January 2003

Theta Digital Intrepid... Five Channels Of Power
Review by Bill Roberts
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  It has been nine weeks since unpacking the Theta Digital Intrepid and I hate the thought of putting this lovely amplifier back in it's huge carton for return it to the manufacture. The arrival of the Intrepid met me staring at a huge carton that I wondered would even fit into my two-seat sports car. I usually have all items shipped to my office and was wondering, Do I have to rent a truck to get this thing home? After measuring the container and deciding I could not get it into the car, I negotiated with a friend to haul it for me! Hey, there is nothing like getting a review product and setting it up for the first time while reading the owners manual. This unit has five balanced and unbalanced inputs and special instructions as per grounding are well laid out in the owner's manual. I had all the requirements for the connections and made the decision to connect the unit in the balanced configuration, turn it on and let it sit overnight powered up.

The first set of listening test will be connected using channels 1 and 2 of the 5 available. These test will also be conducted in my Mastering facility, replacing a faithful amplifier which I have had the pleasure of over 5,000 hours of listening and mastering on so being familiar with the sound of the studio and the integration of previous equipment will help this review, bringing you many performance observances during the times, of many auditions. After a good 125 hour settling in period of non descript idle background playing (I was out of town for a few days) I feel it is time to really get into the music and see what this amplifier is all about. At $3,750, I would not consider this budget equipment. This review sample is finished in the optional brushed cover, which is drop dead gorgeous!

Although I base my reviews on emotion and musicality, there is a lot of room in these pages for nuts and bolts. Specifications if you will. The Intrepid is a zero global negative feedback design, however there is local feedback at minimal delay. Local feedback is the term used when feedback is applied to only one operating point. Global feedback refers to negative feedback applied to two or more points. In the Theta digital website a description is provided and it states, "Local feedback is common in analog circuits. It stabilizes, sets operating points, limits unwanted oscillation, reduces distortion and protects delicate devices from potential damage. Local feedback is applied almost immediately back to the input, with very little delay. Intrepid used local feedback". So the unit is not feedback free, though uses feedback in the most conservative way to prevent harm to the circuitry.

Setup And Listening

I conducted a complete test of some of the specifications in real world conditions and the Theta specifications are conservatively stated. This being said, I will give a report of them later in the review but now, it is on to musical impressions of this amplifier.

After I returned from a business trip, the Theta digital Intrepid was singing along quietly being fed by my Mixing console, which was sourced to a Sony SCD-CE775 SACD/CD player. Left the unit on continuous duty for the obligatory "break-in" period for channels 1 and 2. The owner's manual states that during the first week of operation changes to the sound quality have been reported for the better. Sparing myself the listening of channels 1 and 2 for this period, though channels 3, 4, 5 have yet to have signal applied. Therefore this can be also a test if the validity of break-in itself! I look forward to this opportunity and put this issue to test once and for all. Results will be posted later in the review during my actual specifications results.

The first selection is my all time favorite recording of Bob James Hands Down. The song "Spunky" is a well-recorded analog master presented in DAT form. It is one of my many references that I use on all evaluations. For those who have not heard this track, go get it. It is as good as any recording in the genre of "Funky disco Jazz". For consistency sake, all music that I am using for initial evaluation is coming from the hard drive of the digital workstation, out of the SPDIF digital to an apogee D/A converter to the direct input of my analog console to the amplifier.

Here We Go!

Nice so far as all the definition appears to be there. Imagining is tight and not exaggerated. No boom or overhang on the bass while highs sound slightly subdued, but not more than just a shade laid back. The highs still have all the usual speed I am accustomed to. The lowest octaves seem to be up a little more than I usually hear. Since this amplifier is rated flat to 0.9Hz it is definitely capturing the entire low end. My reference amplifier captures this low end but I seem to feel more air motion (floor motion) than normal. To me, this level of bass power is the new "normal" so the power supply of the Intrepid is quite good. There is plenty of reserve while the house lighting dimmed a small amount with the kick drum. Well that was very enjoyable to say the least. Time to use a more powerful circuit in the house. I have a dedicated 30A outlet for power amplifiers and was not using it at this time. The dimming lights were the trigger that the electrical source needs more AC power! Ok, this is plenty for day one. Time to wire into the big buss and not have lights dimming anymore! I feel that a 20A service would be enough for this amplifier but this shows that amplifiers of this size need a good solid dedicated service.

Next, having corrected the power fluctuation, back to "Spunky". The subdued highs are now a thing of the past. I hear really nice balance and push the level up to "very powerful" and the intrepid is loosing some bass definition at these levels. Now this is definitely exceeding the rated power, but at no time do I hear any grit, distortion or harshness from the 200Hz on up. I was simply asking for more and the bottom end got a shade loose is all. No damage to the loudspeakers and no problem. Since there is an absence of clipping indicators, one can hear when you are running out of pressure in the bass without the nastiness many amplifiers exhibit when asked to go past the limit. At a rated 100 Watts/channel at 8 ohms, you really would have to have a large room and power hungry loudspeakers to ever go there but just like a sports car, sometimes you take it into the red. It is human nature. Solid AC power is a must!

