FWIW, Last night I fired up the system and turned up the volume all the way. Not much noise, and I need to be within 3-5 feet to hear it. For contrast, with the volume at max for phono listening, 1 to 2 oclock range, I can hear the noise from my Ayre P5x phono pre at my listening position. But that noise is very different, less bad, than white noise.
I don't think you should hear much noise, if any.
I have an ARC REFII mkII driving Pass Aleph 2 monos which have 25K ohm (Balanced) inputs with Vandersteen 5A x-over set at 20K (its 20 or 33K)inbetween.
The unit is just over a year old with under 1K hours. My room is very quiet.
Terry |
Do you prefer the ARC sonically to the BAT btw? Curious |
At the risk of having all the ARC fans on my case: I see that Lamm also uses vacuum tube rectifier circuits in his power supply. Thus, far I have not read any Lamm preamp owner crib about excessive while noise levels. (if this is not the case, please point me to the appropriate post). I compare w/ Lamm 'cuz the Ref2 Mk2 is close in price range to the Lamm L2 Ref & is more expensive than the LL2 regular/deluxe.
It seems that if ARC was to charge $10,000 for the Ref2 Mk2, this noise aspect should never have been an issue. What if one were to use the ARC Ref2 Mk2 with a horn system? Problem exacerbated? I went to the Stereophile archives & dug this out from a year 2000 review. Seems like it was on the Mk1 version but,unfortuntely, it seems that it's applicable to the Mk2 version too. Your experience, Classicjazz, seems consistent:
"The Reference Two was quiet for a tube amp, with just a trace of thin white noise when no signal was fed it—a far narrower spectrum than the usual "tube rush." Still, there was a slight price to pay for the raised noise floor compared to the best solid-state preamps: on classical recordings, lower resolution of very-low-level information such as back-of-the-stage reverberant events; and on pop and rock, a de-emphasis of electronic studio effects. The latter was actually a blessing; most of this studio detritus is not supposed to be so obvious in the mix, and isn't with the kind of gear it's usually played through." |
I agree with Reb1208. My Ref2 mk1 also has white noise and will go away when you mute the pre. It is also not variable through the volume control, as the original poster suggests.. I called Leonard at ARC and he said it is the power tube that is used in their design.
magnepanmike |
The ARC uses tubes in the power supply, the Bat is SS power supply. There is your answer. |
Actually the input is 10K Ohms, the balanced output is 440 Ohms for a 22x ratio...
I tried to track down the tech support agent at ARC but he was tied up. I'll try again Monday. Thanks all for your help. |
Well, 1K input Z, as soon asI saw that...this is the most likely problem. Too low for getting the best performance with ARC tubes.
Good luck,
JT |
Tube preamps really do not like anywhere near that low of impedance. You might try asking your amp manufacturer if the impedance can be increased. Generally, there is an input resistor and you can simply substitute another value.
Most tube pre's are happiest when the impedance is around 50K or higher.
I really can't say for sure if this is responsible for the increase in the noise floor. Some tubes have a higher noise floor than others by a substantial amount. If the pre's tubes have been replaced, it's possible this could be an issue. Might check and see if you have replacements(different from the originals) if you purchased used.
If you purchased new---easy---call ARC. Or, call them anyway. They are really friendly people! |
To confirm whether reducing preamp gain will help, you can do a quick test by using SE (RCA) output from Ref 2, if you are using balanced IC right now. The Ref 2 SE output (12db) has a lower gain then balanced (18db). However, if you have in-line attenuators, you can place it in between preamp and power amp to confirm it as well. It's working on my system (Pass X-600+ARC Ref 2 MK1) to reduce the noise floor (humm) quite a few. Hope this helps... |
I'm not too certain about any plug in gadgets to correct the problem. I wouldn't doubt you could Google up some sort of pad to plug in between your pre & amp.
I assume you are using the balanced outputs on the ARC? The specs state that the output impedance halves at the single ended outputs. If you have some adaptors to go SE, it might be worth a try to see if that helps. |
Thanks for the insight.
It sounds like the impedance mismatch. I have amps with 10K Ohms input, 1/2 of what ARC recommends for the RE2. I don't have another amp on hand but maybe that's it? My speakers are Genesis 501s, which are 90 dB efficient. Amps are Gryphon Reference One Monoblocks. Is there a way to compensate for the mismatch without changing one or the other component? |
I doubt gain differences are the problem. While muted, the difference in the two pre's gain capabilities shouldn't matter.
If the noise level isn't at or near zero when the pre is muted, then it sounds like it could be an impedance mismatch...
The tubes would seem pretty unlikely. When they go south, you will definitely know something is wrong. |
My gut reation to you situation is that you have a pre-amp with high gain, and amp with high sensitivity and/or very efficient speakers and you are hearing the noise floor of your pre-amp line stage. I recently got some higher efficiency speakers and had to put in-line attenuators to quiet down the line stage from my ARC SP10. As to whether or not its the tubes themselves - tube "noise" is usually not a steady low level hiss, but takes on a more crackly-spitty sound, however light. Don't know about the BAT but I suspect it may be a matter of its output voltage as seen by the amp. Hope that helps a bit... |
