testing and could get a THD of .0041, effectively removing all the even order components just leaving the odd. Once you find the Null you can just rock the pot back and forth to watch the spectrum change. FUN!
I’m using ARTA and the Cordell Distortion Magnifier and it works great!
I also did some distortion testing and could get a THD of .0041, effectively removing all the even order components just leaving the odd. Once you find the Null you can just rock the pot back and forth to watch the spectrum change. FUN!
I’m using ARTA and the Cordell Distortion Magnifier and it works great!
Nope.
I know that when I cut R5 to 50 ohms I got just about unity out of the front end jfets. With it at 100 ohms I get about .46X at the Junction of R6 and R8.
It sure is a nice circuit as is. It would make a nice preamp as well.
Hi buzzforb,
You are right 30x may be good for people that have not very efficient speakers, let us say 84-86 db/1W.
But I have changed to lowther to be the next years with first watt adventure on the right side.
I even have nearly sufficient sound with the cd-player and the source follower alone, but of course when my friends come they want to hear very loud.....
Otherwise they would say you are working now 2 and a half year with your amps and that is all what is coming out......?
Of course I would try 4,7 uF, some people say you have to go to 2 Hz because of the phase shift......... My Tiny open baffle stops at 65 Hz at the moment.... Nevertheless I enjoy and still hesitate to build a sub.
Gerd