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

[SIY]

I spent some time with their 6SN7 preamp. I thought it was pretty dandy, actually.
No experience with their power amps.
There are currently several opportunities to purchase clones (true clones) and updated variants of the venerable Dynaco power amps of yore. They're worthy of consideration. There's also a cottage industry of improvements to the original designs' rougher edges. Not sure I have a specific recommendation.

The problem is that I like to ask the loudspeakers to do most of the work, not the amplifiers. That approach has been unfashionable since at least the late 1950s.

Perhaps it's worth invoking the name of @SIY in the context of a request for recommendations.
I am not sure that he can be summoned like Beetlejuice -- but it's worth a go!

You rang?

Unfortunately, I’m unfamiliar with these units. This stuff comes and goes… if it is starved plate, you’ll get a very blurry and sometimes harsh sound, which indicates how much distortion they generate.

Coloration by software is a lot easier.

 

[mhardy6647]

You rang?

Unfortunately, I’m unfamiliar with these units. This stuff comes and goes… if it is starved plate, you’ll get a very blurry and sometimes harsh sound, which indicates how much distortion they generate.

Coloration by software is a lot easier.

I actually dropped your name because I thought if anyone had a good, contemporary suggestion for a vacuum tube power or pre amplifier, it would be you!

 

[Chris-E]

I'm surprised by some responses here. I've said my philosophy is put together the best most transparent system you can and flavor to taste if you wish. I don't see the originator of this thread doing anything else. There is no sacrilege of using a Benchmark and having fun with it by some tasteful coloration. How is that different than listening to old recordings made with the old tube gear and the various deficiencies inherent to them?

Thank you for the kind words!

Indeed, I was hoping to make it clear in my original post that I do appreciate, respect, and indeed share the ideal of accurate reproduction and transparency myself. Otherwise I wouldn't have built the audio system I am listening to as I type these lines. I just don't consider it blasphemy to deviate from this ideal every once in a while in search of new ways to rediscover one's favourite music. By the way, given this is ASR: those who consider (random or systematic) experimentation, trial and error, and serendipity as unscientific may not have the most nuanced understanding of science...

I fully respect the research, engineering, expertise that went into a product like the AHB2. But arguing that it is somehow more acceptable to fool around with a "lesser" (profane) amp than with the (sacred) Benchmark ascribes an almost spiritual iconicism to the AHB2 that cannot reasonably explained within the realm of physics and engineering alone. Is there maybe a danger that we (very subjectively and unscientifically) elevate an earthly product of (arguably excellent) engineering into the realm of the supernatural, and then infer normative conclusions about what we consider as un/acceptable with regard to the AHB2? That wouldn't be much better than any other audio myth, would it?

Too much serious reasoning for what I had originally intended with this thread... So... back to tubes and the ABH2?

 

[Daverz]

It's a fairly dumb thing to do, but one thing no one has mentioned yet. Tube preamps like to drive tube power amps because they have high input impedance. Solid state power amps have much lower input impedance than tube power amps. And tube preamps have higher output impedance than solid state preamps. So you could end up with an impedance miss match.

The ABH2 has an input impedance of 50kOhm, so it should be fine with most tube pres.

That said, if the OP is having a problem with lots of favorite recordings being unpleasant to listen to, I don't think adding tubes is going to help much.

 

[Chris-E]

Incorporating Benchmark gear is actually the best way to discover if you like the occasional alteration or distortion because you have a true reference. Or better stated, it helps you identify the scenarios where distortion surprisingly enhances the experience.

Thank you for this! That's exactly why I built my system the way I did. To have a core of rock solid reference components and then get playful (or not) at a later point if and when desired. You wouldn't have similar degrees of freedom to experiment when building a system on a sounded power amp in the first place...

 

[Chris-E]

Just because you appreciate fine dining doesn't mean that you can't also appreciate In-N-Out burger sometimes.

