mgw@cs.brown.edu (Markus G. Wloka) (08/16/90)
Does anyone have experience (practical or hearsay) with the Altec 1570B triode amps? I need an amp to adequately drive my dearly loved Apogee Duetta II speakers. This is a full-range ribbon speaker. The impedance is somewhat low, around 4 ohm, mostly resistive. The efficiency is abysmal, around 79 dB. The speaker is capable of playing very loud, unlike the Quad electrostatic. Therefore, I need an amp with punch. Good amplifiers for the Duettas are readily available. A Krell KSA 160 will work, a Mark Levinson No. 23 is ok, the VTL 300 tube mono amps sound very nice. The Manley Reference 100-200 triode amp will give me the best sound if I am willing to sacrifice some dynamics, according to some guy at Lyric in NY. The above list is not complete, but you get the drift. Macho equipment, cool looking and hot running, very desirable, and I can't even afford the interest on equipment like this. The amp has to be affordable. Being a hopeless romantic, I would not mind owning a tube amp. Here is what I was able to find out about the Altec 1570B: The Altec 1570B mono triode vacuum tube amplifier. It was used in movie theaters in the early 60's. It uses 4 811A power tubes, which were more common to radio transmitters than audio gear. These tubes are reportedly quite common and economical. Its output power is 165 watts, which is pretty monstrous for a triode amp. It probably has to be modified to work with an audio preamp, by removing the input transformer (does it have one?) and making the inputs more sensitive. It sells for around $600-800, used of course, plus the cost of modifications and replacement of old tubes, caps, and resistors. So far, so good, it fits the requirements. My questions: How does the Altec 1570B sound when properly modified? Does it have 4 ohm tabs on the output transformer? Does it have good bass, midrange, treble? Do I have a good chance of approaching the sound of an VTL 300 or Manley triode tube amp? Or is it just an old piece of industrial equipment, powerful but unpleasant sounding? [I have the schematic for the 1568A... the circuitry is pretty clean and simple... a triode driving a cathodyne phase inverter to differential- connected driver. There's an input filter but just a plug for input transformers. Looks like a likely candidate for update and modification. -tjk] -- Markus G. Wloka mgw@cs.brown.edu Dept. of CS, Box 1910 mgw@browncs.bitnet Brown University, 401-863-7668 Providence, RI 02912