An Amplifier Change for my Wilson Sophia 2's?

I have an Audio Research VT100 Mk II with 100 watts of tube power driving my newly acquired Wilson Sophia 2 speakers.  The sound is lovely, and the specs seem to be fine, but I do have to crank the preamp pretty high to get relatively loud music, especially when playing analog.  It got me to thinking that maybe these speakers would be better served by a lot more power.  

If I were to make a move here, I would be looking for a price neutral move.  That means selling (or trading) my amp for its market value (about $2300) and purchasing something at the same price.  

My initial research pointed to Bryston power amps, either an older one from the family of 4B Setreo amps or 7B mono blocks.  Either would deliver more than 500 watts into 4 ohms.

Would this much power make a large difference in the performance of the Wilsons?
Where is the gain set on your phono stage? The gain on your Whest will go up to 72 db which is more than enough for your cartridge. I think 60 db would be about the right setting. Maybe you just need more gain from your phono stage.

Increasing from 100 watts to 400 watts would give another 6 db of volume. Doubling the watts equals a 3 db volume increase. A volume increase of 10 db would sound twice as loud twice as loud.
My Whest is set to 60db (or 55, I'll have to double check).

The Bryston 7B-ST mono blocks provide 800 watts into 4 ohms - so that would be a 9db increase.  That seems very significant.  would that kind of power add more control and authority over the wilson's making them perform better than the ARC 100 tube watts?  Would my ARC tube line stage work well with the Brystons?

You've asked this before in a number of different ways.  Do you expect different responses now?
a Bryston power amp is a sonic match. You can go back as far as 3B model. These power amps have a magical synergy w/ an ARC Ref5 SE pre-amp.
Hi Mark,

I can’t comment on how much amplifier power is likely to be optimal with your particular speakers, or on which amplifiers are likely to be particularly synergistic from a sonic standpoint.

But I agree with JPerry’s comments, to which I’ll add the following thoughts:

1)The two considerations referred to in my first paragraph figure to be inter-related, such that more or less power may be optimal depending on the design and sonic character of the particular amplifier.

2)The amplifier’s effects on volume control position depend on its gain, not on its power capability. There are many amplifiers that provide a combination of relatively high gain and relatively low power capability, and vice versa, although in general there tends to be a **loose** correlation between gain and power capability.

3)How much power is required is often determined by the dynamic range of the music that is listened to. In most circumstances not a great deal of power is required for most recordings, at least most of the time. But on recordings having a particularly great difference in volume between the loudest notes and the softest notes, such as some well engineered minimally compressed classical symphonic recordings, enormously greater power capability can be required to support their brief dynamic peaks than under most other circumstances, and at most other times during those same recordings.

Good luck. Regards,
-- Al


before the issue was volume and noise with the phono stage.  Now that I changed my speakers, my question is about the amplifier speaker match.

Very interesting.  So if an amp i choose has more gain, that could be a benefit for the volume issues I have spoken about before.  And if the amp also has more wattage, it can control the speaker better and perhaps provide a better sound with high dynamic range music?

I am noticing that in order to really hear all of the music, I do have to go fairly loud.  Would the increase of wattage of the amplifier allow me to hear the music better at lower volumes as well?

If the issue appears more with analog, you should experiment by increasing the gain on the phono pre even if it's already at 60 or 65db.

Hopefully you have a decent sound meter. If not, a free smartphone app will work for music that's midrange-centric, but the crappy mics in most phones can't capture low freq. at all (Since phone mics are optimized to capture your speaking voice). When you play music to compare the gain settings on the phone stage be sure to listen at the same volume according to the sound meter. Don't fixate on the volume knob on your preamp. Without an equal volume comparison, nothing else matters.
After you do that, report back at what volume you typically listen at. 

Even at a not super-efficient 89db, the Sophias should get plenty of power from your amp. Have you heard Sophias elsewhere with a different amp that sound more like you expected? If so, please describe.

