What makes an amp sound more direct ?


In our hifi journey we have probably all heard amps with different topologies and implementation. Most of these amps would have an implementation which is a combination of one of these:

1. Single Ended
2. Push-pull
3. Balanced
4. Differentially Balanced
5. Class A, A/B, D
6. High/Low Damping factor
7. Zero Negative Feedback (global & local)
8. Low/Medium/High Negative feedback
9. 2/3/4/multiple gain stages

There will be more such items that can be added to the list. My curiosity arises from the fact that some amplifiers (or even preamplifiers) sound much more direct than others. The ones that does this trick generally seems to do the "they are here" trick very well. While the components which sound relatively indirect cast a sound scape which gives the perspective of "we are there".

Just from my observation, single ended and zero feedback designs sound much more direct than balanced designs especially ones with high negative feedback. Is this a coincidence or is there a valid reason behind this ? 
pani

I agree that zero feedback and single-ended are quite direct sounding.  But, some of the most direct, immediate and vibrant sound can be had from output transformerless tube amps. 

This would be a rough generalization because I've heard some extremely direct sounding push-pull amps too.  Among the very best amps I've heard are the Western Electric 59A (crazy rare and expensive-pushpull), a recently built one-of-a-kind 271a amp (indirectly heated triode-pushpull), and a one-of-a-kind output transformerless amp. 

I own two amps that are not too bad in terms of delivering an immediate and vibrant sound: 1) a modern build of a Western Electric 133a (using vintage parts, including authentic WE input and output transformers and plate-type resistors); and an Audio Note (uk) Kageki (parallel single-ended).

I'm not sure what you mean by "direct" sounding, could you elaborate?

Are you talking about how some amps present a more immediate (forward) sound-stage, while other amps present a more laid back, deeper, sound-stage?
Some make you feel like you are mid-hall, while others make you feel like you are in the front row?
Or are you thinking of something else entirely?
10. Speakers.
jmcgrogan2, it is not exactly a soundstage phenomenon per se. Immediacy...yes. Direct sound is a bit self-explanatory already, the way the sound is directed to the listener. The listener actually feels a touchy-feely with the instruments in the room as if they are being played "for him". Even if the stage is behind the speaker, the way the notes are formed is like looking through a lens whose focus on the objects are spot-on. Sometimes it becomes difficult explain these phenomena even though it is ubiquitous.

Larryi, I had a couple of 300B SETs at home and also the famous Tenor Audio OTL 75 amp (its a push-pull). It was very clear that the Tenor did not have the directness of the SETs but it was clearly faster with wider bandwidth. Interestingly Naim amplifiers have a very direct sound though not in the same league SETs, still...
Similarly the Nelson Pass Firstwatt amps also sound more direct than most of the other typical SS amps including the Pass XA.8 amps.

Recently I heard some SS amps which were very well built, with very high damping factor. Even though they were tonally nice (not SS dry) they clearly sounded "indirect". 
IME, this directness you speak of usually has more to do with the recording technique than anything else.
unsound, I am talking about directness of a system. If you have listened to some horn speakers you will relate to it. They may not sound forward but horn speaker have a way to convey the music in a very focussed way. That aspect also happens in the electronics side. 
I'm not sure its possible to associate "directness" inherently with any electronics.   Speakers and room acoustics would seem to be the main factors.   Some speakers are more directional than others ie more sound firing directly at you versus other directions.   Room acoustics will determine how much reflected sound reach your ears compared to direct.

It may be that many zero feedback and SET amps tend to sound this way in that they tend to work best with higher efficiency speakers many with horns or waveguides that in fact direct more sound towards you, which in genral means the system is more efficient in taht more of the sound produced reaches your ears directly rather than via reduced volume reflections that travel further and are hence not as loud as the direct sound.

Pani,

I think we are in agreement on what is lively and immediate sounding.  I had a friend's Firstwatt amp in my system for two weeks and it sounded very good.  It was very lively, immediate and could hold one's interest in the music for a very long time, just like very good tube amps are good at doing.  The only slight negative for me was the slightly artificial "edge" or hardness to the initial attack of notes.  With that edge can make things sound fast and exciting, after a while, if it is pervasive, the sound becomes "mechanical" (sameness to the presentation) and I lose interest.  I find that to be much more the case with Naim amplifiers than the Firstwatt amp I had in my system and I certain could easily live with the Firstwatt amp (one of the best solid state amps I've heard, and not very expensive too). 

