Babowana, the change you suggested sounds good. The 26.6 volts on the drain concerns me, but the sound is pleasant.🙂
Hahahah.......
I tried it! I connected my Plitron secondaries to R9. I ran 32+ voltage through one secondary lead--through the center tap--out the other secondary lead, and into R9. R9 = 1k and the voltage at mosfet drain is 26.5v. Voltage between fets = 8v.
It's louder, not just ghost-in-the-attic louder, but full and loud! I don't hear distortion either...but with my ears😉
Where to go from here?😀😉
I tried it! I connected my Plitron secondaries to R9. I ran 32+ voltage through one secondary lead--through the center tap--out the other secondary lead, and into R9. R9 = 1k and the voltage at mosfet drain is 26.5v. Voltage between fets = 8v.
It's louder, not just ghost-in-the-attic louder, but full and loud! I don't hear distortion either...but with my ears😉
Where to go from here?😀😉
Same choke load, and I've dropped R9 to 500ohms! The drain's at 29volts! It sounds even better.......I'm going to drop R9 even lower.
Wife's going to bed, I have to sign off. I'll see you guys tomorrow morning!😀
Wife's going to bed, I have to sign off. I'll see you guys tomorrow morning!😀
carpenter said:
Hi Carpenter,
I believe you like the sound at the lower gain.
Ok, then . . . Remove the coil and change R9 to 2.2K and R8 to 500 (or 470).
You will get the drain voltage of 20.5 and voltage gain of about 5.
How to estimate the voltage gain?
Bias = 5mA
R(load) = R9//R8 = 2.2K//500 = 407 (output impedance)
R(source) = 10
R(ds)j of JFET ~ 25 at 5mA bias (datasheet)
R(ds)z of ZVN3310 ~ 200 at 5mA bias (datasheet)
Then voltage gain = {R(load)/R(source)}*{R(ds)j/R(ds)z} = (407/10)*(25/200) = 5
What is the result?
If you have max 2V peak at the input, you will get 10V peak at the output.
As the output impedance of your pre is 407 ohms while the input
impedance of F4 is 47K, the output voltage of F4 will be also about 10V.
Then, the music power at 8 ohm load will be 10^2/2/8 = 6.25W.
Isn't it enough for your lovely music power?
Attachments
flg said:
I'm so upside-down sometimes, I did use the primaries. Sorry.
I removed all resistance on the mosfet drain. The sound is amazing. I picked up 6db gain (at least that's how much I had to turn down the receiver) and can hear details that are just plain spooky!😀
Babowana said:
Hi Carpenter,
I believe you like the sound at the lower gain.
Ok, then . . . Remove the coil and change R9 to 2.2K and R8 to 500 (or 470).
You will get the drain voltage of 20.5 and voltage gain of about 5.
How to estimate the voltage gain?
Bias = 5mA
R(load) = R9//R8 = 2.2K//500 = 407 (output impedance)
R(source) = 10
R(ds)j of JFET ~ 25 at 5mA bias (datasheet)
R(ds)z of ZVN3310 ~ 200 at 5mA bias (datasheet)
Then voltage gain = {R(load)/R(source)}*{R(ds)j/R(ds)z} = (407/10)*(25/200) = 5
What is the result?
If you have max 2V peak at the input, you will get 10V peak at the output.
As the output impedance of your pre is 407 ohms while the input
impedance of F4 is 47K, the output voltage of F4 will be also about 10V.
Then, the music power at 8 ohm load will be 10^2/2/8 = 6.25W.
Isn't it enough for your lovely music power?
Thank-you for all this information, Babowana!🙂 I'll have to pull this aside and give it further study and consideration.
I don't fully understand the symbology on that last sentence. Care to elaborate?
You mean this one?carpenter said:
10 * 10 /16
I'd love to try this with a 24V battery supply. Maybe I can adjust component values to suit. Hm. Need to find a source (or a substitute) for the 2SK170.
paulb said:
Ahh... 10^2 means 10 squared. Gotcha! So 100 divided by 2 = 50 divided by 8 = 6.25. Cool.
The choke loaded cascode is a lot of fun! It's more of a stand alone unit with the F4--when I coupled my electronic x-over I heard quite a bit of hiss. When fed a signal from the receiver (bypassing the x-over) it sounded perfect. Maybe there's too much gain?