So if an amp i choose has more gain, that could be a benefit for the volume issues I have spoken about before.
It would lower the setting of the volume control that you would use to achieve a given volume level, everything else being equal.
And if the amp also has more wattage, it can control the speaker better ...?
Not necessarily.  That depends on several different characteristics of both the amp and the speaker, including amplifier damping factor and output impedance, how much damping is optimal for the particular speaker, how the speaker's impedance varies over the frequency range, the robustness of the amp's power supply, etc.  The bottom line is that it's hard to predict.
And if the amp also has more wattage, it can ... perhaps provide a better sound with high dynamic range music?
Stereophile measured the sensitivity of the Sophia 2 as being 88.3 db/2.83 volts/1 meter.  For its 4 ohm nominal impedance that corresponds to 85.3 db/1 watt/1 meter.  Neglecting room effects an amplifier capable of providing 100 watts into 4 ohms should be capable of driving a pair of speakers having that efficiency to a maximum SPL of about 99 db at a typical listening distance of around 10 feet.  That will be adequate for the great majority of recordings for the great majority of listeners. 

I for one happen to be among those for whom that kind of maximum volume capability would be inadequate, though.  I have a lot of classical symphonic recordings on audiophile-oriented labels such as Telarc, Reference Recordings, Sheffield Labs, etc., that have been subjected to minimal or no compression, and can reach 100 to 105 db at my listening position, on brief dynamic peaks, while being listened to at average levels of perhaps 75 db.
Would the increase of wattage of the amplifier allow me to hear the music better at lower volumes as well?
Again, it's hard to predict, and from a subjective standpoint it may depend on how the distortion characteristics of the particular amplifier vary as a function of the amount of power it is putting out.

All I can add at this point is that if you already haven't it may be worthwhile to research the Audiogon Virtual Systems to see what amps others have used with the Sophias.

One final point:  As with many ARC line stages and preamps, ARC recommends 20K as the **minimum** load impedance that should be presented to the LS25.  Keep that in mind in considering other amplifiers.

Best regards,
-- Al

Once Bob Carver created best amp: Sunfire Sig 600. It’s load invariant and can be used as welding machine as well(hey if needed).

It drives ANY speaker of ANY size super clean.

How about 1.2kW into 4 Ohms would sound like? I heard these speakers with Electrocompaniet AW 250/TaCT RCS2 preamp and the sound was ’hiding’ inside the box with no imaging whatsoever.

After they’ve been connected to this relatively light powerhouse mentioned above (hey, substantially lighter than Electrocompaniet), They started to open and showing soundstaging capabilities.

Using VT100 on Wilson Sophia speaker is similar to using Honda 1.5L engine on FreightLiner trucks. This is having in mind that you have ARC line stage with pretty high gain on the first place. 

wow, I guess you are saying My Sophia's are underpowered!  Obviously there are loads of opinions on this, but I am gravitating towards this opinion as well.  I called Wilson yesterday and spoke to one of the tech guys there.  He told me that Wilsons in general react very well to high powered amplifiers.

i think it's time for me to learn more about amplifiers. For starters I need to better understand the relationship between gain and wattage.

thanks for the input.

Hi Mark,

Regarding the relationship between gain and wattage, as I mentioned there tends in general to be a loose correlation, but one that is so loose that it is typically of no usefulness.

As you’ve probably found, the gain of both integrated amplifiers and power amplifiers is very often not specified. If Stereophile has reviewed the product the measurements section of the review will usually indicate the measured gain. In other cases the gain can be calculated to a reasonable approximation from the specified maximum output power and the specified sensitivity (the input voltage that is required to drive the amp to the specified maximum output power), as follows:

Gain is the ratio of output voltage to input voltage, expressed in db.

The ratio of two voltages, V1 and V2, are converted to db based on the formula (20 x logarithm(V1/V2)).

The rated maximum output power into 8 ohms (or 4 ohms) can be converted into voltage based on the equation P = (Vsquared)/R, where P is power in watts, V is volts, and R is resistance in ohms.

So for example in the case of an amplifier rated at 200 watts into 8 ohms and having 2 volt sensitivity, if we represent the output voltage corresponding to the 200 watts into 8 ohms as "Vout" and the 2 volt sensitivity as "Vin," we have:

200 = ((Vout)squared)/8

From which it can be calculated that Vout = 40 volts

Therefore the gain in db is

20 x log(Vout/Vin) = 20 x log(40/2) = 26 db

That is an approximation, as I indicated, in part because it does not reflect margin that may be built into the maximum power specification. But it will generally be a reasonably good approximation for most purposes.

Also, note that for a tube amp having 4 and 8 ohm output taps the gain will be approximately 3 db less for the 4 ohm tap than for the 8 ohm tap.

If you have a scientific calculator these calculations are very easy to do. Alternatively, the calculator that is built into Windows can be set to scientific mode, although I find using it to be somewhat clumsy.

