Burson Audio OPAs

[Deleted]

XTRProf
I do think that Fullrange speakers may be a perfect match for a valve amplifier with output transformers !
SandyK

[XTRProf]

Jun 27, 2008 10:44:26 GMT @sandyk said:

XTRProf
I do think that Fullrange speakers may be a perfect match for a valve amplifier with output transformers !
SandyK

Well, my friend's system is a full mono block 300B with Lundahl OT and with a Feastex fullranger and the sound, although very good for the mid, was anything but to enjoy fully. He's now going for a PP valve set that he's building with another friend's help. The SS (Fet) Nelson Pass F2 current drive amp, on the other hand, just sounded wonderful with a Coral fullranger. I don't lie and just report what I had heard.

But those megabuck Jadis and AR at the hifi show were just wonderful driving those Sonus Faber (Stradivari I think as there were just too many models to remember).

[dejanm]

There is a lot of prejudices when talking Valve vs. SS ... I will give you only one example. Several months ago here in Vienna I had the opportunity to hear Audio Note CD2.1 MKII + Audio Note Meishu ("normal" version - not a silver one) SET 300B + Audio Note AN-E speakers. Simple system, tube based ( I do not know actually which version of AN-E has been used - they look all the same looking from outside). In the next two rooms Bryston and Leema were playing - two brands that I used to like very much, especially Leema for its strong dynamics. The price is very similar I think ...

When you hear these systems practically side by side, with the same CDs, you hear obvious differences in the philosophy of the sound reproduction. Leema and Bryston are very dynamic, open sounded systems but when you hear Audio Note - I bet nobody will go back to hear these two systems again. In comparison -> they were bright, edgy and artificial sounding. Audio Note was reproducing instruments with such realism that I was simply shocked. I stayed in Audio Note room (actually I came back 4 times) and never entered the other two rooms again.

By the way - transformers are very linear in a certain frequency range. Typically from several Hz to 50 to 100 KHz. They are much more linear than any other active components - if done well. So, definitely there is no need to be afraid of them. They are not evil, although they might be - if used wrongly. But that is true for any other component or technology.

Saying all this, I am not "follower" of valve technology. Or any other ... I like for example very much how Pass Labs Amps are reproducing sound - especially their XA components. I mean - you have good and bad sounding valve and SS HiFi systems. I never saw any reason why I should make a definitive decision about the technology that should be used for HiFi. Couple of months ago I heard excellent Jeff Rowlands amp driving big Magnepans ... Incredible sound and these Jeff Rowlands are Icepower technology ... or digital amps, if you like. I remember peolpe talking that this technology is not good for HiFi. Let them hear extraordinary Jeff Rowlands ...

etc. etc.

[Deleted]

dejanm
I grew up with valve amplification, and have probably replaced more valves than most people have seen, in my earlier days with Telstra. I have built most types of amplifiers except Class D, and have also been to many HI-FI shows. Valve amplifiers like the exotic, and expensive Ongaku can sound fabulous with some kinds of music, but often shit themselves when there is a lot happening at once.(I.M.D.) I built a modern valve preamplifier just over a year ago to see if things had changed. DTV sound had a very pleasant warmth to it, but I soon found that it had shortcomings when complex passages of music were played. Just as I had remembered from previous encounters with valve equipment. Sure, many SS amplifiers are "brash" sounding. I also have built a couple of Mosfet amplifiers, one of 100W/Ch, and the other 240W/Ch. To my ears they have a small amount of artificial warmth to them. BUT a lot of people like that!
I don't.
I find that well designed Solid State amplifiers sound even better, if they have very wide bandwidth. I mean bandwidth far in excess of what any transformer based valve amplifier is capable of.This helps preserve the harmonic structure.
Wide bandwidth,IMHO, is one of the main reasons for the high performance of the modified Jaycar kit amplifier.
I wonder what Rick would think of the Jeff Rowlands, after all, they are only sampling the sound, and filling in the missing gaps artificially. Just like CD audio ?

SandyK

[dejanm]

sandyk,

when speaking about preamps - have you tried passive TVC ? Something like Music First Audio ? I liked it very much ... especially the silver version ...

