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Group order of non-inverted LM3875 pc boards? Anyone interested?

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#941
Hello!
We got quite a lot of people here in europe and Finland getting intrested about this project. Thank`s to Brian, i also ordered couple of sets.
There are several open questions about the pot and the transformer. What is the course of the speaker impedanse to these componets. Will i get 18 or 25V transformer to 8ohm speakers? And how about pot / stepped attenuator? 20K, 50K or100K? Do i need to remove resistors R1/R2 in some combinations of speak. imp./ pot?
There are older conversations in this topic about these things, but i think to ask it again (confused).
 
#942
25V transformer will be fine with 8ohm speakers.

18V is recommended for 4ohm.

22V is a pretty good balance if you can find one.

I am currently using a 100K audio taper pot external to the amp. It's not my final choice (I believe 20k or 50k is a better option according to most folks?) but it works just fine. It was components I already had so I used it until I figure out whether I am going all passive or not on the pre-amp, and whether I want source selection.

C
 
#944
Originally posted by Rubber
And how about pot / stepped attenuator? 20K, 50K or100K? Do i need to remove resistors R1/R2 in some combinations of speak. imp./ pot?
There are older conversations in this topic about these things, but i think to ask it again (confused).
Click to expand...
Hiya Rubber
Hiya C from PE

If you haven't already done so, read BrianGT's Rev B Manual. It suggests volumn control at R3. I asked a similar question in another thread (Variable power supply to control gainclone volume?) and was quoted this by Jan

Originally posted by mrlots2do
Regarding the 100K audio taper pot....
R3 on BrianGT's board is 680 ohm, is there a reason I need the 100K pot. Seems too large, maybe should be 50K but than I don't know nothing. Besides I haven't found them with more than 47K taper pot.
Click to expand...
Originally posted by janneman
I agree, 100k is too much. There's no need for such a large value, and it messes up your S/N ratio.
Some people might have tube preamps and since these often cannot drive as low loads as SS (unless they have a cathode follower or something), for such a case 100k might be required. But then the input to the amp should be at least of comparable input impedance or the pot control law will be upset. The GC's I've seen on the forum cannot handle 100k.
I would go for no more than 20k.
Jan Didden
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It sounds right to me
Phil from PE
 
#945
If my count is right, tomorrow will be 3 weeks since Brian mailed the package to Peter for Canadian and International orders.

Methinks that somewhere out there is a mailman or customs agent either building a whole mess of gainclones or selling a whole bunch of kits.
 
#951
The BG caps have arrived, and I have started getting the orders ready to go out, which have been waiting on them. I am aiming to get all remaining US orders shipped out wednesday (not too many of them left).

Hopefully the components for the international orders will get to Canada soon. I sent 2 seperate packages up to Peter, and neither has arrived yet, so it appears that the delays are customs related. I am very sorry for the delay, as I didn't predict that it would be this long.

Here is a size comparison of the different capacitors:
An externally hosted image should be here but it was not working when we last tested it.

(BG N 1000uF, Panasonic FC 1500uF, BG STD 1000uF [all 50v])

--
Brian
 
#952
I am very sorry for the delay, as I didn't predict that it would be this long.
Click to expand...

Hi Brian and Peter.

I think I speak for everyone (I hope so!) that your efforts are greatly appreciated and we know that any delays are well out of your control. Patience is a virtue 😀

That said, the updates are well appreciated too.
 
#954
SS1 said:
Hey Brian,
How do you compare the performance between the three caps(bg n, bg std, fc)? wow bg n? how much are you selling the bg n?
thanks
Click to expand...

I am actually just assembling the amp now, as I just got the shipment of BG caps. I shipped out all that I had before, and had to wait over 3 weeks for this batch to arrive. I am going to build 2 amps and once they are both broken in, I will take them over to my friend's house, who has a very revealing system, and I will see what he thinks. I am in the process of moving to my first house, so I don't have much setup now. I am hoping to find time to refine my CDPRO2 project in the fairly near future.

As for the BG N 1000uF caps... I am afraid to tell my wife how much I spent on them (~$*** for 4) I will give them a try and see. I just figured that it would be worth trying if they are supposedly the top of the line capacitor from Blackgate. Another reason I bought them now, is since BG is going to stop production soon (will only take orders until the end of September).

--
Brian
 
#955
BrianGT said:

As for the BG N 1000uF caps... I am afraid to tell my wife how much I spent on them (~$200 for 4) I will give them a try and see. I just figured that it would be worth trying if they are supposedly the top of the line capacitor from Blackgate. Another reason I bought them now, is since BG is going to stop production soon (will only take orders until the end of September).
Click to expand...

Haha u better edit ur post b4 she spys u on the forum. She will be like where is my shoes, $200, at?
😀
 
#957
S.C said:
Haha u better edit ur post b4 she spys u on the forum. She will be like where is my shoes, $200, at?
😀
Click to expand...

Oops... did I say $200? I meant to write $20 for the set 😀 😉

Actually, I will try my best to keep an open mind. I am building 2 identical units, with just the different caps, so that I can do some blind tests and see if I can actually tell any difference (with the assistance of friends, of course). It is difficult to comprehend spending 25x more per cap over the Panasonic 1500uF FC, and 5x more than the BG STD.

--
Brian
 
#959
Another reason I bought them now, is since BG is going to stop production soon (will only take orders until the end of September).
Click to expand...

Does anyone know why they are stopping production? I thought with the increased interest/sales they would want to at least maintain current levels. Are they releasing a new product line?
 
#960
ble0t said:


Does anyone know why they are stopping production? I thought with the increased interest/sales they would want to at least maintain current levels. Are they releasing a new product line?
Click to expand...

It looks like the company that makes the capacitors for them is changing their process, so they have no where to have them made. I posted the document that they sent me:
http://www.diyaudio.com/forums/showthread.php?postid=435434#post435434

I hope that they figure out a solution to continue offering these capacitors.

--
Brian
 
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