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Old 20th December 2002, 11:40 AM   #1
lykkedk is offline lykkedk  Denmark
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Default BoZoS unbalanced again.

Hi again, I wrote this new thread, cause I think someone might have misunderstod my quistion.

I'am just building this Balanced Line Stage, which I plan to use, for preamplifieng, lines from my CD, Computer, DVD etc...

None of theese, seem to be balanced equipment.

My CD is a SONY X55ES, which I will connect through GoldPHONO'S (RCA), the output will be golded too. The rest of the input RCA's will be cheaper one's.

The output should go to my Leach-amp which I think have an inputimpedance around 20kohm. The Leach amp is with one powersupply, and two mono-block's, with one RCA for LEFT input, and one RCA for RIGHT input.

I made a little change to the PCB for the line stage, so I could use 1,5k/11w ohm resistor instead of the two 750ohm/3w one's

Actually I have used a lot of time making the PCB (Handmade), and I allready soldert most of the component's to it, hoping to use it unbalanced without making any changes on the PCB, and component's used.

I was planing to use a stereopot for P3/P4, for volume control.

This is, what I really wanna know, so please HELP...

Howto use it unbalanced, maybe with some grounding at -IN, and -out, really i do not know howto do this...

What about R15, I use 124ohm. is this right, when not using P1, and P2.

Well I had not yet bought any pot's, so I am open to any suggestion's.
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Old 20th December 2002, 01:06 PM   #2
Henrik is offline Henrik  Denmark
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lykkedk
Quote:
Howto use it unbalanced, maybe with some grounding at -IN, and -out, really i do not know howto do this...
You simply short -In to ground with wire.
I wouldn´t short the unused output to ground, no need for that.

Quote:
What about R15, I use 124ohm. is this right, when not using P1, and P2.
R15= 124 Ohm is ok!
Lower the gain as much as possible by increasing P5, this way You get the lowest distortion.
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Old 20th December 2002, 01:24 PM   #3
lykkedk is offline lykkedk  Denmark
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[Then I only have to short -IN, and use GND / +OUT, to the female RCA (Phono) ?

What about C1 R9 R11, I dont have to use at all ?? , or could I just leaveout C1, cause I allready soldert the R9 and R11, into the PCB. The reason I ask about leaveout C1 is, that they're pretty big. (Would leave me more space for only one of them) javascript:smilie('')

I wasent thinking, of using P5, I just want to make a short here, that's why I quistion about
R15, because I have seen some schematics, where 430ohms where used in unbalanced operation.
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Old 20th December 2002, 01:41 PM   #4
Henrik is offline Henrik  Denmark
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Quote:
[Then I only have to short -IN, and use GND / +OUT, to the female RCA (Phono) ?
Yes.
Quote:
What about C1 R9 R11, I dont have to use at all ?? , or could I just leaveout C1, cause I allready soldert the R9 and R11, into the PCB. The reason I ask about leaveout C1 is, that they're pretty big.
Those You don´t need, unless You some day wants balanced operation.
Quote:
I wasent thinking, of using P5, I just want to make a short here, that's why I quistion about
Try some diffrent values, I think You will need about 350 Ohm for R15, but that depends.
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Old 20th December 2002, 07:38 PM   #5
2Bak is offline 2Bak  Denmark
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Quote:
was planing to use a stereopot for P3/P4, for volume control.
If running unbalanced only you will not need a pot at P3 but at P4 only (e.i. a stereo-pot for both channels). However if you plan to use - out later (balanced out), then think twice before you buy the pot for P3, cause a stereopot cannot be used as pot for both P3 and P4. Only a 4-channel pot or attenuator can be used for that (balanced).
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Old 21st December 2002, 07:54 AM   #6
lykkedk is offline lykkedk  Denmark
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Yes sure, P4 only
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