ARC LS25 mkII noise level

considering that your main amps are 1Vrms sensitivity - maybe best way for you is to use decent attenuator with output buffer ....... because every modern source will give more than enough voltage for full blast , and buffer will add necessary muscles ;

as they say ARCDB - LS25 - 18uV is amount of noise , IHF weighted
are you using proper balanced connection between amp and pre ?
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
considering that your main amps are 1Vrms sensitivity - maybe best way for you is to use decent attenuator with output buffer ....... because every modern source will give more than enough voltage for full blast , and buffer will add necessary muscles ;

as they say ARCDB - LS25 - 18uV is amount of noise , IHF weighted
are you using proper balanced connection between amp and pre ?

Hi Zen Mod,

I am currently using single ended cables between my LS25 mkII and VS60. VS60 has no balanced inputs.

What does 1Vrms sensitivity imply? That the power amp inputs are too sensitive for the LS25? I figured since they are both ARC, they should be a good match.

And what would be an ideal attenuator be for this set up? Thanks for your patience. I am a bit new to tube hifi amps.
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
Change some tubes then and see. One may have gone hissy.

This preamp has 2 x 6H30 tubes. I've already ordered 2 new ones to see if it is the tubes.

I am wondering what the expectation for this preamp might be. Are these preamps supposed to be dead silent? I see the noise spec to be 14 micro volts. IHF weighted. I am going to assume A curve here. It looks like it is quite silent.

I am getting a significant increase in hum and noise when the preamp is taken off mute.
 
I've already ordered 2 new ones to see if it is the tubes.



Don't hold your breath. The tubes are only used as followers and their contribution to noise is minimal. I have once owned this unit and have no memories of excessive noise but maybe my noise requirements are not so demanding. Otoh, do not judge the sound of high quality tube preamps by the LS25 or any other ARC unit for that matter. Despite what a lot of audiophiles on agon say, they all suck sonically. No opinion about their power amps.
 
looking at schematic - there is no need for pins 1 & 3 tying on LS25 side

anyway - I still think that active stage is redundant , having 1V sensitivity of power amp ;

regarding full compatibility-do not over-estimate their knowledge over their greed .

feed that amp from any source which have variable output and that will be music , comparing to LS25 usage in that situation .

then you can sell preamp and buy something "passive " with buffer
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
Don't hold your breath. The tubes are only used as followers and their contribution to noise is minimal. I have once owned this unit and have no memories of excessive noise but maybe my noise requirements are not so demanding. Otoh, do not judge the sound of high quality tube preamps by the LS25 or any other ARC unit for that matter. Despite what a lot of audiophiles on agon say, they all suck sonically. No opinion about their power amps.

What in your opinion would be a great tube preamp? BAT? ARC has such a good reputation, I thought I'd give it a try. Of course, popularity hardly ever translates to quality so I am just beginning this tube audio journey.

The good thing about popularity is I can sell the LS25 for no loss in equity.
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
looking at schematic - there is no need for pins 1 & 3 tying on LS25 side

anyway - I still think that active stage is redundant , having 1V sensitivity of power amp ;

regarding full compatibility-do not over-estimate their knowledge over their greed .

feed that amp from any source which have variable output and that will be music , comparing to LS25 usage in that situation .

then you can sell preamp and buy something "passive " with buffer

I will try your advice. I'll see if the music is better this way.
 
The good thing about popularity is I can sell the LS25 for no loss in equity.



That is also the reason i sometimes buy used commercial high end equipment -it tends to preserve value ahead of inflation. And i get to sulk at it :)

As for recommendation for other brands, not much help i'm afraid. All the commercial preamps i have owned have been really poor in some respect. For some reason i find it much easier to come to terms with factory made power amps rather than preamps.

It is always useful to keep a good passive attenuator around. These usually work well with tube power amps and even if they show some deficiencies of their own, in comparison to most active preamps they can really shine. My definition of a good pre is thus simple: the transparency of a Shallco attenuator switch but with much better bass and dynamics. Gain, as Zenmod says is entirely optional.
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
That is also the reason i sometimes buy used commercial high end equipment -it tends to preserve value ahead of inflation. And i get to sulk at it :)

As for recommendation for other brands, not much help i'm afraid. All the commercial preamps i have owned have been really poor in some respect. For some reason i find it much easier to come to terms with factory made power amps rather than preamps.

It is always useful to keep a good passive attenuator around. These usually work well with tube power amps and even if they show some deficiencies of their own, in comparison to most active preamps they can really shine. My definition of a good pre is thus simple: the transparency of a Shallco attenuator switch but with much better bass and dynamics. Gain, as Zenmod says is entirely optional.

I see your standards are much higher than mine! I am actually quite happy with the sonic quality of the preamp. Just want to get the noise out. I don't think this is normal for this amp and there must be some reason electrically or otherwise.

It may just be some bad power filter caps in the preamp. The sound of this preamp is more to my liking than the Arcam solid state pre.
 
Yes, I do. I'll try it direct. .........

I hope that meaning of "direct" isn't " without volume control " ;)


...... The thing is the preamp is convenient in that I can plug all my different sources into it. Also, it has a recording loop as I do a lot of analog tape recording.

certainly ; but - I meant that you try that for test , then decide have you enough gain/grunt/music without active preamp
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
I hope that meaning of "direct" isn't " without volume control " ;)




certainly ; but - I meant that you try that for test , then decide have you enough gain/grunt/music without active preamp

:D of course. I'll use my source with an output control.

There is a company called Serious Stereo that makes passive preamps. I might try that if I have to send the LS25 for service. I think it is noisier than it should be. I'll talk with ARC this coming week about it.
 

GeneJazz

Member
2010-10-11 10:50 pm
NYC
I checked it out with my Nakamichi Dragon as a source. It has more than enough volume. I think it sounds just as good with no noise from the preamp. However, I heard from a LS25 owner who states he has no noise from it standing in front of his speakers. So I'll have to get to the bottom of that.

There are some attractive passive preamps but none really have the input capabilities I would need. I need at least 6 inputs with the ability to monitor my recordings.