Zen Mod said:
Your blinking red is too weak to brighten my darkside . . .
Deacrese . . . ? Not increase?
Babowana said:
Your blinking red is too weak to brighten my darkside . . .
Deacrese . . . ? Not increase?
off course that you are right ............ increase resistor to decrease gain .............
"blinkin red" .............
naah ............
edit:
seems that rust never sleeps
Zen Mod said:seems that rust never sleeps
Turn your blinking light low . . . and go to bed . . .
Hey guys,
I went back to the basic JfetBOZ and drive it with 15 volts. I still use the Plitron 1000VA transformer to choke load the drain (no resistor).
Sound is incredible! It's sweeter sounding than the cascode and has less gain, which is what I wanted with my x-over. Now, there's just the slightest hiss from the 110db 1w1m horn. I'll play with the source resistor and see it I can quiet this little beast.
.........and now, I'll sing to the choir....
Oh what fun it is to ride on a one tran-sis-tor gain-stage. Jingle bells, jingle bells, Johnny likes to play.......😱 😀 😱 😉
I went back to the basic JfetBOZ and drive it with 15 volts. I still use the Plitron 1000VA transformer to choke load the drain (no resistor).
Sound is incredible! It's sweeter sounding than the cascode and has less gain, which is what I wanted with my x-over. Now, there's just the slightest hiss from the 110db 1w1m horn. I'll play with the source resistor and see it I can quiet this little beast.
.........and now, I'll sing to the choir....
Oh what fun it is to ride on a one tran-sis-tor gain-stage. Jingle bells, jingle bells, Johnny likes to play.......😱 😀 😱 😉
carpenter said:
You are hopping like a child.
Congratulations again.
Let us see your drawing of the latest one.
Jimgle bell . . . jingle bell . . . you offer me some beer . . .
I am having boring Sunday in the tasteless hotel . . .
carpenter said:
Ok, so most probably the only change would be to replace the 2.2 K drain resistor with 1000 VA transformer. But there's a problem: That transformer wouldn't fit into my "STR8" box...
An option: Make a small banana socket. Then you''ll have two set of plugs: One for 2.2k resistors, or, the other for the connection with the transformer/choke . Hide the tranny somewhere and say how nice and tiny preamp ya have! 😀
Such an Odessey!! Not having a large toroid available ,could you list your preferences in order , of the various mods you've applied?Please include any comments "Golden Ears " might have offered.
Hi all,
Golden ears listened from the bedroom and liked what she heard. I'll try and get her to sit in the sweet-spot later today.
I'm going to order a pair of chokes from Nebraska Surplus Sales. They're rated at 0.7H, have around 30 ohms resistance, and easily handle 5mA. At $15.00 a piece, it's a cheap experiment. Best of all, they're small--on the order of 1.5" x 2".
I'll keep ya posted on my progress.
Golden ears listened from the bedroom and liked what she heard. I'll try and get her to sit in the sweet-spot later today.
I'm going to order a pair of chokes from Nebraska Surplus Sales. They're rated at 0.7H, have around 30 ohms resistance, and easily handle 5mA. At $15.00 a piece, it's a cheap experiment. Best of all, they're small--on the order of 1.5" x 2".
I'll keep ya posted on my progress.
Attachments
I had a bit of hiss from my horn--probably because I fed an unbalanced circuit from that of a balanced. I designed this little fix; it works flawlessly.
I'm so amazed at the gifts Nelson has given us!😀
Edit: I matched the jfet in situation--I just measured the voltage across the source resistor and swapped out transistors until I had a match. So simple. The sound is smoother, very clean, slight increase in gain.🙂 The unused leg can be utilized at a later date when I couple a pair of F4s for the midbass! Bit-chin' 😀
I'm so amazed at the gifts Nelson has given us!😀
Edit: I matched the jfet in situation--I just measured the voltage across the source resistor and swapped out transistors until I had a match. So simple. The sound is smoother, very clean, slight increase in gain.🙂 The unused leg can be utilized at a later date when I couple a pair of F4s for the midbass! Bit-chin' 😀
Attachments
My sweetie, miss golden ears, gave the sweet-spot a go. She likes the F4/JfetBOZ combo more than my ZV7-T. Much more clarity! Now, what to do with all those power-jfets I purchased from Mr. Rollins???????