Best regards,
-- Al

Well, Al,
If you and few other poster were speaking about where 100W per channel can bring Wilson Sophia, it’s not truly the case and I’ll explain why.
That ARC VT100 would be able to supply to my guesstimate only a third or a quarter of specified power which is only 25...30W realistically at highest volume setting. Although tube amps soft-clip, there’s still not enough CURRENT to move drivers and therefore actual power halves or even quarters. ARC line preamps in general have 20dB of gain so combined 80dB of gain is substantially enough -- no need to move gain higher to 73dB.
Mentioned earlier Bryston 3B-st or 3b-sst/sst2 amps can do much better job but still not enough.
As I’ve mentioned before 250W Electrocompaniet amp wasn’t enough either. It was loud enough, but no 3d and imaging.
400+Wpc/8Ohm and 600+WPC/4Ohm is about right ’prescription’ otherwise money wasted.
There’s one Sunfire Sig 600 for sale here on audiogon and I wish to stretch my budget and get it. I was foolish not to get it at more than half of price years ago, but trust me It’s the best amp ever made for any budget.

Increasing from 100 watts to 400 watts would give another 6 db of volume. Doubling the watts equals a 3 db volume increase. A volume increase of 10 db would sound twice as loud twice as loud.
In other words the starting point isn't 100 watts. Try going from 30watts: 60, 120, 240, 480 ... 12dB -- Now these figures bring you much closer to reality.

what at do you think about bryston 4bst or a pair of 7bst monos?  They are in the same price category of my vt100.  
That ARC VT100 would be able to supply to my guesstimate only a third or a quarter of specified power which is only 25...30W realistically at highest volume setting.
I would respectfully but completely disagree with this, Czarivey.

First, most tube amps providing 4 and 8 ohm output taps have the same or similar power ratings when a 4 ohm load is connected to the 4 ohm tap as when an 8 ohm load is connected to the 8 ohm tap. As you realize, a 4 ohm load requires more current but less voltage compared to delivery of the same amount of power into an 8 ohm load. And that difference is accommodated by the different output transformer winding ratios that are used for the two output taps.

In this case the amp is rated at 100 watts, and the measurements provided in Stereophile Volume 20 No. 3 for the original (non-MkII version) of the VT100 confirmed that that rating is essentially accurate for BOTH load impedances, when the corresponding output tap is used. (Aside, that is, for a very slight shortfall of well under 1 db that he measured in one channel, which was suspected to be due to a weak tube).

Furthermore, JA’s measurements of the impedance magnitude and phase angle of an earlier version of the Sophia speaker (linked to below) indicate impedance characteristics that are particularly benign relative to those of many and probably most other speakers that are rated as having nominal impedances of 4 ohms.

-- Al

I've known lots about price categories, but quit worrying about that long time ago.
Sunfire sig 600 was the amp able to make WS speakers literally disappear and bring REAL stage.
If you compare depreciation of 7bst vs. sig 600(both were actually manufactured at nearly same time), 7bst lost near 70% of value getting close to the end of bullet-proof Bryston warranty and sig 600 haven't lost a penny and sold often for higher dollar now than it was new.
That should tell quite something I dare to believe. 
There's no doubt to the quality of that amp despite being one of the first class D amps in high-end audio and if I had $30k+ speakers, I would be more than confident hooking them up to this unit.


The signal response measurements are done at 1kHz. Therefore for some particular reason called 'X', OP asks the question 'Y' for some same reason everything is perhaps 10...12db hungry of SPL and there's one analogy answer that speaks for itself:

If you have glass of water and you try to fill-up the jar, you will need much more than one glass of water.

The signal response measurements are done at 1kHz.
Most ARC amps have lower effective output impedances than the majority of tube amps, and the VT100 is no exception to that. Specifically, it has a specified damping factor of 11, which for the 4 ohm tap corresponds to an output impedance of approximately 4/11 = 0.36 ohms. Per JA’s measurements the minimum impedance at any frequency of the earlier version of the Sophia is 3.26 ohms, with a near-zero phase angle (i.e., an impedance that is almost purely resistive) at that frequency. And at nearly all other frequencies the impedance is significantly higher.

