Benchmark AHB2 in Mono Block Configuration

Recent info from Benchmark Support   

No worries with the AHB2. In mono, it will drive down to 1Ohm. Into 6Ohms, the bridged AHB2 will output 480 watts.The input impedance whether stereo or mono is 50kOhms The amp will draw up to 8 amps. 
Also the specs state that distortion at all levels will be identical to Stereo mode and SNR will be 3db better in mono mode and that it will sound the same in either mode with the difference being available power in mono.   

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I hear things like this all the time. When I want to try something different, I go to my local dealer to listen. Most of the time they will let me borrow equipment. With no charge or even a deposit.

Natural sound in Framingham is great like this!

Well I plan to compare it. 

@jfrmusic I would be surprised if the MSB sounded better WITHOUT the HPA4. Does not make sense to add more gear and complicated the signal path but I always found the LA4 made DACs sound better.

@timothy_m 

Thanks for the information and your experience with the AHB2. 

@yyzsantabarbara 

My AHB2 is Silver and 3 years old. I plan to try it with my new front end when they arrive. If I decide to sell I will let you know before listing it. I will als definitely be selling my Benchmark DAC3 and possibly the HPA4 as well. I want to try the HPA4 as a pre between the MSB and the amp first. 
 

@stereo5 

Thsnks I have watched that video. Very informative. 

In my second system I went with a pair of Benchmark AHB2’s driving 93 db efficient Verity Leonore speakers with a minimum nominal impedance of 6 ohms.  These speakers retailed for $17k 15 years ago or about $25k now if adjusted for inflation.  I would not use price as the determinate since the AHB2’s are so utterly neutral and transparent to the point many people do not like them for just these qualities – what goes in is pretty much what comes out. This system’s front end is digital only – streaming and CD with a R2R DAC.  I had a single AHB2 and tried another and kept it due to the effortless presentation 380W of mono blocks yield.  If you don’t listen at loud volumes and your room is not too big, one may be plenty in both quality and quantity. My space is large.

Some food for thought.  My primary system is all tube amplification.  The frontend on this analog and digital system is 10X more expensive than the speakers, and it sounds glorious.  Is one system better (more perfect) than another? I don’t know but they are both very enjoyable in very different ways.  The point is, do not let the cost of one component be the driver of another.

Try a second AHB2 and see what you think.  Good luck!

@jfrmusic I made a decision today to buy a $10k set of headphones. Problem is I do not have $10k. However, I have a CODA #16 amp that can get me almost there money wise to buy the phones. I will be listening to phones more than the Livingroom system that has the CODA.

I have done extensive listening sessions with my Livingroom system and the CODA and AHB2. Infact, I wrote a thread about it here.

Audiogon Discussion Forum

This is what I feel needs to happen with the AHB2. It is not as strong on the bass as the CODA but on my new Yamaha NS5000 that is really not the case. On other speakers it was not as strong. I attribute that to the dips to 2 to 4 Ohm region.

The AHB2 can sound too hot on the mid and highs. I think that is an artifact of the upstream gear. I have a Benchmark DAC3B on my Livingroom system and it is too hot for the AHB2 (though not the CODA #16). A PlayBack Designs Dream DAC is a future buy and I think this solves the hotness issue. My much cheaper Musetec 005 DAC (sold) would likely also solve this issue on the Livingroom system.

When AHB2 amps are run in mono a speaker that does not dip too much into the 2 Ohm region should be used. My Yamaha NS5000 is likely one of those (I need to double check). One advantage of having monos in my setup would be that the AHB2 becomes even quieter. It also becomes louder by 4 or 6 dB at the same volume level as a single AHB2 (that is a big deal for me).

If you decided to sell your AHB2 and it is silver color give me a DM because I will likely go with monos after the headphone are sorted out. I already have silver a AHB2.

If anyone is curious this is the phone I will get.

(4) RAAL 1995 headphones, Magna and Immanis | Headphone Reviews and Discussion - Head-Fi.org

I am going to spend a few hours next week in Ventura, CA listening.

To OP

There is an excellent review on Dogogo of the Benchmark AHB2 Monoblocks.  The reviewer really loved it.  If you get a chance, check it out it may remove all your doubt. 

