SSLV1.1 builds & fairy tales

[Salas]

Good luck inspecting. Just make sure you test with a right dummy load always.

 

[schubert]

I've been using 13 ohm 3 watt - is that OK? It gets kind of hot but I don't leave it on long (my substitute heat sinks aren't really big enough)

If I tested Idss for all the 2SK117s and got reasonable values (most were in the 3-5mA range) can I assume they're OK, or do I need to test more?

 

[Salas]

You wrote 18V is your target. That would give ~1.39A!!! What is the mA consumption of the target application load?

 

[Salas]

If I tested Idss for all the 2SK117s and got reasonable values (most were in the 3-5mA range) can I assume they're OK, or do I need to test more?

No that would be enough.

 

[Salas]

Do you have any power resistor in the 100-200 Ohm range?

 

[schubert]

Not at the moment, but I can get one.

I tested the BC550C I removed from the board and it does not conduct between be or bc in either direction, and the one currently in the board doesn't conduct on one side either, so I'm thinking both of the BC550Cs in Teabag's kits were bad. I'll try BC550Cs from another source but it will be almost 2 weeks until I get home. More then!

 

[Salas]

Try semis, but I am highly suspicious of the 13 Ohm load you used. Use 150R 5-10W first of all.

 

[schubert]

Yeah, it makes for lots of current but the fuse didn't blow so I thought I'd be OK. Ohmmeter across the power inputs for the B1 board it will be hooked to reads only 47 ohms. Anyway I'll try 100-200 ohms and see what happens.

 

[Salas]

B1 reads 47R bcs of the K170s internal RDS. I won't ask more than 2X IDSS for stereo.
No fuse blows bcs the CCS sets a constant draw. But the voltage shunt part it may very well be taxed.

 

[Salas]

Now that you reveal B1 is the target load, 1K 1W can emulate it as dummy and you can set your CCS down to 120mA for very good extra current and to save heat on the fins.

 

[schubert]

Well I'll be danged - with a 100 ohm load it works just fine. Why is that? And how do I change the CCS current? Is that the current through R101? I'm still learning my way around this stuff.

 

[Salas]

He, he, you should have read the manual better.

You deprived the shunt stage form any spare CCS current, went all to an overloading dummy. Yes, you need change R101 to change CCS goal.

There is a .xls calculator in post#1 grab that one too.

 

[schubert]

I read it and used the calculator but sometimes things don't stick too good It's part of getting old.

 

[RollE2k]

I will use this Shunt psu too feed my I/V stage with +-15v, would it be recommended using a 220u electrolytic instead of an 10uF film-cap for C101/C201? And is it better running 2x1,7v leds instead of a zener?

 

[merlin el mago]

Is better 10uF film cap for I/V also in the Vref area is better LEDs and one fixed low ppm resistor instead the trimmer to avoid drift.

 

[acidbrain]

I am not really done testing but at 15 V I would only use leds (about 7x) and 1R (200 ~400 Ohm) and a filmcap. Filmcaps do sound better, see manual. Together it gives for me the finest sound, maybe a bit cold. I can always decrease amount of leds and increase value of R to make it more cozy.

-If you are unsure just stick to the manual and experiment from there.

"merlin" and I do agree in this matter

 

[RollE2k]

But you would need to make one ugly heck of led-chain to use 7x leds, since there is only room for three of them on the PCB itself. Maybe i'll try with two in series over the the zener-spot so i get four in total then!

 

[acidbrain]

go a few pages back, Merlin used a small vertical printboard with the leds on it attached to the place of the 2 leds.

 

[merlin el mago]

 

[pedefede]

I feel i might go wayyyy too much into irrelevant details, but nevertheless:

I noticed that the wires to the sensing-circuit is about an inch, while the route from the output-zobel-filter is only half an inch. Normally adding, lets say 4 inch wire, would make this difference insignificant.

But i am placing the Bib's less than half an inch from a DAC, meaning the sense wire will be about 40% longer ... And i really noticed how wire length matters A LOT for output impedance on high frequency (for digital)

Does it make sense at all to mount wires instead directly to:
sense: Q104/105
Force: R107/C104
to be able to make it similar length, for force/sense?

Or is it just wayy too late here in DK, and my interest in my hobby has reached pathological proportions?!?