[dyohn]

Placement of instruments in space. How do we predict if a piece of gear will do that with accuracy. There is more to sound then just frequency response. Why do most audiophiles, while acknowledging that digital is convenient, still, by and large, agree that analog reproduction via the stone age tech of the turntable provides the most realistic sound. The SS vs. tubes could be an analog of this situation.

-Roy

IMO one simply cannot predict if any amplifier will "place" "instruments in space" or not.  This is *far* more a function of loudspeaker alignment and placement in the listening space (and all the acoustic interactions happening in the room) than it is anything that any amplifier can or cannot do, and is also affected greatly by each listener's subjective evaluation of the resulting sound space.  I cannot count the number of times when "audiophiles" rave about the "imaging" of their system only to be disappointed when others can't hear it the same way.  And by the way, your analog/digital and "realistic" arguments have nothing to do with this discussion at all.  That is completely different from a discussion about electronics accuracy or neutrality, and reflects another conflation of terms.

[doug s.]

By making a case for adding distortion during the reproduction of the information captured in the original recording you have abandoned the concept of High Fidelity.
Once again there is nothing wrong with a personal preference for a certain type sound associated with added 2nd harmonic distortion. However this preference should be recognized for what it is,a compromise necessary for some individuals to suit their perception of what is required for their individual satisfaction. The individual should also be aware of the price he has
paid. By adding distortion to the playback of your music you have masked information that was present in the recording. In essence you have added dirt to the window through which you are viewing the performance and decreased the transparency of the system and the amount of low level information you might have heard.
Distortion levels from tubes doesn't have to be excessive. The Audio Research Reference 3 line preamplifier has a THD level of about .003% at 2volts out, the SP16L line preamplifier has about .0025% THD. The Audio Research VT200 has a THD of about .08% at 100watts/8ohms. If we as consumers don't demand higher transparency and neutrality from the gear we buy then we will have only ourselves to blame when there is no alternative to colored and distortion laden equipment that fails to transmit the essence of the music to our loudspeakers and our ears.
Scotty

your point about being able to achieve low thd w/tubed gear, yust adds credence to what i have been saying, imo - it is possible to have extremely transparent tubed gear.  and, it will still, (imo), sound better than solid state gear.  i have actually listened to the arc sp16l, and found it to be a wery musical and transparent preamp.  while my melos preamp's thd is rated "only"  <0.07% thd, this is plenty low, imo, and i find its transparency to be exceptional...  it is at least as transparent as the s/s linn kairn w/brilliant slimline power supply, that it replaced, and it is better than the linn in all other areas - dynamics, soundstaging, and that unquantifiable thing known, yes, as musicality...     don't get me wrong, the linn was a nice piece, but the melos thoroughly trounced it...  yes, even w/speakers, amps & room remaining the same, the insertion of the melos improved the imaging, soundstaging, layering, etc...  i agree w/the thought that some things regarding audio electronic gear cannot be measured yet...

ymmv,

doug s.

[miklorsmith]

And by the way, your analog/digital and "realistic" arguments have nothing to do with this discussion at all.  That is completely different from a discussion about electronics accuracy or neutrality, and reflects another conflation of terms.

Hmmm . . . sounding like instruments themselves isn't the standard of transparency?  Can anyone tell me what exactly is on the CD?  Without playing it back on another interpretive device I mean? 

If we're only concerned with the playback half of the equation and not referencing back to *real* sound this discussion is meaningless to me personally.

[cornelius]

In the video world, we calibrate monitors so when the material hits the stations, we know that we delivered picture that's within certain specs and looks good (the monitors have given us a "standard" to base our decisions (look, color correction...)on.  If it looks different at home, it's most likely a poorly calibrated TV - too many people set up their TVs like they're still in the store.

Anyway, my point is that no one here has heard neutrality, because unlike the monitors that we use, there's no way to calibrate an audio system for neutrality.     I've been in and out of many recording studios, and all of these "neutral" systems sound differently.  With speakers, lots of people mention flat frequency response, but often forget about things like time domain... so I think there are lots of factors to juggle, when recreating sound.  IMO, if you want it to sound like music, an illusion needs to be created with some "color".

