Hidden treasures: DENON PMA-250

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Reviews

Denon fans are a dime a dozen, but most of them seem to be fixated on powerful amplifiers. On the other hand, people looking for a good amplifier with low or medium power are more likely to choose a Rotel, NAD, one of the many British amps, or something from the 70s. Lower power Denons (20-40 W per channel) are not very popular and it appears that at some point Denon stopped making those and offered mini systems instead. But in the 80s there were several such models, including one particularly worthy of attention due to availability and low price: the PMA-250.

The amplifier has a very simple design in and out, which is an obvious advantage. The only solutions that are not quite standard are the CD Direct button that cuts off the input selector and passes the signal from the CD input directly, and the volume control potentiometer that has separate adjustments for left and right channel (rather than common volume adjustment for both channels and a separate balance pot). Interestingly, CD Direct does not bypass tone control, only the input selector and tape monitor switches – but it shortens the signal path, audibly improving the sound quality. Apart from that, the amplifier is as simple as possible, while maintaining the standard features. PMA-250 doesn’t even have low, high and loudness filters, and there are connectors for only one pair of speakers. The amplifier is clearly designed for a small, simple system. It was available in black and silver, black fading to dark gold, much like on Protons. The effect actually can look good, unless the previous owner put stickers on the amp – then the surface under the stickers remains black. In any case, silver face version looks better to begin with and does not have the fading color problem.

The PMA-250 is as clean inside as it is on the outside. Wires are few, power supply section and power transformer are separated from the audio sections with a decent heatsink, phono stage and volume control are far from the transformer. The design is mosty discreet (1 IC in the phono stage, 2 in the power amplifier section). With decent PS and cooling, the amplifier handles low impedance speakers very well (within the limits of its power).

Sonically – we liked the amplifier from the first note. It had very good clarity, dynamics, and the presentation was very pleasant. We immediately decided to compare it with a few other amplifiers that can be purchased for a similar price and that we had at hand at the time: Kenwood KA-31B, Fisher CA-2221, and Russian Vega 10U-120S. The A/B comparison showed how good this amp really is. Kenwood and Fisher did not stand a chance: Denon sounded a little brighter, but much more dynamic, created way better soundstage, with greater depth, and it was smoother, more musical. Vocals sounded great – presented with class, without any grain or sibilance. Denon exposed the details, which in the case of the other two Japanese amplifiers were buried somewhere in the background, or inaudible at all. Bass was less generous than from the Kenwood, but present in adequate amounts and very well delivered. Surprisingly, the only amplifier that did not fail miserably in this comparison was the Soviet Vega, which sounded different, but not clearly worse (bass was lower, but shorter, highs and mids a bit softer). In any case, Denon showed class we would not expect from a budget Japanese amp from any period, not just the 80s or 90s. Its sound was actually quite… British. Incidentally, this Denon was highly praised by British reviewers and compared with NADs.

A small hint: it is worth hunting for units with intermittent / disappearing sound in one or both channels. A very common source of problems in this model are solder joints under the volume potentiometer. 5 minutes with a soldering iron and problem solved.

Note that this review is written for the first version of PMA-250. There are also two later incarnations: PMA-250 SE and PMA-250 III. We have not heard those and don’t know if they are as good as the first version, or any good at all (although user reports for PMA-250SE are good). The first version of PMA-250 was manufactured in Japan (more common) and Taiwan (less common). Both units that we had were made in Japan, but the units assembled in Taiwan are based on the same design, If there are any differences, they should be minor. According to user reports, the units made in Taiwan sound great.

Denon PMA-250 is a perfect choice for a system with small and medium-sized speakers in a 10-25 m2 room, and a great alternative for NADs (including the 3020), Creeks and Cyruses. It is extremely hard to find something that good for the price it usually sells for (around 50 euros, less with luck or if the amp needs minor repairs), or twice that price. On top of that, the amp is quite common, so it appears often on auction sites. We liked this amplifier so much that a year later we I bought another one (in silver) to refresh our memory of its sound – the second unit did not disappoint either.

Denon TU-450 is the matching tuner; it is decent. There are units with station memory problems, dry capacitor is usually the culprit.

 

Technical information:

Country: Japan and Taiwan
Manufacturer: Denon (Nippon Columbia C.O.)
Years: 1987-?

