[mikaelmark]

I intend to replace the voltage regulators LM317 and LM337 with Sparkos discrete SS1117-15 and SS7915, as the Lovely Cube will run at +-15 VDC.

Has someone any experience about those voltage regs?

https://sparkoslabs.com/discrete-voltage-regulators/

 

[mikaelmark]

In case someone needs it in the future, I remade the label at the bottom of the case.

Also have in mind that if only DIP Switch no. 2 is on, then the Gain will be 18dB.

I don´t know why this are only being illustrated for some labels/pictures!

 

[mikaelmark]

I just made some picture modding, to include the 18dB Gain:

 

[zxzxzx207]

Ah yes I noticed the 18dB one as well, never included it as I just preferred even numbers i guess haha. Btw if you just started making the amp, I silk-screened out my label on aluminium

If you're interested you can have one for the cost of shipping as I had to print quite a few.

 

[zxzxzx207]

 

[mikaelmark]

Sparko told me the 100 Ohm resistor´s should be removed and that 1K1 resistor´s should be shorted when installing the discrete voltage reg´r SS1117-15 and SS7915. So the Zener mod (see earlier post´s in this thread) should will not actual here.

Also, a Mica Wafer should be used between this voltage reg. and heat sink: https://www.elfa.se/Web/Downloads/-1/_7/kjE-1_7.pdf

 

[mikaelmark]

The use of Mica Wafer for insulation between a voltage regulator´s tab and heat sink, seem´s to be important, as the tab will have voltage on it and are NOT grounded. I assume this is only for safety, if the heat sink will be in touch with the grounded enclosure (I have mistakenly done this fault for the LM337 without the mica, and was heard a loud BANG, then it was dead - but after a while it worked but may get some noise to the sound).

Also, when using Mica Wafer´s, Thermal Compound should be applied at both side´s of the Mica, due to the risk of overheating otherwise. And don´t forget to isolate the hole at the tab if using metal screw to the heat sink.

There are also recommandation´s about using Mica insulator´s for transistor´s, so maybe the BD139/140 heatsink´s should have Mica inslutator´s, altough the tab for the heat sink´s are grounded!? Any thought´s about this?

https://books.google.se/books?id=wU...QAQ#v=onepage&q=mica thermal compound&f=false

 

[zxzxzx207]

If you want to make your life easier, just use silicon heat transfer pads. cut to size and apply. They are not electrically conductive. I've used it in the past in a few of my builds. When using thermal paste make sure to use non conductive and non capacitance paste.

 

[Dukei]

I agree with zxzxzx207, as it still considered low voltage any type of insulation is ok to insulate with. I'd go with the most common and cheapest heatpad

 

[mikaelmark]

If you want to make your life easier, just use silicon heat transfer pads. cut to size and apply. They are not electrically conductive. I've used it in the past in a few of my builds. When using thermal paste make sure to use non conductive and non capacitance paste.

I will Arctic MX-2 thermal paste for both side´s of the insulation.

But, should the transistor´s BD139 and BD140 (SOT-32) also be insulated to it´s heat sink?

There are some recommendation´s about grounding the heat sink´s (supposedly due to eliminating EFI/EMI that may generate noise otherwise), and I understand that voltage regulator´s LM317 and LM337 must be insulated to the heat sink because the tab are not connected to ground. But this is not true for the transistor´s.

http://www.learningelectronics.net/circuits/high-power-headphone-amplifier-using.html

I hav´nt used any insulation so far, but maybe there should be some advantage´s?

Any thoughts or recommendation´s about this?

 

[mikaelmark]

If you want to make your life easier, just use silicon heat transfer pads. cut to size and apply. They are not electrically conductive. I've used it in the past in a few of my builds. When using thermal paste make sure to use non conductive and non capacitance paste.

Are below what you referring to (0,3 mm Sil Rubber, Thermal Gap Pad):

https://www.elfa.se/Web/Downloads/46/02/07564602.pdf

It seem´s to be quite similar to Mica wafer; Dielectric strenght: 5 versus 6 kV mm and thermal resistance: 0,4 K/W. And if using the Sil-pad, I assume thermal paste should be used, however!?

And for insluting the mounting M3 screw for the heat sink, this polyamide insulator should be fine: https://www.elfa.se/Web/Downloads/-2/_5/ktE-2_5.pdf

 

[zxzxzx207]

https://www.google.com/amp/s/www.westfloridacomponents.com/wfc/amp/product/G321APF03.html

They make them precut too. With the pads no thermal paste is needed. The one I'm using has to be cut to size but it's a lot cheaper.

 

[Dukei]

If the the BD139 and BD140 have metal tab on the backside and they share the heatsink togheter, then they should be insulated.
Don't forget to isolate the screw aswell, (if you are using metal screws).

 

[zxzxzx207]

https://imgur.com/a/9wDR22H

So this is my build, 99% complete, just waiting for an ITO top to come and I'm done

For LT317 and LT337 its mica + nylon washer and thermal paste
BD139-16 and BD140-16 is just thermal grizzly kryonaut.

 

[vintageaxeman]

https://imgur.com/a/9wDR22H

So this is my build, 99% complete, just waiting for an ITO top to come and I'm done

For LT317 and LT337 its mica + nylon washer and thermal paste
BD139-16 and BD140-16 is just thermal grizzly kryonaut.

What is an ITO top please?