[dotnet]

Jun 29, 2008 13:11:26 GMT dejanm said:

By the way - transformers are very linear in a certain frequency range. Typically from several Hz to 50 to 100 KHz. They are much more linear than any other active components - if done well. So, definitely there is no need to be afraid of them. They are not evil, although they might be - if used wrongly. But that is true for any other component or technology.

I meant transformers used for power transmission, specifically. For RF signal transmision and similar applications core materials with virtually zero remanence and coercitivity (such as certain ferrites) can be used, giving good linearity in a certain operating range. Unfortunately, those materials have a low maximum flux density and saturate very quickly. Hence, they're unsuitable for power transmission.

Materials with sufficiently high flux density (like the ones used in output transformers) also have a high remanence and some coercitivity. This results in a fairly broad magnetic hysteresis and thereby high distortions. To make things worse, the permeability of ferromagnetic materials (the constant that translates the field strength applied by the coil into magnetic flux inside the core) isn't constant at all, but changes with field strength. It also changes over time, depending on what magnetic fields the material has been exposed to.

Finally, output transformers driven from a real source impedance and driving an inductive load act as high-pass. They also have their own resonant frequencies and a range of other sound-affecting properties.

That's why I was saying they're evil

Cheers
Steffen.

[Deleted]

Yeah, with that other little property called "back EMF" they make rather good car ignition coils,though.

[Deleted]

dejanm
Years ago I played briefly with a passive preamp, but they have too much rolloff at the HF end unless VERY close to the Power amplifier,and for many sound sources, a modest amount of gain is required. If you are referring to using a transformer, no, and I wouldn't for many of the reasons already mentioned. I don't have a problem with AUDIO transformers used for low output moving coil stepup,or specialised microphone use.

SandyK

[XTRProf]

Jun 29, 2008 21:21:09 GMT @sandyk said:

dejanm
Years ago I played briefly with a passive preamp, but they have too much rolloff at the HF end unless VERY close to the Power amplifier,and for many sound sources, a modest amount of gain is required. If you are referring to using a transformer, no, and I wouldn't for many of the reasons already mentioned. I don't have a problem with AUDIO transformers used for low output moving coil stepup,or specialised microphone use.

SandyK

Hi Alex,

I'm not sure why you are having a roll off when the passive pre is properly implemented. Check here for some response graphs and the bandwidth is typically more than 100KHz and more when all the steps as specified are taken correctly. A passive pre, whether PVC or TVC, and having enough source gain always sounds better than any active pres. The only disadvantage, at least to my ears, is just don't have as much wag as an active pre but the music coming out from it is usually more pure and musical than any active pres.

[XTRProf]

As to audio output trans, according to the Lundahl site and datasheets many can output a frequency of 20Hz to 80 KHz +/- 0.3 db. Check the pdf specs here. Ya, there should be some differences when it comes to audio trans as compared to power transmission trans. When an audio trans is built, optimised and properly implemented just for audio only, they should not have the same problems as in power transmission trans.


Similarly, the same goes for Tamura audio trans specs here! More info here as well.


Now to apply it into audio application as in Audio Research tube power amp here . The specs is

POWER BANDWIDTH: (-3dB points) 15Hz to 150kHz
POWER OUTPUT: 600 watts continuous at 16 ohms from 20Hz to 20kHz. 1kHz total harmonic distortion typically 0.5% at 600 watts, below .05% at 1 watt.

[Deleted]

XTRProf

Have you ever made a passive preamplifier ? They all have a fairly high output impedance and are prone to HF rolloff unless very close to the amplifier.They can be improved by the use of twisted wire interconnects etc. to achieve low capacitance, then they are prone to the ever increasing amount of RFI and EMI. Many sources simply do not have sufficient output level for them to permit a realistic output level, without a major increase in the gain of the amplifier itself, and the attendant tradeoffs when this is done.

I'm not sure why you are having a roll off when the passive pre is properly implemented. Check here for some response graphs and the bandwidth is typically more than 100KHz and more when all the steps as specified are taken correctly.

