Category: Amplifiers
At the dawn of the digital age in 1982 fairly well caught many manufacturers of guard so to speak. You see the DAD(Digital Audio Disc) which came to be known by its most popular name Compact Disc and later shorten to just CD. The CD was to be an audiophile item in many ways. The original intent was that this medium was to be recorded in real time with no compression, limiting or editing of any kind. So in essence with that in mind, the wide range dynamics of the eary CD's presented many playback problems with the gear of that day. When one got the volume up high enough to hear the lowest passages, then would come the crescendos that would cause most amps to clip and fry voice coils of most speakers.
NAD was perhaps the first to recognize this problem and started building their amps with dynamic head room to handle the demanding transients of those early CD recordings. Dynamic headroom was the buzz words of the day.
Very close on their heels was Denon when they released a string of "Real Time Audio Technology" integrated amplifiers to address the CD medium. The ensuing review will deal with one of those eary units the venerable Denon PMA 757 integrated amplifier from 1984.
If memory serves me correct there were three in this series the PMA 737, PMA 757 and the Flagship PMA 777. All of these entries were designed to handle the complexity of the Compact Disc as we knew in those early days.
The audiophile community for the most part holds integrated amplifers in disdain and for many reasons they are right to do so. Many manufacturers have exploited this design for nothing more than marketing and profit. The vast majority of integrated amps are poorly engineered, designed and the build quality to put it bluntly very cheap. Although in recent years this has changed for units from Pass Labs, Levinson,McIntosh and others, have raised the bar to lofty heights for integrated amplifiers. Certainly electrons do not know if they are traveling on one chassis or two chassis. A properly designed integrated amplifier can execute the demands of separates. On the plus side it eliminates another box to deal with or to find the synergey between an amp and preamp. The design is not flawed, just in many cases he execution of the design of the integrated amplifier is severly compromised.
To be further candid the Denon PMA 757 is a compromised integrated as well. But with that being said, the compromises made were without attendant degradation to the overall sonics of this very fine integrated amplifier.
HIGH SPEED DUAL SUPER NON·NEGATIVE FEEDBACK CIRCUIT
Dual super Non-NFB circuit clearly eliminates static distortion generated at output transistors. This techhnique reduces static distortion. to essentially zero. The signal itself is not fed back to the input, and the dynamic characteristcs of the amplifier are greatly improved. High slew rates of ±2oo V Ips, have been achieved.
WIDE FREQUENCY BAND EQUALIZING AMPLIFIER
Conventional NF and CR equalizers have been improved to produce a high quality "wide-frequency-band equalizer". Distortion caused by changes in input impedance is minimized. As a result, a 90 dB S/N ratio for MM cartridges (75 dB for MC) was achieved. Also, a RIAA curve deviation of only ±0.2 dB from 20 Hz to 100 kHz has been attained.
COMPLETE ELIMINATION OF CAPACITORS FROM SIGNAL PATH
Direct DC survo circuitry completely eliminates large-capacity coupling capacitors. These capacitors badly degrade signal quality from signal path. As a result of the new circuitry, the music source can be clearly and accurately reproduced.
A HEAVY DUTY POWER SUPPLY
The PMA-757's high capability, stable power supply section consists of a high performance oversized torodial power transformer and a large capacity block capacitor to achieve superb regulation and S/N ratio.
PROTECTION CIRCUIT FOR SAFETY
If an unexpected problem occurs, such as speaker terminal short or generation of direct current in the output, the protection circuit functions simultaneously. This prevents speaker and amplifier damage. A muting circuit is also provided in order to eliminate noise generated at power "on-off".
POWERFUL DRIVING CAPABILITY
The heavy duty power supply can provide adequate power to drive speakers with a low 4 ohm impedance. Output performance is impressive:
100 WRMS per channel from 20 Hz to 20 kHz
Also dynamic headroom of 3.0 dB is assured.
ELEGANT DESIGN
The DENON design is not only elegant, but also functionally efficient. Due consideration to internal structure and careful selection of parts prevent system components from deteriorating.
OTHER FEATURES
• DAD terminal
• High speed protection circuitry without deterioration of sound quality
• A high speed protection circuitry
• Easy to operate push-button function selector
• Illuminated functions for improved legibility
• 2 sets of speaker terminals (A or B, A+8, off)
• 2 sets of tape deck I/O terminals
• 1 phono terminal accepts MM or MC Phono Cartridges
• Subsonic filter for eliminating unnecessary low audio frequencies of iess than 20 Hz (6 dB/oct)
As you can see the PMA 757 was designed without the faults of the past and to address the then digital age. Plus the build quality was very high indeed when compared with units from other manufacturers. For this period of time Denon raised the bar very high in design and execution of the PMA 757.
