Dynaco FM-3 Stereo Tuner
Picture courtesy of and copyright © Roger Stevens. Please visit his site in return for his kind permission to use the image.
Your FM-3 Dynatuner is one of the most thoroughly researched and field tested components in the high fidelity industry. More than four years of engineering effort have been devoted to this one design with two specific goals in mind: one, performance which cannot be improved at the present state of the art; two, assurance that this performance level can be achieved and maintained by the user in the home.
Side-by-side listening comparisons of the Dynatuner with tuners several times its cost demonstrate the great extent to which these goals have been achieved. Published specifications cannot define the clear superiority of the Dynatuner in low distortion reception of both very weak and exceedingly powerful signals, its remarkable freedom from the problems of cross-modulation and severe multipath effects, its high order of suppression of impulse-type interference, its exceptional capacity to handle severely overmodulated signals without distortion, and its unique ability to maintain full stereo separation with the weakest signals.
These comparisons can be demonstrated using Dynatuners built and aligned by novice constructors, and it is this that represents a fundamental difference from other designs. The Dynatuner is a fresh engineering concept, not an adaptation of an existing production unit. Every portion of the circuit has been carefully investigated in terms both of performance maxima and of the overall stability of operation and simplicity of adjustment required of a kit design. The net result significantly surpasses on all counts units which require that certain sections be pre-built and aligned, and which are therefore incapable of complete home alignment.
The Dynatuner provides the same top performance in your home as in the laboratory, as it can always be properly aligned using the unique procedure detailed in the manual. This ability o be aligned without test equipment, with an alignment as accurate as can be performed in the laboratory, means that after shipping, after aging, after tube replacement, or after any other cause for change in alignment, the unit can be restored to peak performance.
In addition to the adjustment requirements, the basic engineering objective was to produce a tuner design of adequate sensitivity for fringe area reception, with distortion levels of the recovered audio signal comparable to that measured on the best of audio amplifiers. The concentration of effort to reduce distortion has also produced a tuner which is unquestionably one of the very lowest distortion tuners available at any price.
The significant advantages of etched circuit construction in terms of reliability, reproducibility and durability are amply demonstrated in the Dynatuner. Their use has further accomplished the ultimate goal of improved performance. In no other tuner -- kit or factory wired -- has exact component placement and lead layout been so accurately defined. The excellent specifications of the Dynatuner are possible, and guaranteeable, unit to unit, lab model to production kit, because of the extraordinary uniformity which etched circuits provide, and the inherent stability of the circuit configuration.
There has been no intent to enter the sensitivity specification race (claims often engineered by the advertising department). However, using the sensitivity standards proposed by the Institute of High Fidelity Manufacturers this tuner belongs in the highly sensitive class and, in fact, will provide listenable reception of more stations than tuners of ostensibly higher sensitivity rating.
There are many parameters in addition to sensitivity and distortion which are part of a completely satisfactory tuner design. Some are measurable; some are intangible. The design requirements for a premium quality kit lead automatically to a distinctly superior factory assembled tuner as well. Extensive field testing under adverse and marginal conditions has proven the Dynatuner to be as fine a tuner as can be obtained today regardless of price or specification claims.
Outputs: Audio output.
Usable Sensitivity: 4 microvolts for total noise and distortion 30 dB below 100% modulation.
Signal-to-Noise Ratio: 70 dB @ 100% modulation level.
Harmonic Distortion: Less than 0.25% @ 100% modulation.
Drift: Less than 0.03%.
Frequency Response: ±0.5 dB 10 cps to 15 kc.
Capture Ratio: 5 dB.
Selectivity: 54 dB.
Audio Hum: 73 dB below 1 volt output.
AM Suppression: Greater than 63 dB.
IM Distortion: Less than 0.5% from 10 microvolts to 100,000 microvolts @ 100% modulation.
Audio Output: 2 volts @ 100% modulation.
Output Impedance: less than 5000 ohms.
Discriminator Peak to Peak Separation: Greater than 900 kc.
Antenna Input: 300 ohms balanced. 75 ohms unbalanced.
Dial Calibration Accuracy: 0.2%.
Power Consumption: 55 watts.
Tubes: 1 6AQ8 (ECC85); 1 6AT8A; 2 6BA6; 2 6AU6 (EF94); 2 12AX7 (ECC83); 1 EMM-801; 1 6V4 (EZ80); 1 6BL8 (ECF80).
Stewart Hegeman, Ed Laurent (multiplex circuitry by Sid Lidz)
Essentially a re-packaging of the FM-1/FMX-3 units with redundant circuitry eliminated and the new front panel and knobs added. Introduced in 1964. Thanks to Ned Carlson from Triode Electronics for the scans of the classic reviews!
click here to see the 1964 review of the FM-3 in Stereo Review magazine.
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Copyright © 2000,2001 Greg Dunn