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Old 3rd July 2012, 06:56 PM   #3561
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hi olav, yes the 240ohm i have talking is the input and output series resistor, now i have no series resitor at the output as ZM told me and replace the 1K input gate resistor with a 220ohm charcroft Zfoil ( stupid expensive but so good!) . i also use some NewclassD regulator i have as power supply . and a LDR as volume pot .. in a word it kills my threshold sl10 preamp..
and everything i had before
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Old 3rd July 2012, 07:02 PM   #3562
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Smile Tnx - Tnx - Tnx

Hi again Juanitox!!!!

Now I really have something to keep my DARK authumn-evening occupied. I will try them all little by little(or order everything) when the light of summer is withdrawing.

Tnx again Juanitox.

Olav
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Old 3rd July 2012, 07:30 PM   #3563
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Surely winter is not approacing yet ? We have only just gone past the summer equinox.
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Old 4th July 2012, 04:48 AM   #3564
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Default Not really end of summer ...

Quote:
Originally Posted by KatieandDad View Post
Surely winter is not approacing yet ? We have only just gone past the summer equinox.
Hi KatieandDad!

No - a long and warm part is still waiting(down to sunny Spain the 12 of July to enjoy the warmth of the south) - but when the rays of the Sun recedes later this year, and my wife an youngest girl is off on 1 week school-excursion - my soldering-iron will be a little busy. Not to forget my new Alp12P that also is on the list this fall. Need one new speaker beside the Alp10.2.

Have a nice building time everyone!!

Best
Olav
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Old 5th July 2012, 06:33 PM   #3565
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Well, here's my completed B1 and matching chip amp, in Par-metal chassis. Huge thanks to everyone who's contributed to this forum -- I've spent forever reading through and figuring all this out. Especial thanks goes to 6L6 for helping me out in PMs, and for his great build thread with nice photos -- I used his idea for the PSU. Thanks also to Steve Slater at Apex Jr., and of course thanks Nelson Pass for the awesome project.

The littlest board is a summing/low-pass filter for a subwoofer output -- thanks goes to AndrewT for suggesting that in this thread.

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Old 5th July 2012, 09:21 PM   #3566
6L6 is online now 6L6  United States
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A very sincere congratulations on a pair of projects beautifully completed!!

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Old 19th September 2012, 09:12 PM   #3567
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I have confused myself regarding gain when going from balanced to unbalanced. Since the B1 provides no gain, I want to get this correct.

I am taking the 2 legs (+ and -) directly from a voltage DAC (AKM DAC on a Behringer DCX). I am doing this by replacing the analog output section with a 1:1 line transformer. When I measure across the outputs (+ and -) on the secondary side I get 1.75 v RMS and the DC has been cancelled. As I should get. When I measure across just one leg I get half the voltage relative to ground. Also, as I should get.

My question: when I go into the (unbalanced) B1 buffer (by connecting the - leg to the RCA shield and the + leg to the RCA center) will the B1 "see" a voltage of 1.75 RMS or will it "see" half that voltage. IOW am I losing 6dB?
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Old 20th September 2012, 01:51 AM   #3568
udailey is offline udailey  United States
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Are you sure you should build this B1? Why balance only to go single ended and lose balanced benefits? There is a balanced B1.
It will see half because you will ground one of y8our signals.
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Old 20th September 2012, 07:20 AM   #3569
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by WithTarragon View Post
...........I am taking the 2 legs (+ and -) directly from a voltage DAC (AKM DAC on a Behringer DCX). I am doing this by replacing the analog output section with a 1:1 line transformer. When I measure across the outputs (+ and -) on the secondary side I get 1.75 v RMS and the DC has been cancelled. As I should get. When I measure across just one leg I get half the voltage relative to ground. Also, as I should get......
there's something wrong.
The transformer balanced output signal is not referenced to ground. It should be floating.
You should not be able to measure half voltage from one pole of the transformer to ground.

If instead of using a pair of B1s, you used another transformer at the input end, then again you would be floating the balanced inputs.

It's when you replace the transformers, at either end, with electronics that the ground references come in. That's the big disadvantage of electronically balanced signal transmission. Transformer coupled signals float and give best attenuation of interference.
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Last edited by AndrewT; 20th September 2012 at 07:24 AM.
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Old 20th September 2012, 07:56 AM   #3570
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by WithTarragon View Post
I have confused myself regarding gain when going from balanced to unbalanced. Since the B1 provides no gain, I want to get this correct.

I am taking the 2 legs (+ and -) directly from a voltage DAC (AKM DAC on a Behringer DCX). I am doing this by replacing the analog output section with a 1:1 line transformer. When I measure across the outputs (+ and -) on the secondary side I get 1.75 v RMS and the DC has been cancelled. As I should get. When I measure across just one leg I get half the voltage relative to ground. Also, as I should get.

My question: when I go into the (unbalanced) B1 buffer (by connecting the - leg to the RCA shield and the + leg to the RCA center) will the B1 "see" a voltage of 1.75 RMS or will it "see" half that voltage. IOW am I losing 6dB?

proper wiring of your xformer can be made in 3 ways :

1. ballanced symmetrical - CT of secondary must be connected to DAC audio gnd ; no galvanic isolation (few other possibilities , when CT is connected to receiving end GND -then there is galvanic isolation ; also possible tying both sending and receiving gnd's .......... then there is not galvanic isolation )
2.pure balanced - CT NC , entire secondary is floating
3.unbalanced - one end of secondary connected to gnd , other side is hot ; same choices as #1 regarding connecting out gnd - if connected to both sending and receiving end , there is no galvanic isolation ; if connected just on receiving side , there is galvanic isolation

with appropriately wired switch(es) you can flip between all iterations

search on Jensen site - plenty of useful pdf files , with nice pictures
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Last edited by Zen Mod; 20th September 2012 at 07:59 AM.
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