SMR logoTheta Digital Dreadnaught Power Amplifier Review
In his long-awaited Theta Digital Dreadnaught review, Nigel Pond discovers an amplifier of note; a design equally at home with all types of music and movies.

Theta Digital Dreadnaught Multi-channel Power Amplifier Review

Introduction

Theta Digital Dreadnaught     Power amplifier? Theta? That was my initial reaction when, in 1999, I first heard the news that Theta Digital was preparing a power amplifier for release. In recent years Theta has become well known for its digital products - CD, LD and DVD transports (https://smr-home-theatre.org/Reviews/Theta/), digital-to-analogue converters and surround processors (Casablanca and Casa Nova), so news that Theta was striding out into the power amplifier market, which at the moment is almost entirely an analogue domain, was a little surprising. After reading some of the promotional material, it sounded like this amp was going to be a little out of the ordinary and any amplifier named - albeit incorrectly spelt - after the early twentieth century British battleship, H.M.S. Dreadnought starts out with an advantage in my book! So I made a request for a review sample. Theta and Bryan Stanton of Theta's PR agency duly obliged and one day way back in June 2000 a large (and very heavy - more on that later) box was waiting for me on my return home from work.


Desi
gn Concepts

     To design their first power amplifier, Theta enlisted the services of Charles Hansen of Ayre Acoustics, whose designs were refined and turned from a concept into a construction design by Theta engineer David Reich (previously of Classé). The Dreadnaught has a somewhat unusual design for this sector of the power amplifier market - it is described by Theta as a "zero feedback, fully balanced differential" amplifier. Let me explain what they mean (most of the following is derived from Theta's technical description or "white paper" for the Dreadnaught). Feedback is a term used to describe the application of the output of an electrical circuit back to its input. Most of us are aware of feedback in the form that exists at rock concerts and live TV broadcasts, it's that loud, high-pitched, squealing noise caused when a microphone is too close to a loudspeaker - the speaker output "feeds back" into the amplification circuit - think of it as the audio equivalent of holding one mirror up in front on another. In this context feedback is bad - very bad, and can quickly damage components in the signal path, and it sounds pretty nasty too. In the context of an amplifier, however, feedback is used in two different contexts, both categories of "negative feedback". The first is local feedback: most power amplifiers consist of several amplification stages and feedback is "local" when it occurs only within one stage. The second form is "global feedback", where the feedback encompasses two or more amplifier stages. Local feedback is good and is used in many analogue circuits to do several things: limit unwanted oscillation, reduce distortion, and to protect components from damage. It is applied almost immediately back to the input with very little delay. The Dreadnaught uses local feedback in each of its three stages. Global feedback is also commonly used in circuit design - to reduce distortion and lower output impedance. With global feedback there can be a significant time delay between input and feedback due to the number of stages that the signal must pass through - this can cause audible artefacts such as smearing of the sonic image. The Dreadnaught does not use any global feedback.


Theta Digital DreadnaughtConstruction and Build

     Remember I said the box was heavy? It is. Weighing in at 115lbs (52.2kg) for the 5 channel version, it posed rather a problem for me - how to get it down into my basement home theater space. Usually I get my wife, Kris, to help out with the heavy-lifting, but she was away in Europe on a business trip. I certainly couldn't carry it downstairs myself, so I improvised. I managed to manoeuvre the box onto a mat and drag it over to the basement stairs. From there, I was able to slide the box down the stairs, standing below it to prevent it speeding out of control - sounds ugly but it worked, so well in fact that I have used this method subsequently for other big boxes. The only problem is that it doesn't work too well for getting equipment out of the basement!

     I asked for a sample in Theta's "ebony" colour, which is basically a brushed black finish, the same as my Theta DaViD DVD transport, and it looks equally attractive. My review unit came with racks ears for fitting the amp into a standard 19" rack, but my rack was full so I detached the ears and opted for placement on the floor and then later on a Sound Anchors stand (I cannot speak highly enough of the quality of Sound Anchors stands - really solidly built and the perfect base for a heavy amplifier - http://www.soundanchors.com). As I mentioned above, the Dreadnaught is modular. There is space for 5 amplifier modules, tucked in behind the power supply. The "standard" amplifier module is a balanced, single channel rated at 200 watts into 8 ohms, 400 into 4 and "even more into 2 ohms". You can order a Dreadnaught with as few as 2 amplifier modules for a stereo configuration, the full five or any number in between. Theta has also recently released a two-channel module (which I have not had the opportunity to take a look at) so in theory you could order 5×2 channel modules for a 10 channel configuration.