When one of my monoblocks (Monarchy  SM-70Pro) went out for repair, I used the single as stereo for a couple weeks and noticed quite a degraded change.  Upon return  of the second unit, it became apparent that having the monoblocks in place made everything tighten up; imagining, separation, detail... everything sounded organized and made me appreciate them together. 

Caveat, in monoblock configuration, I can also bi-wire and run balanced, to which could add to the elevated performance. 

@zlone I was looking for the remote for the Mjolnir (though I do not need one). No wonder I could not find it.

The Holo Serene may work for you. It is a bit warmer than the LA4 but has all the other sonic attributes of the LA4. 

The Mjolnir is a much better sounding unit than the Freya+. The Freya+ was a fun listen but would not have worked long term for me.

@yyzsantabarbara Thanks for info on the Mjolnir, it is tempting, but without a remote, it is a non-starter. I wonder how the Kara compares?

Note I came from a Freya+ -> Coda 07x - Benchmark LA4 progression, similar to yours. I just tried out an Ayre K-5XEMP, and it adds quite a bit of body to the sound. It is not quite a fit for me, but made me aware of another house sound.

I see some posts above on the CODA. Let me chime in on this too.

I used a Benchmark LA4 on the CODA #8 and the CODA #16. They both are good with the #16 approaching great. The #8 lacks some clarity that I like with the #16 and AHB2.

Another amp that I like more than the #8 is the Sanders Magtech. I recently heard from someone with informed knowledge on this that CODA was involved in the design of that amp. The power supply is from Sanders. This amp, which I bought from Sanders used for $4k, is even better than the #8. I think it is the top end that is better than the #8. I love the Magtech on my Magnepan LRS+. The #16 is also great on the LRS+, but I use it elsewhere.

@zlone I am currently listening to the Schitt Mjolnir preamp (from 2023) with the Sanders and the LRS+. Great sound, a bit too warm for me for long term listening, I like the Holo Serene and Benchmark LA4 for long term preamp duties. The Mjolnir is a pure Class A preamp and a very nice unit. It is a 2-channel preamp and headphone amp, though the headphone amp does not work well with my funky RAAL CA-1a phone. Do not let the price fool you.

Schiit Audio: Audio Products Designed and Built in Texas and California

Edit: I am doing some testing on my office with the Holo Serene preamp and the Schitt Mjolnir. I cued up the Isley Brothers 3+3 on both preamps and for my ears the utter neutrally and clarity of the Serene wins over the warm Class A of the Mjolnir. The only thing the Serene lacks is a balance control. If I can make my off centre seating work without the balance control I am keeping the Serene with the Sanders. A great combo.

@jfrmusic The watts are higher in mono but those watts cannot be used continuously (say 30 minutes) at 2 Ohm, which some speakers dip too. The single AHB2 can continuously drive a 2 Ohm speaker but at 190 watts (I think).

@jfrmusic

Checkout @arafiq system. He has extensive experience with Harbeth’s. He is using Vitus SS amp. Maybe he can chime in to share his experience with Vitus.

And S510’s are on another level than T/5X subs :-)

@yyzsantabarbara 

Interesting experience with the ABH2. Although I don’t understand how the mono ABH2 would fair worse than a single driving lower ohm speakers since the power is significantly higher with the mono configuration 

@azlon 

I agree and also I will most likely sell my HPA4 as the volume control on the MSB will be sufficient. 

As to tube amps. Been there not going back. 
To all: Thanks for your thoughtful responses. I appreciate it. 

Your budget is out of my league but I have been most impressed with Ayre Acoustics amps. I have compared them to Bryston and they consistently sound more grainless, transparent, and musical. This is the $12K stereo amp I am referencing. At 52lbs, it’s not a hernia machine either. VX 5-Twenty. 

I agree with others you might want to add another brand there, +1 for Coda, a #8 would be a perfect fit. Not a big fan of bridged monos, though likely not an issue with those speakers. Depending on what kind of improvement you are seeking, I would not put Benchmark or, from what I have read, Bryston, in the category of warm sounding. I am currently looking to replace my LA4 preamp, it is just too clinical and lean sounding for me. 

I’ve owned many different Harbeths including the C 7. Have you ever considered using a tube amp? The combination of both is outstanding. I am using Quicksilver 70 watt mono amps with the Harbeth HL5.  50 watts minimum is sufficient with those Harbeths!

