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Old 29th January 2010, 10:56 AM   #61
jtktam is offline jtktam  Canada
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Thanks andrewT

I finish the build last night, and powered it up with a 15v wall wart.. would 18v make a big difference?

I didn't have any stereo 25k pot laying around, so I used a 50k pot.. i heard that a 25k is ideal for "transparency" reasons.. any good place to pick one up from?

I was in heaven.. it started to sound better and better over the 2 hour period.. and then I notice that it gets louder .. to the point I had to turn down my 23 step pot about 6 steps.. is that normal??

also I had built mine (Peter Daniel inspired me) in aluminum U channel.. would there be a need to shield the top? it looks pretty slick now since you can see all the stuff inside

I will post pics later when I get home..

-joe

Last edited by jtktam; 29th January 2010 at 11:08 AM.
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Old 29th January 2010, 11:34 AM   #62
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by jtktam View Post
.........then I notice that it gets louder .. to the point I had to turn down my 23 step pot about 6 steps.. is that normal?........
Hi,
that sounds odd?
6steps seems like something between 6dB and 18dB of extra attenuation.
Only a fault in the amp would allow that amount of extra gain.
Check the output offset. Cold, warm and hot.
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Old 29th January 2010, 11:37 AM   #63
jtktam is offline jtktam  Canada
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Sorry for my newbie-ness

how do I check the output offset?

I am using a 50k pot, just in case that matters

-joe
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Old 29th January 2010, 11:50 AM   #64
AndrewT is offline AndrewT  Scotland
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turn the pot down to zero volume. Remember, that was the position that gave zero ohms at it's output.
Now remove the speaker from the amplifier.
Measure the DC voltage and the AC voltage at the speaker terminals. Start by setting your Multimeter at highest volts scale and gradually work your way down, on both AC and DC, till you get a reading.
AC voltage should be less than 1mVac preferably less than 0.1mVac.
DC voltage should be less than 50mVdc and preferably less than 10mVdc for all operating temperatures and conditions.
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Old 30th January 2010, 01:24 AM   #65
jtktam is offline jtktam  Canada
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both are fine

I think I was just overly cautious

pics:

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Old 9th February 2010, 12:17 PM   #66
jtktam is offline jtktam  Canada
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it sounds better and better everyday

bested my friend's nuforce preamp and another's naim integrated amp

-joe
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Old 9th February 2010, 02:06 PM   #67
jleaman is offline jleaman  Belgium
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Quote:
Originally Posted by jtktam View Post
it sounds better and better everyday

bested my friend's nuforce preamp and another's naim integrated amp

-joe
Very nice and clean :0 great work!
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Old 18th February 2010, 03:29 PM   #68
jtktam is offline jtktam  Canada
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i didn't deviate from the standard part list.. I want to experiment a bit.. anybody using different caps?

-joe
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Old 19th February 2010, 12:01 AM   #69
jleaman is offline jleaman  Belgium
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Originally Posted by jtktam View Post
i didn't deviate from the standard part list.. I want to experiment a bit.. anybody using different caps?

-joe
Input caps are a personal preference or pick.!
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Old 20th February 2010, 04:03 PM   #70
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I built within the last weeks two versions of B1 buffers. I like it very much and I am looking for the right place within my sound chain to use them.

For sure, I use a B1 after the output trannies of my CS4398 DAC.

My first take was based on a strip board with 2SK389 in the BL version. Symmetrical PSU based on two LM317. No input cap.

Click the image to open in full size.

Click the image to open in full size.

The result was very impressing, also my Aikido Phono preamp sounded much better when I connected a B1 to the output.

So, I made a PCB based on the following schematics (with Express-SCH/Express-PCB, for files just drop me a PM):

Click the image to open in full size.

Main differences to the stripboard variant:

- both channels separated from PSU by RC (10 Ohm / 220uF Oscon, bypassed by 0.1uF Wima very nearby the 2SK389)
- Dale resistors in the signal path (still missing on the picture below)
- use of the V-version of the 2SK389 (higher current)
- input cap (avoiding magnetizing of the preceding trannie during startup) 0.39uF

Click the image to open in full size.

Click the image to open in full size.

The board is made by the toner transfer method.

And the result?

Awesome, the second version with the higher current beats everything I used as linedriver before.

Thanks for the nice and simple circuit, Nelson!

Franz

/Edit

BOM

Br301 EDF1B
Br401 EDF1B
C1 0.39uF
C2 10uF
C3 220uF
C4 220uF
C101 0.39uF
C102 10uF
C103 220uF
C104 220uF
C301 1000uF
C302 0.1uF
C303 10uF
C304 1uF
C401 1000uF
C402 0.1uF
C403 10uF
C404 1uF
C101a 0.01uF
C102a 0.1uF
C103a 0.33uF
C104a 0.33uF
C1a 0.01uF
C2a 0.1uF
C3a 0.33uF
C4a 0.33uF
D301 2N4148
D302 2N4148
D303 LED
D401 2N4148
D402 2N4148
D403 LED
P301 1k
P401 1k
R1 330R
R2 1M
R3 330R
R4 1M
R5 100k
R6 10R
R7 10R
R101 330R
R102 1M
R103 330R
R104 1M
R105 100k
R106 10R
R107 10R
R301 100R
R304 R-LED
R401 100R
R404 R-LED
U1 2SK389
U101 2SK389
U301 LT317
U401 LT317

Last edited by Franz Gysi; 20th February 2010 at 04:14 PM.
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