I personally did not like the Tenor OTL 75 amp I heard.  It really did not deliver the kind of liveliness and immediacy which is the raison d'etre of OTL amps.

Most of the higher powered solid state amps I've heard sound dull and lifeless unless they are being used to really pump up the volume level.  These things do not play well at lower volumes.  But, if one needs high power, solid state may be the way to go; most higher powered tube amps sound hard and glassy and unpleasant.  Give me low-powered amps, and speakers that play well with them. 

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From my experience and reports I read from others, it does seem that use of negative feedback typically results in a more laid back presentation than otherwise. That would seem to infer a different tonality between the two in general. So avoiding that is probably a good move in the interest of achieving a more "direct" sound than otherwise.

I owned one near zero feedback amp in recent years as an experiment and yes it tended to be more direct and forward than most others I have owned.
Well, I can tell from experience feeding the CD player output directly into the amp does wonders for directness and transparency. That's my uber modded Oppo into an all tube class A Woo audio headphone amp.
'Direct' is a term that I don't really understand, but I do understand that when we got rid of the feedback in our amps, they seemed to sound much more like real music. Palpable, with all the instruments more distinct and available to the ear, if that makes any sense.

Its been known since the 1950s that the application of negative feedback can add higher ordered harmonics, which contribute to 'glassiness', 'hardness', that sort of thing, which IMO/IME takes you away from the sense of real music and is instead more like a good hifi.

So this means that our amps won't drive as many speakers correctly as they would if we had feedback, But its been my contention because of the negative attributes of feedback that any speaker that requires that of the amplifier will likely never sound like real music- instead they will always sound like good or excellent hifi. For some this might be a rather indistinct line in the sand but I've always wanted the stereo to sound real.


Atmasphere,

I heard your setup with the large Classic Audio horn loaded speakers and United Home Audio in the larger ballroom at Capital Audiofest a few weeks back. A RTR tape of the Beatles White Album was playing.

It was a treat in that larger dedicated room in particular. The sound was very distinctive from most anything else there. It did have a certain warmer and seemingly more direct aspect to it than any other setup I heard that day. By direct I mean with that particular setup the location of the speakers in the room seemed somewhat apparent from listening.

In that large room, I think that was a good thing resulting in a large more focused primary soundstage in the middle of the room which was more realistic. A wall to wall holographic soundstage detached from the speakers in a room that large would have been a nice trick but not sounded realistic or lifelike.

There are pictures of the setup on the United Home Audio website if anyone is interested.

FWIW.


I think the goal should be to have the illusion of the performance being in the "room" with the listener.  Realistically, this is best achieved with dynamic, high current capable speakers hooked to fully balanced push-pull high current/high powered amp(s).  Class A or A/B sound best to my ear.  All aspects of a system contribute to the overall gestalt of course, but flea watt amps will not pressurize a room and deliver the dynamic control necessary to give you the excitement of being in the presence of live musicians.  Wilson, Krell, Dynaudio etc...can deliver full scale music without constraint (upper end models).  None of this matters if you do not have the right cables, power cords, preamp and source(s).  This does not mean that there aren't any other number of ways to get beautiful, lively and engaging music in the home...there are a myriad of ways for sure, but "live" sounding, unconstrained dynamic and accurate reproduction of the source requires a wide bandwidth power amp with lot's of headroom.  I left out horn systems and super high efficiency designs because I have not heard any that could do what I required of them to put me in the presence of the performers, especially at realistic volume levels while maintaining accurate tone and soundstaging.  Of course...IMHO!
I’m not sure what "direct" sounding means....

I have a Musical Fidelity M6si. I previously looked for information on the manufacturers site as to its design type and couldn’t seem to find the data. At one point I asked the dealer who replied "Class A/B". Some questions:

- Is the M6si class a/b?
- can an amp be a combination of designs mentioned (1-9)?
- If reply is M6si is not class a/b, then what is it?
- How can a lay person know what the design type of their amp is unless the data is provided? 

Thanks.

Mapman, Thanks for your comments!

