Futterman H-3A power amplifier Specifications

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Description: All-tube output-transformer-less stereo power amplifier. Output: 90Wpc with 16-ohm load. Frequency response: 5Hz–90kHz, +0, –0.5dB; –3dB at 200kHz. IM distortion: <0.05% at 90W (continuous sinewave) into 16 ohms. Damping factor: 200. Stability: Unconditionally stable with any kind of load. S/N ratio: better than 93 dB below 90 watts. Sensitivity: 2.0V in for 90W out. Input impedance: 270l ohms.
Dimensions: 17" W by 1O.25" D by 7.5" H. Weight: 29 lb. (Relatively light weight due to absence of output transformers.)
Price: $288, including cage (1967); no longer available (2019).
Manufacturer: Harvard Electronics Co., New York, NY 10025 (1967). Company no longer in existence (2019).

COMPANY INFO
Harvard Electronics Co.
New York, NY 10025 (1967)
Company no longer in existence (2019)
ARTICLE CONTENTS

COMMENTS
John Atkinson's picture
I chose this review to republish on the website because this was the very first example of that extraordinary beast, the output-transformer-less tube amplifier, that I encountered!

John Atkinson
Technical Editor, Stereophile

Ortofan's picture

... an output transformer or a coupling capacitor?

As an experiment, buy a pair of "computer-grade" 800µF aluminum electrolytic capacitors, connect one in series with each channel's output of your amplifier and determine what effect, if any, they might have on the sound quality.

scottsol's picture

You should have realized, and I have verified this from the Acoustat .comments, that publishing old material is a colossal waste and that nobody could possibly be interested.

John Atkinson's picture
scottsol wrote:
You should have realized, and I have verified this from the Acoustat .comments, that publishing old material is a colossal waste and that nobody could possibly be interested.

With all due respect, the page views stats show that you are wrong.

John Atkinson
Technical Editor, Stereophile

scottsol's picture

My post was intended as a satirical play on that ridiculous comment in the Magnepan 20 thread. The Acoustat reference was a mistake as I had just posted about the 2+2.

michelesurdi's picture

how time does fly.nowadays it is quite common to suggest that tube amps apparently deli ver more than their rated power.

Bogolu Haranath's picture

Manufacturer's specs say ......... IM distortion <0.05% at 90W continuous into 16 Ohms ....... S/N ratio better than 93 db below 90 Watts ....... Damping factor 200 ........ SNR of 93 db is approx. 15 to 16 Bit resolution ....... Can an OTL tube amp achieve a damping factor of 200? ....... Beast indeed :-) ..........

Bogolu Haranath's picture

Certainly, Futterman was ahead of his time, prepared for future-proofing ......... He was thinking about hi-res audio in the 60s, with that kind of SNR :-) ........

T-NYC's picture

The amp was ideal with QUADs if you told Julius that's what you planned to use. He adjusted the output to lower wattage running pure class A. He also strongly recommended Rogers LS35A (15 ohm) for use with this amplifier.

Herb Reichert's picture

they were broken I fixed them (new caps and tubes) tested them and hooked them to both Quad 57s and LS3/5a. For about 48 hours I was completely taken with their midrange. Then I sold them quick while they were still working. lol

hr

Ortofan's picture

... Hoovie's Garage approach to Hi-Fi.

Bogolu Haranath's picture

Wonder whether HR also has a photo-album diary? :-) ........

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