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First off I am serial gear changer. I never seem to be happy with what I have and am always chasing something that seems unattainable.

 

My current issue started with the introduction of a BHK preamp and the subsequent sale of my Krell FBI. The FBI is one hell of an integrated and the preamp section had fended off many contenders. That was until the BHK was introduced. Contrary to some of the older Krell's the FPB series is actually quite warm and rich but still a tight and powerful sound. With the BHK installed I could not believe how much more bass impact and depth I was getting. The downside, it brought the soundstage a little further forward and it could get a little fatiguing, something I had never had with my Duntech Sovereigns in the past.

 

I decided to sell the Krell FBI as I now had a preamp that seemed to be next level. The FBI went and a Pass Labs X250.5 landed as a replacement. At this point I was playing strictly vinyl but hadn't been listening as my turntable was off getting warranty repairs. I bought another turntable in the interim so outside of the speakers a lot components had changed. I had had the X250.5 in the past but with very different speakers. At the time I did not think the Pass Labs would be a slouch in the bass and dynamics department compared to the Krell and I did prefer the mid-range of the X250.5 over the Krell last time I heard it albeit with different speakers.

 

Upon firing everything up I was extremely disappointed. The bass was no longer impactful and the sound was soft and mushy. Given the amount of component changes I had no idea what to blame but seemed to pick on the turntable. Still I have no idea why the sound is the way it is but I am starting to consider possible impedance mismatch????

 

Last week I scored a Directstream dac, a component I was familiar with having lived with one in my system for a months in the past. I got it working last week and had a list of tracks in my mind to revisit. I have not been listening to hi-fi as of late, I chop and change so much gear and get in these ruts where nothing sounds good anymore. Then the obvious critiques come to mind, "Why did I sell this", "I should have left it as is". Curiosity gets the better of me and I have to try other gear.

 

Back to the root of my main issue. The Pass Labs has an input impedance of 20k and the BHK preamp is 200 ohms output impedance. Compared to the Krell which had input impedance 100k the difference is substantial but whether it would actually make an audible difference, I don't know. With the Directstream, which has a little lower output than standard, I can turn the BHK up to 100 on certain tracks. I do listen loud but even at 100 I could take it further. This was not the case with the Krell, it seemed limitless. On vinyl I can crank the BHK to mid 80's but have a fair whack of gain due to my SUT.

 

Is the lack of gain, bass dynamics and softer sounded a possible impedance mismatch? Could it be system synergy? Or is the Pass Labs a whimp compared to the Krell? Is it a combination of  things?

 

My system consists of:

 

Duntech Sovereigns

Pass Labs X250.5

BHK Preamp

Directstream Dac

Icon Audio PS3 Signature Phono

Sota Nova SME IV w/ Windfeld TI

 

I bought the Coincident Statement preamp last week but haven't plugged it in yet. I wanted to hear the Directstream in my current system before confusing me further.

 

 

Edited by kelossus
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Many Many moons ago....    

I had the system absolutely cranking last night for the first time in forever and was blown away at how effortlessly it was driving those big old Sov's. Sound wise it was excellent too with the overal

I believe the vast majority of buyers simply aren't aware of how hard they are to drive, and they can just get away with it because they always have. It makes for really good measurements and numbers

The only thing I can add is the  Coincident, although lightening fast, is going to be a step back in terms of bass impact compared to the bhk - having owned both. I dont think it will be a solution to your issue.

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4 minutes ago, AudioGeek said:

The only thing I can add is the  Coincident, although lightening fast, is going to be a step back in terms of bass impact compared to the bhk - having owned both. I dont think it will be a solution to your issue.

Sounds like bass impact is a strong suit of the BHK preamp in general. None of the other preamps I tried came close to the BHK.

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I'm no expert on this but impedance seems OK with 200 ohms out and 20k in, but gain is another aspect altogether and a separate thing.

Edited by muon*
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To be frank, I think you made a mistake with the X250.5.  I listened to the x350.5 at home a few years back. Bass was flabby, and lacked control. 

 

  Your Duntechs need an amp that will control them. Unfortunately,  the Pass does not cut it imo.

 

  Not sure about the PS preamp as have not heard it but in theory the tube input stage should give better spaciousness but perhaps a slightly softer sound.   The PS preamp unity gain is 80 on the volume control so there may be some mismatch vs the FBI integration you were used to. 

