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BA-3 Amplifier illustrated build guide
BA-3 Amplifier illustrated build guide
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Old 30th May 2016, 07:53 AM   #101
MASantos is offline MASantos  Portugal
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Quote:
Originally Posted by AndrewT View Post
most heatsinks are rated for a deltaT of 70C to 80C degrees.
most heatsink manufacturers issue de-rating data/tables for their heatsinks when DeltaT is less.

For a deltaT of around 13C degrees expect the de-rating factor to exceed 1.5
i.e. 60W into 0.2C/W and using a DF of 1.6 gives DeltaT = 60 *0.2 *1.6 = 19.2Cdegrees
If Ta = 28C, then Ts = 47C
Since hifi2000 doesn't provide us with such data, the best we can do is to follow Papa's rules: always get the biggest heatsink you can, and after that use the palm rule! I have a small infrared laser thermometre, so that helps!
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Old 30th May 2016, 08:21 AM   #102
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by AndrewT View Post
For a deltaT of around 13C degrees expect the de-rating factor to exceed 1.5
i.e. 60W into 0.2C/W and using a DF of 1.6 gives DeltaT = 60 *0.2 *1.6 = 19.2Cdegrees
19.2 is pretty close to my estimated value of 20 after derating
I always knew deep down I couldn't be too dumb.

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Old 30th May 2016, 08:24 AM   #103
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by MASantos View Post
Since hifi2000 doesn't provide us with such data, the best we can do is to follow Papa's rules: always get the biggest heatsink you can, and after that use the palm rule! I have a small infrared laser thermometre, so that helps!
No need to lose sleep over this, I have that very case you are inquiring about, the heat sinks can easily do what you are asking them to do.
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Old 12th June 2016, 09:53 PM   #104
Tyson is offline Tyson  United States
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I have a bit of an odd question regarding the BA3 I built together with 6l6(Jim). I'd like to change out the 10uf caps on the input board to a smaller value, so that the amp will roll off the signal below 150hz.

What cap value should I change in order to make that happen? You might wonder why I want to do this.... its because my speakers run planar magnetic drivers for the midrange and I'd like to only send them a signal from 150hz and up. I have a separate bass section that has it's own amps, so I don't need a full range signal from the BA3.

I know that the formula to calculate this is:

1/RC = 6.3 * F

R= ohms
C = farads (not microfarads)
F = frequency

I know that F will equal 150, but I need to know the input impedance of the BA3's output boards (I'm using the complimentary, push-pull boards from the DIY Audiostore). Does anyone know their input impedance? Because that should give me R, and then I can calculate C.
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Old 12th June 2016, 11:14 PM   #105
Zen Mod is offline Zen Mod  Serbia
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BA-3 Amplifier illustrated build guide
aroundish 5-6K
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Old 13th June 2016, 04:04 AM   #106
Tyson is offline Tyson  United States
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THANKS Zen Mod! So if my math is correct, I'd need a .2uF cap - does that sound right?
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Old 13th June 2016, 08:09 AM   #107
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Old 10th December 2016, 07:34 PM   #108
qwertyl is offline qwertyl  United Kingdom
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Today I did a bit of listening to my newly built BA-3 (front end + power amp in separae chassis). I am impressed by dynamic, control, resolution, very delicate high frequencies, but comparing to Aleph J there is less colours, less presence and human voices sound a bit worse - is this something that can be cured by adjusting P3? I haven't touched it yet.
Aleph J sounds better at low volumes, BA-3 I kept increasing volume, it is very relaxed.

Last edited by qwertyl; 10th December 2016 at 07:36 PM.
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Old 10th December 2016, 08:04 PM   #109
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.....is this something that can be cured by adjusting P3?......
yup
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Old 10th December 2016, 08:59 PM   #110
6L6 is offline 6L6  United States
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BA-3 Amplifier illustrated build guide
Also you are hearing the differences between the AJ and the BA-3... The BA is pretty neutral whereas Alephs are quite colored, but the colors are so incredibly beautiful that nobody cares.


The BA-3 is still my favorite amp, with the AJ in a very close second, despite their differences.

As ZM says, you can adjust P3 and tune to taste.
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