Listed below are the audition LPs and CDs used for this review.
Music Used For Evaluation:
LP Playback:
Bob James - Hands Down (Columbia FC 38067)
Hiroshima - Self Titled - (Arista MFSL1-525)
John Coltrane - Blue Train - (Blue Note BST 81577)
Wes Montgomery - Bumpin' - (Verve V6-8625)
Rickie Lee Jones - Self Titled - (Warner BSK 3296)
Wynton Marsalis - Live Blues Alley - (Columbia PC2-40675)
Eric Gale - Forecast - (KUDU Records KU 11)(CTI Records)
Kenny Burrell & Grover Washington Jr - (Blue Note BT 85106)
Earl Klugh - Finger Painting - (Blue Note MFSL 1-025)
Larry Carlton - Friends - (Warner 23834-1)
Sadao Watanabe - Autumn Blow - (Inner City IC 6064)
Doobie Brothers - Minute by Minute - (Warner BSK 3193)
Santana - Zebop - (Columbia FC37158)
Pat Metheny Group - American Garage - (ECM 1-1155)
Frederick Fennel - Cleveland Symphonic Winds - (Telarc 5038)
Paul Desmond/Jim Hall - Complete Recordings - Mosaic(MR6-120)
Time Out - Dave Brubeck Quartet (Columbia CS 8192)
Paul Desmond - Self Titled (Artist House AH - 2)
Ahmad Jamal - But Not For Me - Argo LPS 628
Bill Evans - At The Montreux Jazz Festival - Verve V6-8762
Bill Evans - At Montreux II - CTI 6004
Sunken Cathedral - American Gramophone - AG 361
No Bass Hit - Concord Jazz Label - CJ-97
Oscar Peterson - Night Train - Verve V-6 8538
Gerry Mulligan Reunion Chet Baket - Pacific Jazz ST 90061
Bill Charlap - New York Trio Stardust - Venus VHJD 22
Michael Garson - Serendipty - Reference Recording RR20
Bill Charlap - Things We Did Last Summer - Venus TKJV19111
Ahmad Jamal - Extensions - Argo 758
Tommy Flanagan - Plays Harold Arlen - Inner City IC 1071
Jazz At The Pawnshop - Proprius - 7778-79
Barry Harris - At The Jazz Workshop - Riverside RLP-1177
Adam Makowicz - The Name Is Makowicz - Sheffield Labs 21
CD's Used For Evaluation.
Ben Webster At The Renaissance (Contemporary Records OJCCD-390-2)
The Royal Ballet Gala Performances (Classic Compact Discs CDSCD 6065)
Jurassic Park Motion Picture Soundtrack (MCAD 10859)
We Get Requests - The Oscar Peterson Trio (Verve 810047-2)
You Won't Forget Me - Shirley Horn (Verve 847482-2)
On Every Street - Dire Straits (Warner Brothers 26680-2)
Trio Jeepy - Branford Marsalis (Columbia CK44199)
Paris Jazz Concert - Louis Armstrong (RTE 1001-2)
Braveheart Motion Picture Soundtrack - London Symphony Orchestra (London LC0171)
Patriot Games Motion Picture Soundtrack (RCA 07863 66051-2)
Highlights From The Plugged Nickel - Miles Davis (Columbia CK 67377)
Private Investigations Best Of Dire Straits (HDCD) - Dire Straits (Warner Bros 49891-2)
Straight Up - Bob James Trio (Warner Bros 945956-2)
Land Of Giants - McCoy Tyner (Telarc 83576)
New York Reunion - McCoy Tyner (Chesky 5173324)
Gladiator Motion Picture Soundtrack(Decca 2894670942)
Copland - Appalachian Spring (Telarc CD 80078)
Frederick Fennell - Holst Suites (Telarc 80038)
Tchaikovsky - 1812 Overture (Telarc 80041)
John Williams - American Journey (Sony 89364)
Bizet - Carmen (Telarc 80048)
Live At Sweet Basil - McCoy Tyner Trio (Evidence ECD 22106-2)
Paul Desmond & The Modern Jazz Quartet - Red Baron JK57337
Jimmy Smith - The Unpredictable - Verve 8230308-2
Dexter Gordon - Our Man In Paris - Blue Note 7 46394 2
Mike Garson - Jazz Hat - Reference Recording RR 114
Bill Evans - Live In 1975 Switzerland - Gambit 69232
Bud Powell - Essen Jazz Festival - 1201Music-1QGN9
Cannonball Adderley - Know What I Mean - Riverside OJCCD105
Bill Evans - Ronnie Scotts 1980 - Gambit 69242
Tommy Flanagan - Over C,s - Prestige - OJCCD 1033-2
Ahmad Jamal - Chicago Revisited - Telarc CD 83327
Now for the obligatory specifications:
Power Amplifier Section:
Both channel driven 80 Watts minimum rms per channel(8 ohm Load) with less than 0.03% total harmonic distortion from 20 Hz to 20 kHz. 100 W + 100 W (4 ohm Load)20 Hz to 20 kHz at T.H.D. 0.05%.