  The preamp measures well on the Stereophile review, so I don't think the issue lies there.

 

  Its the Pass power amp.

  

Edited by metal beat
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@metal beat how low do the Duntechs go? as the X250.5 boasts a power output of 250 watts per channel into eight ohms and 500 watts into four.

 

Those specs are from a review of the Pass amp.

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6 minutes ago, muon* said:

@metal beat how low do the Duntechs go? as the X250.5 boasts a power output of 250 watts per channel into eight ohms and 500 watts into four.

 

Those specs are from a review of the Pass amp.

In terms of impedance? Nominal Impedance Variance, 4 ohms 3.0-4.5.

 

Haven't seen a graph showing phase angles or anything to determine how hungry they are but those old Dynaudio woofers need a heap of current to get them going. The magnet is so undersized so I think they really on current to make anything happen. Seriously I am drinking a cup of coffee and it's substantially heavier than the magnetic assembly on the 12" Dyn.

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5 minutes ago, muon* said:

@metal beat how low do the Duntechs go? as the X250.5 boasts a power output of 250 watts per channel into eight ohms and 500 watts into four.

 

Those specs are from a review of the Pass amp.

 

The Duntechs impedance is around 3 ohms or in real life lower. The Pass does not have the bass control to do the Duntechs justice.   Can't say I have ever seen a Pass review when power doubles down to 2ohms - which the Krells do.

 

  I saw those specs as well when I listened to the x350.5.  Listening was similar to what Kelossus is experiencing. 

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I don't know how the Pass does with 3 ohms so I'm at a loss :blush: I would have thought it might be OK, but then I really don't know.

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Maybe you should bi-amp?

If your open minded to class D get a hypex nc2000 for the bass drivers - 2.5kW into 4 ohms, use the pass for the mids/tweeters.

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@kelossus, I have a couple of observations that hopefully might help with your situation.

 

Firstly yes absolutely the change in turntable could be the culprit or at least a contributing factor.

The wrong tonearm for a particular cart or setup could easily lead to a poor bass response.

It would be well worth throwing the dac into to mix to see what it does may help to figure out if you're current turntable is working well or not.

 

The next point that is important to note is synergy in a system is extremely important and it sounds like all the changes have basically thrown any synergy your system had out the window.

 

I completely agree with @metal beat that the Pass X250.5 could well be the main cause of the flabby bass.

The Duntech's are a speaker that need a lot of grunt to perform and while the Pass might have sounded great in a different system it just may not be enough to drive the Duntechs properly.

 

Once you have your source sorted I would then look at getting an amp that is capable of driving the Duntech's well and has the type of sound signature that you like.

Then it is a matter of finding a preamp that matches well with the chosen amp and system as a whole.

While the BHK pre might be very good it would have been designed ideally to match well with the BHK amp and might not necessarily match well with the Pass or Krell.

In the meantime it can't hurt to plug in the Coincident to see what you can learn from that change.

 

My biggest advice would be to focus on building synergy in your system rather than chopping and changing all the time.

It may be tempting but if everything doesn't match well it doesn't help your system at the end of the day and won't necessarily shine the best light on a particular component anyway if it's wrong for your system.

 

Best of luck getting your system back on track @kelossus. :) 

 

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I just came out of a bi-amp system so I need a few years break before going down that route again.

 

I will roll the other preamp through the system tonight and see how it all goes. I will stick with the dac as it's a familiar source and I don't have my phono stage here.

 

Looks like this may change to a "help me upgrade my power amp" thread. I think with both the BHK and Coincident on hand I should be able to find some sort of synergy. The Krell didn't pair too well with the BHK but it may have been good with the Coincident. Two power amps come to mind and are within budget, a FPB400CX and Sanders Magtech. Never heard the Sanders but hearing a few members carry on about them makes me interested.

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8 minutes ago, kelossus said:

I just came out of a bi-amp system so I need a few years break before going down that route again.

 

I will roll the other preamp through the system tonight and see how it all goes. I will stick with the dac as it's a familiar source and I don't have my phono stage here.

 

Looks like this may change to a "help me upgrade my power amp" thread. I think with both the BHK and Coincident on hand I should be able to find some sort of synergy. The Krell didn't pair too well with the BHK but it may have been good with the Coincident. Two power amps come to mind and are within budget, a FPB400CX and Sanders Magtech. Never heard the Sanders but hearing a few members carry on about them makes me interested.