WTF, has the attenuation curve for a DACT attenuator got to do with a passive preamp? This is in relation to the input stage of an amplifier, when used in the same chassis via short interconnects. FTR, I use a DACT 2, and even the difference between a short length of cable, and a similar length of higher quality low capacitance cable to the input of the preamplifier is clearly audible,let alone through a typical interconnect.
As for these so called wide bandwidth transformers, they cost an arm and a leg if of high quality, are bulky, and very heavy. As well, these days are only available from a few specialist companies. A friend of mine tried to get a wider bandwidth transformer custom made for him by a major transformer mjanufacturer, and was told they were no longer able to obtain suitable high quality iron. -3dB at 150KHZ won't do justice to many normal high quality recordings, let alone 24/96 and 24bit 192 KHZ recordings. Still, that doesn't matter much if you use typical full range speakers ? BTW, I have seen all this crap before from the likes of Lundahl.
.05 % distortion ? Whoopee !!
Many amplifiers these days are capable of .0005 % , or even less ! And yes , the difference is quite noticeable using loudspeakers which have distortion levels 100's of times higher.
SandyK


P.S.
Isn't this supposed to be a thread about Burson Audio OPAs ?

[XTRProf]

Yup, I'm using a PVC, albeit a China made one, and it sounded wonderful in my system. Better than the SS Electrocompaniet or Naim Audio or AR hybrid pres, except in the wag department, which I had used b4. Now I'm going the full length thru DACT precision parts when I have the time to build a better quality PVC. Later on, maybe a TVC, when I have the time and fund again. So far, I have not heard any of your roll off symptom as described by you here. If fact, the treble is even more lifelike than thru the active pres and those brands are really branded type, btw.

Distortion figures are not everything. A good, example , is a guitarist prefering tube amps over SS although obviously the SS amp will walk rings round the tube amp. I even remember the helicopters were considered horrors when they were first conceived and designed as they are the most unstable flying machines around for all aero engineers theoretically. But now we have the Apache attack helicopters, one of the best support helicopters that the airforce will ever get. There is also the X wing fighter, which to most top notch aero designers will consider it a disaster to build as again they are the most unstable in flight. But do you know they are still going into it as they have advantages that no stable fighter aricraft will have. In fact, the next generation US fighter jets will be based on the unstable X wing design. Hmm, looks like Starwars X fighters will materialise after all.


PS: Yes, it's a Burson thread. Let us have a beer backstage then and let the music do the talking, can we? Alex, Exit right and I Exit left ..................

[dejanm]

Well, never mind that its a thread about OPAs ... This subject may be more interesting ... So while waiting that you left the room, I will try to put some comments here ... Let me tell you one story ... true story ...

I own one TVC build around S&B copper trainies of the 3rd generation. The same were used in a previous version of Music First Audio TVC preamps. All the switches are Shallco, all connectors are silver WBT, wiring is silver/gold Mundorf, etc. You can see it on the picture:



The story is about building this TVC.

First of all, freq. response is really higher than 100 KHz. If that is of any importance ...

Second, the guy who assembled this thing for me was very sceptical about the whole project. He owns a HiFi company and he is electrotechnical engineer building amps and preamps based on SS. For him transformer on the signal path is an evil ! But I paid for his services, so he agreed to essemble this unit for me in a way I wanted it. In the middle of the process this guy called me on the phone and told me something like: Listen, I put today squares from my generator through these transformers (S&B) and this is not going to work well. Actually I believe this is not going to work at all. You should see what is coming out. And I saw it ... and it was terrible.. and I said let's continue ... By the way, I listened to Music First before and I was delighted with the sound I heard ...

So we continued, and at the end he couldn't believe what was coming out of this TVC. In order to get a better picture, we took several other preamps and tested them in the same system with this TVC. The system was: CDP Primare CD 31, Amp was Pass Labs 150.5 and speakers were made by this guy based on ScanSpeak drivers. Preamps that we tested: Copland 305, EAR 864, Pass Labs X2.5. And this TVC was clear winner. From the others I liked the sound of EAR very much but it had a considerable lack of bass in comparison to TVC.

