Good day!
When building/developing/finetuning an amplifier, I generally work on a single channel - I think most people do so?
But how do you listen to your (mono) proto amp? For the moment I am summing a stereo signal to mono, feeding this to the amp, and listening to a single speaker - but thinking about "improving" this. So my question is:
How do you develop and listen to your newly created (mono) amplifiers?
Cheer, Erik
When building/developing/finetuning an amplifier, I generally work on a single channel - I think most people do so?
But how do you listen to your (mono) proto amp? For the moment I am summing a stereo signal to mono, feeding this to the amp, and listening to a single speaker - but thinking about "improving" this. So my question is:
How do you develop and listen to your newly created (mono) amplifiers?
Cheer, Erik
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You can use a true mono source, like an LP, if you are afraid of screwing sound by mixing channels. A purist may go even further by using a true mono cartridge, like Ortofon's SPU. Also, there are many CD re-issues of old mono recordings.
As a side note, down-mixing of multi-channel recordings to two channels, which most recording companies are guilty of, indeed royally screws the sound. Deutsche Grammophon is probably the worst offender.
The best mono records of the past are not flat, as one might think - they have a lot of spatial information. One example is Mercury Living Presence. They did true mono recordings by placing a single U47 microphone in a sweet spot of a recording venue. Played through a high quality mono system, these records sound 3-dimensional. Resolution of micro detail is a key. It is similar to HD TV being perceived as having more depth than now defunct low resolution format.
As a side note, down-mixing of multi-channel recordings to two channels, which most recording companies are guilty of, indeed royally screws the sound. Deutsche Grammophon is probably the worst offender.
The best mono records of the past are not flat, as one might think - they have a lot of spatial information. One example is Mercury Living Presence. They did true mono recordings by placing a single U47 microphone in a sweet spot of a recording venue. Played through a high quality mono system, these records sound 3-dimensional. Resolution of micro detail is a key. It is similar to HD TV being perceived as having more depth than now defunct low resolution format.
I also build a single channel amplifier for tests and development.
At first I optimize the performance of the amplifier with test equipment.
I pay attention to get minimum THD, flat frequency response, best possible transient response at high and low frequencies, optimum S/N, optimum GNFB, etc.
When listening I connect my standard pair of speakers in series, located in the living room, because this is my reference.
The mono signal is simply formed with a mixer, nothing special in here.
At this point, my main focus is on measurement results. Listening has bigger role later when the stereo version is ready.
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Mono can give a sense of depth due to relative loudness of instruments. Early recordings were "mixed" in this way by having a single microphone and the musicians at various distances from it, maybe stepping closer when they took a solo. Our image of depth is created in ours brains due to learning, experience and psychoacoustics
Hate to be a pedant, but SPU stands for 'Stereo Pick Up'. Their mono cartridge predates the SPU (C25 series).
There's gobs of spatial information in a mono signal. Perceived depth isn't dependent on two channels.
Scottjoplin did already correctly mention that even in a mono source some "depth of image" information is included.
Clues are level and ratio between direct and reverberant soundfield and that is all what is needed to create the illusion of spatial depth. Even a rudimentary illusion of different height is possible by smart use of psychoacoustic effects.
Might be so (while questioning the "violent" part
) but imo it is a quite artificial distinction between "proxies for illusion" and "real spatial" information, as everything between the two loudspeakers (provided it is a two channel stereo setup) is still an illusion....
It's a turn of phrase I use when two people are debating the same point but subtle wording stops them realising it .
I must admit to forever being suprised how much our brains can infer. I have a wonderful DG mono LP of a Tenor and piano and when listening you are convinced the singer is standing in front of the piano. I have no way of telling if he was, but it sounds that way
Not bad for a bone that was once part of our jaws
.I must admit to forever being suprised how much our brains can infer. I have a wonderful DG mono LP of a Tenor and piano and when listening you are convinced the singer is standing in front of the piano. I have no way of telling if he was, but it sounds that way
Not bad for a bone that was once part of our jaws
It's a turn of phrase I use when two people are debating the same point but subtle wording stops them realising it
I must admit to forever being suprised how much our brains can infer. I have a wonderful DG mono LP of a Tenor and piano and when listening you are convinced the singer is standing in front of the piano. I have no way of telling if he was, but it sounds that way
Not bad for a bone that was once part of our jaws
1.) I know
2.) Yeah, it´s interesting what our brain is doing to reach consistency between sensory input and remembered experience. I think i mentioned it earlier (when linking the old papers describing the first public demonstration of stereo) that already the inventors knew that a lot of this depends on listener´s experience with real acoustical events.
As scottjoplin pointed already out, a monoaural source nevertheless is able to tranport level differences (which is a clue for greater distance) and a difference between direct and reverberant/reflected sound (which makes usually the difference between a low level sound source nearby or a higher level sound source being farther away) but in any case as the loudspeaker does not move it is still an illusion....
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many thanks for all replies.
I only have digital sources, and listening to mono is not my objective - the question was more: how to make the best out of a single chanel amp when used to stereo? `
I think I will do as Artosalo: make an arrangement to easily connect the amp under test with my main speakers.
wish you all a nice sunday, Erik
I only have digital sources, and listening to mono is not my objective - the question was more: how to make the best out of a single chanel amp when used to stereo? `
I think I will do as Artosalo: make an arrangement to easily connect the amp under test with my main speakers.
wish you all a nice sunday, Erik
I don't. And i think it is a mistake, unless you are building an amp for a mono system. Subjectively a stereo amp is voiced very differently to a mono. A great example from the past is the Williamson amp, which at least imo sounds much better in mono.
When developing a new idea into a working circuit, not just building a new take on a known design, I always build a single channel amp fed by known bench power supplies. Many of my "ideas" don't get past this point, so why make two failures and more unneeded power supplies?
This is usually done on a prototyping system of some sorts whether it's clip leads, a hacked up old PC board from a failed design, a piece of perf board, or in the old days, tube sockets and sky wired parts screwed to a piece of plywood. Any listening done is obviously mono through a set of "test" speakers.
I built a set of low budget speakers ($150 for the pair) that sound far better than their cost, and will eat a 125 WPC tube amp cranked to the edge of clipping for hours. Hard to blow, and each driver cost under $20 if I do blow one. Initial testing is with the tweeter turned off in case of oscillation.
Once that design is working it gets thoroughly bench tested and subjected to my usual torture testing, and once I'm satisfied, I will hook it up to my Yamaha NS-10M' Studio's in mono with the speakers in their usual location. I have owned these speakers for over 20 years and I know how certain CD's sound on them, and what to listen for. These are my "reference."
If I am still inspired by the design, I will make a stereo PC board with power supply and do some real testing, both analytical measurements and critical stereo listening with several sources on several speaker systems.
Unless there is a need, I strive to make my amps as neutral as possible. Obviously certain tubes and OPT's will color the sound, and this may or may not warrant some attention. Purpose built amps do get tweaked for their intended purpose. Guitar amps are the obvious case, but subwoofer amps and amps that are part of a bi-amped or tri-amped system also need attention.
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