The Sanders should definitely have enough grunt to drive the Duntech's and from personal experience a Sanders Preamp I have heard was quite good.

I should add a word of caution though you want to be careful with fanboi products as they get tend to get strongly raved about by a vocal few but in reality they don't always meet that high expectation or necessarily have the right sound signature for your tastes.

 

I seem to remember something about a Krell amp and @Tubularbells who might have some additional insight for you with his Duntechs.

 

Once you figure out the amp there are a few very good preamps in the classified section at the moment that might also be worth looking at namely an Esoteric, a Boulder, an AVM and a Conrad Johnson though a lot of money for that one.

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Is there a possibility that you could experiment with synergy in real life by borrowing some components to listen to? From a dealer or a friend? Yours is a tricky system to pontificate about BUT if you were able to substitute more freely (especially regarding power requirements and such) for a while you would not have to keep making costly assumptions.

 

Just my 2c worth.

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Not much I can offer here as im in the same boat with the same speakers and have my eye on a FPB400CX for sale here that im waiting to hear back on that will hopefully solve the issue once and for all but Id bet no ones had more amp dramas than I have especially the past 12 months.

 

Id also agree with the comments on the Pass amp as I got burned buying one back when I had the JBL's  which even on those rated at 96db efficiency didn't seem to have enough horsepower so didnt last long (I then stupidly bought a Audio Research and it was even worse!).

 

If your open to suggestions id potentially look into some Class D offerings as ive currently got a 500w Nord hooked up and its surprisingly good (but needs a good few hours to come on song) otherwise unless you got big bucks to spend its back to an old school 25+ yo Krell or similar.

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3 minutes ago, Tubularbells said:

otherwise unless you got big bucks to spend its back to an old school 25+ yo Krell or similar.

Yeah that can be the problem with needing big power... big amps tend to come with a big price tag too....

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54 minutes ago, doogie44 said:

Is there a possibility that you could experiment with synergy in real life by borrowing some components to listen to? From a dealer or a friend? Yours is a tricky system to pontificate about BUT if you were able to substitute more freely (especially regarding power requirements and such) for a while you would not have to keep making costly assumptions.

 

Just my 2c worth.

Yep that certainly makes sense.

 

If anyone in Brisbane thinks they have an amp up to the task I am willing to give it a go. I wouldn't want to waste a dealers time when I have no intent to purchase.

 

I know someone with an ME1500 I could give a crack but they don't play well with tube pre's.

 

 

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Dealers also have second-hand gems which pop up. It's a wide market as well. These might represent the 'earlier' versions of the current stock types. No harm in stating your needs and actually hearing the amplifier lineage? Plus, you might be looking for a certain type of amp--and therefore be willing to pay a premium if it appears second-hand from a dealer cheaper than new? Anyway, it seems you're in the market as such, so a dealer won't be offended (in my experience). 

 

Disclaimer: I have bought the majority of my serious gear second-hand at dealers.

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4 hours ago, muon* said:

@metal beat how low do the Duntechs go? as the X250.5 boasts a power output of 250 watts per channel into eight ohms and 500 watts into four.

 

Those specs are from a review of the Pass amp.

20 amps maximum output current if I remember rightly, I rarely took notice of such amps. It won't be mean, but neither will it come close to doubling into 2 ohms at a guess. The manual recommends 4 ohm or higher speakers, so I'd be guessing the issue here is current.

 

As I'm from the UK originally I don't have that sentimental thing for the Sovereign. I know it's heresy, but a speaker that fiendish, no matter how good it sounds, is not appropriate for a serial gear changer and should probably be let go to someone building an endgame system that will rest on appropriate amps.

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6 hours ago, kelossus said:

First off I am serial gear changer. I never seem to be happy with what I have and am always chasing something that seems unattainable.

 

Same here and it never ends. It also takes a significant hit out of your pocket each time you decide to buy and sell.

 

Having read the frequency of change above I would recommend focusing on the power amp and Sovereign combo, and getting that right first. Forget the preamp and source units for the moment as they add confusion to the chain. Perhaps revisit the older Krell units and see if you can find one that really pleases.

