XA30.5 and noise

[superlian]

XA30.5 / noise in the system or house

I experience some noise in my system. My dipole speakers are "home-made"

Sonos - SPDIF - Buffalo II Dac - Balanced Cable - XP10

Woofers:
Singel ended Cable from XP10 - First Watt B4 active crossover, lowpass 12 dB 300 Hz - XA30.5 - Acoustic Elegance LO 16 ohm x2 in parallell

Mid/High:
Balanced Cable from XP10 - XA30.5 - full passive crossover:
Bandpass 6 dB 300 hz / 12 dB 3000 Hz - JBL 2119
Highpass 18 dB 3000 Hz - Radian 475Pb-Beryllium in Autotech Tractrix 1000 horn

The speakers sounds very good and the amplifiers are extraordinary grain free but ruthless revealing with an impressing midbass (and bass).

I experience more noise/hum in theese amplifiers than others i had before. Both XA30.5 sounds identical and are ca 6 months old. I am 99% sure they are OK. I have also switche they bass amp to mid/high and vice versa. The noise is both in the mid and in the tweeter region.

I have heard that constructions with a lot of Mosfets have some noise, that it is the "nature" of that type of amlifier.

For the record, i have tested First Watt F2J, F3 and a norwegian bipolar push pull 50 Watt class A transistor amp (with the same gain as XA30.5) on the mid/high and all of them are significant more quiet.

I appreciate advice and suggestions 🙂

 

[Zen Mod]

what's happening when you change low/high gain setting on XA30.5 ?

 

[superlian]

Is it a setting like that? Where?

 

[Zen Mod]

open top lid on amps , take a picture of back area - showing input XLRs and brown caps around them ..... and post here

you'll see 2+2 places for jumpers , showing 30db title near them , positioned left and right of input caps

they all need to be jumper-less , for ~27db gain , and having jumpers installed for 30db of gain

however - is noise objectionable without any stage connected to XA30.5 inputs ?

btw. regarding noise difference with all other amps you tried - they're all of much lesser power or both power and gain

 

[6L6]

With no input connected to the XA30.5 do you hear the noise?

 

[superlian]

With no input connected to the XA30.5 do you hear the noise?

Yes

 

[biju55]

do you hear this noise in both channel ?

 

[Apogee]

Nice system!

I noticed the nice picture on the wall. Is there any chance that you are using dimmers in the room (or on the same circuit)?

Also, have you checked your mains supply to make sure the grounding is good?

I'm sure someone from Pass Labs will assist shortly as they are very good about such things.

 

[Nelson Pass]

You can assume it's a ground loop, which is very common with active
crossovers.

I would approach it by getting some "cheater" plugs which isolate the AC
power socket's Earth connection and trying it on one power amp and also
a power amp plus the preamp, leaving at least one component Earth grounded
(for safety purposes).

A little experimentation will probably reveal something.

😎

Very nice speakers, BTW

 

[Zen Mod]

Pa , OP sez that noise is there , even with nothing connected to XA30.5 input ; though , I hardly believe that something is wrong with amps

btw. I'm , you never sez that any of my speakers are nice ..........

 

[superlian]

OK, so this is the jumpers, nice to know 🙂

 

[superlian]

do you hear this noise in both channel ?

Yes, both channels and both amps

 

[superlian]

Nice system!

I noticed the nice picture on the wall. Is there any chance that you are using dimmers in the room (or on the same circuit)?

Also, have you checked your mains supply to make sure the grounding is good?

I'm sure someone from Pass Labs will assist shortly as they are very good about such things.

I have LED dimmers but on another circiut. I have a separate exclusive 16A HiFI circuit. I will doublecheck if the dimmer influence in any way.

 

[Zen Mod]

OK, so this is the jumpers, nice to know 🙂
.....

so , jumpers are in place ;

pull them out , for 3db gain less

that can't harm

 

[superlian]

You can assume it's a ground loop, which is very common with active
crossovers.

I would approach it by getting some "cheater" plugs which isolate the AC
power socket's Earth connection and trying it on one power amp and also
a power amp plus the preamp, leaving at least one component Earth grounded
(for safety purposes).

A little experimentation will probably reveal something.

😎

Very nice speakers, BTW

The First Watt B4 filter has been very kind in company with several amps. B5 also. I dont think B4 is causing any trouble.

I will do some testing with a cheat-plug on one powe amp.

The noise is not that big problem, it is more or less like a typical valve amplifier. A groundloop from my experience is much worse.

 

[superlian]

Neither the dimmable LED light in the ceeling nor the electrical heated floor add any kind of noise.

I have also pulled out all the power cables to other components except one XA30.5. I connected a iPhone directly and played some music. Everything works very vell but the same fundamental noise is present.

Is i wrote in earlier post, it is not a big problem, i just experience more noice than usual. In comparison First Watt F2J and F3 (both factory build) are completely silent.

I have heard that the tradeoff with huge transformers is a little more noise. Could this be a part of the explanation? Despite this, one of my other amps, a bipolar class A <40-50 Watt with 2x500 VA is much more quiet.

 

[superlian]

At last but maybe not least, my speakers are very dynamic and revealing with a sensitivity of 95 dB.

 

[Apogee]

Lian,

How are you connecting the amplifiers? Are you using the RCA jacks or the balanced inputs? If using the RCA inputs, do you have the jumpers installed in the XLR connectors?

 

[superlian]

Lian,

How are you connecting the amplifiers? Are you using the RCA jacks or the balanced inputs? If using the RCA inputs, do you have the jumpers installed in the XLR connectors?

When i use RCA i use the small "gold jumpers" yes 🙂

And the noise is there both with balanced and with single ended connection.

 

[Zen Mod]

XA30.5 :
Output Noise 150 uV unweighted 20-20 kHz

F3 : Noise 100 uV unweighted, 20-20 KHz

so ........ XA30.5 is having 3.5db more noise then F3