change Pass labs Amp from 30dB to 26dB

[davidYuen]

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]

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]

but curious and for fun.

Woa, brave guy given the price of these amps

 

[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.

 

[PixelPlay]

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

 

[Nelson Pass]

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]

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.



Thanks for your help,
Greg

 

[h_a]

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]

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]

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

Cyclotronguy

 

[wayne]

The gain is not jumper adjustable on that PCB version.
The pins by the headers are bias test points. We test with a connector.
If shorted by an errant probe it can be very bad.
The other pins with no jumpers on them are for DC operation.
Putting four jumpers here bypasses input caps.

 

[PixelPlay]

Thanks for the info, all makes sence. It seems that the jumpers next to the input caps are closed thus bypassing the caps already.
Cheers
Greg

 

[cyclotronguy]

Gain setting jumpers

Jumpers for gain setting were clearly marked as to gain figures.

Cyclotronguy

 

[PixelPlay]

Seems that the 2004 model does not have that feature.

 

[wayne]

You are correct the 2004 version had no gain jumpers. I also spelled Neutral wrong on that revision on the silk screen (Nuetral).

 

[PixelPlay]

That makes it unique then
Hopefully on day I'm able to upgrade to 2 X150.5 and 1 X250.5
Going to be a long while though as my first child due in January.

I will probably put a resistor on the ic to bring the gain down.
Cheers
Greg

 

[slowikpl]

Hi guys ,

How about this Jumpers on my XA 160.5?

An externally hosted image should be here but it was not working when we last tested it.

It says DB30 -

I think thath this will 26dB gain move to 30dB. And will the sound loose some of the quallity if i go for the 30dB?

 

[cyclotronguy]

Gain jumper

Putting the gain jumper on shorts out a series resistor in the signal path, it does not actually change the gain of the amp, only the amount of signal the amp sees.

Cyclotronguy

 

[slowikpl]

Ok. If I go for 30dB it goes louder I assume? I have the preamplifier Pass XP20 and I want to be little bit quieter on the gain level of 01. How can I manage this?

 

[cyclotronguy]

Slowikpi

Contact "service@passlabs.com" with the unit serial numbers.

Cyclotronguy