 

Not in the same league I went from a KAV-300i to a KAV-400XI then back to a KAV-300i to get some old French Celius 202's to work with a 2-ohm impedance drop. For the reasons you have mentioned RE Krell oversaturation/loudness I sold the amp and speakers. I then moved to tube amps and have never looked back since. Having said that I've also purchased another KAV-300i to have it on standby. ?

 

You may want to consider the Neo-Classic 250's or 500's for your Sovereigns. @wooferocau appears to have used the 250's with his Sovereigns. ?

Edited by xlr8or
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6 hours ago, kelossus said:

Sounds like bass impact is a strong suit of the BHK preamp in general. None of the other preamps I tried came close to the BHK.

 

Kelossus, we all sympathise with your plight and wish you well. It sounds to me like you just need some Grunt, which for those particular speakers might only be affordable in Class D (why not).  Get urself some 1200W/ch class D's and see what the Duntechs can do, if they dont sound great then move 'em on. I really think that decent grunt is not talked about enough on this forum.

Best, Trip

 

Edited by tripitaka
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6 hours ago, kelossus said:

 The Pass Labs has an input impedance of 20k and the BHK preamp is 200 ohms output impedance. Compared to the Krell which had input impedance 100k the difference is substantial but whether it would actually make an audible difference, I don't know.

You can at least rule that out as the cause. 100x the output impedance is still absolutely fine matching.

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I know you're having trouble with the analog side too, but I just wanted to check that you don't have the attenuator pad on in the Directstream? that very much could lead to unsatisfying volume, and subdued dynamics, in my experience

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Thank you everyone for your responses.
 

9 minutes ago, sakabatou said:

I know you're having trouble with the analog side too, but I just wanted to check that you don't have the attenuator pad on in the Directstream? that very much could lead to unsatisfying volume, and subdued dynamics, in my experience

What is the attenuator pad? I have selected the "high" output from the setup on the front panel. The volume is also fixed at 100.

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2 minutes ago, kelossus said:

Thank you everyone for your responses.
 

What is the attenuator pad? I have selected the "high" output from the setup on the front panel. The volume is also fixed at 100.

you're all good then.

If it is in "low" there's a -20db pad in the signal path

 

the other issue is that the RCA output is significantly lower than XLR

Edited by sakabatou
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Posted (edited)

At my budget of around 6k I am sure there are amps up to task. The hard thing is finding them on the 2nd hand market.

 

Pretty sure we have ruled out and impedance mismatch so the Pass Labs just isn't up to the task.

 

I am obviously an impulsive buyer and hearing the BHK with the Krell sent me down a regrettable rabbit hole. ....While a sensible precaution, trying before you buy is seldom an option with 2nd hand purchases. Most are interstate and you have to be quick. I should have waited until I had the Pass Labs and the Krell and made my selection based on simultaneous listening. I just jumped the gun given that I had owned both amps at the same time but with drastically different speakers.

Edited by kelossus
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6 hours ago, metal beat said:

To be frank, I think you made a mistake with the X250.5.  I listened to the x350.5 at home a few years back. Bass was flabby, and lacked control. 

 

 

  

Agreed........ I tried several Pass Labs with the Sovereigns....  They lacked power and control always sound restrained and flabby.

 

The Manley 250 Neo,s with KT77,s  sounded wonderful with the Sovereigns.. as did my Krell KSA 250 and KMA 160 mono,s..?

 

My last Amp ( ands still current)  i used on the Sovereigns, was the Esoteric  S1 Grandioso.. It defies its modest 145watt @ 8ohms !!

 

 

 

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I've seen a Convergent Audio Technology JL2 Signature Mk II stereo power amp come up a few times in the SNA classifieds. Although double your budget that's also another tube-based option to consider.

 

 

Edited by xlr8or
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On that note ......DONT let anyone tell you "TUBES" cant/wont power the Sovereigns  adequately !!

 

I rate the  Manley 250,s as on of the best amp/s i have ever used.   

 

Also...as seen in the pics, the Manley "Snappers" with 4 each of KT77,s  did a superb job of powering the Sovereigns....actually better than the Pass Labs X250.5 !!  :shocked:

Edited by wooferocau
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7 minutes ago, wooferocau said:

On that note ......DONT let anyone tell you "TUBES" cant/wont power the Sovereigns  adequately !!

 

That's a pretty comprehensive statement, without any regard to room size or listening level preferences.  The OP's original amp, Krell FBI, produced a lazy 1200W/ch.

