Hello from the Whisky trail

[his047]

This is my first post to the list, so hello!

I am a long-time Audiophile. By birth I am Danish but left Denmark to pursue an academic career abroad in 1985. Before I left Denmark I purchased a Radford STA15 which sparked a lifelong love of that brand and its products. I still have the STA15 (which I bought second-hand in 1978) though it rarely sees any use these days. It is thoroughly revised and all Electrolytic capacitors have been replaced with film types (which was a clear improvement).

Throughout my life I have had a plethora of equipment. Audiolab 8000 C+P; Kenwood L1000C+L1000M; Sansui AU11000a; modified Meridian 105 (2x15000µF in power supply: the original is 2x6800µF) ; Borbely DC100; Hafler D200; Radfords of various ilks, both MA 50s and STA 15+25s; Conrad Johnson PV14, Audio Research LS16; and, being Danish, a lot of Bang and Olufsen stuff. Speakers have included Meridian M10s; Audiovector M3 Signature (active three-ways with Radford STA 15+STA15+STA25); Celestion SL600s, Sl 6 and SL6si; Quad ESL63/Gradient SW63, Bang and Olufsen Beovox 5700; Rogers LS3/5a; KEF LS50. Turntables have included the SOTA Star Sapphire, Mørch GS6a, Linn Sondek, Thorens TD124, Garrard 401 and Technics SP10 with arms from Mørch, SME, Ortofon Schick and (now) a Mørch DP-8. Current cartridges include Ortofon MC200 with vdHul stylus in a special Mørch armtube and the Ortofon MC7500 and Dynavector DV17 mk2. Current pre-amp is the Benchmark DAC2.

All this to say that I have been around the block a few times.

My current setup includes a set of ML Vantage which are driven by the Meridian 105s, Benchmark, DACT MC/RIAA, Oracle Delphi VI, Mørch DP-8, Ortofon MC7500.

This presentation brings me to a question, or rather two questions. I have tried the Radford MA50s with the Vantages with very disappointing results. I should probably preface this with the fact that I have used the MA50s with Celestions, Kefs, Rogers and, importantly, Quad ESL63s. The latter combination is, frankly, magic. A phenomenal openness combined with impressive control of the bass. One of the best combos I have ever hear, but unfortunately also a combination that creates much marital discord. Hence my current Vantages.

But the Radford MA50s sound absolutely awful with the Vantages. Soggy bass, muted dynamics and a constant low-level snarl that indicates that the amplifiers are not stable when loaded with the Vantages. So, the questions: have any of you had a similar experience of really awful amplifiers with the Vantages (I would imagine, but have not tried, that the Kenwood L1000M is also dreadful: the protection circuits oscillate when loaded with .6Ω, which is awfully close to what the Vantages present around 20 kHz). Secondly, do any of you have an impedance graph for the Vantages?

Finally, Greetings to you all from Northern Scotland which is currently being buffeted by hurricane-level winds.

 

[OKA]

Hello to you from another new member.

I have the Celestion sl700se and Sl6s and Vantage, and needed to clean (shower) the Vantage to get it right.

Sorry, cannot help you much with your question, but have you tested the Vantage with other amps?

 

[roberto]

Hola and welcome,

First of all, you have to understand your Vantages. The bass is driven by an internal amplifier of 200 Watts on each Vantage. The bass is not powered by the power of your amplifier. Only the Stat panels. These panels, their load is 4 ohms. Your amp must be capable to drive 4 ohms. The crossover point is circa 450Hz. The circuit into each Vantage, makes to your power amplifier to read below 450Hz as an open circuit. The load for bass to your amp is around 4000 ohms...your amp reads this as an open circuit.

The stat panels are a capacitive load, not a resistive or inductive load. This could be your problem with your Radford power amp. I have a tip regarding the 20KHz. Most professional mics, their frequency response top is no further than 18KHz...at 20KHz there is no much music. Don't worry about that.

The sensitivity of your Vantage is 92dB/2.83V/m. This means that with 20 watts/channel you can get a good SLP, not at 100dB, but enough to enjoy the music and also, any kind of music.

Happy listening!

 

[his047]

Dear Roberto,
I think you have misunderstood the way the Vantages work: First of all the electrostatic panels are not driven directly by the signal. The voltage of the signal is boosted to several kilovolts by being put through a transformer which together with the cross-over presents a complex load to the amplifier. It also is a difficult load that dips very low at high frequencies. ML quote an impedance as low as 0.8Ω @ 20 kHz. This is enough to make e.g. the Kenwood L1000M produce some rather nasty distortion due to an interaction between its protection circuit and the speakers: 0.8Ω is awfully close to a short circuit.