I think the goal should be to have the illusion of the performance being in the "room" with the listener. Realistically, this is best achieved with dynamic, high current capable speakers hooked to fully balanced push-pull high current/high powered amp(s). Class A or A/B sound best to my ear. All aspects of a system contribute to the overall gestalt of course, but flea watt amps will not pressurize a room and deliver the dynamic control necessary to give you the excitement of being in the presence of live musicians. Wilson, Krell, Dynaudio etc...can deliver full scale music without constraint (upper end models). None of this matters if you do not have the right cables, power cords, preamp and source(s). This does not mean that there aren't any other number of ways to get beautiful, lively and engaging music in the home...there are a myriad of ways for sure, but "live" sounding, unconstrained dynamic and accurate reproduction of the source requires a wide bandwidth power amp with lot's of headroom. I left out horn systems and super high efficiency designs because I have not heard any that could do what I required of them to put me in the presence of the performers, especially at realistic volume levels while maintaining accurate tone and soundstaging. Of course...IMHO!

I find that a better model for what a stereo should do it that it can graft the room onto the particular musical event as it is happening.

'High current' as stated above is not needed though. What is needed is the combination of power and efficiency such that the system does not have to strain to present the music at a life-like level. Horns have no troubles doing accurate tone and soundstaging; they can do that in spades. So as long as you have the headroom its all good. I use the same rule of thumb for almost any amplifier- don't run it much past about 20% of full power for best results. This usually means the speaker has to have some efficiency.

Now its also an interesting phenomena that if you want a system to sound more like real music, its to your advantage to run a loudspeaker of higher impedance; 8 ohms being better than 4 and 16 being better than 8. This is because nearly all amplifiers have lower distortion into higher impedances and that can be heard as smoother and more detailed. Because of this simple fact (which you can see in almost all amplifier spec sheets BTW) 'high current' is not essential as you don't need high current for 16 ohms.

There is always some debate by what is meant by high current. To sort out a lot of the marketing hype I use the Power formula. It turns out that for most speakers you need a lot less current than is usually thought. For example to do 500 watts into a 4 ohm load you only need 7.9 amps.

apparently you've never heard a good OTL
apparently you've never heard a good OTL

That would be incorrect because most solid state amps are OTL. I also owned the Tenor 75 OTL.
Lotta ways to skin a cat in audio...as long as it does it for you!  The only way to compare system outcomes is to experience them firsthand.  Each of our individual biases and expectations can put us at opposite ends of the audio spectrum.  I remember listening to an audio associates system($100k Avalon/OTL/Walker etc).  He liked playing it at a very low volume level and the system used cabling that produced a hum that was clearly audible through the music.  Very quirky and frustrating to me....but he liked it!  I want to be immersed in the space of the event with all the dynamics and atmosphere intact.  Most "serious" audiophiles may be a little to anal for me...I like to turn it to 11 for both jazz and classical!!  Play on
You will not get consensus on this. There are many ways to get the "direct" effect, and it can be done quite well with nearly any type of amp. The key is the quality of the amp and the rest of the system. 

As far as the "you are there" or "they are here" discussion, imo it's fairly worthless. 

Kevlar and sometimes carbon fiber midrange drivers in spears. Usually too forward / direct for me. 
"You will not get consensus on this"

In our attempts to distinguish between live vs. reproduced and everything in between the two I would only say, "Ain't that the truth".

The issue of direct sound IME I would generally attribute to SET designs with little to zero feedback running VERY highly efficiency speakers, IMMOSTHO and certainly not with all music all the time. 
Now that you mention everything in the entire chain is important, including the room. As we are learning everything from fuses to wire and cable direction, elimination of comb filter effects in the room, resonance control and vibration isolation, even treating the CDs. I'd even go so far as to say cleaning the electrical contacts on the wall outlets of non audio outlets including all outlets in other rooms contributes significantly to obtaining that direct sound.

Just to make this discussion more "direct", the fact that I posted it on amp/preamp forum indicates that I wanted to discuss this aspect from the amplification perspective. No, not all amps can be made to sound direct. Thats not my experience at all. When we talk about house sound of any brand, it comes mostly from a certain topology that they employ in the amplifier and that signature sound normally remains in the system. For example ARC and Wavac sound very very different though both of them are equally deep into valves. An ARC can never sound as direct as a Wavac or Audio Note. OTOH an ARC carves out a huge sound space well beyond the speaker boundaries as its house sound which a Wavac doesnt do. It is a design thing. It is clear that Wavac and Audio Note being 0 feedback SETs do the direct thing well. But I am sure there is more to it. For example an amplifier based on ultra-short signal path with only 1-2 stages of amplification would probably sound more direct than a 4 stage behemoth (in general). 
As above- guys, we have having too many posts removed???