Pass X150 and BAT VK3IXSE gain problem

[Mark Veter]

Hi all. I have a Pass X150.
Previously I had a Mark Levinson 28 preamplifier and it was a near perfect match, both electric and timbrically

Now I bought a BAT VK3IX SE pre but I'm not happy about the matching with the Pass.

impedances should be ok:
1k Ohm output impedance the BAT and 22k ohms input impedance the PASS. The ratio is 1:22. Confirm?
It is a rule that minimum ideal ratio is 1:10?

However the Pass gain is too high (30db?) and therefore I can not increase the volume over 25/100 and 40/100 with SACDs

I also perceive a sense of fatigue and dirty sound. there is not a much black background like with solid state preamps.

I would like to know :

1. there is a way to decrease the gain of the Pass through internal switches?
2. Anyone has yet matched BAT preamps with PASS X series power amps ?

Please help me ,

Marco

 

[Dennis Hui]

Marco,

I suggest you contact Pass labs (service@passlabs.com) with your amp's serial number.

Cheers,
Dennis

 

[Mark Veter]

Ok. I wrote them.
I’m waiting for a reply

 

[Zen Mod]

open the lid , take photo of motherboard , post here

 

[Nelson Pass]

X250 gain is 26 dB last time I looked, and this is the first time the
subject has come up.

Single ended or balanced?

 

[Mark Veter]

Balanced

 

[Nelson Pass]

The amp has the same gain either way, but the source might easily
have twice as much running balanced.

You can reduce the gain arbitrarily by inserting resistance in series with the
to inputs. For example, 10 Kohm will drop it about 6 dB, 20 Kohm 12 dB and so
on. It won't hurt the performance of the amp, but it is necessary to have both
+ and - lines treated the same.

 

[Mark Veter]

Thank you so much Nelson.


So... just buy these attenuators to reduce the gain of my X150 Pass. Wonderful!

But ... what about input impedance?

It is still a "only" 1:22 ratio.

1KOhm BAT: 22KOhm Pass

It's enough ? This is a good sinergy?

 

[Zen Mod]

if you add 10K in each input leg , Rin goes by 20K .... resulting in 42K

 

[Mark Veter]

Ok. Thank you!

 

[Mark Veter]

It exist an XLR version of this resistances ?

 

[Zen Mod]

clarify question

 

[Mark Veter]

is there an XLR version of the RCA line level attenuators?

 

[Zen Mod]

probably is

however , every technician can adapt your cables , inserting 0.25W metal film resistors in XLR male plus on f your cables

plenty of space in them

 

[Mark Veter]

Ok. Thank you all.

 

[Mark Veter]

Please, another question...

Why the Pass Labs XP20 pre balanced output impedance is so high (1000Ohm) while the input impedance of Pass Labs X series amps is around 20.000 Ohm and the balanced input impedance of the new XP22 pre is only 50Ohm?

If I will buy an XP20 (1000Ohm) pre may I have problems with the impedance of the Pass X150 amp? (22.000 Ohm)
It is better the XP22 ? (50 Ohm)

 

[Nelson Pass]

I don't think that input impedance figure is accurate, but I don't have
the actual number in front of me. I'll ask Wayne when I see him later
today.

 

[Mark Veter]

Thank you

 

[Mark Veter]

News ?

 

[wayne]

The XP 20 output impedance is higher than the XP 22 but it was designed to drive the .5 series just fine and has never been an issue. The XP 22 is about 50 Ohms out and does sound better, it is ten years newer.