Apologies, Five Guys over In-N-Out here... Guilty of yet another taste abomination. Just irony.... ;-)

 

[Chris-E]

You rang?

Unfortunately, I’m unfamiliar with these units. This stuff comes and goes… if it is starved plate, you’ll get a very blurry and sometimes harsh sound, which indicates how much distortion they generate.

Coloration by software is a lot easier.

Maybe there is a market for distortion plugins for the RPi that integrates with Volumio and Moode? Should have enough CPU power, no?

 

[Chris-E]

The ABH2 has an input impedance of 50kOhm, so it should be fine with most tube pres.

That said, if the OP is having a problem with lots of favorite recordings being unpleasant to listen to, I don't think adding tubes is going to help much.

Yes, the two preamps I had considered before starting this thread (Freya+, MP 701-MK2) should be unproblematic. The Schiit for sure, and the MP specs ask for power amp imp of >=10kOhm.

It's not lots, but there's quite a few commercial Tier 2/3 Euro-Pop from the 90s (don't blame me - just grew up with that stuff) that suffer from bloated, 'mushy mids' from overlapping instruments and hyper-compression that results in sharp treble. That's completely absent in, for example, Michael Jackson, George Michael, any recordings by Decca, Deutsche Grammophon.... etc... So I'm confident that it's the mix/mastering rather than my setup per-se...

 

[Chris-E]

A heartfelt Thank You! to everyone who has contributed to this thread so far, and as such has donated some of their time and expertise to this discussion! What a vibrant community! I couldn't have wished for a (tube-like) warmer welcome to ASR! I'm overwhelmed by the quantity and quality of feedback received, and it will likely take me a couple of days to follow up on the various leads and recommendations. I'm looking forward to seeing this thread developing further, and I will definitely keep you posted as my experiments take shape. For now this AHB2 is safe in a pet-free, smoke-free, and tube-free household!

 

[Daverz]

It's not lots, but there's quite a few commercial Tier 2/3 Euro-Pop from the 90s (don't blame me - just grew up with that stuff) that suffer from bloated, 'mushy mids' from overlapping instruments and hyper-compression that results in sharp treble.

I would experiment with the EQ features in your RME DAC.

 

[MaxBuck]

Just because you appreciate fine dining doesn't mean that you can't also appreciate In-N-Out burger sometimes. Even if 99% of the time, high-fidelity with something like the Benchmark AHB2 and true faithfulness to the source material is the way to go, if the OP occasionally likes fast food, even though people like to say the DSP works -- it's much easier to plop in something like a Schiit Freya+/Freya N into the chain.

Incorporating Benchmark gear is actually the best way to discover if you like the occasional alteration or distortion because you have a true reference. Or better stated, it helps you identify the scenarios where distortion surprisingly enhances the experience.

I guess. Still seems peculiar to me, but each to his own.

 

[Chris-E]

After this helpful and lively discussion I've decided to go ahead and give the Musical Paradise MP701-MK2 a go. The unit arrived today, and live A/B switching between signal paths works flawlessly as intended. Cable management still needs improvement. But very first impressions suggest this is going to be an interesting weekend of listening...

 

[MAB]

Yes, played with the EQ and Loudness. Neat features. RME now has a computer/iPad based "remote" app for the ADIs. Full control of the EQ and DSP... View attachment 330458

I have an RME ADI-2, it is a great DAC. The PEQ is awesome. The performance is also incredible. I mostly use if for headphones, but it is a great preamp. The pro model has analog input if you need that.

Regarding tube preamps, I have had many. Not many modern tube preamps are appropriate, the only one I would consider for your situation is a Sonic Frontiers. Line 3 if you really want. I had mine upgraded by Chris Johnson. The volume control upgrade was a good move, the coupling cap upgrade was pure waste of money though, and cost more than the volume control. I see you are enticed by tube rolling and even capacitor rolling! That's an incredible waste of time, bigger waste of money, for no audible.