     A quick word about the power supply - the Dreadnaught has a single 2.2KVA toroidal transformer, Theta supporting the theory that with this configuration any single channel confronted with a full level input will have the full current capacity of the transformer available to it. The transformer has three sets of secondary windings, one each for the output stage, the input and driver stages, and the control circuitry. Each channel has its own current bridge and capacitor bank, and fully discrete regulation circuits for the input and driver stages.


Front and Back

Theta Digital Dreadnaught     The Dreadnaught is not your usual square "black box" amplifier. The front panel has a curvy design with handles built into the sides - invaluable for manhandling. In the flat centre section of the front panel are three LEDs, labelled "Surround", "Standby" and "Thermal", one large pushbutton labelled "Standby" and a second, smaller button labelled "Surround" - more on those later

     The rear panel configuration depends on the options that you order. Each balanced module sports an RCA input jack; a female XLR input jack; 3 LEDs (thermal overload, fuse rail + and fuse rail -); two little toggle switches, one for switching between the unbalanced and balanced inputs, the other for designating the particular input as on the "surround" or "stereo" buss (more on that in a moment, I promise). The most striking feature of the rear panel is the speaker cable connector - a new design from Cardas, I believe - which has a single large screw-wheel which clamps a cross-bar down simultaneously on the +ve and -ve spades (spades, or at a pinch, bare wires, are the only methods of connection available on the balanced module). I have never come across a speaker connector which is as easy to hook-up or as sturdy as this one. Back to the buss feature - the Surround button on the front of the amp toggles on and off those channels which have been assigned to the surround buss by their rear toggle switch, so, if you are a two-channel purist, you can switch off all but the left and right main speakers for music-only listening, making the full capacity of the power supply available to just those channels. The rear of the unit also has two handles to ease handling and positioning of the amp; (optional) RJ45 and DB-9 connectors for RS-232 control; two 3.5mm jacks for standby and surround buss remote triggers (these are current pulse triggers - see https://smr-home-theatre.org/Reviews/xantech/ for compatibility with the more common constant voltage trigger sources); main power switch; system fuse; and an IEC-type AC power input connector, so you can use one of those tree-trunk sized, add-on power cords if you really must.


Performance

     So how does the Dreadnaught sound? In a word: stupendous, amazing, mind-blowing, astonishing! OK that's several words but I think you get the idea: I really, really, like this amp& a lot. During the extended period that I have had the Dreadnaught in my system, I have thrown just about every conceivable type of source material at it, and it has not flinched once. In the usual movie soundtrack torture tests (such as the opening scene of Saving Private Ryan; the storm sequences from The Perfect Storm; the helicopter sequences from Apocalypse Now; submarine interiors from Das Boot and U-571; various DTS demo discs) the Dreadnaught never came close to running out of steam, even at reference level, and I suspect that the manufacturer's power ratings are on the conservative side. There was no hint of muddiness or confusion with all five channels active. The Dreadnaught is not however only a master of crash, bang, wallop performances. Soundtracks which are more dialogue intensive or where the effects are more subtle (like The Truman Show, Contact, Sex in the City, The Sopranos, Amistad, Bedazzled, Chicken Run) are reproduced with great ease. It is equally impressive with Dolby Pro Logic sources - I listened to the standard PCM track on my Japanese import of The Phantom Menace, and in straight Pro Logic mode, it was very impressive. The Dreadnaught is no slouch when it comes to music either: 5.1 sources like Roy Orbison & Friends: Black & White Night, The Bee Gees: One Night Only, Peter Frampton: Live In Detroit or James Taylor Live at the Beacon Theatre sounded the best I have ever heard them. I also gave some of my favourite CDs extended listening through the Dreadnaught. One of my favourite recent purchases is the late Eva Cassidy's Songbird which is a remarkable CD on any equipment - processed in Music Logic mode by my Lexicon MC-1 and amplified by the Dreadnaught, it is truly outstanding (I would recommend this CD to anyone - Eva Cassidy is surely one of the greatest ever female vocalists and her untimely death a great loss). My collection of Renaissance and pre-Renaissance choral music (performed, for example, by The Tallis Scholars, The Anonymous Four, and The Sixteen) has never sounded better. I even span up a few of those black vinyl thingies on the Dual record deck that Alan Maier restored for me and listened to a few of the albums that I have not heard in years - Emerson, Lake and Palmer's Works from 1977 brought back (mostly) pleasant memories of preparing for my exams in Grammar School.

