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2v or 6v into a tube pre-amp? what would you do (and why?)


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Ok, I've asked this question to the manufacturer of both pieces of equipment involved and gotten 4 different answers..  no lie.  Anyway...  I want to understand the why of something and maybe Ic an make up my own mind..


so the dCS Rossini has the ability to output (XLR Balanced) either .2v, .6v, 2.0v, or 6.0v... the later two being the recommended outputs unless using something like Apple Airplay etc..


I'm currently using the Rossini with just an Amp, as the pre-amp isn't due to arrive for a week or so...  the pre-amp (as listed in my signature) is a McIntosh C1100, which is a 100% tube pre-amp..   I don't know what type of volume control the Mc has (assuming digital), but the dCS is a digital volume control and so I assume I will want it set to the maximum (0.0db) once it's connected to the pre-amp... and then use the pre-amp volume knob, right?   But the bigger question is what voltage AND WHY?  2 or 6?  someone mentored more dynamic range in the 6v output, while someone else mentioned distortion possibly and over load?


Someone who knows more than me, and / or maybe owns a similar setup chime in and tell me what you would do?

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5 minutes ago, sandyk said:

McIntosh Laboratory MC462 power amplifier Specifications ...

www.stereophile.com › content › mcintosh-laboratory-...

Voltage gain: 29dB, 8 ohms. Input sensitivity: 4.2V balanced, 2.1V unbalanced.


You will need to greatly attenuate the output unless you use 2.0V out, otherwise you will

substantially degrade the Signal to Noise ratio. You will most likely already need to use way too much attenuation with an amplifier with 29dB gain.  What is the typical volume control setting on your valve preamp at present ? Is it well left of the middle of it's range ? Valve Preamps do not normally like higher input voltages , and were often designed for more like 1V RMS input signals.

To get most benefit from a higher voltage source signal, you need a Power Amplifier with much lower gain, or having switchable Input voltage settings. 

Thanks but I’m not going directly into the MC462... I’m going into a C1100 preamp ... can’t find anything about the input  other than its limited to 20v balanced.   But if I read you correctly.. sounds like the 2v is a good choice. 

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Well.. that’s interesting... so should I in fact use the 0.6v and not the 2v??  Wow... had no idea.  Got an email response form McIntosh just now where the guy said to use the 2v. 

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@Bill Brown wow, Bill, thanks for that very well put explanation on what was said above..  So my choices are .2v and .6v also... wonder if the .6v is the wise choice based on what you told me since from what even dCS has to say, you want to run the volume (digital volume) at 0.0db or max...  My dealer (McIntosh dealer) also seems to think the Pre-amp will allow me to trim the input voltage via some kind of setting...   


But to understand you completely...  I essentially don't want any voltage above 900mv into my pre-amp, otherwise it has to attenuate that excess... so even at 2v, it's too high.. and I might end up needing to run the volume at higher than 0.0DB from the dCS, maybe closer to -10db?


I'm obsessed with a perfect match you see... and the other other source I'll be running is a McIntosh SA/CD player which will mostly play via SPDIF connection to the DAC anyway unless I'm actually playing an SA/CD, in which case I'll have no choice but to use the built in DAC for the MCD600 player.


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@Bill Brown... thanks very much for that wealth of wisdom and calculations... its surprising that .2v might be the solution and a blessing that dCS even offers this.. .6 might even be ideal depending on how it sounds after I play around with it.  Even in their own owners manual they don't imply this is the normal voltage setting for using with a pre-amp, they mention something about Apple Airplay, but they imply that 2v is the normal with 6v for "some pre-amps".


I guess I will start with .2 and work up from there..   counter intuitively, It seems the lower the voltage in, the better ... I'd expected it to be totally the opposite.  Moreover, I've been using the setup without the pre-amp (As that's not due to arrive for a week) at 6v and occasionally 2v.. seems to sound good, but I can see how it would be easy to over drive the amp at full volume with the 6v setting based on how loud it gets even at -15db.. much less closer to 0.0.


Is the volume on the C1100 a digital volume control also?  My main concern is that I don't want to leave any signal behind in the chain... I want the most clarity and resolution. 



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10 minutes ago, lucretius said:

Is that a volume control I see on the dCS Rossini?  If so, disable (bypass) it when the C1100 is inline.

Apparently there is no way to do that, so I will just leave it maxed ...

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15 minutes ago, sandyk said:

 0.2V suggests that they may have already digitally (most likely) attenuated it already.


Which I would want to avoid, and frankly listening to the system as it stands now with the C1100 not in the mix (it comes next week), and with the Rossini directly into the Amp,  even at 2v it's not remotely loud... at 6v it comes to life..  

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3 minutes ago, sandyk said:

 Then unless you like (need?)  a little Tubey artificial warmth along with S/N degradation etc. along the way, why do you need the C1100 ?

the short answer is, especially when listening to classical music, I prefer that warm sound (albeit not when it's too in your face, and the C1100 was less so than the other pre-amps I tried)..  The other part is the logistics of running an SACD player (I have a decent collation of SACDs)  and eventual plans to add a Phonograph and getting good headphones makes that a bit more convenient (possible). 

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26 minutes ago, Bill Brown said:

Truthfully, though, this is all sort of "how many angels can dance on the head of a pin" kind of stuff anyway.  It is a beautiful system that will sound great no matter what you do.  I would just play with it, pick a setting, and forget it/listen to music.



True ... sort of a first world problem among first world problems.... but much like a video game I used to play years ago called world of warcraft, where you could either be a "casual" and play it that way, or hard core, and min/max your player to the highest possible level.... this hobby is the same, and I'm in that min/max mode these days... but I'm sure it will wear off. 

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1 hour ago, Bill Brown said:

Thank you.  Yes, I have the input sensitivity at the the lowest setting on my Benchmark amp and with the analog/automatic gain switching of the RME DAC usually listen at -0 to -6db of digital attenuation (with higher quality recordings).  I think it is a good way to go.  As long as the output stage of a DAC is well-designed and the volume control is implemented well (and it has one, not all do, of course), I don't see the need for a separate preamplifier.  It is nice to avoid the expense (the good ones are $$) of a separate preamplifier.


Again, this isn't to say that @992Sam won't enjoy the heck out the sound he gets from the Macintosh preamp.  He may fall in love with its tube gain stage, there are certainly many that do.




Yes, the pre-amp is a must on two fronts, expanding into Photo eventually and my current SACD requirement, but I also LOVE the sound of a good tube pre-amp... This one specifically is by far the nicest sounding one I've heard yet... I'm very excited to add it to the mix, and once I do, and sort out the ideal input setting for the dCS ... I'll post back here to share my findings.

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