OP, I have owned CODA amps, and previously had a Bryston 4B3. The Bryston was competent but that's not saying much IMO. CODA makes great value amps and currently I am running an S5.5 in my second system, a wonderful amp but perhaps not quite enough grunt for you unless your speakers are 88db or above.

As a few others have mentioned, given your new super-resolving source stack, don't skimp, get an amp from a next-level manufacturer like Gryphon, Esoteric, Block or T+A etcetera, otherwise you're not going to get everything your source stack has to give.

FYI I have a Gryphon Diablo 300 in my main system and it continues to wow me every time I run it - and especially when I run it HARD. It's like that girlfriend you once had way back when you were the Dude, the girl that the harder you went at it with, the louder/faster/BETTER it got.

If your speakers need a lot of power BUT are hard to drive a single AHB2 would be the way to go. Monos can sometimes be a little limp with very hard to drive speakers, such as the Thiel CS3.7. Some people with that combo like it but my experience was that when music called for a dynamic burst of power the AHB2 mono could not deliver it for the CS3.7.

My other amps handled those power demands much better. At that time my other amps were the CODA #8, KRELL DUO 175XD, and D-Sonic Class D (with Pascal module).  The KRELL and the AHB2 were my 2 fav sounding amps, but there were times when the AHB2 could not deliver.

I replaced the monos with a single AHB2 on the CS3.7 and it sounded a bit better, not a huge difference. The single AHB2 is rated for 2 Ohm while the monos can handle 2 Ohm on short bursts. At lower volume the AHB2 stereo was better on the CS3.7. 

Now my CS3.7 is a bit of an edge case and most speakers do not live in the 2 Ohm region. I currently have a 6 Ohm Yamaha NS5000 speaker that I use with a CODA #16 amp. I also have a AHB2 stereo amp that I occasionally switch too. It drives the NS5000 great. In this case, monos maybe even better since it does not go into the 2 Ohm region. I no longer have monos to test this out.

I owned a few Brystons, 4B ST, 7B SST, and the HPA-1 headphone amp. They all had a bit of hardness on top. I have not owned the 4B3 but when I heard it at a demo with Vandersteen Treo CT that hardness on top was still there but in a much-diminished capacity.

A few weeks ago, I had a friend over to hear my speakers. This guy knows his audio and is a professional in the audio business and former musician. We did a A/B test with the CODA #16 vs the AHB2 stereo. I think it was on the Stones Sympathy for the Devil track that the bass was preferred on the AHB2 over the CODA. On all the other tracks the bass was good on both.

On the Stones track my friend said the bass region was a bit confused sounding on the #16, but on the AHB2 it was perfect. I was rather shocked for 2 reasons, First the #16 is a bass monster and my prior experience with the Thiel and AHB2 did not ever consider the AHB2 to be strong on bass (accurate yes). The second thing that surprised me is that I knew my friend hated the AHB2 from his past experience. He still did not like the mid and top but I think a better DAC on my system would have solved that. The AHB2 is so revealing that any weak link in the system will stick out. The plan is for a future DAC upgrade.

For me the AHB2 mono beats Bryton as long as the speakers do not dip into the 2 Ohm region a lot.

The difficulty for me concerning many desirable Amps is many are very large and very heavy. Not sure if can handle a 75-80 pound amp by myself. Getting it home and setting it up. The Brystons are reasonable in weight. And of course the Benchmark is a feather weight.

I wouldn’t necessarily categorize the Benchmark as a level below something like Bryston just because it is cheaper.  One way to look at it is those accurate electronics (I.e. Benchmark) will allow all the goodness from your front end to come through.  In all actuality, at that point the speakers would probably become the limiting factor.  But that’s ok if you like them - Harbeth can be magical for sure.  But as for the amps, I’ve owned both AHB2 monos and Bryston 2.5B3 Monos. The Bryston has a bit of a bump in the bottom end, whereas the Benchmarks are very flat. The Bryston has excellent bass, but also a bit more emphasis in that mid bass area. Again, you’d have to try it, but given the sound profile of Harbeth speakers which are slightly warm, I believe the Benchmark will be more synergistic.

@jfrmusic 

You made the right decision on source equipment (end-game)! Now, you just need to put the icing on the cake. I would audition as many amps as you can, and don't just limit yourself to Bryston.

