2SK170 BL MC step up amp

[batty]

I have some 2SK170bl lying around and want to make an amp for my Denon DL103 to go into the MM input on my Copland. I have an SUT but wanted to try SS. I'm looking for a simple circuit that has the option of gain switching to allow for lower output MCs further down my MC road.

Anyone know of a cct diag, preverably running off a 9v supply.

No RIAA eq needed.

 

[Salas]

This one fits most spec you described except for gain switching.

 

[h_a]

The Ono front end comes to mind; pretty similar to Salas' version but with a cap multiplier to remove PSU-noise. The LM-regulators however should do pretty well also.

Hannes

 

[Salas]

*The above circuit has a cap multiplier after the 7809 also.

 

[batty]

Thanks guys.

Is the o/p taken from junction of C3/R5? and could I use a PP3 battery with +ve connected where the bottom of R1 joins?

Cheers

Steve

 

[Salas]

O/P at C3,R5 node. R1 is the load resistor, +Ve goes on top of it. Keep whatever is there after the 7809 or at least put 100R in series from PP3's + to R1's top and keep C2. 430 Ohm R2 loading good for DL103. Will drain 14mA per channel, not too long a listen with a PP3...

 

[batty]

OK thanks Salas, probably a 12vdc adaptor to feed the 7809s unless I can find a 15v version.

I am thinking of building inside the same box as the SUT just for ease of build and swapping cables over. all for fun you understand.

What type of caps

 

[Salas]

12VDC adaptor far away to avoid fields still OK. Panasonic FC electrolytics or alike low ESR for the 1000uF ones and PP or Teflon (best) for the 0.47uF Cout. The C4,5 0.1uF for 7809 termination can be MKT.

 

[gpapag]

There:
http://www.diyaudio.com/forums/power-supplies/184068-psu-rc-multistage-filtering-2.html#post2486919

Tony suggests having a minimum of 5Vdc difference between input-output on LM 317.

It is my observation in praxis that this holds true for fixed voltage 3 leg regulators as well. It garantees specified regulation action from the chip.

This 5V difference is hidden in many of the performance curves supplied by the manufacturers of the voltage regulators.

Salas thanks for providing this schematic.

Regards
George

 

[batty]

what would the max input be for a 7809, would 18V be to much to drop to 9v.

 

[gpapag]

You can have it working safely with up to 25Vdc input.


http://www.alldatasheet.com/datasheet-pdf/pdf/231443/TI/UA7800.html
With the current you are drawing in this application, temperature rise would not be an issue.

Regards
George

 

[Salas]

35V max in. 9V drop x ~15mA = 135mW. No worries.

 

[smpkje]

You can use 78L09 as well.

 

[Salas]

Don't know how they internally bias the TO-92 equivalent but the datasheets give 27dB worse rejection performance than the TO-220 one.

 

[gpapag]

Dear Salas

With 35V in and 9Vout, Vdrop is 26V. This, times 15mA makes a 390mW.
Still not too high, but 35Vin is according to some manufacturers above from what they allow.

But I won't argue with you, because the nice schematic you provided before, is ideal for building a pre to be installed just behind the cartridge on the headshell.
I would like to try this.
But I am lucking the Fets.
Do you know any source in Athens?

Regards
George

 

[Salas]

I did not suggest he uses 35V input. He asked what is the max input. 35V absolute max is on the datasheet. 18VDC adaptor is OK.

Sometimes a couple of places like Fanos & Meni Kodoravdi take orders or have some left from adding a few to previews special orders.

 

[gpapag]

Thanks for the info. I'll contact them.

Regards
George

 

[offanonone]

Would V grade 2sk170 be ok for this ? I have about 12 waiting for a good use.

I will probably use with a Ortofon Vivo Blue (about £200 in the UK)

Thanks,

John

 

[Salas]

Yes, with R1=120 Ohm and circa 12mA IDSS each K170V.

 

[batty]

I have bought the remaining parts i needed and dug out an old 16V ac supply. I will need to build a bridge rectifier out of 4 of the diodes I have to get some DC to the 7809s. and a smoothing cap 4700 x 25v should do it.