As you’ll probably realize, the result of the interaction of that kind of amplifier output impedance with those speaker impedance characteristics will be not much different than would occur with a solid-state amplifier, namely very little variation of output voltage as a function of frequency. And yes, in a narrow range of frequencies in the area of about 40 to 50 Hz, where the speaker’s impedance rises to around 14 ohms (assuming the speaker’s impedance characteristics are similar to those of the earlier version of the Sophia), and also in the upper treble region where the impedance also rises significantly, the amplifier’s power capability will therefore probably be significantly less than at 1 kHz. As a result of limitations that presumably would occur in output voltage, however, not as a result of limitations in output current as you had stated.

However in the rest of the deep bass region, as well as in the mid-bass and mid-range regions, which encompasses the regions where most music contains most of its energy, the 1 kHz power capability measurements can be expected to be essentially applicable.

-- Al

Wilsons are pretty efficient and you have a fair amount of power. I agree with those who suggest that you may need more gain in your phono or line level preamps. I have heard many Wilsons from Sophia to Alexandria XLF, and they always sounded great with tubes, esp. ARC and VTL. 
I have run Sophia 2's with 30W OTL's (Berning)  60 W OTL's (Atma's)
and class A and AB SS from 40W to 200W and always had plenty of volume. Yes, some differences in sound, but never anything unpleasant.
They are fine floor standing speakers and do well with just about any power.  I guess something may be off in your source or pre amp to amp match.
Or maybe you are chasing high sound volumes that really rock.  In that case my best suggestion is the old original KlipschHorns, and be sure to stick them in the corners of the room.  But do not do that to Sophia's.
Good luck.
Would it make sense to replace the tubes, assuming that the ones installed are no longer capable of peak performance? Just a thought. 100 tube watts should be enough for these speakers.
So clearly there are a lot of viewpoints on this subject!  That is to be expected as I am learning that speaker - amplifier matching seems to be one of the black arts.  Thank you all for your posts.

To sum up, some say speakers need loads of wattage to get control, tight bass, and better imaging.  some say even hungry speakers do fine with lower wattage tube amps.

I spoke to Wilson Audio and their man that I spoke to said that the speakers do indeed react well to lots of wattage.

There are two issues I am raising here.  One, I feel I am raising my volume control too high to get where I want to be, and this is a gain issue.  The 2nd is the question of wattage and control, and what to feed my Sophia 2's so they deliver their best work.

One suggestion was the preamp (phono or one stage) was not giving enough gain.  If I followed that route and get a preamp that has more gain, such as the ARC LS26 with 24db of gain, compared to 18db of gain in my LS-25, that would solve only one of the issues, and I would not know if the extra power amp wattage will be adding a lot of improvement with the Wilsons.  (side note, I checked the specs on all of the ARC REF line stages from the Ref 1 to the Ref 10, and all have super low gain.  Much less than my LS-25!  If I were to pony up for a Ref 3 at some point, I don't think I would have enough gain to drive the speakers to the volume I like at all!  Seems odd to me.  Perhaps if one wants a Ref series line stage, one needs a particularly high gain amplifier, but I digress).

For my budget ($2200), I am leaning towards the Bryston 4BSST at the moment.  23db or 29db of gain (selectable), 500 watts in 4 Ohms, this has the right price point, solid warranty, 6db increase in gain, and 5 times the wattage.  (Al, it also has 20K load impedance that you warned about for matching to the LS-25.)

Today I am going to read up on how amplifiers work, so I can better appreciate Al's comments, which are a bit over my head!  Time to study.
check  bryston 7 bst or 7 bsst in the second hand market. phenomenal value and double the power. ( make sure of voltage ). most of them are still under warranty ( 20 years ) . a friend is using with McIntosh tube preamp with great results. another good option is quad QMP monoblocs.
I was looking at the 7bst and 7bsst.  Only trouble is that the 7bst will only give 23db of gain in a balanced output, and the newer 7bsst model is out of budget.. For those reasons i am thinking that the 4bsst is the right way to go.
There are substantial differences in the sound of the various
iterations of Bryston amps and you should try to get the SST2
series if you can......
even if you got a 3b, you’d have 250w into 4ohms which
would better the ARC and you should be able to get that around 2K
used.....the 4b doubles those numbers and there’s one on gon for 2900, that you should be able to get for you shouldn’t have to go back 3 models in series iterations to get in your price should be able to get 500w plus into 4ohms and stay where you need to be with a later edition of the bryston’s with the Torus transformers etc......I ran 7bsst2’s with my very current hungry Magnepans and I now have the 28bsst2’s with those same speakers........It’s not about’s about headroom and overall control. Are your speakers controlling your amp or vice versa ?