     I also experimented with the Dreadnaught's buss system, assigning left and right main channels to the stereo buss and the others to the surround buss, via the toggle switch on the rear of each channel module. I also connected the output from my Xantech switching module to the surround trigger input of the Dreadnaught and set up my MC-1 so that selecting the CD input sent a trigger to the Xantech and thence to the Dreadnaught, switching it into stereo mode (I also made sure that I had put the MC-1 into two-channel mode). The system works as advertised and although, personally, I don't listen to two channel sources in straight stereo any more (not when the MC-1's Music Surround and Music Logic modes are so good), I can see that for the two-channel purist, it would be a useful automation feature, as well as ensuring that the power supply of the amp is devoted only to the two active channels.


Conclusion

Theta Digital Dreadnaught     The Dreadnaught is a top-notch performer, right up there with the best power amplifiers available. I didn't find it lacking in any respect, and I pushed it as hard as I could. Admittedly my speakers are not the most difficult to drive (Von Schweikert VR-2000s - 8ohm nom. impedance, 91dB sensitivity; LCR-30 - 8 ohm, 92dB and TS-200s - 8ohm, 90dB) but the Dreadnaught had plenty in reserve for more difficult loads. In fact, I have heard the Dreadnaught driving the superb Revel Salons (6ohm - 3ohm, 86dB - http://www.revelspeakers.com/) in my dealer's listening room and it showed no signs of strain at reference level. The build quality of the Dreadnaught is also exemplary. There are only two downsides, the potential importance of which depends on the location and set up of your system: the Dreadnaught is big and because of its design it runs very warm - both good reasons not to try to shoehorn this amp into your average "entertainment centre" or equipment rack. This is also good because an amp that looks this great deserves to be out on display on a stand on the floor. That probably means that it will be hard to fit the Dreadnaught into a room which is used for purposes other than as a dedicated home theatre - the potential for tripping over it, spilling things in it, or the cat sleeping on top of it in the warm, is too great, but it will help keep your home theatre room warm in the winter.

     However, performance of this quality does not come cheaply: the basic chassis with power supply lists for $1,950, a single-channel 200w balanced module for $810 and a two-channel module for $1,000. That makes a 5 × 200w channel unit $6,000, but that is not uncompetitive in comparison with similarly performing amps and considerably cheaper than some of the more esoteric monoblock competition. But I would consider that money well spent, buying you what is, in my opinion, an amp that can hold its own with the very best multi-channel amps around and probably most of the specialist monoblock and two-channel designs. After buying the Dreadnaught, I don't think you would need or want another amp for your home theatre, except perhaps a second Dreadnaught if Tom Holman's 10.2 system concept ever makes it into the home!

For those who cannot quite afford the Dreadnaught, Theta has recently introduced a smaller, less expensive, amp - the Intrepid - which employs the same design principals as the Dreadnaught and which I reported on from CES (https://smr-home-theatre.org/ces2001/home_theater/page_10.shtml)

There is one other downside for me: now that I have finished the review, Theta will probably want the review sample back - getting it out of my hands, er& I mean my basement, will not be easy.


2001.

 

More information can be found upon the Theta Digital web site.

Text Nigel Pond; HTML SMR Home Theatre and Images Nigel Pond & SMR Home Theatre cannot be reproduced without permission. The images on this page are digitally watermarked: Digimarc http://www.digimarc.com/

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