Now The Acid Test!

Have been working on a 50 song, 50 band CD during my job as mastering engineer. Approximately 600 hours have been invested in this mastering job due to the nature of 50 different studios, 50 different bands, and 50 different renditions of the same song. This is a mastering engineers nightmare! Using old faithful (McIntosh MC2500) I was almost complete with this three CD album until listening to the tracks using the Intrepid. All of the tunes had a bass balance problem. The reference amplifier was telling a different story from the intrepid and I am inclined to believe the Intrepid simply because it has more complete bass on everything I put through it. Oh No... do I have to go back and touch up the 50 songs again? You bet!

It was important that this project sound at least presentable all the way through and some of the tracks were not well recorded or produced. Many of them would not pass muster on even a modest system when I got them and although they were sounding "pretty good now" the Intrepid was the tool to make them all sound "better than pretty good". The first thing noticed was the detail in the bass was not where it needed to be. Was picking up some breath bumps in some of the tracks that the reference amplifier simply did not show. There was sub harmonics in one track that could not be detected previously and you could feel them moving things around in the room with the Intrepid. Having power below 20Hz is essential in mastering. You must hear all of this. I did not use the spectrum analyzer for any of this mastering and should have. As is I now had to go back and invest another 60 or so hours repairing some of the music!

Now what does this have to do with how this amplifier sounds? Plenty. Anytime you can insert a piece of equipment in the chain and hear something time and time again that you did not hear before means the unit is simply passing more of the signal to your loudspeakers. This is a very high complement for the Intrepid.

Now it is time to go on to other music. Another really fine artist that I enjoy listening to is Keiko Matsumi. She is a pianist that has enjoyed high record sales in the "smooth jazz" genre. I know her recordings note by note and her piano is usually dark and a shade high in the mix for me but her playing is a blast to listen to. As with everything else put through this amplifier, I am hearing much more detail. The only thing possibly negative about this experience so far is I am getting all this nice sound and only utilizing 2/5^th of the unit! Upon various recordings, can not find major faults with this piece of equipment. It is quiet, there are no fans, it runs slightly luke warm (left side only since that is where channels 1 and 2 reside) and it is quite visually attractive. Attractive does matter to most audiophiles and it scores 100% in this category. Fine machine work. No flaws.

My requirements could use another 3dB of sheer bottom end power as I do find myself at time hitting the bottom with more authority than the Intrepid can deliver but face it, this amplifier is designed for home theater use and this is where it will reside next!

To The Theater!

This time I am forced to use the unbalanced RCA jacks on the rear of the amplifier. Yes, and all of them. I built a 5 input, 5 output tube pre-amplifier for the home theater system. My signal path is to come out of the DVD players' analog outputs and into the 5-channel line pre to the Intrepid. The home theater system does not have the finest of loudspeakers available but it is a very nice, well thought out system that always provides the goods. There are 5 separate attenuators in 0.5dB steps on the pre-amplifier for balancing the channels. One huge beef I have with DVD authoring is the inconsistencies from production to production. Of the DVD's I own, only a handful can utilize the standard balance settings I worked to find. These are:

Attack Of The Clones
Super Speedway
And believe it or not, Bachelor Party also is well done for an oldie (funny too)

Remember the "break in" test? I conducted it before I moved it to the home theater room and it is coming so be patient. The thing that strikes me with the intrepid is balance. All of the loudspeakers finally sound "right" I usually hear some form of nastiness in the rear speakers of many HT setups and I chalk this up to poor authoring. Not here, the rear channels remain the great clear sound that was meant to happen in HT. I am using four matched Boston Acoustics loudspeakers for the front and rear and I basically bought drivers and built the center channel using the same elements as contained in the Bostons.

A pair of subwoofers in mono for home theater are placed on either side of the video screen. These are self-powered with a single 12" woofer. Nothing fancy, but they are crossed over at 50Hz and have them so far in the background that rarely does one ever notice their thumbprint on the sound. The balance I am speaking of is how a helicopter seamlessly moves through space over your head. This was not achieved with other setups. A receiver simply has not showed itself that can do this. Receivers in general are both front, then quick to the rear, not a motion to the rear. The balance of this amplifier is amazing! The naturalness of the sounds are really startling and this proves if you have a fine amplifier and matched speakers, there is no need to spend $40K on loudspeakers for home theater in my opinion unless you have a room as large as most folks houses. Well I have gone over some on this review and as I promised, some surprise reporting here as well.

Break-In: Myth Or Truth?

