Altec 1570B
The Altec 1570B is a green-chassis power amp with a pair of 811A tubes and enough plate voltage to kill you. Treat it with respect.
Contemporary coverage of the model was thin but pointed. Vacuum Tube Valley (p.15) ran a 1570B modification write-up, and it led with a blunt safety warning: the voltages inside can exceed 1000 V, and a screwdriver or finger in the plate supply can kill you.
Overview
The Altec 1570B is a tube power amplifier, and in the enthusiast press its reputation is bigger than its paper trail. No factory specification sheet has surfaced, no dated catalog listing, no mainstream hi-fi review. The model is known almost entirely through the specialist audio press and the people who own one. Sound Practices (Issue 17, p.11) called it "a famous push-pull 811A amplifier," and reported that it put out 165 W from 70 Hz to 20 kHz. That's a serious number for a tube amp of any era. It explains why the 1570B turns up in the conversations of people who run big, inefficient speakers.
The tube complement is a pair of 811A's run push-pull. The 811A is a transmitting tube, not an audio tube in the usual sense. Owners and tinkerers report a stock plate voltage of 930V at 175W on that pair. Vacuum Tube Valley (p.15) put the warning bluntly: voltages inside a 1570B can exceed 1000 V, and a screwdriver or finger in the plate supply can kill you. That is not marketing copy. Know it before you slide the amp out of a rack.
Sound Practices noted that people "crazy enough to run 'these green monsters' at home seem to like them a lot," and "green monsters" is the phrase that stuck. The green chassis is apparently the 1570B's visual signature. Collectors describe it as rare and collectible and increasingly hard to find in good condition, which suggests most surviving examples were rode hard and put away hot.
Key Features
Push-Pull 811A Output Stage
The 811A is the core of the design. A pair of them, run push-pull, gives the 1570B its 165 W rating according to Sound Practices (Issue 17, p.11). The 811A is a big, hot, high-voltage tube, and a push-pull pair favors grunt over gentleness. It also makes the amp demanding to service, because the output stage sits at voltages that leave no margin for a careless probe.
165 W from 70 Hz to 20 kHz
Sound Practices (Issue 17, p.11) reported 165 W across a 70 Hz to 20 kHz band. Treat that as a single-source figure — no factory sheet has surfaced to confirm it — but it's the number the enthusiast press has circulated for decades. For context, 165 W of tube power is enough to drive speakers that would make a lesser amplifier fold, and the 70 Hz low-frequency limit means the amp is doing real work down low rather than handing off to a sub. Whether it delivers that figure in a given example, decades on, depends entirely on the condition of the tubes and the power supply.
Lethal Plate Supply — Over 1000 V
Vacuum Tube Valley (p.15) warned that voltages inside a 1570B can exceed 1000 V, and that a screwdriver or finger in the plate supply can kill you. This is not a footnote. It's the defining practical fact of ownership. Any 1570B that hasn't been serviced by someone who knows high-voltage tube gear is a hazard, and even one that has been serviced deserves respect every time the chassis comes off. The stock plate voltage on the 811A pair is reported at 930V at 175W, which sits right at the edge of that warning.
The Green Chassis
Sound Practices (Issue 17, p.11) called them "these green monsters," and the green chassis is apparently the 1570B's visual signature. It's the detail that makes the amp instantly identifiable, and it's become the shorthand for the model in enthusiast circles. The color is cosmetic, but it's also useful: it tells you at a glance that you're looking at a 1570B and not one of Altec's other tube amps.
Peerless Transformers
Owners chasing parts reference the 16492 output transformers, the Peerless Altec 17173 split choke driver transformer, and the Peerless 6410 power transformer as the iron associated with the 1570B. These parts show up in the used market as vintage components. The output winding arrangement is reported as two 60V windings, with a 4 ohm tap taken at the 75% point - close enough to the 70.7% point to serve as a distribution tap. That's an unusual arrangement, and it matters to anyone trying to match the amp to a specific load.
Modification-Friendly Design
The 1570B has a modification culture around it. One documented mod swaps in a capacitor input power supply, raising plate voltage to 1250V for a potential of 250W. That is a modification, not a factory spec, and it pushes the amp further into dangerous territory. Owners also discuss redoing the bias circuit, and one well-known Altec technician is referenced in enthusiast circles for his 1570B mods. Service documentation exists - a 1570B power amplifier manual and schematic circulate as PDFs - which is more than can be said for a factory spec sheet.
Historical Context
Production years for the 1570B can't be confirmed. No original factory specification sheet, dated catalog listing, or mainstream hi-fi review has surfaced, and the model is known mainly through the enthusiast audio press. An article on the 1570 and its modifications was reviewed by Joe Rosen in October 2001, so the amp was still being written about and modified well after its production era. For company context, Altec was formed in 1938 from the All Technical Services Company, but no explicit lineup or family positioning for the 1570B is documented in the available sources.
Collectibility & Value
Collectors describe the 1570B as rare and collectible and increasingly hard to find in good condition. No reliable market price has surfaced in the research. One eBay listing for a "Vintage Altec Lansing Original 2U Power Distribution 1570B A" at $500 is not usable as an amplifier price - the item is described as a power distribution unit, not an amplifier, and its model identity is ambiguous. A dealer listing showing a sale price of $0.00 is a placeholder, not a value. Anyone buying should expect to pay for condition and completeness, and should budget for service. The amp runs at lethal voltages, the tubes are specialized, and the transformers are vintage parts that appear only intermittently in the used market. Service manuals and schematics exist, but they don't make the amp safe to open without experience. This is a piece for someone who already knows high-voltage tube gear, not a first project.
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