Let’s be bold here and propose something — you can never have too many amplifiers! Even if your principal system is an astonishingly high quality audiophile set-up, what about the rest of the house? Or what about the 11 channels required for a full (or 7.1.4 at least) Dolby Atmos system?
Well, the extremely flexible can deal with just about all these requirements.
This is a 12-channel power amplifier which provides enormous flexibility in how it can be used. For one thing, it need not be 12 channels.
It can be 11, or 10, or any number down to six. You don’t waste the leftover amplification —the 12-channels are grouped as six ‘zones’, each with a left and right channel, and each zone can have its two channels bridged to one, for higher power output.
Each channel can be entirely independent, even to the point of having its volume set separately to all the others. Each pair of channels can, as mentioned, be bridged, or can be set to mono (i.e. with the left and right signals mixed down to one signal, and then output by both left and right channels). Each zone (pair of channels) can be grouped with others to one of two separate buses. All channels can be switched on manually or by means of an external 12V trigger, or each zone can have its own 12V trigger or be set to automatic signal detection.
Are you starting to get a sense of the flexibility available here?
Let’s consider one scenario. You have a 7.1-channel home theatre receiver with Dolby Atmos support. You can use four of the 1250’s power amps for the four ceiling or Atmos-enabled speakers, for full 7.1.4 Dolby Atmos. You can also plug the receiver’s Zone B outputs into one of the bus inputs and have it go to up to eight other speakers (or more, but we’ll get to that).
Here’s another: perhaps you want to use one of the multiroom streamers which are proliferating at the moment. You might use a system that has multiple source components, or one of the PC-based multichannel source devices. Either way this amp will power speakers throughout your home, grouped entirely according to the capability of the sources and your preferences.
So, what about those dozen amplifiers? They are Class-D units, which means amongst other things that their negative terminals are not grounded, so double the care with speaker wiring is required. Each is rated at 50W into eight ohms, full audible bandwidth, with all 12 channels running. Parasound rates the THD at less than one per cent at full power, and less than 0.05% at ‘typical listening levels’.
Fifty watts might seem a relatively modest output claim (do remember, though, that the difference between 50 and 100 watts is only three decibels), but there are two ways to increase the power delivery. One is to use lower-impedance loudspeakers. With four ohms instead of eight each amp is good for 90W — and remember, that’s with all channels driven.
The unit is actually rated to support two-ohm loads (still at 90W). The main reason for this is to allow each output to support two loudspeakers, so the unit can in fact drive up to 24 loudspeakers. There are A and B speaker terminals provided for each channel.
The other way to increase the output is to bridge two amps together into one. This is achieved by the simple expedient of sliding a switch. Now you might think that combining two 50W channels into one could deliver 100W, but you’d be wrong. With the Parasound 1250 it delivers 160W into eight ohms (again, all channels driven). Into four ohms that increases to 200W. In this mode, two ohms are not supported, so only the Speaker A terminals can be used.
Again, remember you can bridge some of the channels and leave the others in unbridged mode, allowing the flexibility of delivering high power levels to some channels and modest ones to others.
Inputs are via RCA sockets, except for one of the two Buses, which can be either line-level or speaker-level. Again, all or any or none of the amps can be set to run from either one of the Buses.
All the speaker connection terminals are plug-in blocks with screw clamps (see below). Given the number of wires that might end up being connected, that’s a convenience, since you do the wiring to the blocks in comfort and then plug them in when you’re finished. The clamps accept wire up to 12 gauge (very slightly more than 2mm in diameter). The block for the speaker-level inputs are smaller, but are high impedance so heavy wire is not required. Screwdrivers are included for both types.
The unit itself is standard component width and is provided with ears for rack mounting. Thanks to the efficiency of Class-D amplifiers, the whole thing is relatively light at 7.7kg and requires no cooling fan, although adequate ventilation should be provided.
The construction is fully metal, of course, with a machined-aluminium front panel and ventilation slots at the sides and top. There is only one front control: a soft power button. A simple display at the centre of the front simply shows the 12 channels illuminated — all of them if the unit is set to manual switch on or triggering, or only those that are operating if set to zone switch on.
A mechanical toggle power switch is on the rear panel, as are the other controls. The zone trigger/signal detect selectors are tiny sliders.
Setting up the system proved to be surprisingly easy. The important thing is to pause and think carefully, working out what you want each of the channels to do before launching into it. You’ll be bridging pairs for big, power-hungry loudspeakers, likely sticking with single amps for Atmos ceiling speakers. If you’re using some of the channels to drive a bunch of speakers throughout your home, or some other extended space, you’ll likely want to set all those channels to one or the other of the bus inputs, and perhaps set at least some of the stereo pairs to mono.
Once you’ve planned what you’re doing, then it’s just a matter of flicking the switches and doing the wiring. We weren’t looking forward to the wiring because the terminal blocks looked small and fiddly, but they turned out to be easy to use, capable of accommodating medium thickness speaker cable (tinned or untinned) and with their screws maintaining a tight grip on the cable.
We mostly ran the unit as a full home theatre power amp using a high-end Dolby Atmos-supporting receiver as the front end. We bridged two pairs of amps for the front left and right speakers, just to be on the safe side, and then drove the four height speakers, centre channel and surround speakers with single channels. That’s 11. (We could have used the 12th channel for a single rear surround, but in our listening room we’ve found rear surround to be of little use so we didn’t bother. If we wanted two rear surrounds we’d have gone back to a pair of the receiver’s built-in amps.)
With stereo music the amp surprised us: the music was delivered with a combined honey-like smoothness and precision of truly high-quality amplifiers. As we write we’re listening to the Frescobaldi’s ‘Cento partite sopra passacaglia’ performed on harpsichord by the Baroque specialists Capella Corelli, and while the detail is immaculate, the tendency for stridency from the instruments has been completely eliminated, reminding us why, although now somewhat out of favour weith listeners, the harpsichord was the dominant keyboard instrument for a century.
Moving forward by nearly 400 years, Radiohead’s ‘Pyramid Song’ was delivered with an almost eerie presence to Thom Yorke’s vocals, while the dynamic lift with the entry of the band into the song was completely unlimited.
We ran several of our favourite Atmos-ey scenes from ‘The Hunger Games - Catching Fire Part 1’, with impressive dynamic impact and precision in the hemispherical imaging provided by this disc.
And you know, after all this, the unit was only somewhat warm to the touch. Thus the efficiency of Class D.
It’s hard to think how a power amplifier could be any more versatile than the Parasound ZoneMaster Model 1250. But that’s not the end of it, because this isn’t merely a workhorse; it’s also an audiophile-quality product in its own right.
+ Astonishing versatility, High quality sound, High efficiency
- Nothing against
Power output: 12 x 50W into 8 ohms,
12 x 90W into 4 ohms, 6 x 160W into 8 ohms, 6 x 200W into 4 ohms (all channels driven, 20-20,000Hz < 1.0% THD)
Frequency response: 10-60,000Hz @ -3dB
Typical listening level THD: < 0.05%
S/N ratio: > 112dBA
Inputs: 6 x stereo analogue audio (RCA, can be thought of as 12 mono), 2 x stereo analogue audio bus inputs, 1 x stereo speaker level bus inputs (detachable terminal block)
Outputs: 2 x stereo analogue audio bus loop outputs, 12 x stereo speaker outputs (detachable terminal blocks)
Other: 1 x 12V master trigger I/O, 6 x 12V zone trigger I/O
Dimensions (whd): 437 x 108 x 369mm
Warranty: Two years
Contact: Network Audio Visual