I can honestly say that no test ever conducted personally is as conclusive as this one. Allowing a component to settle in for a week or so will change your perception of it. After exhaustive trials on channels 1 and 2, I immediately connected up the previous unused channels 4 and 5. The result: The new channels sounded brassier, were not as solid in nature and lacked the timbre that channels 1 and 2 was giving. I believe that something physical happens at the molecular state to conductors once they have been exposed to heat and current flow for a prolonged period of time. Immediately connected channels 1 and 2 back up to confirm my feelings. Channels 4 and 5 did break in rather quickly as opposed to 1 and 2. Reason for this, I guess, is that they had bias through them for the complete time but no signal. You can believe or disbelieve as you choose, though it does state clearly in the owner's manual that this was noticed by the manufacture as well. You can take that for what it is worth. I am a believer.

Specifications that I measured were only those of maximum undistorted power of channels 1 and 2, each independent and together. I also did some tone burst on all 5 channels simultaneously. I used a waveform analyzer to see where clipping started.

Results:

Incoming voltage is 122V AC 60Hz

Chan 1: 8 ohm 30Hz 1 second, 143 Watts
Chan 2: 8 ohm 30Hz 1 second, 147 Watts
Channels 1 and 2: 30Hz 1 second, 137 Watts (1) 139 Watts (2)
All 5 channels at 8 ohms: 30hZ 1 second, 121watts (1) 119 Watts (2) 118 Watts (3) 124 Watts (4) 120 Watts (5)

The above shows that the power supply is capable of delivering enough current to allow all 5 channels to exceed the rated power without clipping.

In Summary

My objective in reviewing is to compare a piece of equipment to another from memory and emotion. I also look for flaws and ways to improve upon the technology. Review to be informative, entertaining and accurate. With the Theta digital Intrepid, I found little that could be improved on and given the price... and find it to be a very good value too. The only performance issue I could find that was different than previously experienced with other equipment was the bass definition when pushed hard. Usually amplifiers will start complaining in the higher frequency ranges long before the bass give up the ghost. With the intrepid, bass extension and dynamics showed strain before any mention of the high frequency range did.

Balance wise, it is quite good. I did not destroy any tweeters in the process and the hardest I played this amplifier, the temperature never exceeded 60^oC. Sure it became fairly warm, though with no fan and adequate ventilation it would be very rare situation to achieve thermal shutdown. There was a time when it was driving a 2 ohm load spec for pure curiosity and it exceeded my ability to measure accurately the true power output. My guess is that the Intrepid would achieve approximately 330 Watts per channel. I do not think Theta intended all 5 channels be driven at 2 ohms but this brute could possibly do it short term with no ill effects. The use of the 232 port is something I did not try but I am sure it will do its intended function flawlessly just as this amplifier provided music.

This product is highly recommended for the price and I would love to have a two-channel version of it with double the power. The Theta Citadel looks like it would be a premium amplifier for the application of two channels as the Intrepid being an affordable higher end piece is to five channel. A suggestions of having five small green LED's on the front panel that would turn red in the event of clipping could be helpful. A great product well worth auditioning for home theater buffs looking to achieve great sound.

*Soundscape, depth behind speakers was not as good as I have experienced in 2-channel use, for 5 channel this point is moot

** Extension in the room was a factor that bothered me. My reference amplifier if listening from another room sounded like an actual performance going on in the listening room. The intrepid for some unknown reason did not do this. If you were in the room with it, it sounded great but the sound would not travel outside that domain nearly like my reference amplifier. This is under investigation and I am at a loss to explain this phenomenon.

Specifications

Inputs: Analog Audio 
1 Single-ended (RCA) per channel, 1 Balanced (XLR) per channel

Input Impedance: 50Kohms. Single-Ended or Balanced, for each phase

Input sensitivity: (Single-Ended) 1.5V RMS
                         (Balanced) 0.75V RMS  

Gain: (Single-Ended) 25.5dB
         (Balanced) 31.5dB

Polarity: (Single-Ended) Non-Inverting.
             (Balanced) Pin-2 = Positive, Pin-3

Outputs: 1 balanced output per channel

I/O RS232: 1 DB9 and 1 RJ45 connector

Modes/Processes:
     Standby: All channels are muted and output bias is reduced to 40%.
     Thermal: One or more channels has overheated; amp automatically switches to Standby.

Power Output: (8 ohms-one channel driven) 100 Watts
(8 ohms-five channels driven) 100 Watts
(4 ohms-one channel driven) 200 Watts

Frequency Response: 0.9Hz to 350kHz (-3dB)

THD+Noise: <2%

Signal to Noise Ratio: >100dB (unweighted)

Dimensions: 17.75 x 6.25 x 20.5 (WxHxD in inches)

Weight: 58 Lbs. Stand alone (26.3 Kg), 64 Lbs. 
            Boxed with accessories (29 Kg)

Price: $3,750

Company Information

Theta Digital Corporation
5330 Derry Avenue, Suite R
Agoura Hills, CA 91301

Voice: (818) 597-9195
Fax: (818) 597-1079
E-mail: info@thetadigital.com
Website: www.thetadigital.com