Secondly, the active amplifiers are driven through a voltage divider network which is followed by a passive frequency divider network (AKA a "crossover"). The frequency divider network therefore also loads the main amplifier which delivers a full-frequency signal to the speaker. The one impedance curve I have seen for the Vantage shows that Impedance varies between 100Ω around 20 Hz to 0.6Ω at 20 kHz. Hence I requested to know if anybody else has access to impedance measurements for the Vantages that confirmed these results. This is also why I think that my problem with the Vantage/Radford MA50 may be a stability issue.

And for the same reason I am asking for advice about good amplifiers for the Vantages.

 

[OKA]

I knew that my amp would be fine with ML. Back in Denmark you might find some used Dynamic Precision. Mine are ca 30 years old and still going strong.

 

[roberto]

Hola his047,

Your explanation is correct. I just tried to express in little words for people who is not too knowledge as obvious you are. Please excuse my dare.

On the other hand, because you do know what you are talking about, you should use an output transformer to drive the stats. A tube amp works beautifully with electrostatic panels, great for capacitive load. And again, you do not need to reproduce those 20KHz, they are not into the most professional recordings. Yes, the impedance drops like a brick on electrostatic panels, a difference with a tweeter that the impedance increase as the frequency goes up.

Try Conrad Johnson power amp, like the Classic 62SE. It uses teflon caps, with metal foil resistors and the output tubes are the KT-120s. Highly recommended for your Vantages. You can find another used models for much better price. Conrad Johnson uses the most expensive parts available in the electronic industry. Quality has no regret!

Again, my intention was to let you know that if you have horrible bass performance, it is coming from the amp, not from the Vantages. Obvious, you did know his already. Again, my excuses!

Happy listening!

 

[his047]

Dear Roberto,

not a problem at all.

The thing that puzzles me, though is that the Radford MA50s are valve amplifiers and have an output transformer. In other words, some valve amps are not compatible with the M-Ls. And in the same way, the sound with the transistorized Meridians is very good. And obviously OKA is very happy with his Dynamic Precision Transistorized amps. So my purpose was to see if we could put ML-heads together to create a list of Good and Bad amplifiers.

I am currently expecting some LC-Audio PWM-amplifier modules which I shall put to the test with the Vantages. I have no idea what to expect, but will update when I have them readied and tested

 

[roberto]

Hola his047,

Please keep us posted with your findings. Again, remember that the stats represents to the amp a capacity load, so the behavior of the amp design might be the clue. I do know that ML stat panels are easy to drive with output Xformers. This problem does puzzles me too. I have here in Costa Rica, customers that are using only 22 watts/channel with excellent results. So power is not also the problem. The Vantages sensitivity is 92dB/2.83V/m. This allows to you the possibility to use a lot of different power amps with no problem.

I did ask about the load, and I got the same response to you. The bass is not representing a load to the amp. There is not energy bass, just the bass signal. The impedance for the bass is like an open circuit, and it is circa 4000 ohms. Think of this: two amplifiers working in the same woofer? But I do not want to argue with you regarding this.

Please tell us how we can help to you to make better your quality sound.

Happy listening!

 

[his047]

So, finally, I have put together the LC-Audio Zap-Pulse 2.2. There is a later 2.3 version and a "special edition" as well, but this is a bog-standard 2.2. I bought two modules second hand in Denmark for a ridiculously low price (500 DKK, roughly = $75). In addition, I have bought the LC-audio transformer (42+42 Volt + 15 Volt AC) and their "Predator" power supply (roughly $230). I have put this in a disused enclosure from an old faulty DAC from Woodside/Radford. The amplifier is a PWM amp and gives out around 2 x 200 Watts while drawing only a miniscule 5 Watts when idling. (you can read more about it here: http://www.lcaudio.com/index.php?page=70)

Well, what can I say? Admittedly, I have only had it working for maybe ten hours and I reserve judgement until the modules have run for a week or two. But I have been listening most of the day on this and my first impression is that this is a truly superb amplifier. Very impressive bass response with a lot of control. Midrange is perhaps a little hard, but then, only a few days ago I went to see Elvis Costello in Ednburgh and the midrange there was a lot more "cutting" and harsh than what I hear with the Zap-pulse. Treble is there, not too much and not too little.

I was a little worried about the switch from two mono-blocks to a stereo amplifier, but I must say that the Zap-pulse has better three-dimensionality than the old Meridian mono-amps. So all in all I would say they are here to stay and that they have (so far) solved most of my complaints about the Vantages.

 

[his047]

Just a quick update. I have updated the PWM amplifiers to the LC audio zap-pulse 800XE. This is still an extraordinarily good combination with the Martin Logans.
It often happens that I promise myself that this is going to be the final stereo that I have. But this time I actually believe it. There could be more bass, but what there is is ample for my use and it is extraordinarily well defined. Clarity is superb, but three-dimensionality is somewhat lacking. But boy, can it play music!