bf245b transistor orientation/chip protection

[chokesrule]

Hi, I am building this sp/dif buffer as suggested on the Lampizator site the schematic is on the page
CD Transport Digi-Lampizator

It is a simple question :do I have the flat side of the "D" facing the signal wire ????? I take it the sp/dif signal enters the transistor on the centre pin.....It is not that I am too lazy to experiment , I am just worried wrong orientation would blow the signal generator chip or something nasty and the Quad 99 I am using is made of very very flimsy parts , I think it would be hard to repair..Thanks Alan...
ps if I am worried about blowing chips can you protect them by using a diode in series along the signal wire??

[chokesrule]

the link has not worked hopefully the picture of the schematic will appear here


you will have to scroll to the bottom of the page for the diagram

[Tfan69]

hello,
this is the pin configuration of the bf245b, signal enters in G pin, which is at bottom looking at D

[Luke]

are these optimised for the sa7220, or can i use this on any chip?

[chokesrule]

Tfan69....does the power come in on the "s" or "d" pin then??????.....sorry for being so thick...

Luke .....I have no idea I was just going to connect it and see what happens....I do not even know what spdif generating chip I have ...all I know is is that a stock quad 99 is a very very poor affair indeed and needs all the help it can get

[Tfan69]

just look at the scheme and the pin image, power enters from d

[chokesrule]

Hi, Tfan...I have built the buffer and am running it off a 9volt battery for a minute...its built as a external unit and plugs into the rear digital output socket on the player....and outputs to an external dac.... SO ....all rca grounds /battery ground and resistor grounds share the same rail........Before I plugged into the player , I put a multimeter on the output hot pin and found it is outputing 0.3volts DC before any sp/dif signal is applied....I was suprised to see the DC as I thought the 10 uf capacitor was supposed to block it....I have double checked everything and cannot see how I have varied from the diagram....so is this an acceptable amount of dc to be going to the dac or have I indeed messed up??? I have not plugged the unit in as I am worried about the dc....is my grounding right?

[mjf]

hello.
you can connect a res (typ.100k or so) from output cap to ground.......so that (big) cap can be charged.
are you shure that output cap reads 10uf ? or is it 10 nf (red schematic with the tube)?
greetings

[chokesrule]

its definately a 10uf non polar just a cheap brand...i have left the thing powered and now when I read the pin i see....0.02volts dc....could this be evidence of the so called "burn in" of a electrolytic???? is 0.02v safe for the dac? I will raid my parts bin attach a resistor like you said .....see what happens

[chokesrule]

it worked......o.oovolts...so I tried putting a 75ohm ...and the same result.....listening to it now.....can't say I am hearing any improvement in sound quality or details etc...maybe 9v is not enough...will have to mess around with the resistors as well