I personally would avoid tubes. I still have several lying around. An old McIntosh MC-30 and C-8 that are part of a console. The SFL-3 sounds as close to neutral as any, which is why it is about the only one I would consider. The tube sound is a fantasy in any case, all that even order harmonic distortion is not actually their sonic signature. People grasp for straws trying to describe the sound of their tube gear when 99% of the perceived sound is in their head, fully imagined. Wait until you think you might have a tube gone bad...

Get the RME DAC. If you want warmer or different sound, use the PEQ. If you really think you crave even order tube distortion, or some sort of tube-like EQ, or tube-like compression profile that you imagine they have, get a DSP plugin. It's way more effective and actually has flexibility to create a personal taste.

 

[MAB]

After this helpful and lively discussion I've decided to go ahead and give the Musical Paradise MP701-MK2 a go. The unit arrived today, and live A/B switching between signal paths works flawlessly as intended. Cable management still needs improvement. But very first impressions suggest this is going to be an interesting weekend of listening...

View attachment 332561

I see!

 

[Chris-E]

I have an RME ADI-2, it is a great DAC. The PEQ is awesome. The performance is also incredible. I mostly use if for headphones, but it is a great preamp. The pro model has analog input if you need that.

Regarding tube preamps, I have had many. Not many modern tube preamps are appropriate, the only one I would consider for your situation is a Sonic Frontiers. Line 3 if you really want. I had mine upgraded by Chris Johnson. The volume control upgrade was a good move, the coupling cap upgrade was pure waste of money though, and cost more than the volume control. I see you are enticed by tube rolling and even capacitor rolling! That's an incredible waste of time, bigger waste of money, for no audible.

I personally would avoid tubes. I still have several lying around. An old McIntosh MC-30 and C-8 that are part of a console. The SFL-3 sounds as close to neutral as any, which is why it is about the only one I would consider. The tube sound is a fantasy in any case, all that even order harmonic distortion is not actually their sonic signature. People grasp for straws trying to describe the sound of their tube gear when 99% of the perceived sound is in their head, fully imagined. Wait until you think you might have a tube gone bad...

Get the RME DAC. If you want warmer or different sound, use the PEQ. If you really think you crave even order tube distortion, or some sort of tube-like EQ, or tube-like compression profile that you imagine they have, get a DSP plugin. It's way more effective and actually has flexibility to create a personal taste.

Thank you for the recommendations. The MP has only arrived today, so I am just getting started A/B'ing the RME's output via the MP vs. directly into the Benchmark. Differences are subtle but noticeable. I have been a bit weary of the noise floor the MP would introduce. Thankfully that doesn't seem to be a practical issue at all when not keeping one's ear glued to the tweeter when no music's playing. From my listening position the noise of the MP is inaudible. Arguably, of course, the direct chain RME --> AHB2 is dead quiet.

 

[Blumlein 88]

Thank you for the recommendations. The MP has only arrived today, so I am just getting started A/B'ing the RME's output via the MP vs. directly into the Benchmark. Differences are subtle but noticeable. I have been a bit weary of the noise floor the MP would introduce. Thankfully that doesn't seem to be a practical issue at all when not keeping one's ear glued to the tweeter when no music's playing. From my listening position the noise of the MP is inaudible. Arguably, of course, the direct chain RME --> AHB2 is dead quiet.

Are you keeping levels matched as you do this comparing of Benchmark and MP?

 

[Chris-E]

Are you keeping levels matched as you do this comparing of Benchmark and MP?

Yes... I know that there'll be comments coming that level matching is only possible when measuring them... and I agree... In the absence of measuring equipment I've matched them 'by ear'. I know, not optimal... But levels are definitely within 3db... I'd rather say prob. 1-2db... There's no audible drop in level when I switch...
So my 'poor man's methodology' as of now is to adjust the level via the MP's attenuator to match the XLR output of the RME that goes directly into the BM. Then I control the volume for both channels via the RME's digital volume control. Having good results switching level-neutral and there's no clicking or signal bleeding / crosstalk (unlike with some of the Douk / Nob XLR-switchers reviewed on ASR.