[rajacat]

Placement of instruments in space. How do we predict if a piece of gear will do that with accuracy. There is more to sound then just frequency response. Why do most audiophiles, while acknowledging that digital is convenient, still, by and large, agree that analog reproduction via the stone age tech of the turntable provides the most realistic sound. The SS vs. tubes could be an analog of this situation.

-Roy

IMO one simply cannot predict if any amplifier will "place" "instruments in space" or not.  This is *far* more a function of loudspeaker alignment and placement in the listening space (and all the acoustic interactions happening in the room) than it is anything that any amplifier can or cannot do, and is also affected greatly by each listener's subjective evaluation of the resulting sound space.  I cannot count the number of times when "audiophiles" rave about the "imaging" of their system only to be disappointed when others can't hear it the same way.  And by the way, your analog/digital and "realistic" arguments have nothing to do with this discussion at all.  That is completely different from a discussion about electronics accuracy or neutrality, and reflects another conflation of terms.

I just switched from a digital amp to a tubed amp. I didn't change the placement of the speakers, acoustical treatment or alter the listening room in any way. I found that the tube piece created a more realistic (accurate! ) recreation of the sound stage. It's deeper, wider and I can place the instruments more accurately in that space. I don't know for sure but the digital amp probably would measure better (actually IMO my Heathkits sound very "neutral" but since they're modded no specs. are available) using the most common measurements. But I believe that these specs. only tell part of the story and they can only partially predict real world accuracy (realistic  ). Science continues to progress so one day maybe you will be able to design an amp. just by the numbers but that day is someday in the future.

BTW... I believe that neutrality and "realistic" when used in an audio context, are nearly but not quite synonymous, realistic being a bit more subjective. Most garden variety AV receivers have excellent specs. but lack the "x" factor. 

-Roy

[*Scotty*]

dyohn, while soundstaging is influenced by the loudspeaker and the room it is in, the loudspeaker can only reproduce what goes into it. I can substitute one amplifier for another and in so doing switch between an enveloping soundstage that fills the room and musical wallpaper stuck to the wall exhibiting neither height, width or depth.
Scotty

[Freo-1]

Placement of instruments in space. How do we predict if a piece of gear will do that with accuracy. There is more to sound then just frequency response. Why do most audiophiles, while acknowledging that digital is convenient, still, by and large, agree that analog reproduction via the stone age tech of the turntable provides the most realistic sound. The SS vs. tubes could be an analog of this situation.

-Roy

IMO one simply cannot predict if any amplifier will "place" "instruments in space" or not.  This is *far* more a function of loudspeaker alignment and placement in the listening space (and all the acoustic interactions happening in the room) than it is anything that any amplifier can or cannot do, and is also affected greatly by each listener's subjective evaluation of the resulting sound space.  I cannot count the number of times when "audiophiles" rave about the "imaging" of their system only to be disappointed when others can't hear it the same way.  And by the way, your analog/digital and "realistic" arguments have nothing to do with this discussion at all.  That is completely different from a discussion about electronics accuracy or neutrality, and reflects another conflation of terms.

I just switched from a digital amp to a tubed amp. I didn't change the placement of the speakers, acoustical treatment or alter the listening room in any way. I found that the tube piece created a more realistic (accurate! ) recreation of the sound stage. It's deeper, wider and I can place the instruments more accurately in that space. I don't know for sure but the digital amp probably would measure better (actually IMO my Heathkits sound very "neutral" but since they're modded no specs. are available) using the most common measurements. But I believe that these specs. only tell part of the story and they can only partially predict real world accuracy (realistic  ). Science continues to progress so one day maybe you will be able to design an amp. just by the numbers but that day is someday in the future.

BTW... I believe that neutrality and "realistic" when used in an audio context, are nearly but not quite synonymous, realistic being a bit more subjective. Most garden variety AV receivers have excellent specs. but lack the "x" factor. 

-Roy

I'm with Roy on this one.  I recently switched over to a custom DYI tube preamp, and I find it to be very neutral, natural sounding, and detailed. The music seems to sound more realistic (like performers are in the room). It is a BIG improvement over an Audio Research piece it replaced.

