Salas SSLV1.3 UltraBiB shunt regulator

[tmas]

I just twisted the +15V DC supply wires and all leads on the transformer. The scope probe leads are shielded coax. No effect on my scope trace.

 

[Salas]

Compare with another transformer and make sure Quasimodo itself is built without error working as intended.

 

[tmas]

I have just tried it on an Avel Lindberg 15VA #Y236001 torroid.

With Cx=.01uF Cs=.047uF Rs=9 ohms I get the trace on my scope shown on the attached photo.

 

[Salas]

It works properly

 

[tmas]

Here is photo of the best I can achieve using the default values.

Cx=.01uf Cs=.15uF Rs=83 Ohms

 

[codyt]

I apologize if this has already been covered or is common knowledge, but is it generally a bad idea to put additional reservoir capacitance after the UltraBIB? I'm currently using my U-BIB in a bipolar config to power my BA3 preamp. Initially, I used a couple of big 10KuF caps in between the reg and pre – as a way to split the power to both channels and with the naive assumption that more capacitance is always better . I'm wondering if its necessary, or even detrimental?

 

[Salas]

Its better to have the reg inside the preamp's box thus using relatively short and thick rail output cables and put no extra capacitors. They dominate and slow down the reg although it did not protest.

 

[codyt]

Thanks for the feedback! The reg is in the same box, and I just pulled out the extra reservoir capacitors. Noticing more presence/detail in the high frequencies. I haven’t measured anything yet, but I’d certainly call it an improvement!

 

[Salas]

Good move

 

[donhughes111]

Here is photo of the best I can achieve using the default values.

Cx=.01uf Cs=.15uF Rs=83 Ohms

What do you mean by "default" values"?

Don

 

[tmas]

Those are the default values for Cx and Cs when using the Quasimodo Test fixture to help design your snubber for use in the Salas SSLV boards.

 

[aguaazul]

I have a 36 volt transformer (18 x 2) 175 VA and I'm looking for 26 volts 250 mA output.
Is this transformer going to cook the JFETs?

 

[Salas]

It's possible it will cook J1

 

[Salas]

But it would bring much extra heat to M1 anyway for just 26V output goal

 

[aguaazul]

Thanks for the fast reply! I'm thinking this 28v 100VA Toroidal Transformer I'm looking at is safer.

 

[Salas]

Safer and you keep the big one for proper projects. Nevertheless for 250mA even a 50VA 28V transformer would surely suffice. No need for 100VA.

 

[tmas]

Its better to have the reg inside the preamp's box thus using relatively short and thick rail output cables and put no extra capacitors. They dominate and slow down the reg although it did not protest.

My layout will necessitate 9-12 inch cable pairs to carry my +/-15V from my regs to the op-amp circuit board I am powering.

I have 20 or 22 AWG stranded wire on available to use. I did plan on twisting the pairs.

I am running CC=120mA .The AD744 op-amp I am supplying spec. is Quiescent current Max.=5.0mA. Short Circuit Current Typical=25ma.

Are the wire lengths and gauge appropriate for my application?

 

[Salas]

Twisting is good for less inductance since length adds. Also keep them near metal surfaces wherever possible. Thickness for that long cables better be 12 AWG to keep resistance lower. The system should play relatively cleaner the shorter the cables distance between shunt and load down to 10cm or so. Because of less inductance and resistance being added at the shunts output impedance. When must be remote try to keep those factors moderate with some gauge hyperbole in the umbilical cables.

 

[tmas]

Thank you!

 

[Salas]

You are welcome.

Twist tight using the power drill.