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Tube Preamp for Benchmark AHB2 or Class D/SS Poweramp?

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Chris-E

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You really need a voltmeter. The changes you are looking for are so much smaller than a few dB. And your ear is so affected by volume and perception that you are lost before you started!

Consider first the fact that time and time again, experts from the subjective and the objective side of things routinely fail to hear the differences between amps. My favorite is the 1987 study involving Futterman, Levinson, etc. plus a pioneer receiver, see page 78 (but enjoy the rest of the old mag...;)):
https://americanradiohistory.com/Archive-HiFI-Stereo/80s/HiFi-Stereo-Review-1987-01.pdf
The experiment was certainly level-matched. Nobody could tell the difference. I worked in a store that sold Levinson amps at the time, to be honest I wasn't surprised. This happens over and over, when it comes time to listening without peeking, nobody can tell. Even when they can, it is found that the amps are severely frequency response mismatched, or level mismatched, or not properly functioning. There is an AES article on it, it is behind a paywall since it is a journal publication, it is referenced here. Even Benchmark creates a FUD when they talk about crossover distortion, where they cite a severely broken amp to make their case. And, to be clear, Benchmark makes SOTA amp, no doubt they pair them with a SOTA marketing department:cool:.

And as far as electronic interactions, preamps seem way less likely to have a sound signature, unless they are broken or oddballs. And since many of our industry's esteemed experts (including staunch subjectivists who believe in all sorts odd and very expensive purchases) have already tried and failed to tell amps apart, hard to imagine subtle differences in preamps making a difference. I can tell you my SFL-3 only had a sonic signature when a tube was going bad. Aside from the volume control upgrade which addressed a noise issue, it was just a preamp. I couldn't tell the difference between the SFL-3 and a Bryston, Apt, Yamaha, or any other preamp for that matter, nor could anybody in their right mind.

You should also get a UMIK or other measurement microphone and get comfortable making measurements in your room. You will quickly learn that speaker placement is important, and the type of preamp just doesn't matter. Unless you use the PEQ on the RME, which is also makes a dramatic difference in the sound and how you can mange your room and the impact it has in changing the sound.
Thank you so much for taking the time to write these insightful and well-meaning paragraphs!
The UMIK-1 is on top of my shopping list, and it seems like I have just added a voltmeter. ;-)
Thanks you also for sharing the link to the blind test paper. I am by no means an expert in audio engineering, and these are all great opportunities to learn. I don't consider myself to be either an ideological objectivist or subjectivist. I'll see if a more accurate levelling of both signal paths makes it easier to confirm some of the findings from my ad-hoc listening session earlier today...
 

Blumlein 88

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Well, I own both versions, and have never heard any crosstalk at all. Then here is the measurements by Amir where the crosstalk measurement was identical to the AP analyzer. I've also measured it and can find none. The other version which Vintage Flanker measured has only the tiniest amount like well below -100 db which you'll never hear. I don't know about the person in that other thread, but I wonder if the cross talk was from interaction of the other devices.

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MAB

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Thank you so much for taking the time to write these insightful and well-meaning paragraphs!
The UMIK-1 is on top of my shopping list, and it seems like I have just added a voltmeter. ;-)
Thanks you also for sharing the link to the blind test paper. I am by no means an expert in audio engineering, and these are all great opportunities to learn. I don't consider myself to be either an ideological objectivist or subjectivist. I'll see if a more accurate levelling of both signal paths makes it easier to confirm some of the findings from my ad-hoc listening session earlier today...
Appreciate your participation here!
A nice measurement mic is a revelation, mostly about our room, secondarily about speakers and setup in the room. And lots of humbling lessons on how to make good measurements, not introducing systematic issues like inadvertently changing setup, or levels, etc.

I have way too much classic gear, enjoy gear with a range of artifacts, and enjoy too many live shows under non-ideal listening circumstances to call myself strict. But I never realized how much predicting our ears do and how poor they are at actually measuring differences. And how good our brain is at augmenting what we thought we heard. It's like we actively want to hear things that aren't there. Lots of that discussion occurs here as well. The science of how we actually hear explains the money vortex that consumes part of high end audio. You actually have a great starting point since your RME DAC/Pre and Benchmark amp are stone-cold noise and distortion free.
 
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Chris-E

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Well, I own both versions, and have never heard any crosstalk at all. Then here is the measurements by Amir where the crosstalk measurement was identical to the AP analyzer. I've also measured it and can find none. The other version which Vintage Flanker measured has only the tiniest amount like well below -100 db which you'll never hear. I don't know about the person in that other thread, but I wonder if the cross talk was from interaction of the other devices.