By the way, I think DYI is the way to go (especially at the cost point). One can use higher quality parts at a better price point than almost all of the commercially made gear. 

[*Scotty*]

Freo-1,Which Audio Research preamp did you replace with your DIY preamp.
Scotty

[Freo-1]

Freo-1,Which Audio Research preamp did you replace with your DIY preamp.
Scotty

I actually had two Audio Research preamp(s): An SP-6E, and an SP-12.

[*Scotty*]

Freo-1, Both Audio Research preamps you mentioned were produced in 1982, allowing for some sonic improvements in the last 26 years and given doug s's positive report on the performance of the Audio Research SP16L one might not go too far astray in recommending an audition. It might be a neutral tube preamp and a place to start building a neutral tube based system. There are currently 3 for sale on Agon.
Scotty

[Freo-1]

Freo-1, Both Audio Research preamps you mentioned were produced in 1982, allowing for some sonic improvements in the last 26 years and given doug s's positive report on the performance of the Audio Research SP16L one might not go too far astray in recommending an audition. It might be a neutral tube preamp and a place to start building a neutral tube based system. There are currently 3 for sale on Agon.
Scotty

I do not think that there has been much (if any) sonic improvement in tube gear over the years. There is an argument to be made that caps/resistors may be slightly better. In fact, one could argue that the currently made gear often does not sound as good, as they have to rely on sub-optimal current production tubes.  May audiophiles believe that the SP6E or SP8 sounds better than any of the currently made equipment. (YMMV) 

The DYI preamp just completed has the best of both worlds, using point to point wiring, top quality resistors/caps, a NOS Freed power transformer, a NOS high quality choke, and best of all, NOS tubes.  I would easily put it up against anything made by Audio Research.   

Given all that, I'm sure Doug's recommendation is worth investigating.

[bpape]

I can tell you that the new Audio research Ref 3 preamp is IMO head and shoulders superior to the SP6 series.  Fast, clean, neutral, yet still able to throw that wonderful, 3 dimensional soundstage and a smooth midrange that tubes are famous for. 

I haven't heard the ModWright but from people I know whose ears I trust, it has a lot of the same virtues.

Bryan

[doug s.]

Freo-1, Both Audio Research preamps you mentioned were produced in 1982, allowing for some sonic improvements in the last 26 years and given doug s's positive report on the performance of the Audio Research SP16L one might not go too far astray in recommending an audition. It might be a neutral tube preamp and a place to start building a neutral tube based system. There are currently 3 for sale on Agon.
Scotty

tho the sp16 is nice, i'd still take the melos sha-gold-r i posted about earlier on this thread, over it...  
http://www.audiogon.com/cgi-bin/cls.pl?preatube&1229506116&/Melos-SHA-Gold-mar-reference-

oops - awreddy sold.     but, here's another excellent deal, imo:

http://www.audiogon.com/cgi-bin/cls.pl?preatube&1227906640&/Melos-333-tube-preamp-box-and-

it's an early iteration, w/o remote, but it will still sound nice.  (it should be a two-box affair, and actually is the model above the sha-gold-r.)  and, now that melos designer mark porzilli will be opening a melos service/repair/upgrade facility in 2009, it won't be obsolete.

doug s.

[*Scotty*]

doug s, Were you able to do an AB comparison between the SL16 and your Melos,I was thinking there might be more used SL16's out there than the Melos. I can't really comment or recommend anything based on first hand experience as I haven't used anything but combination of custom, DIY gear or modded equipment for nearly 20 years. It's kind of hard to recommend the preamp I use when it's no longer produced.
Scotty

[doug s.]

doug s, Were you able to do an AB comparison between the SL16 and your Melos,I was thinking there might be more used SL16's out there than the Melos. I can't really comment or recommend anything based on first hand experience as I haven't used anything but combination of custom, DIY gear or modded equipment for nearly 20 years. It's kind of hard to recommend the preamp I use when it's no longer produced.
Scotty

no, i never did a direct a-b.  but, i was quite familiar w/the rig w/the sp16 - it had arc's s/s (100.2?) amps, driving proac 2.5's.  and, i have had proacs in my system, tho not the 2.5's.  actually, that arc/proac system was in my house for several months, in another room, so i was quite familiar w/it.  while it was a great sounding rig, i always felt it was missing yust that last bit of air, and dynamics compared to my system.  i was conwinced it was the preamp - i always wanted to put my melos preamp in that rig, but it was my then-brother-in-law's rig, and i think he yust didn't wanna go there...   

doug s.

