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Old 5th June 2011, 01:37 PM   #1
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Default change Pass labs Amp from 30dB to 26dB

Hi

My Pass Labs X150.5 is set at 30dB gain (according to the spec.), I want to change it to 26dB gain for bi-amp configuration (w/o active crossover) with my new XA100.5 (26dB gain) to drive awaited Salon2 in a small room. I prefer to modify its internal circuits (say replacing some resistors). I know my ideas are strange, but curious and for fun.

I have tried to find out some hints in Internet, but no luck. Any advice is welcome.

Also, do anyone know why there are two dB gain settings for the X.5 as well as XA.5.

Thanks in advance.
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Old 6th June 2011, 02:29 PM   #2
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The amplifiers are shipped at the default 26 dB. There are 2 jumpers per
channel on the input that modify the input resistors for 30 dB. If you simply
remove (park) the jumpers, then the gain is 26 dB and the jumpers are
no longer in the circuit. No need to get out the soldering iron.

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Old 7th June 2011, 06:53 AM   #3
h_a is offline h_a  Europe
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Quote:
but curious and for fun.
Woa, brave guy given the price of these amps
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Old 11th June 2011, 12:55 PM   #4
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From internet, Bi-amp seems a promising configuration which divides and conquers the most complicated loads (i.e. speaker).
Wish some pioneers produce a pre-amp for bi-amp configuration, leave us have easier lives.
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Old 24th November 2011, 10:56 PM   #5
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Default Dear Papa

Dear Papa
I am in a similar situation, I am currently building a pair of Linkwitz Orions V3.5 and thus require identical unbalanced gain on all amps used.
Thus far I have:

DIY Aleph 2ís 26db

X150.5 26db with jumpers answered above. (which are the jumpers that you are referring to?)

X150 (until I can afford another two .5ís, going to be a long time as we are expecting our first child after Christmas), however I am unable to find any literature apart from it being 30db. Is this balanced or unbalanced and hopefully there is a way of changing it to 26db unbalanced as the Orion ASP does not have an option for a balanced connection to the amps.

Thank you kindly for all of your help and dedication, may we all fill our homes with Papas projects

Happy Thanksgiving
Cheers, Greg
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Old 25th November 2011, 03:48 AM   #6
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Quote:
Originally Posted by davidYuen View Post
From internet, Bi-amp seems a promising configuration which divides and conquers the most complicated loads (i.e. speaker).
Wish some pioneers produce a pre-amp for bi-amp configuration, leave us have easier lives.
Done. XP30 or First Watt B2 (announcing momentarily).

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Old 25th November 2011, 03:59 AM   #7
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Default X150.5 jumper image

Here is an image of the x150.5 2004 edition, just wondering which jumpers to select for the 26db. Apologies for the quality.

Pass-X150.5-jumpers.jpg

Thanks for your help,
Greg
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Old 25th November 2011, 06:43 AM   #8
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Hi Greg,

don't forget, lowering gain is easy even without modifying the amp, just use a voltage divider (2 resistors) at amp's input (maybe within a connector). Increasing gain is the tough part usually.

Hannes
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Old 26th November 2011, 11:37 AM   #9
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Originally Posted by Nelson Pass View Post
Done. XP30 or First Watt B2 (announcing momentarily).

Wow, good news! The price and comment(from a local magazine) are reasonable and really good.

Can't visit Pass web site at the moment for detail spec., wish to have cutoff frequency for two outputs to save the power.
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Old 28th November 2011, 10:32 PM   #10
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Those jumpers in the photo are test points, do not short

Cyclotronguy
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