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That's reassuring that you've never had crosstalk issues with the Douk devices. From this other user's experience I feared it could be an issue in my setup, because the ADI-2 doesn't allow for selectively muting of either the XLR or RCA line outs. It's either both on or both off. Crosstalk could have been an issue then when going RCA via the tube preamp, while the (higher output level) XLR output can't be muted and both signals run into the switch. In the end I went with the Heritage Audio as it's rated at min -100db channel separation and adds in the flexibility of switchable 2in/2out and a stepped attenuator...
 
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Chris-E

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Appreciate your participation here!
A nice measurement mic is a revelation, mostly about our room, secondarily about speakers and setup in the room. And lots of humbling lessons on how to make good measurements, not introducing systematic issues like inadvertently changing setup, or levels, etc.

I have way too much classic gear, enjoy gear with a range of artifacts, and enjoy too many live shows under non-ideal listening circumstances to call myself strict. But I never realized how much predicting our ears do and how poor they are at actually measuring differences. And how good our brain is at augmenting what we thought we heard. It's like we actively want to hear things that aren't there. Lots of that discussion occurs here as well. The science of how we actually hear explains the money vortex that consumes part of high end audio. You actually have a great starting point since your RME DAC/Pre and Benchmark amp are stone-cold noise and distortion free.

Thank you for your kind words!

Being curious about how we as humans only ever have mediated access to what some may call an 'objective reality' out there, and what this means for how we perceive the world and make sense of it, is a pretty accurate description of my day job. That's why I don't question the importance of measurements and quantifiable/reproducible data, and I applaud robust methodologies that serve their intended purpose. In my view, striving for perfection and accuracy in reproduction is essential to establish a point of reference against which other sonic experiences can be compared and evaluated. Hence me getting the RME and Benchmark after years of casual ASR readership. It's a bit like the pianist who spends years and years mastering technique and interpretation through classical training, and then decides to start improvising, bending the rules, ending up as a jazz virtuoso.... Maybe a bit stretched, but I first wanted to build a setup that's getting the basics right. And then branch out exploring some of the deviations... :)

Room measuring, eq correction, and acoustic treatment with absorbers/diffusors etc. is one of the next rabbit holes I see myself jumping into... Just one step at a time... :) But yes, I all agree with all you're saying there...

Also, I just went through the multimeter measuring / levelling threads on ASR as per both your suggestion. Do I get this right that a device such as this (https://kaiweets.com/en-gb/products/kaiweets-km601s-10000-counts-rechargeable-smart-multimeter) would be sufficient for my needs? The manual states frequency response 40Hz - 1kHz, T-RMS. Practically, I would use, for example, a 1kHz or 500Hz sine wave as audio input and measure and level-match the voltage in both signal chains at the XLR cable feeding the Benchmark power amp? Once levelled, I could still control the volume in both chains via the RME's digital volume control (as this would equally impact both line outs), or via the stepped attenuator on the Baby RAM...? Or am I making a mistake here?
 
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SIY

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Thank you for your kind words!

Being curious about how we as humans only ever have mediated access to what some may call an 'objective reality' out there, and what this means for how we perceive the world and make sense of it, is a pretty accurate description of my day job. That's why I don't question the importance of measurements and quantifiable/reproducible data, and I applaud robust methodologies that serve their intended purpose. In my view, striving for perfection and accuracy in reproduction is essential to establish a point of reference against which other sonic experiences can be compared and evaluated. Hence me getting the RME and Benchmark after years of casual ASR readership. It's a bit like the pianist who spends years and years mastering technique and interpretation through classical training, and then decides to start improvising, bending the rules, ending up as a jazz virtuoso.... Maybe a bit stretched, but I first wanted to build a setup that's getting the basics right. And then branch out exploring some of the deviations... :)

Room measuring, eq correction, and acoustic treatment with absorbers/diffusors etc. is one of the next rabbit holes I see myself jumping into... Just one step at a time... :) But yes, I all agree with all you're saying there...

Also, I just went through the multimeter measuring / levelling threads on ASR as per both your suggestion. Do I get this right that a device such as this (https://kaiweets.com/en-gb/products/kaiweets-km601s-10000-counts-rechargeable-smart-multimeter) would be sufficient for my needs? The manual states frequency response 40Hz - 1kHz, T-RMS. Practically, I would use, for example, a 1kHz or 500Hz sine wave as audio input and measure and level-match the voltage in both signal chains at the XLR cable feeding the Benchmark power amp? Once levelled, I could still control the volume in both chains via the RME's digital volume control (as this would equally impact both line outs), or via the stepped attenuator on the Baby RAM...? Or am I making a mistake here?
That's even more than you need.

A tone at some tolerable frequency or level is fine. Ditto pink noise (the meter's response doesn't matter).
 
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