[*Scotty*]

doug s,At least there are a couple of preamps you can recommend from first hand experience. The problem facing someone shopping for tube power amp is much worse than shopping for
a preamp. Every time you attach a speaker to a tube power amp assuming the speaker has a flat response curve at the listening position in your room,you now have a deviation from flat response based on how it interacts with a tube amps output impedance. Checking the the published response curves from the Stereophile reviews it gets pretty grim in some cases. All it takes is a plus or minus 0.5dB hump over three octaves to color your impression of what the amplifier is doing right or wrong. The deviation from flat response when driving a real world load is not a published specification and to date the only place I've seen it is in the pages of Stereophile. Thank !!! I am not shopping for a tube amp. Of course if you have one that works for you with your current loudspeakers you better test drive those new ones you are considering before you buy them. The deviation from flat will be different with new ones and it may not work for you. If I was looking for a tube amp I would want to know what it did when driving a loudspeaker instead of a resistor. YMMV applies here.
Scotty

[jon_010101]

All it takes is a plus or minus 0.5dB hump over three octaves to color your impression of what the amplifier is doing right or wrong. The deviation from flat response when driving a real world load is not a published specification and to date the only place I've seen it is in the pages of Stereophile. Thank !!! I am not shopping for a tube amp. Of course if you have one that works for you with your current loudspeakers you better test drive those new ones you are considering before you buy them.

Fortunately, these variations are reasonably consistent between "good" tube amplifiers (Audio Research, McIntosh, etc.), dependent mostly on the speaker impedance variations.  So the deviation from flat response for a given pair of speakers is going to have approximately the same "shape" for tube amps with respectable damping factors ~10-20.  An 0.5dB deviation is still small compared to room variations - and even ear-position variations - for most speakers, and may be comparable to some speaker cable effects (capacitive Kimber vs. inductive lamp cord).  The biggest problem is when you try comparing some low-feedback amps - which often have a damping factor of ~1-2! :barf:  An unfortunate trend in tube amps is to reduce feedback and tolerate very poor damping, and relatively high distortion, but the net result is excessive coloration to make the amp sound "different" from others.  Definitely not a positive step towards high fidelity, but I s'pose it has proven marketable 

BTW - many kudos to Stereophile for actually measuring amps - same for soundstage.com.  I wouldn't buy any amp without seeing third-party measurement reports, a schematic, and a high-res under-the-hood pic.   

[*Scotty*]

jon_010101, One of the things that has me less than thrilled with tube amplifiers is their rising distortion characteristics as they try to amplify low frequency signals. I as understand it this because the output transformer core  saturates as the power level goes up and  the frequency goes down. Is this a lack of iron in the core and could a bigger output transformer help or is there a decoupling between the output tube and the transformer as the frequency goes lower? Would more money spent on a higher wattage rated output transformer help reduce this problem. Also why don't output transformer secondaries and tube amplifiers in general have a lower output impedance. The VT200 has about a 1 ohm impedance,it doesn't seem like much of a stretch to ask all tube amps to meet some standard in this area.  I am ignoring negative feedback's impact on the output impedance. I would like to see it low before feedback is applied.
What gives? Can you recommend any tips to the prospective tube amp buyer beyond what you mentioned in your previous post?
Scotty

[jon_010101]

Hi Scotty,

In listening, I'm not sure it's that big of a deal in practice - For amps with sufficient output transformer core capacity and primary inductance (which provides the coupling you speak of), this distortion shouldn't become audible (>.5%) until relatively high powers, at frequencies which don't come into play too often.  This bass distortion will be audible for typical "little" tube amplifiers (say, a vintage tube receiver, or a single ended amp) driving too-big speakers.  But for a McIntosh, Audio Research, or Citation, much less-so.  Since loudspeaker distortion tends to be highest in this range, too, the effects are generally not too detrimental or obvious.  For serious bass applications, using an active crossover with a solid state amp driving a subwoofer would be a smart improvement, though.

