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


992Sam

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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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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 from the DAC, 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. 

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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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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12 minutes ago, 992Sam said:

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.   Can you see if you’ve got better luck?

 I was going by this "I'm currently using the Rossini with just an Amp"2

 

C1100

  • Total Harmonic Distortion
    High Level: 0.005%
    Phono: 0.05%
  • Frequency Response
    +0, -0.5dB from 20Hz to 20kHz
    +0, -3dB from 10Hz to 100kHz
  • Maximum Volts Out (Balanced / Unbalanced)
    20V RMS / 10V RMS
  • Sensitivity High Level (Balanced / Unbalanced)
    900mV / 450mV
  • Sensitivity Phono (Moving Coil)
    0.45mV
  • Sensitivity Phono (Moving Magnet)
    4.5mV
  • Signal To Noise Ratio (High Level)
    107dB
  • Signal To Noise Ratio (Moving Coil)
    79dB
  • Signal To Noise Ratio (Moving Magnet)
    77dB
  • Voltage Gain (High Level)
    15dB
  • Voltage Gain (Moving Coil)
    60db
  • Voltage Gain (Moving Magnet)
    40dB
  • Input Impedance (Balanced / Unbalanced)
    50K ohms, 25K ohms

 

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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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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I realized I may have implied your amp had a tube output stage, but I know it is SS.  The commonality it has with tube outputs is the transformer output (actually an autoformer with Mac, unique in that regard and a neat concept).

 

Bill

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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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On 10/26/2020 at 1:12 PM, 992Sam said:

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?

 

Assuming your using the balanced connection, you can use an input anywhere from 900mV to 20V.  I'd say go with the 6V for the balanced connection.  Pro gear (which usually uses the balanced connection) is generally hotter -- up to 10V out.

 

OTOH, if you choose the unbalanced connection (450mV to 10V per C1100 manual), go with the .6V or the 2V (depending on the effect on the volume control).  Note that most consumer gear (which is what uses the unbalanced connection) would usually be somewhere between .7V to 1.3V where a CD player could be 2V output.) 

 

On 10/27/2020 at 8:00 PM, 992Sam said:

I guess I will start with .2

 

.2V is too low!

mQa is dead!

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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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On 10/28/2020 at 11:00 AM, 992Sam said:

I guess I will start with .2 and work up from there..

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

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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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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1 hour ago, 992Sam said:

 

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..  

 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 unless you have other sources to select ?

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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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.

 

Bill

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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No worries. :)

 

Most of us have been there (I know I have)!

 

Bill

Labels assigned by CA members: "Cogley's ML sock-puppet," "weaponizer of psychology," "ethically-challenged," "professionally dubious," "machismo," "lover of old westerns," "shill," "expert on ducks and imposters," "Janitor in Chief," "expert in Karate," "ML fanboi or employee," "Alabama Trump supporter with an NRA decal on the windshield of his car," sycophant

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If the amplifier can receive 6v without overload, I would definitely choose it. I have tried different voltage from my DAC and 6v sounds, I am not kidding, much better than 2v. The sound becomes more dynamic, effortless, and believe it or not, much clearer. I would contact the amplifier supplier and hear which voltage exactly your amplifier can take at the XLR input. If it's a power amp, I would be very surprised if it could not handle 6v.

 

That there should be a sound difference is not peculiar from a scientific perspective either, as S/N is always better on/with a stronger signal. The reason to this is that the audio signal becomes less sensitive to external noise. A weak signal is (everything else held equal) more sensitive to EMI/RFI compared to a stronger signal, and 3 times as strong is no minor feature we are talking about.

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16 hours 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.

 

Bill

 

Truthfully, why this type of comment to a serious question? I do not believe it’s stupid to try to get the best SQ out of one’s system and discuss which “things” and implementations that does.  

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