Ultrasimple MM/MC RIAA preamp 2

[Stanco]

Not only 2Sk170GR but also LSK170 difficult to find....

 

[Zigis]

I find 2SK170BL. I think it is close.

How can I measure Idss ? I newer work with JFETs before.
Wen I find pairs, better is larger Idss or smaller, for first stage, for second ?

 

[EC8010]

Higher Idss for the first stage for best noise.

 

[GlidingDutchman]

Can one stack the SK170 devices for better characteristics?

Is this circuit really worth while?

D

 

[lcsaszar]

How can I measure Idss ?

Connect gate to source. Then the FET will be a constant current source. Connect it to 9 to 15V and measure the current. Excpect around 5mA, in any case less than 20mA.

 

[xann]

Hello.

The 2SK170 is easy to find in ebay, very cheap, and in matched quads.

Sorry for my english. Bye.

 

[tschrama]

You can use 2SK170BL .. Idss iun the 8-to12mA is no problem. You can insert a 10-22 or even 47Ohm resistor betwwen the source and ground to properly bias the stages, whitout altering noise and transductance too much...

I did bought some 2Sk170GR just this week from ebay... 3$ a piece no less!!

 

[Zigis]

Good idea about Ebay!
I purchase 2SK170BL yesterday:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=200226753902&ssPageName=STRK:MEWN:IT&ih=010

 

[GlidingDutchman]

Can one stack the SK170 devices for better characteristics?

Is this circuit really worth while?

D

<< RANT >> HAVE ANYBODY EVEN READ MY POST???

D

 

[Zigis]

Thanks for tip, oshifis,
I tray it, wen fets arrived.
Zigis.

 

[tschrama]

<< RANT >> HAVE ANYBODY EVEN READ MY POST???

D

My friend, what characteristics?

Noise: will go down with the square root of parrallel devices, but idle current for be proportional increased, and you need to degrease the load resistor to keep the same idle drain voltage.

Linearity: does not nessecerely improve, but you might end up with less low order, and more high order distortion.

input capacitance: will also go up, and likely bandwidth will go down.

 

[GlidingDutchman]

My friend, what characteristics?

Noise: will go down with the square root of parrallel devices, but idle current for be proportional increased, and you need to degrease the load resistor to keep the same idle drain voltage.

Linearity: does not nessecerely improve, but you might end up with less low order, and more high order distortion.

input capacitance: will also go up, and likely bandwidth will go down.

Thank you - that is all I wanted to know.

D

 

[GlidingDutchman]

Re: ultrasimple mm/mc riaa preamp 2

This crude little riaa pre is too good to be true.

Indeed it is!! Whoa - I am gobsmacked. Just now listening to Brothers in Arms using an Ortofon Salsa MC cartridge (0.3mV out)

This phonostage is a diamond in the rough!

Cheers Mad K!!

D

 

[johnm]

Hi Gliding Dutchman!

Would you mind sharing your layout? I happen to have exactly the same strip board lying around and I'd love to build this to try out on my Denon 103R and Garrard 401.

Many thanks

- John

 

[GlidingDutchman]

Hi Gliding Dutchman!

Would you mind sharing your layout? I happen to have exactly the same strip board lying around and I'd love to build this to try out on my Denon 103R and Garrard 401.

Many thanks

- John

John

I just soldered the parts onto the tag strip in a "random" fashion with no "propper" layout (ofcoarse according to the design!).

A friend of mine and I am working on a higher gain stage in a similar fashion to MAD K's - I'll send you the details of that circuit as I believe it would be a better match for your Denon 103R.

The above circuit works well with low output MC cartridges but higher gain would be a benifit.

Also checking out the circuit to run from 12vdc (incl IC regulators etc).

Cheers
Dewald the GD

 

[johnm]

Many thanks Dewald - look forward to seeing the revised design

- John

 

[Zigis]

Hi GlidingDutchman,
nice building, I am on half way building this too.
What kind PS you use, battery or regulated?
Thees violet el caps are on output?

Zigis.

 

[GlidingDutchman]

Hi GlidingDutchman,
nice building, I am on half way building this too.
What kind PS you use, battery or regulated?
Thees violet el caps are on output?

Zigis.

Hi Zigis - currently I am running it from a Pb Acid battery (2x 12vdc) but I am looking into doing a IC regulated PSU.

The violet caps are the outputs yes - will be replaced by some plastic film types in due course.

D

 

[GlidingDutchman]

Many thanks Dewald - look forward to seeing the revised design

- John

John - I'll post the new schematic for discussion. I am having trouble getting the thing to work. Actually back to the original design as per Mads K.

In comparson with the EAR 834P it can most certainly do with a touch more bass or will that be treble attenuation?

D

 

[tschrama]

I had the same feeling... it was a bit bass-light... I cured it by making a proper inverse-RIAA, and adjusting the filter section untill it was within 0.5dB...