Scope Design: JFET Input EXICON Output 10 Watt Class A

[huggygood]

Yeh, I will order pcb's as soon as the gerbers appear here - hopefully thanks to prasi's great work.

I have all the components for this simple elegant design which measures well according to simulation by lineup.

I would also say Vunce will be having a go at it.

There is a chance that I will also get on the train, I have k1058 and j162 in stock.

 

[lineup]

I have changed 2 capacitors and added a Zobel in output.
C1 = 47pF, compensation tested with Scope
C3 = 10uF, not any benefit making it bigger

 

[gary s]

Thanks lineup for the latest mod, hopefully prasi can incorporate these on his great pcb design with a revised version..

Also I asked you some questions in post #15, can you have a look at that and give us builders your brief answers, thanks again.

Although the added zobel network could be wired off the pcb, the 2 cap value changes would not need any change to the pcb layout.

 

[gary s]

Looks interesting as always Lineup!

Anyone know where to find some ECX10 over here in Australia? Seems to be unavailable / unobtanium from the usual sellers.

Also available slightly cheaper at Audiophonics in France. Altronics here in Oz has the P but not the N. I don't think you will find them in stock as a pair anywhere in Australia - so OS purchase will be required.

 

[TNT]

Would it work down to, say... +/- 12,0 volts without any changes?

//

 

[huggygood]

Seems available at "Profusion"

 

[lineup]

This is the suggested JFETs:
https://diyaudiostore.com/products/matched-jfets

Eventuell you can have to increase the balance potentiometer: R7

R10 should be chosen to give like 2.5mA across the LED

 

[prasi]

Thank you prasi!
You always support us! 🙏
PS. please, if you will find the time post the diy friendly single side pcb in pdf.

Hello Thimios,
here you go. both diy pdf and gerbers with modified design as per #42.

 

[lineup]

This is the 20kHz square with C1=220pF
I think this is a good value. 47pF is too small.

 

[SomekPoland]

here are build files and gerbers.

You're so quick! Great layout as always!

 

[thimios]

Thank you mr.pcb!

 

[lineup]

This is the scope square at 1kHz with C1=220pF

 

[prasi]

Hello Thimios,
here you go. both diy pdf and gerbers with modified design as per #42.

here is a parts size guide for info. i dont have any part numbers.

 

[tombo56]

This is the 20kHz square with C1=220pF

@lineup
Forget that virtual oscilloscope. Square wave response of 2 MHz bandwidth amplifier is much better. Here is 100 kHz response from my amplifier with EXICON laterals:

Your amplifier should have the same.

 

[lineup]

"The S version has been tested and graded into colour bands based on the technical spec shown below to ensure close matching. We cannot guarantee a specific colour band upon request but orders will be supplied from the same colour band. If you have a particular requirement, please contact us before ordering."

I recommend buying the S version.
ECX10N20-S
ECX10P20-S

 

[tombo56]

There is no benefit from S version where single MOSFET per rail is used. S versions are meant for using devices in parallel. It does not provide any P and N channel matching. From the leaflet:

• The test bands are different for N channel and P channel
• There is no benefit from having the same colour dot as the test bands are not the same.

 

[gary s]

Thanks again prasi for the quick update to the pcb, great job as always.

 

[gary s]

Hi again prasi, is it worth changing the silk screen on your pcb for the value of C3 back to 220pF (was 47pF) as lineup has shown in post #49?

I will wait on your reply before I order my pcb's, thanks.

 

[huggygood]

This is the suggested JFETs:
https://diyaudiostore.com/products/matched-jfets

Eventuell you can have to increase the balance potentiometer: R7

R10 should be chosen to give like 2.5mA across the LED

I still have a few K170s from my old Plantefeve assembly, but no J113, I must have some J200s somewhere.

 

[lineup]

I repeat.
Buy these JFETs: https://diyaudiostore.com/products/matched-jfets
The balance potentiometer R7 can be necessary to increase the value.
From 10 Ohm to 20 or 50 Ohm.
It all depends on how well matched the JFETs are.