I am not saying that TVC is a best concept in the world. I am not generalising that TVC is better than ... whatever ... SS or valve ... I am just saying that it plays really good. And having in mind the price of these units, especially if you make them by yourself, it is a very good value ...

Concerning electrical parameters ... Well, I am myself electrotechnical engineer. And I like to hear the argumentation that was provided in previous posts. And I am not claiming that I know ... something ... Actually, I believe that I do not know much about HiFi. And I do not have clear explanation. But this TVC sounds really good ... to my ears. It may be though that somebody else will not like it ... But that wouldn't be really something new ...

[dotnet]

Jul 1, 2008 5:10:35 GMT XTRProf said:

When an audio trans is built, optimised and properly implemented just for audio only

[/b][/color], they should not have the same problems as in power transmission trans.[/quote]

I think we're getting our terminology crossed here. A tube amp output transformer is very much a power transformer (in the way I used the term above). Its purpose is moving *watts* across, while doing impedance matching. Contrast that with signal transformers, where the electrical power involved is miniscule. These include the MC step-up and microphone transformers Alex mentioned.

Cheers
Steffen.

[XTRProf]

Jul 1, 2008 7:34:31 GMT dotnet said:

Jul 1, 2008 5:10:35 GMT XTRProf said:

When an audio trans is built, optimised and properly implemented just for audio only

[/b][/color], they should not have the same problems as in power transmission trans.[/quote]

I think we're getting our terminology crossed here. A tube amp output transformer is very much a power transformer (in the way I used the term above). Its purpose is moving *watts* across, while doing impedance matching. Contrast that with signal transformers, where the electrical power involved is miniscule. These include the MC step-up and microphone transformers Alex mentioned.

Cheers
Steffen.[/quote]



Hi Steffen,

In the Lundahl datasheet catalog link above, there are some tube output transformers with very good frequency response. That's why AR tube power amps (although not using Lundahl) can have frequency response to 150KHz -3db.



Cheers and fyi. Exit left ................

[Deleted]

XTRProf
Which transformer in the Lundahl catalogue has a -3dB bandwidth of 150KHZ ?
Alex

[XTRProf]

Jul 1, 2008 11:19:35 GMT @sandyk said:

XTRProf
Which transformer in the Lundahl catalogue has a -3dB bandwidth of 150KHZ ?
Alex

Jul 1, 2008 10:23:01 GMT XTRProf said:

In the Lundahl datasheet catalog link above, there are some tube output transformers with very good frequency response. That's why AR tube power amps (although not using Lundahl) can have frequency response to 150KHz -3db.

Err, did I say Lundahl? Exit left ................... ;D

[Deleted]

XTRProf
Most of the Lundahl transformers seem to max out at about 70KHZ, which is about as good as you can normally get, even from an industry leader such as Lundahl.
So where can we purchase a valve output transformer that is only -3dB at 150KHZ ?

Alex

[XTRProf]

Jul 1, 2008 12:29:40 GMT @sandyk said:

XTRProf
Most of the Lundahl transformers seem to max out at about 70KHZ, which is about as good as you can normally get, even from an industry leader such as Lundahl.
So where can we purchase a valve output transformer that is only -3dB at 150KHZ ?

Alex

Ask Audio Research if they are willing to accomodate you. ;D Exit left ..................... THE END for the day ..................

[rowuk]

I am not sure that the reason that bandwidth is required in solid state circuits has anything to do with other types of circuits. It is true that our ears only "hear" so much but that things happening outside of our human "passband" can audibly modulate other things that do end up in the pass band.
My problem with this naive argumentation is that this is not how real instruments work. Unless you are sitting on stage next to the instruments, even 15KHz isn't getting to your $150 seat in the concert hall. The BS about harmonic structures just does not hold up.
The reason that you need extreme bandwidth in solid state is because their distortions are very audible when not properly addressed (as is also true of tube equipment). I listen to both types of amplification extensively as well as to a lot of real music (I have only posted about my symphonic ventures but also play lead in a jazz band as well as a heavily amplified salsa formation). I hear no evidence of loss of detail in decent tube equipment, although the soundstage is considerably different than with solid state. The difference for me is more "black" between notes with solid state - like turning up the contrast on a TV picture. With tube, I often find myself forgetting about the playback, with solid state I go into analytical mode.
I would suspect if there were "serious" flaws in one type or the other, I would notice it on my 1st generation uncompressed or eq'ed recordings of my own concerts.
To me it is like comparing fine red and white wines. It just depends on the day!

