JFET/MOSFET complementary-differential preamplifier

[PMA]

I have a new JFET/MOSFET complementary-differential preamplifier, please visit

PRE complementary-differential preamplifier

and see the attached images.

 

[Bonsai]

Looks very nice PMA - simple and elegant!

🙂

 

[PMA]

Thanks, Bonsai. And sounds good 🙂

 

[gk7]

Yes simple and elegant (and good sounding), and important to mention IMHO: It´s actually a John Curl design.

 

[PMA]

It might be Erno Borbely as well, and others 😉

 

[kASD]

I like it🙂

 

[PMA]

R1 and R2 values have to be selected according to Idss of the matched JFETs. But the task is not very difficult, and digital multimeter is enough to make it.

 

[chlorofille]

Pavel,

How does this differ sonically to the Dispre 2 jfet ?

 

[PMA]

Hi chlorofille,

yes, it sounds a bit different, and I would guess that listener's taste would judge.

Regards,

 

[kannan_s]

Hi PMA
I expected a small Power amp based on this topology as we see many pre amps are around. Probably you would be the one to come with some DIY design ?
thanks for bringing out JC' s ideas
Kannan

 

[gk7]

From the photographed pcb on your website I concluded that the cap multipliers are shared or am I mistaken ? Would it not be better to have separate ones for each channel ?

 

[PMA]

They are not shared. You will count 4 transistors - multipliers in the PCB.

 

[PMA]

This is a setup to match JFETs 🙂

 

[gk7]

Ah ok, those behind the volume pot belong to cap multipliers too.

 

[AMV8]

PMA
I think your pre amp looks great.
Interestingly I just built a pre amp that is similar ( based generally upon the borbelly line amp ) using J fets in a symmetrical differential at the input and with 2 mosfets at the output connected to the input in a similar way to the one you have choosen.
My measurement equipment will a lot more basic than yours but I seem to get lower overall distortion when I cascode the front end jfets.
I had not adjusted R1 or R2 but I have been adjusting Re. Have you found that adjusting R1/R2 instead of Re gves lower distortion?

 

[chip_mk]

Do you use monolithic JFET or matching by hand?

 

[mlloyd1]

picture in 1st post shows 2sk389/2sj109.
more info on his website.

mlloyd1

Do you use monolithic JFET or matching by hand?

 

[PMA]

Have you found that adjusting R1/R2 instead of Re gves lower distortion?

Hi AMV8,

yes, because the key is to keep input JFETs in the most linear portion of the transfer characteristic, and R1/R2 serve only to set appropriate Vgs bias of the output MOSFETs. For more info, please visit

Distortion in JFET input stage circuits

Regards,

 

[PMA]

Do you use monolithic JFET or matching by hand?

Both. The 2SK389/2SJ109 are very difficult to purchase, in fact almost impossible. For this reason, there is a PCB design for 2SK170/2SJ74, and the devices are hand-matched.

Regards,

 

[Federmann]

Both. The 2SK389/2SJ109 are very difficult to purchase, in fact almost impossible.

Why do not you, constructs from inaccessible parts?