At reasonable powers, many tube amps can pull off a nice 10Hz sine wave with distortion that isn't appalling, so it is often a cost limitation more than anything.  Output transformers involve trade offs, and a bigger core does not necessarily mean better overall performance without a fancier coil winding.  A lower-power output transformer is easier (cheaper) to build to perform well at high frequencies, due to reduced parasitics.  So, there are always compromises to worry about.  A do-it-all 100W output transformer might cost 3x as much as an "average" 100W output transformer.

(IMHO) In most cases a damping factor of 10 or higher (output impedance <0.8R for ~8R load), or even 5 or higher, will be sufficient to minimize the frequency response variations to levels where they become negligible compared to other factors.  The AR amp definitely achieves its damping factor via negative feedback.  To have low output impedance, some form of feedback is necessary, although it doesn't need to be a global feedback loop.  Triode push-pull output stages have fairly good damping, as triodes have intrinsic negative feedback that is otherwise "removed" in a pentode.  A pentode output stage using cathode feedback or "local" feedback of some sort can also be excellent (McIntosh and Quad use this approach).  Before additional feedback (say, a big fat global loop), these approaches might lead to an initial damping factor of ~4.  Much better than an ultralinear amp with DF~1 before feedback (look at measurements of a Prima Luna on stereophile!)  The vintage classics, which DO use a lot of feedback, typically aimed for a DF~10-20 - McIntosh, Williamson, Citation, Marantz etc.  But, damping factor isn't the only figure of merit - stability into a real load is also VERY important - and higher DF means more feedback, which can jeopardize stability.

So, if I were to provide some basic tips for tube-amp-objectivists, given what measurements you might find available - I'd look for:

• A damping factor of 5 or greater
• Enough juice to never exceed 0.5% THD in listening on the speakers of interest
• A stable, reasonably-wiggle-free square wave at 1kHz and 10kHz
• Good (-1dB) bandwidth to at least 40kHz, and down to 10Hz, with no visible "peaks" at high frequencies
• THD+noise <0.1% at 1 Watt @1kHz - and low THD+noise at lower powers, too
• Semi-affordable tubes that are appropriate to application
• Good design (beyond fancy aluminum or chrome), and substantial transformers
• Snake-oil free

Of course, I'd still want to listen to it, and there is some art to interpreting the plots   But from detailed measurements, a basic schematic, and some internals pics, I think it's possible to form a guesstimate of how a tube amplifier might sound.

A sampling of commercial amps that measure (by my standards) quite well, that can be found on Stereophile's web site: Quicksilver Horn Mono, McIntosh MC2000, Music Reference RM200, Audio Research.  I could list some iffy ones, too, but I'll resist

[Freo-1]

I can tell you that the new Audio research Ref 3 preamp is IMO head and shoulders superior to the SP6 series.  Fast, clean, neutral, yet still able to throw that wonderful, 3 dimensional soundstage and a smooth midrange that tubes are famous for. 

I haven't heard the ModWright but from people I know whose ears I trust, it has a lot of the same virtues.

Bryan

Do not necessarily agree. The SP-6E was very close to the SP-8, in that the line stage used 6DJ8. While the REF 3 is a fine sounding unit, it's a matter of opinion regarding sound quality. Many audiophiles prefer the sound of SP-6E/SP-8 units (especially in Asia). Granted, a refurbishment would be required to accurately compare.  I do not buy the "hype" that new tube gear is better than older gear.

The point I was making is that you can make a DIY preamp that can sound as good (or better) than the commercial units. Granted, yo have to be able to do a lot of legwork (like obtaininh high quality parts, such as NOS potted Freed power transformers, chokes, NOS tubes, etc).