Continuous power: 2x25W into 8 ohms and THD 0.05%, 2x40W into 4 ohms
Music power: 2x60W into 8 ohms, 2x90W into 4 ohms

Speakers: 4-16 ohms

Input sensitivity:
CD, Tuner, Aux, Tape: 150 mV, 47 kOhm
Phono (MM): 2.5 mV, 47 kOhm

Frequency response: 5 Hz – 150 kHz (+0/-3 dB, 1W),
Power bandwidth: 10 Hz – 40 kHz (THD 0.1%)
10 Hz – 40 kHz (thought w pe┼énym zakresie mocy)

Tone control:
Treble: +/- 10 dB at 10 kHz
Bass: +/- 10 dB at 100 Hz

S/N ratio: >72 dB (phono input), >96 dB (line inputs)

Power consumption: 80W

Dimensions: 434 x 257 x 85 mm
Weight: 4,9 kg

4 comments

  1. Ted

    “the volume control potentiometer that has separate adjustments for left and right channel (rather than common volume adjustment for both channels and a separate balance pot). ”

    Glad I read this review because I had somehow never noticed this before! I couldn’t figure out why I couldn’t get my setup properly balanced! However, this amp is still extremely loud when connected to my turntable. No idea what’s going on there, but at least it’s properly balanced now.

    Great review!

    1. rafal lisinski Post author

      Glad our review was helpful Ted!

      Not sure why the amp is extremely loud with your turntable, its PHONO input sensitivity is fairly standard (2.5 mV 47 kOhm). The sound from turntable connected to PHONO input is usually a bit quieter sound than from other sources (like CD, tuner) connected to line input (for example AUX).
      Here are some of the possible reasons:

      1. Your turntable has an MM cartridge with a very high output. Some carts are louder than average. If that’s the case, either live with it or change your current cart to something quieter (with lower output).
      2. Your turntable has a different type of cartridge, for example a piezoelectric crystal or ceramic cartridge. If that’s the case, you should connect it to a different input (AUX, TAPE, CD, TUNER – any of these will work). PHONO input is only for turntables with MM (moving magnet) cartridges.
      3. Your turntable has a built-in phono stage (phono pre-amp) or is connected to your Denon amp via a separate phono stage. Some turntables (particularly modern ones) have built-in phono stages, also many people use external phono stages like NAD PP1 or TEC TC760LC. If that’s the case, you should also use a different input.

      If in addition to extremely loud sound you also have excessive bass from your turntable, that would indicate reason 2 or 3.

      If you give me more details (exact turntable model, cartridge name and model, if anything is connected between your turntable and amp) I can check specifications and maybe figure out what’s going on in your setup.

      1. Ted

        Hey! Thanks for reaching out.

        I’ve gone over some of this and I can’t quite put it together, but here is my current setup:

        MCS 6700 turntable with a fairly standard AT95E Audio-Technica cartridge. It’s an older turntable so I don’t believe it has any built in pre-amp and I’m connecting it through the phono input on the receiver and running a pair of Polk TSi100 speakers. Just for the sake of experimenting I’ve tried plugging it into a non-phono jack on the receiver and it was whisper quiet. The turntable (phono) and my iPod (aux) are nonetheless both aggressively loud. I usually run them at a volume of “2” out of “40.”

        What’s strange is that I have a Technics SA-R477 receiver that I sometimes use (preferring the Denon as it’s a better fit for my super-basic setup as you note in your review) and the turntable/iPod have totally normal output.

        I’ve read that this receiver has a bit more oomph than others and I’m thinking about just buying/building some RCA line level attenuators to drag the system down a couple of dB. I’m not sure if you have any additional insights, but I nonetheless still really appreciate the review you wrote (helped me rediscover how great this receiver is) and the information you have posted above.

        Cheers

        1. rafal lisinski Post author

          OK, it’s not your turntable or cart. MCS 6700 does not appear to have a built in pre-amp and AT95E is a standard MM cartridge, so everything’s connected properly.

          One note, Denon PMA-250 is an amp, not a receiver. Receivers have built in radio tuners. Your Technics SA-R477 is a receiver.

          Your Technics receiver could have a different input sensitivity, but I suspect the difference lies simply in the volume potentiometer characteristics. Potentiometers have different attenuation curves, which is one of the reasons why some amps get loud faster than others while having similar rated power. I don’t remember my PMA-250s getting loud too fast, but my speakers are not very efficient.

          RCA line level attenuators would do the trick, but I would advise against using them with a turntable. A better solution would be to plug attenuators in the tape loop. This way thy will attenuate a line-level signal (as opposed to phono-level signal, which is much weaker and more susceptible to loss, distortion and interference), and one pair will work for both phono and aux inputs. And you can easily put them in/take them out of the signal path by switching the TAPE MONITOR button. Actually a regular stereo volume potentiometer in the tape loop would work perfectly. I use this solution in amps that have volume level imbalance at low volume levels (and unfortunately many do).

          Cheers

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