JfetBOZ mods

Jump to Latest
#201
Ok, so I'm trying to understand how to use my scope. I turned up the volume on my receiver, which is sending the 1000hz signal via the CD player.

My scope's test leads are 10x and the scope is set at 0.1volts/div. This means that each division is 0.01volts. Correct me if I'm wrong...anybody!

To the best of my knowledge:

I have 0.015 volts to the gain-stage.

This was measured on the balanced lead that's connected to the inverting transistor which feeds the F4. Incidentally, the balanced lead feeding the non-inverting transistor is reading about twice the voltage of the inverting side.

I have 0.27 volts out of the gain stage.

So, 0.27 divided by 0.015 = 18

This is the gain?

Edit: I ran the receiver at 25db down (the volume I listen to the home theater--very loud!) and had no clipping. This is also the volume used when I sampled the above readings.
 
#202
puting yor probe in 10x means that you are attenuating input by factor 10;
always leave probe in "1" ie . not "10x" if you can ;

so - please confirm few things :

-you are running input of little stage in balanced mode ?
-you are using inverted (-) leg on output - to F4 , using it unbalanced , but without grounding + leg ?


find enclosed your (I hope I found it) last - valid schematic , and give us few words with exact schematic, maybe even with few dots to help us understand your measuring

if you have gain of 18x ( ie. ~25db) it's not for surprise ...... you are running it open loop, with miniscule amount of feedback .

I'll do - in your boots - one of two things :

1. try source degeneration

2. try to make it as susy stage

then - decide what's better for your ears
 

Attachments

  • jfet.png
    jfet.png
    12.2 KB · Views: 403
#203
inductor

The choke you ordered and transformer you used must have iron core. Iron core has losses at high frequencies. and it increase with frequency.

So, I think it is better to use ferrite core, and it can improve the high frequency response somewhat.😀
 
#206
Zen Mod said:
puting yor probe in 10x means that you are attenuating input by factor 10;
always leave probe in "1" ie . not "10x" if you can ;

so - please confirm few things :

-you are running input of little stage in balanced mode ?
-you are using inverted (-) leg on output - to F4 , using it unbalanced , but without grounding + leg ?
Click to expand...

The test leads are 10x, not the scope. I'm stuck with them until I purchase new leads.

The answer is "yes" to your other questions.

Here's the schematics with voltage values that I'm currently using:
 

Attachments

  • jfet.png
    jfet.png
    31 KB · Views: 364
#210
carpenter said:


The test leads are 10x, not the scope. I'm stuck with them until I purchase new leads.

The answer is "yes" to your other questions.

Here's the schematics with voltage values that I'm currently using:
Click to expand...


if you running input balanced - how on earth you have 0,015 on left input and 0,03 on right input........

you must using it unbalanced on input , too?
with floating right side input?
 
#211
Zen Mod said:



if you running input balanced - how on earth you have 0,015 on left input and 0,03 on right input........

you must using it unbalanced on input , too?
with floating right side input?
Click to expand...


No. Both inputs are being used--only floating output on non-inverting jfet. I'm not certain why there's an imbalance. You can bet I will look into the matter further, though.🙂
 
#212
carpenter said:



No. Both inputs are being used--only floating output on non-inverting jfet. I'm not certain why there's an imbalance. You can bet I will look into the matter further, though.🙂
Click to expand...


so - then is mistake in your measuring approach ;

when you are measuring input voltage - you must place probes between positive and negative points of input ; in this case they are + input and - input , and you must disregard ground . input is two pole , not 3 or 3,5 pole :clown:

when measuring output , you also must put probes between positive and negative points of output ; in this case they are ground and negative output ; disregard positive output .

am I guessed right?
 
#213
Zen Mod said:



so - then is mistake in your measuring approach ;

when you are measuring input voltage - you must place probes between positive and negative points of input ; in this case they are + input and - input , and you must disregard ground . input is two pole , not 3 or 3,5 pole :clown:

when measuring output , you also must put probes between positive and negative points of output ; in this case they are ground and negative output ; disregard positive output .

am I guessed right?
Click to expand...


My scope only has one probe. It is a dual input scope, though. So, I'm not sure what you mean when you say probes (plural).

I checked the voltage amp feeding the x-over; it reads matching voltages on both outputs. The x-over, itself, gives a mismatch in output voltages.

I must need a new x-over? Several days ago I ordered 25 pcs. TL072 op-amps in order to play with ESP's electronic x-over design. Nice thing about DIY: when things break, you can always study and build new components yourself! 😀 😀 😀
 
#217
carpenter said:
I have a little alligator clip hanging from my probe tip. Is this the negative probe you speak of?

I'm quite the nube when it comes to scopes.
Click to expand...


yes ;
tip is hot, alligator clip is neg side of probe .............. on both pics abobe - aligator clip is on "B"

http://www.bcae1.com/oscope.htm

and - for mucho other things - go to the root of site :


http://www.bcae1.com/
 
You must log in or register to reply here.
Top Bottom