The BA-3 as preamp build guide

[iluminator]

ok

 

[iluminator]

MEPER, all good, go for it.



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Thank You so much

 

[iluminator]

What can I improve?

 

[Itsmee]

The 74/170 are dissapating 360mW each, you can half it by cascoding, set the drain to aprox 13V.

 

[iluminator]

The 74/170 are dissapating 360mW each, you can half it by cascoding, set the drain to aprox 13V.

Yes, You right but now jfets have a small Cu heatsing
and the layout looks like this..

now the voltage on jfet is below 18V


I'm very happy because it plays better than previously built CEN

 

[iluminator]

now

 

[iluminator]

my power supply

hot power supply for this analog

 

[Itsmee]

Add 10uF across the TL431, they are a little noisy.

 

[iluminator]

Add 10uF across the TL431, they are a little noisy.

in this way?

 

[Zen Mod]

it would be more interesting to find even more scarce and even more expensive JFets for lousy CCS

 

[iluminator]

it would be more interesting to find even more scarce and even more expensive JFets for lousy CCS

Hallo Zen Mod


Yes yes, but
I have a few pieces left, and I was not sure if they are originals, that's why they are suitable for the power source
can be done on lm317 with resistor 180-190R

 

[Zen Mod]

nothing wrong with 2N5486 or mmbf5486

don't be silly , use your own head , instead of blind copying

I was always amused with Papa Borbely's waste of most precious dual JFets in regulator ...... but - it was his Trademark and Demonstration of Force - "look - I have so many of these , so I can use them everywhere"

we (amateurs) aren't in that position

 

[Itsmee]

in this way?

 

[iluminator]

nothing wrong with 2N5486 or mmbf5486

don't be silly , use your own head , instead of blind copying

I was always amused with Papa Borbely's waste of most precious dual JFets in regulator ...... but - it was his Trademark and Demonstration of Force - "look - I have so many of these , so I can use them everywhere"

we (amateurs) aren't in that position

I make a prototype from what I have at home, without investing in new parts, I make too many changes while working 🙂

 

[Itsmee]

Have a look at the Sony Vfet front end, if you include the cascode you can add a little feedback, R29 & R30.
Sony VFET Amplifier Part 2

 

[iluminator]

Have a look at the Sony Vfet front end, if you include the cascode you can add a little feedback, R29 & R30.
Sony VFET Amplifier Part 2

I have an F5 cascode with +-40V voltage.
When I rebuild the amplifier on B3, I will use your advice
thank you

 

[anhton82]

Hi everybody,
Could I decrease R13 to 47ohm for lower gain? Because, I use 100k Volume.
Thanks.

 

[jphabc54]

Hi everybody,
Could I decrease R13 to 47ohm for lower gain? Because, I use 100k Volume.
Thanks.

Yes, reducing R13 will reduce gain. Whether 47R will reduce it too much for you, I don't know. R13 @ 47R will give you R13/R11 = 47/22 = ~2.1 gain. I reduced R13 on mine to 100R. With a 10k pot, that is more than enough gain for an F5 on 88db sensitive speakers.

 

[anhton82]

Yes, reducing R13 will reduce gain. Whether 47R will reduce it too much for you, I don't know. R13 @ 47R will give you R13/R11 = 47/22 = ~2.1 gain. I reduced R13 on mine to 100R. With a 10k pot, that is more than enough gain for an F5 on 88db sensitive speakers.

Thanks. So better I will change the Volume to lower 50k. And increase R13 around 100R.

 

[Zen Mod]

can't see what's value of volume pot having with anything gain related ??