By the way, after reading Ricks recommendation, I added transformer isolation to my digital playback equipment (Neutrik transformers). Getting the grunge out of the signal has only had positive effects on playback in my living room! The recordings of violins and harpsichords, trumpets, oboes and other "natural" instruments all got a little closer to the original.

[Deleted]

The BS about harmonic structures just does not hold up.

Rowuk.
IN YOUR OPINION ! Tell that to people like Graham Slee and others. Where do you think that "black between notes " comes from? It becomes more evident when you increase 3 things . Bandwidth, channel separation, and S/N. The human ear is very sensitive to the rise and fall times of a waveform. The harmonic structure being retained, means faster rise and fall times.
I have often heard it said, and regularly reported ,that musos are among the worst judges of sound quality .
Since more and more musos have been making their own recordings in home studios, the SQ of CD releases has continued to deteriorate. Can all the blame be laid at the feet of the major record companies ?
I am not saying that YOU fit into that area, but perhaps you can see what I mean ?
Let's NOT turn this into a slanging match? I may have industrial hearing damage, but the modded SC HA turned out O.K. using these philosophies, didn't it? Rick also mentioned previously a study, which found that people with hearing damage were often able to pick the absence of the higher frequencies, and sometimes have a high degree of acuity in this area.
Flame suit on !
SandyK

[XTRProf]

Hi Alex and all,

No need flame suit, man. You have just put your points IYVHO across that's all whereas others have put theirs across to alleviate this understanding of the topic. We don't need to always end up with flame suits in everything we write here, right?

Somehow of other, what Rowuk had written is reflected by another sound engineer friend of mine who sells pro audio equipment to studios. I somewhat agreed with what Rowuk and my friend had said as they are most of the time in realtime capturing sound with the best techniques and equipment possible and cannot be that far off. We are not, btw. If we care to go to live lounges and concerts, the real music that we hear always tend to be rounded, mellower but clear. There isn't much soundstage and imaging as well, unless we are very close to the performers, and the sound tend to be one FAT mono. I emphasise CLEAR and not those digitalis grain here.

In terms of bandwidth, noise and distortion, there will always be a threshold in what are aceeptable and what are too far fetch. When the bandwidth is too little, yes, the harmomics will be affected when measured into the passband. But is this musically accetable and like by most? That will be the holly grail none will be able to give a definite answer. However, remember what we hear at lounges and concerts, perhaps the bandwidth becomes not too important and is more pleasant bandwidth limited. Just like all pro guitarist will use tube amps over SS with all the distortion, noise and bandwidth limitation not as high as SS. On the other, if we have a bandwidth that's so wide, technically, wouldn't we be going into those noisy RFI and EMI areas for audio? I emphasise AUDIO and not VIDEO or Radio application, We are talking of AUDIO here, btw, and I'm sure non likes to hear RFI and EMI in their AUDIO signal. here.

Btw, what I'm talking is with reference to LIVE music and not measured sound. Technically the measurements may prove one thing but it's the LIVE music experience that we should gauge the final product of whatever beliefs, technically, objectively or subjectively. Also, please don't gauge AUDIO with RF and VIDEO signals as then we don't have a common objective to the LIVE musical sound event. If we wanted to talk about RF and VIDEO, we should not be talking of AUDIO anymore but TELECOMMUNICATION and SATELLITE transmissions.

Dear fellow hifi nutties ............., I rest my case. Exit left ............... ;D

[XTRProf]

Jul 1, 2008 7:10:42 GMT dejanm said:

Well, never mind that its a thread about OPAs ... This subject may be more interesting ... So while waiting that you left the room, I will try to put some comments here ... Let me tell you one story ... true story ...

