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

[Bill Brown]

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.

 

Bill

[Bill Brown]

Ah yes, I just remembered as well that @992Sam will be running an SACD player and an LP system, where a preamp is mandatory (I have converted to digital files exclusively).  I expect the Macintosh to be a wonderful performer for him.  As the common pathway for all of the sources a great preamp is considered by many to be the heart of a system.

 

Bill

[sandyk]

4 hours ago, Bill Brown said:

This is lower than the norm, but it's something I welcome because preamplifiers in general are used to attenuate, not amplify, the levels of source signals" JA in Stereophile measuring an integrated amp

 That's not quite correct. Many people have lower level sources than the 2V RMS from a standard

CD /DVD player . They often include FM Stereo, Phono Preamps, Tape Decks and these days DTV, which often varies dramatically in level between SDTV and HDTV transmissions where different types of Audio were used, including Dolby Surround. In my case, my DIY Class A Preamplifier was designed to have only 3.2 x gain to compensate for those marked differences in level, which in the case of DTV, even when using a STB set to maximum output level into a high quality DAC via Coax SPDIF still needs level adjustment . Even then I need to further attenuate the output from my Oppo 103 when playing CD and other digital sources plugged into it.

 

IIRC, Kal's setup is very different to that of most members because he is a multi channel person.

[992Sam]

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.

 

Bill

 

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.

[Summit]

16 hours ago, Bill Brown said:

 

"Stupid" isn't a word I used.  I would ask you to not put words into my mouth.  Also, why would I write so much above about a subject that I think is "stupid?"  Did you read near the top where I emphasized the importance of gain staging in some detail?

 

My point above is not that it isn't worth thinking about and that it wouldn't be fun to experiment, but that in the end, his equipment is so well-engineered that any combination of settings will work fantastically (a point I have repeatedly emphasized).

 

I would also encourage you to read a bit on the effect of S/N measurements after gain and subsequent attenuation:

 

"But if we look back at the system, we see that for most situations, we have more gain than we need. Maybe 15 to 20dB (10X) more gain than we really need. And that can lead to noise. Why? Because any noise that occurs after the volume control does not get attenuated. In fact it gets amplified. You've cut down the signal from the CD player by 17dB, so now it's 17dB closer to the noise in every circuit that follows. Any noise from the preamp, the cables, bad connections, etc. will be also be amplified 30X by the power amp. You took a medium level signal of 320mV (0.32 volts) and divided it down to 44mV so its now much closer in level to all the noise living in the bottom of the system."

https://www.diyaudio.com/archive/articles/160464-de-lite-amplifier-next-thread.html

 

"One consequence of this is that the more you attenuate the signal the more you reduce the SNR (since the noise is fixed). So gain management consists of adjusting and/or selecting a chain of components that will amplify the signal enough to listen to and not much more."  @Kal Rubinson in Stereophile

 

"The maximum gain for both balanced and unbalanced inputs to balanced outputs was just 0.2dB. This is lower than the norm, but it's something I welcome because preamplifiers in general are used to attenuate, not amplify, the levels of source signals" JA in Stereophile measuring an integrated amp

 

• Low Gain – The AHB2 has a low gain setting that optimizes the gain structure of professional monitoring systems. Maximum rated output is reached at an input signal level of 22 dBu. This places the upstream equipment in an ideal operating range to maximize the SNR of the monitoring chain. Most power amplifiers have far too much gain, and this degrades noise performance of the overall system. The AHB2 has an ultra low-noise input amplifier with two gain boost settings that can be enabled to allow direct interfacing with Hi-Fi components that usually operate at significantly lower signal output levels.

https://benchmarkmedia.com/blogs/application_notes/14680625-the-ahb2-a-radical-approach-to-audio-power-amplification

 

"The DAC1, DAC2 and DAC3 all have internal pads on the XLR outputs that should be used to set the output levels to the range that is required by the downstream device. This will allow direct interfacing to virtually any pro or consumer product.

Turning down the volume control is not a substitute for selecting the proper pad setting!

Excessive use of the volume control skews the measurements by adding excessive noise. This in turn impacts the linearity measurements, which at their low end are really SNR measurements. The tests should be run at or near maximum volume (or the calibrated switch on the back of the DAC1 should be enabled)."

 

Jon Siau, Benchmark designer

 

"The wideband S/N ratio, measured in the high-gain, stereo condition with the input shorted to ground and ref. 1W into 8 ohms, was very high, at 89.3dB. Reducing the measurement bandwidth to 22Hz–22kHz increased the ratio to 106dB, while switching an A-weighting filter into circuit increased it further, to 108.5dB. Referenced to the AHB2's clipping power of 100W, this is equivalent to a dynamic range of 128.5dB, which is close to the specified 132dB. The S/N ratio did increase by around 3dB in the lowest-gain condition, implying that the specified ratio was measured in that mode."

 

https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-measurements#HkauPY4Q0eXu8lOd.99

 

"To maintain the full dynamic range within the best operating level, RME's ADI-2 FS includes electronic switches, which give control over input and output level via two keys from the front plate, for a perfect adaptation to the levels +4 dBu, +13 dBu and +19 dBu. Two compact level meters provide 6 LEDs each. Multiple brightness stages and peak hold functionality make read- ing and adjusting input levels easy and convenient."

 

0. Mode ANA (Analog In to Analog Out)

   •  Signal to Noise ratio (SNR) @ +19 dBu: 123 dB RMS unweighted, 126 dBA

   •  Signal to Noise ratio (SNR) @ +13 dBu: 119 dB RMS unweighted, 122 dBA

   •  Signal to Noise ratio (SNR) @ +4 dBu: 112 dB RMS unweighted, 115 dBA

https://www.rme-audio.de/downloads/adi2fs_e.pdf

 

The last shows the best dynamic range with the least attenuation (the closest to wide open, i.e.the least attenuation of preceding gain).

 

I'll quit.  The Liverpool game is about to start. :)

 

My implication throughout this thread is that there are things worth considering, but should be approached as fun.

 

Bill

 

 

I did not put any word in your mouth. I said that 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. My comment was a respond to your “How many angels can dance on the head of a pin?” How many angels can dance on the head of a pin? is a figure of speech, which implies that it is wasting time debating topics of no practical value, or questions whose answers hold no intellectual consequence.

 

https://en.wikipedia.org/wiki/How_many_angels_can_dance_on_the_head_of_a_pin%3F

 

Only you know why you have wrote so much about the gain stage in amps and preamps then the topic is about 2v or 6v output voltage transmission into a tube pre-amp. To me it’s clear that you are confusing the difference between output voltages and how much gain an amplifier or DAC has internal. That some amps may have a gain stage with too much gain has nothing to do with how strong the transmission signal should be between two devices. Anyway, in most modern High End amps we can select how much gain it should “use”, so that we chose/match which we like best depending on system and gear.

 

TDLR In both praxis and theory a higher voltage line level signal will suffer less loss in transmission, and be less subject to degradation by interconnect quality and airborne noise. How much gain an amp has is another subject and lowering the output transmission voltage won't fix the problem of too much internal gain, because you will also lower the audio signal.