Single supply, three-pole compensated class-B retro amp

[LKA]

"How much wider / taller than the original?"
148x90 vs 163x90 mm

 

[thimios]

latest pcb version

• power supply with two capacitors
• added output RL network

I will wait to share gerbers

 

[attalostesla]

hi,
What changes should be made to make it work with low voltage?
20V (laptop PSU) and 40V,
thanks,

 

[OldDIY]

40V

I will assume that power from 40v will allow you to get 30w / 4ohm. For optimization, you will have to recalculate (reduce) the resistor values.
I would not consider 20V power supply
You can use a DC-DC boost converter.

 

[LKA]

correct, you get 30W/4R from a 40V supply (unloaded), forget about 20V

 

[LKA]

I built it into the box.

 

[twocents]

latest pcb version

• power supply with two capacitors
• added output RL network

Hi LKA. It's been very quiet around here lately. Are there gerber files and schematic available for your latest pcb? Looks like a very interesting and easy build.

 

[twocents]

@LKA, I was fortunate to get a pair of boards (and a few caps) from member 002 for building this amp. However, I have trouble sourcing the Toshiba
2SC4793 / 2SA1837 components - they are obsolete. Are there any replacements that can be used here?

 

[002]

I asked LKA the same question and the answer was:
2SC5171 / 2SA1930 or TTC011B / TTA006B (Observe pinout changes)

 

[RM]

I have lots of these, however at $5/pcs and shipping they might wind up being quite expensive. Sorry about that.

R

 

[LKA]

UTC
https://gb.profusion.uk/uk/2sc4793g-tf3t
https://gb.profusion.uk/uk/2sa1837g-tf3-t

TOSHIBA
https://www.win-source.net/products/detail/toshiba-semiconductor-and-storage/2sa1837-2sc4793.html

KEC
https://www.alibaba.com/product-det...offerlist.normal_offer.d_title.48e64c67QaXFOx

 

[twocents]

I asked LKA the same question and the answer was:
2SC5171 / 2SA1930 or TTC011B / TTA006B (Observe pinout changes)

I see on the BOM you shared earlier you included some substitutes - Thank you for that 002. I might find some of the subs from our local suppliers.

 

[002]

If I'd known you were missing 2SC4793 / 2SA1837 I could have sent you some over
I can source them locally from a reputable source.

 

[dansa69]

If I'd known you were missing 2SC4793 / 2SA1837 I could have sent you some over
I can source them locally from a reputable source.

Could you share the source for these transistors? I am from Australia too.
Thanks.

 

[002]

Wagner Online:
https://www.wagneronline.com.au/2sc...lectronic-components/2sc4793-21857/959282/pd/
https://www.wagneronline.com.au/2sa...lectronic-components/2sa1837-21101/959280/pd/

 

[dansa69]

Wagner Online:
https://www.wagneronline.com.au/2sc...lectronic-components/2sc4793-21857/959282/pd/
https://www.wagneronline.com.au/2sa...lectronic-components/2sa1837-21101/959280/pd/

Thank you! Thank you! Thank you! You saved my life!

 

[LKA]

the 2SC4793 and 2SA1837 have full plastic case TO-220FP

try these from KEC
https://www.aliexpress.com/item/100....order_list.order_list_main.35.5b991802Un6A0Y

 

[002]

the 2SC4793 and 2SA1837 have full plastic case TO-220FP

The ones from Wagner are full plastic case. They just have stock / wrong photos for a lot of their parts.

 

[dansa69]

The ones from Wagner are full plastic case. They just have stock / wrong photos for a lot of their parts.

I have noticed that the photo on their website is wrong. That's fine. Wagner seems to be reputable supplier. I bought other parts from them before. I just did not think to look for these transistors as well. I tried RS, Element14, Digikey, Mouser, Altronics, Jaycar. I just missed Wagner/WES. Didn't want to buy from eBay as there is a high risk on buying fakes.

 

[LKA]

I already bought these KEC transistors from aliexpress. Static measurements (hFE, junction capacity) show that they could be a good alternative for Toshiba. I still want to try it in a real amplifier.