I own one TVC build around S&B copper trainies of the 3rd generation. The same were used in a previous version of Music First Audio TVC preamps. All the switches are Shallco, all connectors are silver WBT, wiring is silver/gold Mundorf, etc. You can see it on the picture:



The story is about building this TVC.

First of all, freq. response is really higher than 100 KHz. If that is of any importance ...

Second, the guy who assembled this thing for me was very sceptical about the whole project. He owns a HiFi company and he is electrotechnical engineer building amps and preamps based on SS. For him transformer on the signal path is an evil ! But I paid for his services, so he agreed to essemble this unit for me in a way I wanted it. In the middle of the process this guy called me on the phone and told me something like: Listen, I put today squares from my generator through these transformers (S&B) and this is not going to work well. Actually I believe this is not going to work at all. You should see what is coming out. And I saw it ... and it was terrible.. and I said let's continue ... By the way, I listened to Music First before and I was delighted with the sound I heard ...

So we continued, and at the end he couldn't believe what was coming out of this TVC. In order to get a better picture, we took several other preamps and tested them in the same system with this TVC. The system was: CDP Primare CD 31, Amp was Pass Labs 150.5 and speakers were made by this guy based on ScanSpeak drivers. Preamps that we tested: Copland 305, EAR 864, Pass Labs X2.5. And this TVC was clear winner. From the others I liked the sound of EAR very much but it had a considerable lack of bass in comparison to TVC.

I am not saying that TVC is a best concept in the world. I am not generalising that TVC is better than ... whatever ... SS or valve ... I am just saying that it plays really good. And having in mind the price of these units, especially if you make them by yourself, it is a very good value ...

Concerning electrical parameters ... Well, I am myself electrotechnical engineer. And I like to hear the argumentation that was provided in previous posts. And I am not claiming that I know ... something ... Actually, I believe that I do not know much about HiFi. And I do not have clear explanation. But this TVC sounds really good ... to my ears. It may be though that somebody else will not like it ... But that wouldn't be really something new ...

Entry left .................


Wow, that's some mean pre there. Care to share how much you pay for that without the labour cost as I'm interested to build one as well when fund and time permits. Especially the S&B trans, how much and where to get? How many db steps? 24?



Exit left .......................

[Deleted]

On the other, if we have a bandwidth that's so wide, technically, wouldn't we be going into those noisy RFI and EMI areas for audio?

IMHO, NO ! The wider the bandwidth, provided the equipment is well designed, appears to reduce the effects of impulse type EMI.
Graham Slee has received excellent reviews for his recent phono amps,partly because they are far less affected by clicks and plops from the record's surface. This is because Graham uses VERY fast, wideband opamps in his recent designs, instead of the normally used lower noise types, with a much lower slew rate.
BTW, although I opt for the widest possible bandwith in my own gear, it does not appear to be susceptible to EMI.

Ask Audio Research if they are willing to accomodate you.

XTRProf
That is a copout ! We both know that transformers of that type rarely even get to -3dB at 70KHZ. See if you can obtain a wider bandwidth type for your next ancient technology project !

Alex

[rowuk]

Alex,
we have no flame war, we are looking at the same picture from two sides. The symptoms of less clarity and harmonic structure (where our definitions are certainly different) are not directly caused by bandwidth, SN(within reason) or channel separation. Improving them does increase the SQ on solid state gear. I am sure that there are other ways of getting there too! Maybe one day we will understand the mechanism that leads to changes in SQ that are not presently measurable.

Harmonic structure determines the sound of each instrument and each person playing it. In a live recording situation, we have acoustic interferences where the fundemental tones and harmonics add and subtract creating further tones at very low level. Those sum and difference tones are missing in many studio recordings because the instruments are very closely mic'd. They create a noise floor much greater than any decent amplification and mask the same.

The etched detail in high end solid state reproduction CAN be an exaggeration (if we compare to the original source). The best mix boards from Neve also use transformers as do some of the finest microphones. I think that tells a story of its own (that there are many roads to perfection).

I am convinced that both valve and solid state work equally well but have a different perspective. That means that we all can find what suits us best regardless of the TRUTH (that not even necessarily being the live original - the recording engineer and producer are also artists!).