 

I know 'watts arent watts', but I have a large listening room and if some kind person wants to bring some tube amps over to impress me then in return I will provide some very decent wines ?

 

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13 minutes ago, tripitaka said:

I know 'watts arent watts', but I have a large listening room and if some kind person wants to bring some tube amps over to impress me then in return I will provide some very decent wines ?

 

 

Well bottles ain't bottles either. Who would want to swap some old sexy Hammersmith UK vintage Genalex Gold Lion KT77's with a decent red when the only thing they would have in common would be red plating. ?

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43 minutes ago, xlr8or said:

I've seen a Convergent Audio Technology JL2 Signature Mk II stereo power amp come up a few times in the SNA classifieds. Although double your budget that's also another tube-based option to consider.

 

 

Parasound jc5 one of the best amps I've ever owned for power and sound.

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2 minutes ago, xlr8or said:

 

Well bottles ain't bottles either. Who would want to swap some old sexy Hammersmith UK vintage Genalex Gold Lion KT77's with a decent red when the only thing they would have in common would be red plating. ?

 

Well said 'kind person' would take their amps home, after drinking my wine, was that not clear?

 

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2 minutes ago, tripitaka said:

 

Well said 'kind person' would take their amps home, after drinking my wine, was that not clear?

 

 

Thermionically and vacuum sealed clear. ?

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One observation, the input sensitivity of the BHK preamp is listed as:

 

Sensitivity

Unbalanced 1.3V/33KΩ
Balanced 1.3V/66KΩ

 

That is going to take a bit of driving with a phono stage and a SUT.

Edited by Telecine
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1 hour ago, wooferocau said:

Agreed........ I tried several Pass Labs with the Sovereigns....  They lacked power and control always sound restrained and flabby.

 

The Manley 250 Neo,s with KT77,s  sounded wonderful with the Sovereigns.. as did my Krell KSA 250 and KMA 160 mono,s..?

 

My last Amp ( ands still current)  i used on the Sovereigns, was the Esoteric  S1 Grandioso.. It defies its modest 145watt @ 8ohms !!

 

 

 

People quite often put too much credence on the spec sheet.

I've heard a measly 25 watt class a amp happily drive a pair of speakers that a 100 watt amp couldn't manage and a 500 watt class d amp that really couldn't do much at all.

 

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17 minutes ago, Telecine said:

One observation, the input sensitivity of the BHK preamp is listed as:

 

Sensitivity

Unbalanced 1.3V/33KΩ
Balanced 1.3V/66KΩ

 

That is going to take a bit of driving with a phono stage a SUT.

Oddly enough the SUT has more audible gain than the Directstream DAC in my system.

 

 

In regards to valves, I definitely wouldn't rule them out even though I am extremely skeptical as to how they would perform. 200-300 watts of valve amplification ain't coming cheap.

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5 hours ago, kelossus said:

Yep that certainly makes sense.

 

If anyone in Brisbane thinks they have an amp up to the task I am willing to give it a go. I wouldn't want to waste a dealers time when I have no intent to purchase.

 

I know someone with an ME1500 I could give a crack but they don't play well with tube pre's.

 

 

Absolutely try the big ME, it is a known working solution with Duntech’s.  However, unless your friend has a matching ME preamp to couple it to then chances are you will have an  unpleasant time. Very annoying but ME amps simply demand the matching preamp to show what they are capable of.

 

Another alternative is a monster Bryston 14B. An arc welder and warmer sounding than the ME, also much more preamp friendly. The later models are better than earlier ones, SST2 would fit the brief and budget perfectly if you can find one.

 

@christosd can expand with his experiences running big Duntech’s.

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54 minutes ago, Martykt said:

People quite often put too much credence on the spec sheet.

I've heard a measly 25 watt class a amp happily drive a pair of speakers that a 100 watt amp couldn't manage and a 500 watt class d amp that really couldn't do much at all.

 

All very true, and independent review measurements, or understanding the purpose or limits of a particular design can often show why. 
My Marantz amp would possibly not drive the Sovereigns well, yet the new and less powerful (into 8 Ohms) Model 30 at a third of the price should.
 

That doesn’t mean that the PM-10 doesn’t do a better job with my own speakers, or with 99% of all loudspeakers. 
 

The X250 has a specific design goal and driving the Sovereigns isn’t it. So?

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