Total Harmonic Distortion: 0.005% (20Hz-20KHz at -3dB rated output 8 ohm load.
Intermodulation Distortion: Below 7 kHz/60 Hz;1/4 0.003% at amplitude output equivalent to rated output
Output Bandwidth: 5 Hz - 80 kHz (IHF T.H.D 0.03%)
Transmission Characteristics: 1 Hz - 250 kHz ~~ dB (at 1 W output) 150 mV
Input Sensitivity: 150 mV
Input Impedance: 47 k ohm
Output Impedance: 0.08 ohm (1kHz
Output Terminals: Speaker: A and B Load 4 - 16 ohm A+BLoadS-160hm Headphone/Stereo headphone (310 mW/S ohm)
Equalizer Amplifier Section:
Equalizer Amplifier Output: Maximum Output: 12 V (at 47 k ohm Load)
Rated Output: 150 mVTotal harmonic distortion: less than 0.002%(at 1 kHz,8 V output)
Input Sensitivity/Input Impedance: PHONO MM 2.5 mV MC 200/.J.V TUNER 150mV DAD, VIDEO/AUX, TAPE150mV 47 k ohm
RIAA Deviation: PHONO MC within ±0.3 dB (20 Hz - 100 kHz)
S/N Ratio: PHONO MM 87 dB (input terminals short-circuited for 2.5 mV input)MC 70 dB (input terminals short-circuited for 250 /lV input)
TUNER, TAPE, DAD, VIDEO/AUx110 dB (input terminals short-circuited)
Tone Control Adustable Range: BASS - 100 Hz ±8 dB TREBLE - 10 kHz ±8 dB
Filtering Characteristics: SUBSONIC 20 Hz, 6 dB/oct
Loudness Characteristics: Low frequency 100 Hz + 7 dB High frequency 10 kHz + 6 dB
Power Source: 120V60Hz
Dimensions: 17 x 5 1/2 x 16
Weight: 27 Pounds.
The phono section of the PMA 757 is very good indeed, but when paired with a Denon Moving Coil phono cartridge moves this into the range of superlative. The MM section seems to work best with Grado MI phono cartridges. The other phono cartridges that were used seemed somewhat lacking in the overall tone and signature as compared with the Denon MC and Grado MI.
The line stage is truly one of the strengths of the PMA 757 and in particular the DAD (CD) section. The Denon really comes to life with CD playback and it appears great attention and detail was paid to this circuit. Very few integrated amps or for that matter preamps of damn near any price have the sonic signature of the Denon PMA 757 in CD play back. Very wide soundstage, with great presence and a layering in of the music, that you just have to experience for yourself. And as jaded as I am now some 54 years in this hobby, I was blown away by the CD performance of the PMA 757. I kid you not I have several high end preamps here and none of them have CD playback like this. Many of those high end units clearly best the PMA 757 in analog playback and that is a given. I clearly acknowledge that. But in CD playback this venerable PMA 757 is a total eye opener.
Functionaly it has the look and feel of a more costly unit. The fit and finish is first rate. The controls have that solid silky feel. The function controls when engaged have a lighted indicator that is easy to read from across the room. Came in two finishes Silver or Black. This one is the black finish and is luxurious in its appearance.
Since the inception of Denon in 1910 they have always produced superlative products that have been the benchmark in the category they compete with. Sure over that span they have had a few clunkers, but very few indeed. While not always first to market, when they do appear, it is first rate all the way and well worth the wait.
The PMA 757 is just one of those products that was worth the wait. While this unit is some 27 years in age, it is remarkable in its ability to be able to compete with some of the finest integrated amplifiers in the market palce today. Retail in 1984 was $450.00 and today adjusting for inflation would sell for $959.95. Now in the preowned market sell for $200.00 or less and is an outright steal at those used prices. If looking to put together a second system or to introduce budding audiophiles the PMA 757 will not disappoint. I am impressed way beyond my jaded expectations.
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