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Mauro Penasa's INV GC/REF GC group buy.

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#141
Let's say next Wednesday is the close for adding a transformer to your order.

For those of you in the US at $7.70 shipping, your shipping fee will not increase. Those of you under $7.70, you will go up to $7.70, whish is a flat rate box in the US.

Outside the US, it will be more. I'll try to figure out how much more exactly (there are only two of you).
 
#142
So, there are a couple folks who wanted in after the close (you know who you are). I want to put a time limit of payments.

Please pay your invoice by Tuesday, July 12 @ 6:00pm EST.

If unpaid after that time, kits will go to the next in line. Not trying to be a dink, just want to keep everyone happy, and make sure I don't lose too much $$ (this does end up costing money).

I'm pretty excited to get things rolling. I should be building the kits next week.

[EDIT] I guess "dink" is acceptable... who knew?
 
#144
I will query their UK branch for prices, shipping should be considerably less within the EU. Guess they won't reply before monday though.
And just to be clear on this, are we talking about a 2x12V or a 2x24V toroid? (aka do you by 24-0-24 mean 2x12)
The schematic calls for 2x12 right? Is there some general guide for reading schematics? i get the feeling i'm guessing wrong most of the time 🙄
 
#147
BrianDonegan said:
Nope. The schematic calls for two 24VAC inputs. So, these are 48Vct transformers with two 24V secondaries.
Click to expand...


Actually they should be dual 24V secondaries, not 48V center tapped. Though either would work, but you would have to modify the 48VCT version.

[EDIT] Actually now that I look at he board, I believe I was wrong. It looks like it is intended for 48VCT.[/EDIT]
 
#151
While you're at it

And certainly not to kill the goose....consider the LM4781 for 3 channels in the same footprint...X 2 = 6 channels in a size suitable for the smallest room or workstation.

Also, PE has 48VCT buy-out transformers for $7...unknown pedigree and VA, but they weigh over 5 lbs.
 
#154
In response to Brian and a few others here are a few notes regarding Trafo selection:

1) For 8ohm speakers the indicated +/- 24V AC input is ideal.

2) For 4ohm speakers the same 24V(48VCT) trafo will work, but be careful not to push the amp too hard, and ensure good heat sinking. You are a little over what the spec sheet recommends for 4ohm loads with these 33-35V rails. It would be better(closer to the spec sheet) to use a 20-22V to get somewhere close to 28V rails.

3) Don't skimp too much on the current rating for the trafo, 300VA is probably as low as I would go.

Cheers!
Russ
 
#158
They're here...
 

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#159
Russ White said:
In response to Brian and a few others here are a few notes regarding Trafo selection:

1) For 8ohm speakers the indicated +/- 24V AC input is ideal.

2) For 4ohm speakers the same 24V(48VCT) trafo will work, but be careful not to push the amp too hard, and ensure good heat sinking. You are a little over what the spec sheet recommends for 4ohm loads with these 33-35V rails. It would be better(closer to the spec sheet) to use a 20-22V to get somewhere close to 28V rails.

3) Don't skimp too much on the current rating for the trafo, 300VA is probably as low as I would go.

Cheers!
Russ
Click to expand...

Based on those pictures, weights and dimensions, I'm guessing that the 25VCT transformers are good for 150-175 VA, and the 48VCT transformers are good for ~200VA. I just picked up a few myself for various projects.

I think that the 48VCT should be sufficient for a stereo pair... If you really want to go for overkill, you could parallel them like Brian suggested.. But you'll only really benefit if you're constantly pushing the amp hard.
 
#160
Russ,

My boards arrived.

Brian,

I plan to get 3 of the PE transformers. I'm going to try one to a board. My use won't require that the chips run full-out
If there is any benefit to others in a group buy, I'll participate. A concern would be double shipping on a relatively small number of heavy items.
So, we'll see any additional interest and decide later this week.

Thanks to both of you for your efforts in all of this.
 
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