Oktava MK-012 mod

DsRob · 14th March 2007, 04:01 PM

I'm having trouble finding this last part to mod my MK-012,
Scott Dorsey suggested putting a 10µf 25v Tantalum Cap in the FET to bipolar location,
some one said to put a 1uF in there, are 1uF and 10uF the same, what one is right?
I've heard Polypropylen ones would be better, can the voltage be higher than 25?
Everything I could find with 10uF Polypropylen or Polyester are very big, what is everyone using in this location and where will I find them in Europe.
Thank you for any help,
Rob

sekim · 14th March 2007, 04:52 PM

After running SPICE simulations of this circuit, my opinion is that a 1uF is fine for that part. 25 or 35 volt Tant will be ok - which is probably what is in it stock.

Provided the stock microphone has a quiet FET in it (if not you could do a 2sk170 or similar) the biggest improvements come from (1) changing the coupling cap between capsule and FET - I like using silver mica for these and (2) changing the output coupling caps to something better.

DsRob · 14th March 2007, 05:43 PM

Quote:

Originally Posted by sekim

After running SPICE simulations of this circuit, my opinion is that a 1uF is fine for that part. 25 or 35 volt Tant will be ok - which is probably what is in it stock.

Provided the stock microphone has a quiet FET in it (if not you could do a 2sk170 or similar) the biggest improvements come from (1) changing the coupling cap between capsule and FET - I like using silver mica for these and (2) changing the output coupling caps to something better.

Thank's for helping.
The mic is a newer model, at the moment there is a elect cap in the FET to bipolar location.
I will be changing the coupling cap and the bias resistors, the FET seem ok,
I've found everything I need so far, but I just can't find a descent cap that will fit,
the one I was thinking of getting is a 10µF,63VDC, Polyester,radial,Evox-rifa... but I don't think it will fit.
Are there any other uF sizes that will fit?

Audiopool · 23rd April 2007, 06:42 PM

Since Toshiba seems to be discontiuing the 2SK170, it can be good to know that Linear Systems makes replacements for both the 2SK170 and the double FET 2SK389 (also common in audio apps). The Linear Systems LSK170 is what you should look for if you're on to making the Dorsey mod. The noise specs are the same.

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14th March 2007, 04:01 PM	#1
DsRob Gear interested Join Date: Mar 2007 Posts: 3	Oktava MK-012 mod I'm having trouble finding this last part to mod my MK-012, Scott Dorsey suggested putting a 10µf 25v Tantalum Cap in the FET to bipolar location, some one said to put a 1uF in there, are 1uF and 10uF the same, what one is right? I've heard Polypropylen ones would be better, can the voltage be higher than 25? Everything I could find with 10uF Polypropylen or Polyester are very big, what is everyone using in this location and where will I find them in Europe. Thank you for any help, Rob

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14th March 2007, 04:52 PM	#2
sekim Gear addict Join Date: Dec 2005 Posts: 360	After running SPICE simulations of this circuit, my opinion is that a 1uF is fine for that part. 25 or 35 volt Tant will be ok - which is probably what is in it stock. Provided the stock microphone has a quiet FET in it (if not you could do a 2sk170 or similar) the biggest improvements come from (1) changing the coupling cap between capsule and FET - I like using silver mica for these and (2) changing the output coupling caps to something better.

23rd April 2007, 06:42 PM	#4
Audiopool Gear nut Join Date: Mar 2004 Location: Denmark Posts: 146	Since Toshiba seems to be discontiuing the 2SK170, it can be good to know that Linear Systems makes replacements for both the 2SK170 and the double FET 2SK389 (also common in audio apps). The Linear Systems LSK170 is what you should look for if you're on to making the Dorsey mod. The noise specs are the same.