2SK170 BL MC step up amp - Page 2 - diyAudio
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Old 10th May 2011, 11:30 AM   #11
gpapag is offline gpapag  Greece
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You can have it working safely with up to 25Vdc input.


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

Regards
George
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Last edited by gpapag; 10th May 2011 at 11:37 AM.
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Old 10th May 2011, 12:30 PM   #12
Salas is online now Salas  Greece
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35V max in. 9V drop x ~15mA = 135mW. No worries.
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Old 10th May 2011, 12:46 PM   #13
smpkje is offline smpkje  Greece
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You can use 78L09 as well.
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Old 10th May 2011, 01:13 PM   #14
Salas is online now Salas  Greece
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Don't know how they internally bias the TO-92 equivalent but the datasheets give 27dB worse rejection performance than the TO-220 one.
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Old 10th May 2011, 01:25 PM   #15
gpapag is offline gpapag  Greece
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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
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Old 10th May 2011, 01:38 PM   #16
Salas is online now Salas  Greece
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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.
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Old 10th May 2011, 01:51 PM   #17
gpapag is offline gpapag  Greece
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Thanks for the info. I'll contact them.

Regards
George
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Old 10th May 2011, 04:15 PM   #18
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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
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Old 10th May 2011, 05:39 PM   #19
Salas is online now Salas  Greece
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Yes, with R1=120 Ohm and circa 12mA IDSS each K170V.
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Old 16th May 2011, 01:29 AM   #20
batty is offline batty  Australia
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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.
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