 

[Blumlein 88]

Yes... I know that there'll be comments coming that level matching is only possible when measuring them... and I agree... In the absence of measuring equipment I've matched them 'by ear'. I know, not optimal... But levels are definitely within 3db... I'd rather say prob. 1-2db... There's no audible drop in level when I switch...
So my 'poor man's methodology' as of now is to adjust the level via the MP's attenuator to match the XLR output of the RME that goes directly into the BM. Then I control the volume for both channels via the RME's digital volume control. Having good results switching level-neutral and there's no clicking or signal bleeding / crosstalk (unlike with some of the Douk / Nob XLR-switchers reviewed on ASR.

I'm going to be blunt. Trying not to be rude. You are wasting your time. You'll come to some conclusions, and they'll mean nothing other than how you come to feel with conviction about the differences you've heard.

How is it necessary to use a "poor man's methodology"? You've spent pretty big money on each piece of gear, but cannot afford a small amount for a basic voltmeter? You'll waste hours of your time or at least a weekend to come to conclusions with no merit at all rather run by a hardware store and purchase an inexpensive voltmeter? Oh, and the Douk/Nob switchers, they don't have any appreciable crosstalk.

If you didn't know, then you didn't know. However, you do know. Why proceed with a process that you know has no chance of any meaning or any useful results?

 

[MAB]

Yes... I know that there'll be comments coming that level matching is only possible when measuring them... and I agree... In the absence of measuring equipment I've matched them 'by ear'. I know, not optimal... But levels are definitely within 3db... I'd rather say prob. 1-2db... There's no audible drop in level when I switch...
So my 'poor man's methodology' as of now is to adjust the level via the MP's attenuator to match the XLR output of the RME that goes directly into the BM. Then I control the volume for both channels via the RME's digital volume control. Having good results switching level-neutral and there's no clicking or signal bleeding / crosstalk (unlike with some of the Douk / Nob XLR-switchers reviewed on ASR.

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.

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.

 

[Chris-E]

I'm going to be blunt. Trying not to be rude. You are wasting your time. You'll come to some conclusions, and they'll mean nothing other than how you come to feel with conviction about the differences you've heard.

How is it necessary to use a "poor man's methodology"? You've spent pretty big money on each piece of gear, but cannot afford a small amount for a basic voltmeter? You'll waste hours of your time or at least a weekend to come to conclusions with no merit at all rather run by a hardware store and purchase an inexpensive voltmeter? Oh, and the Douk/Nob switchers, they don't have any appreciable crosstalk.

If you didn't know, then you didn't know. However, you do know. Why proceed with a process that you know has no chance of any meaning or any useful results?

Apologies, I have misread your question as you being interested in my ad-hoc subjective listening impressions comparing both signal paths.
The "poor man's methodology" was meant as a figure of speech, referring to a quick and dirty approximation of output levels. I will look into the volt meter option for sure, and thank you for suggesting that. Even better that it's affordable!
Regarding your other points: I wouldn't consider this initial and not strictly goal-driven experimentation with the new preamp as wasting time. Indeed, one could argue that the playful deviation form the imperative of rationality and the pressure to arrive at "useful" and "meaningful" results is a constitutive feature of what we would call a "hobby". My point of departure for this thread was that I wanted to experiment with placing a tube component into my signal chain to subjectively explore its impact on my perception and evaluation of its sonic outcomes. I know that this will not result in an objectively more accurate reproduction of the source material.
Also, I don't read your comments as rude at all. I understand that you seem to care deeply about your suggestions, and how a comparison between both signal paths should to be done. As such, I appreciate your expertise and guidance along my journey!