Why does the APT Holman preamp sound so good? - diyAudio
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Old 26th December 2004, 06:41 AM   #1
mattjk is offline mattjk  United States
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Default Why does the APT Holman preamp sound so good?



... and the phono section is amazing.

The sound is slightly better than my pass x2.5
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Old 27th December 2004, 08:35 AM   #2
djk is offline djk
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I like many aspects of that preamp.

The sound is not up-to-date, TL072 opamps were OK 25 years ago, better are available now.

The capacitors are horrible.

The power supply regulators have much room for improvement.
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Old 27th December 2004, 09:05 AM   #3
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Quote:
TL072

Is the Pass that bad?
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Old 27th December 2004, 09:07 AM   #4
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Any schematic ?
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Old 27th December 2004, 10:08 AM   #5
djk is offline djk
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"Is the Pass that bad?"

No

I have found 90% of people cannot hear in the audiophile sense, and of the 10% that can, 90% of those pick the worst unmusical sounding gear.

The 1% that could tell whether something was musical never seemed to have any money.

I would describe the APT as uncolored, but lacking in dynamics, lifeless.

"Any schematic ?"

Unfortunately, yes, but I am moving and not likely to find it anytime soon.
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Old 27th December 2004, 10:51 AM   #6
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Default Yessssss!..why?....why?.... i am crazy to discover those things!

fourty years researching and having not too much idea that "what" makes a good sound!

I have a friend that said to me that the good sound is the one he has at home, the most pretty wife is the one he has at home.

Others said that must have mirrors, some say that must have CCS.... others said without differential sounds different, others that triple darlington is magnificient, others say that better is to use a single darlington...others say that....i could not "capture" what makes a good sound!

But i have one idea of it...beeing with your wife.... with deep passion..can you understand how deep is the love i am talking about?..... welll....the sound that is playing in that moment is the best amplifier on earth.because ...you will not perceive nothing more than hormons circulating, heart beating strong...you will hear a lot of things.... the only thing that you will not capture is the sound.

Some very inteligent guy or girl, once told that the best sound is the one you do not perceive it playing..... maybe, as not disturbing you anyway...if distorted you will perceive, if too high you will also perceive..... if disappear is a good amplifier..this makes some sense too.

regards,

Carlos

regards,

Carlos
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Old 27th December 2004, 01:36 PM   #7
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Quote:
I have found 90% of people cannot hear in the audiophile sense, and of the 10% that can, 90% of those pick the worst unmusical sounding gear.
Not a very nice thing to say especially since you have no facts to back up your claims. Maybe you are in your self proclaimed majority.
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Old 27th December 2004, 02:24 PM   #8
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schematic?
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Old 27th December 2004, 05:41 PM   #9
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Default AES Article

Tomlinson Holman wrote about preamplifier design in "New Factors in Phonograph Preamplifier Design" AES May 1976, Vol 24, Number 4.
From memory he suggested that many solid state preamps of the day had reactive components to the input impedance and that this was one of the major sonic differences as compared to the best tube designs of the day.
He also paid attention to rejecting low frequency warp and rumble at the input before any amplification.
I was told many years ago by a reliable source who was there, that much of this paper came from discussions at Advent and that Holman did more to raise awareness of the issues. I believe that the topology covered in the AES paper was first used in the phono section of the Advent Receiver. I do also believe, IIRC, that the Apt Holman phono section is very similar.
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Old 28th December 2004, 12:09 AM   #10
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Default Holman Patent

See patents 4,032,855 and 4,117,412
http://patft.uspto.gov/netahtml/search-bool.html

From: http://www.tech-diy.com/patents_amplifiers.htm

Phonograph preamplifier network with infrasonic cutoff response
4,032,855
Holman, II June 28, 1977
A phonograph preamplifier network with infrasonic cutoff response. The preamplifier network is an active filter configuration with a high gain, high input impedance differential amplifier provided with an RIAA equalization feedback filter network coupled between the amplifier output and inverting input. An RC filter network is coupled between the inverting amplifier input and ground potential to provide a single, low frequency real axis pole. In addition, an input filter feedback network is coupled between the preamplifier input terminal and the non-inverting input of the amplifier, and further bootstrapped to the amplifier inverting input. The network provides a pair of low frequency off-axis complex poles. The RC filter and the input filter feedback networks are adapted to control the infrasonic frequency response of the active filter preamplifier network so that the preamplifier network is characterized by an 18 dB per octave roll-off response at frequencies below a predetermined infrasonic frequency, and a relatively flat response at frequencies in a range adjoining and above that infrasonic frequency.
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