@jfrmusic I know what I would do.  I would order the 2nd AHB2 and compare it to your single amp and see if you can tell a difference.  I would also get a home demo of the Bryston and demo it against the single and dual AHB2.   That is a perfect comparison scenario.  You may find that a single AHB2 is all you need or pick one of the other two options.

Have you adjusted the gain switch on the back of your AHB2 and can you tell a difference other than volume?  I think the middle position sounds the best - fuller with more body (even when adjusted to the same general volume) - than the lowest gain position.  I have read that technically it should sound the same so maybe it is just in my head.   

@jeffreyw 

I was conflicted about spending that much on the front end but I sounded so great. I remember from my old analog days not paying enough for the front end.  Once I committed to a Linn Turntable and Arm and Koetsu cartridge I was finally satisfied. I didn’t want to go through the endless upgrade path. Plus at my age time is a consideration. 

@audphile1 

sorry Coda and Luxman 

@audphile1 

I will check out Coda and Kidman. And thanks for suggesting the Harbeth forum. 
 

@jeffreyw 

Yes the Benchmark doesn’t match the quality of the new front end. That’s why I’m looking for an alternative. 
 

@12many 

My dealer carries Bryston. He has all the equipment I purchased so I can demo the exact combination in the showroom or borrow the Bryston for a few days. He doesn’t carry Benchmark. I just got the Harbeths and really like them. So they’re staying. 

You can easily try the AHB2 with the option to return. Is there anyway to demo the Bryston with an option to return it? Even if this cost a few hundred for the trial, it would be worth it. Ideally, you would have both for a week or so and then decide for yourself. I don’t think you will know how they sound to your ear, in your system, and your room unless your try them both. I have an AHB2 and have read many reviews and you might like either one better. The 4B3 is about $7500 and two AHB2 are $7000 so the reality is they are about the same retail price. At the end of the day, both are detailed SS amps with a great reputation so either way it will sound great. Please keep us posted because I may be making a similar decision some day.  

Given what you spent on the front end, are you going to change your speakers as well?

@jfrmusic 

You have insane source equipment roughly $26K retail. However, you're feeding this signal into a $3500 amp. This is a big system imbalance no matter how good the perception of the Benchmark is (yes, it plays well above its price). I would not scrimp on a new amplifier, considering it appears you have a healthy budget.

The world of audio amplifiers is your oyster. Give the source components a chance to sing!

@jfrmusic btw worth exploring what folks use with this level of digital and your speakers on a Harbeth forum. 

@jfrmusic Luxman and CODA are known to have great synergy with Harbeths. Take a look at their integrated amps and even separates. I would definitely not add another Benchmark. It’s not going to be on the level of your digital front end.

@lalitk 

I had dual REL T/5X subs but could not get them to integrate to my satisfaction with the Harbeths. The T Series RELs are really low end re enforcement rather than deep below 30 hz subs unless you move up to their bigger units. I liked the low end of the Harbeths which are -3db at 45 hz and my frequency analyzer shows output below 35hz. The RELs we’re just doubling up the natural low end of the Harbeths and it had a negative effect on soundstage and openness. 

Edit…sorry, I meant your Harbeth C7s, not SHL5s.

@jfrmusic 

I glanced at Harbeth C7es-XD specs, doesn’t look like they need whole lot of watts to drive them. I think you will get much better result with adding dual subs (like REL S510’s) over mono blocks. 

Some people have done the bridging and liked it a lot while others have not. This tells me that it's system dependent. With the number of AHB2 amps that come up, and go on the used market, it would be very easy to try it yourself. That's the only way to know for sure. I know... everyone says that, but this time it's so very true.

So you went with the N20 ?  Nice!  That’s quite a digital front end combination with the MSB.  I had Harbeth M40.2 paired with the AHB2 monoblocks.  It was by far the best amplification synergy I had with those speakers.  I preferred them to a stereo Luxman M900u.  Since you already have one, you know how it sounds and whether you like the sound.  Adding another one may or may not change the sound.  The M40s can use that extra power.  Adding a second one did improve the sound IME.  Bass became tighter and everything more focused.  I’m not sure about the SHLs.  I think you’d just have to try it to see for yourself.