Specialists > Audiologists
Phase Splitters Good or Bad ?
rollo:
I call it the Humpty Dumpty effect. Can the signal actually be put back together properly ? Are SET designs without such an advantage ?
charles
tmazz:
Like everything else in audio, amplifier design is a series of trade offs. No one circuit topology does everything right, they all have advantages and drawbacks. Set Designs are simple and have very few components in the signal path. but the also produce high amounts of second harmonic distortion and tend to require large (and expensive) output transformers because of the DC current that flow continuously through the primary windings. They are also extremely limited in the power output they can produce from given tube. (for example SET circuits designed around using a single KT-88 in triode mode will produce about 5 watts whereas a KT-88 used in a class AB push-pull circuit can easily produce 50.)
SET amps are also notoriously inefficient, although the cost of providing AC power toan amp is rarely a concer to a high end audiophile, especially at the low output wattages that most high end SET amps produce.
Push pull circuits do produce more power but at the cost of more circuit complexity such as the require for a phase splitter.
While this is a downside, it also allows the amp to be with a much wider selection of speakers including designs that have efficiency ratings that would them from being used with SET amps. The use of lower efficiency speakers/higher wattage amps also lowers the impact of noise in the system. Several milliwatts of noise into a 100+ db efficient speaker can produce some easily noticeable sound, whereas that same amount of noise put through a speaker system with an 89db or lower rating might barely move the cones.
So is it really not a matter if phase splitters are good or bad. If you use a push pull design, you need the phase splitter. This is just another way of asking is a SET topology "better" than a push-pull topology. And in my mind that is a question that has no definitive answer. They both have pluses and minuses and they both can be the right or wrong choice, depending on the rest of the equipment being used with them.
Once again we are back to the same place, Synergy Synergy Synergy and personal preference. But then again, isn't that what this whole hobby is about?
dBe:
--- Quote from: tmazz on August 12, 2017, 10:34:01 AM ---Like everything else in audio, amplifier design is a series of trade offs. No one circuit topology does everything right...
Once again we are back to the same place, Synergy Synergy Synergy and personal preference. But then again, isn't that what this whole hobby is about?
--- End quote ---
I've heard amps of every type that have just knocked me out, and those same amps in applications that sucked. Like you said - synergy. We need to chose wisely :thumb:
steve:
Years ago, I designed a phase splitter that was so good that I could not tell any difference when it was in or out of the system. Great, natural sonics, little artificial flavorings. Difficult to design, some. Made it to my monoblocks.
A phase splitter does not pull the signal apart and then put it together again, but I think I understand what is meant. Almost all phase splitters will have different output impedances (Z) per left and right output, although some designs only slightly. 180 degree out of phase is also important over a wide range of frequencies, and that can be achieved as well. This is best achieved by using high Gm and low plate resistance tubes. Of course SS is more complex by definition.
Simply put, the input signal is applied in such a way that the two output signals are 180 degrees out of phase over a very wide frequency range. Voltage is the main consideration, but some current is also needed to charge and discharge the output capacitance, interconnect capacitance, and amplifier input capacitance. The capacitances will depend upon the IC capacitance and device/gain of the amp input device.
Cheers
Steve
rollo:
--- Quote from: steve on August 12, 2017, 07:00:11 PM ---Years ago, I designed a phase splitter that was so good that I could not tell any difference when it was in or out of the system. Great, natural sonics, little artificial flavorings. Difficult to design, some. Made it to my monoblocks.
A phase splitter does not pull the signal apart and then put it together again, but I think I understand what is meant. Almost all phase splitters will have different output impedances (Z) per left and right output, although some designs only slightly. 180 degree out of phase is also important over a wide range of frequencies, and that can be achieved as well. This is best achieved by using high Gm and low plate resistance tubes. Of course SS is more complex by definition.
Simply put, the input signal is applied in such a way that the two output signals are 180 degrees out of phase over a very wide frequency range. Voltage is the main consideration, but some current is also needed to charge and discharge the output capacitance, interconnect capacitance, and amplifier input capacitance. The capacitances will depend upon the IC capacitance and device/gain of the amp input device.
Cheers
Steve
--- End quote ---
Thanks for explanation Steve. Synergy of components is a well known fact. But actually what is behind synergy ? Is it electrical characteristics of each component that meld together ? Is is something else related to sonic character of components ?
I find it a tired argument or phrase used to explain why certain components go well with each other. T
here must be an engineering reason I would like ALL to know. Maybe I should start a new topic.
charles
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