The A.N.T. Audio Kora 3T Phono Stage circuit published.

[fap]

G'day all, yes I agree with Alex. I tend to only trust a properly soldered connection.

Twenty five odd years of being a Ham Radio operator and a former telecommunications maintenance technician has taught me that! Regards, Felix (vk4fuq).

[Salas]

Originally Posted by x-pro

Here is a noise floor comparison between the Kora 3T MM SE and MM LE units I've done some while ago.

That 10dB improvement reflects the upper part of the SRPP contribution we should suppose? Because the lower part owes to be dominated by the K170 en?

[Salas]

P.S. No, you wrote its the MM. So its due to the Mosfet parts change only.

[x-pro]

Originally Posted by Salas

That 10dB improvement reflects the upper part of the SRPP contribution we should suppose? Because the lower part owes to be dominated by the K170 en?

The noise graph is for 2 MM units, so there is no 2SK170 involved there. The noise difference is only due to the two different types of FETs in M1 and M2 positions. As I've said earlier, the BSS139 has a noise voltage density about 15-20nV/sqrtHz at 1kHz, the "LE" type FET has less than half of that, about 6-7nV/sqrtHz at 1kHz. In the MC version the noise contribution of the input 2SK170 is dominating, however there is still some difference in the noise between the SE MC and the LE MC units, about 1.5-2dBA.

Originally Posted by Salas

P.S. No, you wrote its the MM. So its due to the Mosfet parts change only.

Yes, I was late with my answer, sorry!

Cheers

Alex

[UV101]

I was looking for a phono stage to build and this could be it.

Would you consider allowing pcb's to be made for a group buy on the forum?

Also, is it just the quality of component choice that is changed for the better versions?

Thanks for sharing, Ian

[andyr]

Originally Posted by fap

G'day all, yes I agree with Alex. I tend to only trust a properly soldered connection.

Regards, Felix (vk4fuq).

Sure Felix, I agree that's optimal. But it means you can't readily change cartridges. Which (facility) is a good thing to have. Just like not having coupling caps is "optimal" ... but not that many components go this way.

I have no doubt it will be better than your ESP phono stage ... but, once you've got your Kora up and running (with the soldered resistor of your choice installed ), I could send up my JFET phono stage for you to compare. (You have my email address.)

Enjoy.

Regards,

Andy

[x-pro]

Originally Posted by UV101

I was looking for a phono stage to build and this could be it.

Would you consider allowing pcb's to be made for a group buy on the forum?

Also, is it just the quality of component choice that is changed for the better versions?

Thanks for sharing, Ian

Hi Ian,

I am not sure that I should authorise a group buy of an untested pcb. On one hand the Kora 3T circuit is so simple that it can be built on a strip-board in one evening, on another hand I may offer the original pcb (or even a kit) for DIY. The pcb would fit one of the Hammond aluminium enclosures perfectly and would at least guarantee that the performance of the circuit won't suffer from a bad layout. It won't be very cheap thought .

On the second question - I've described the differences in the post #18.

Cheers

Alex

[UV101]

Hi Alex, thanks ;-)

If you we're considering offering some sort of kit or even just the pcb, I would definitely be interested ;-)

[x-pro]

Originally Posted by UV101

Hi Alex, thanks ;-)

If you we're considering offering some sort of kit or even just the pcb, I would definitely be interested ;-)

PM me.

Cheers

Alex

[UV101]

Pm sent, Thanks, Ian