change Pass labs Amp from 30dB to 26dB

davidYuen · 5th June 2011, 01:37 PM

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.

Nelson Pass · 6th June 2011, 02:29 PM

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.

h_a · 7th June 2011, 06:53 AM

Quote:

but curious and for fun.

Woa, brave guy given the price of these amps

davidYuen · 11th June 2011, 12:55 PM

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.

PixelPlay · 24th November 2011, 10:56 PM

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 2’s 26db

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

X150 (until I can afford another two .5’s, 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

Nelson Pass · 25th November 2011, 03:48 AM

Quote:

Originally Posted by davidYuen

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).

PixelPlay · 25th November 2011, 03:59 AM

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

h_a · 25th November 2011, 06:43 AM

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

davidYuen · 26th November 2011, 11:37 AM

Quote:

Originally Posted by Nelson Pass

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.

cyclotronguy · 28th November 2011, 10:32 PM

Those jumpers in the photo are test points, do not short

Cyclotronguy

5th June 2011, 01:37 PM	#1
davidYuen diyAudio Member Join Date: Jun 2011	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.

24th November 2011, 10:56 PM	#5
PixelPlay diyAudio Member Join Date: Jan 2007 Location: Melbourne, Australia	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 2’s 26db X150.5 26db with jumpers answered above. (which are the jumpers that you are referring to?) X150 (until I can afford another two .5’s, 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 __________________ "Live each day as if it is your last"

25th November 2011, 03:59 AM	#7
PixelPlay diyAudio Member Join Date: Jan 2007 Location: Melbourne, Australia	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 __________________ "Live each day as if it is your last"

25th November 2011, 06:43 AM	#8
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	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 __________________ fresh matched IRFP240/IRFP9240 fets \|\| AlephJ/JX-kits F5 transistor kits \|\| Burning Amp BA-1/2/3 transistor kits

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6th June 2011, 02:29 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	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.

11th June 2011, 12:55 PM	#4
davidYuen diyAudio Member Join Date: Jun 2011	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.

28th November 2011, 10:32 PM	#10
cyclotronguy diyAudio Member Join Date: Sep 2001 Location: Northern California	Those jumpers in the photo are test points, do not short Cyclotronguy

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