What preamp creates the largest soundstage?

If DHT preamps are not the best at creating 3D soundstage why would manufacturers use them? Perhaps they are just stupid?

They're not stupid. A good designer can work to achieve the goals that a preamp has to provide in a number of different ways. Its not hard to build a DHT-based preamp, and one of the advantages is that the tube doesn't have a lot of gain, which works nicely with digital sources. All you have to do though is to be sure you get the *bandwidth*; keeping the distortion down isn't that hard with almost any triode, DHT or not.


The designer might like the linearity curve, he also might realize that to set his preamp design apart from others he has to do something different and using DHTs is a good example of that. When we introduced our preamp (the MP-1) it was the world's first balanced line preamp for home audio; we did that as there are so many advantages of operating balanced (as long as the balanced standard is supported), but also for the simple fact that in 1989 when we did this, placing yet another single-ended preamp on the vast heap of such preamps available at the time was done at one's own peril. Another way to put this is 'marketing' :)


Now as to DHTs in general, most of them are used in SETs. SETs have many disadvantages, but one advantage they do have is that as power is decreased the distortion becomes unmeasurable. If you have a speaker with great enough efficiency to take advantage of this, you can show off that 'inner detail' for which so many of them are known. With most push-pull (not all) amps as power is decreased there is a certain point (generally about 5-7% of full power) where distortion reaches its minimum and then goes back up! So SETs can have a very musical presentation especially if you have a high efficiency loudspeaker.


Its one way to get there, but by no means the only way. We make OTLs that **also** have the same quality of distortion decreasing to unmeasurable as power as decreased. They are also triode and no feedback, and have that relaxed organic quality SETs are know for, but with power, speed, detail and bandwidth that SETs are not. And that's just one example... the bottom line is no matter what, engineering has to be the over-arching principle, that and the understanding of how the ear perceives sound.

Ralph, would monoblock versions of a stereo amp have any improvement of the soundstage?

They often do because there is less crosstalk.

DHT preamps produce the most 3D /holographic soundstage.Probably because those same tubes do the same thing when used in power amps.

This statement is entirely false. Soundstage is not created by how the filament interacts with the input signal! And we can also show easily enough that SETs don't rule the roost when it comes to creating a 3D soundstage.


To get the soundstage right, the circuit has to have bandwidth such that phase shift does not exist in the essential regions where it makes the most difference to the human ear. For the most part this is the Fletcher-Munson  curve frequencies, about 3-7KHz. If the preamp lacks bandwidth past 30KHz its not going to get this right.


So a DHT preamp would only work if its bandwidth met this criteria. It would be doing this because of bandwidth and low distortion, not due to the DHT.


I recommend to anyone that is interested in getting to the bottom of this sort of thing to get a decent set of microphones and a good studio quality recorder. Go out and make a good, 2-mic recording that you can stand to listen to over and over- and then produce it on LP and a digital format. In the case of LP you don't have to produce 500 copies or the like; a test LP is fine. Now you'll have a real reference- because you were there at the recording session and you have the master tapes or master file.

There is no "soundstage" below about 80-120Hz.

This is true. But if the low frequency cutoff of the amplification is only 20Hz, phase shift will exist up to 200Hz. Admittedly, not a lot going on there either. But the phase shift can affect impact of bass notes so its worth getting that bit right as well.

The biggest 3D soundstage comes from directly heated triode [DHT] preamps.

This statement is false. To get a proper soundstage that is faithful to the input signal, the preamp must have wide bandwidth so there are no phase shift issues in the audio region. To do this the bandwidth must be 10x lower than the lowest frequency to be amplified (2Hz) and 10x the highest frequency to be amplified as well. Because phase shift will only be to 10KHz, you can sort of get away with 100KHz on the top end, 200KHz is better. This insures that all the phase relationships that are vital to the soundstage information are amplified correctly.

line stage, phono not needed, must have remote.

@meiatflask
Based on your budget, our MP-3 line stage is our most likely candidate.

Atmasphere- 5k out the door is a hard stop.

@meiatflask

OK- and no phono section, right?

@meiatflask

Do you have a budget for your preamp?

Atmosphere- is the mp-3 balanced only for input and output? Can I use RCAs?

@meiatflask


You can use RCAs.

The MP-3 (and also our MP-1) is fully balanced and differential from input to output. Because it has differential inputs, it doesn’t care if the source is balanced or not. So its equipped with two monitor inputs that employ RCA connections. Additional RCA connections can be optionally added in parallel with the two Aux inputs and the phono input. Additionally, RCAs are optionally available for the outputs. A switch is then provided to switch from single-ended to balanced operation.


The outputs of these preamps are direct-coupled using a patent we developed, which is the only other way other than using an output transformer to meet the requirements of the balanced line standard (AES48). A nice side benefit is the direct-coupled output is more transparent with greater bandwidth both top and bottom.

phantom_av-  it has been years since I have listened to Atma-sphere.  I will check into them.  Per their website, the preamps do not appear to have a remote, which is important to me.

A remote is available for both the MP-1 and MP-3.