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Audiolics Anonymous Chapter 28

Electraprint DRD SET Amplifier, Part 2
Article By Bill Gaw

 

Electraprint DRD SET Amplifier  As  promised last month, this column will primarily discuss the sound of Jack Elliano’s creation -  his DRD amp. But first I’d like to discuss a topic near and dear to Audiolics, namely Audio Gremlins. You know what they are. Those little changes that suddenly appear in our systems for no rhyme or reason. I don’t mean changes in atmospherics, electricity, state of mind, etc., that change the sound of our systems. But the sudden onset of major changes in sound that drive us crazy! They come and go for no discernible reason. They tend to occur more frequently in more complex systems, thus are the bane of Audiolics - and are more difficult to track down - the higher end the system. Sometimes I wish I hadn’t gotten the high-end bug and would have been content with a receiver, two speakers and zip cord.

For the past month, I have had the best sound, both 2 channel and surround, that I have ever experienced from my or any other audio system. But this came to a crashing halt on Saturday night. I was watching a movie in HDTV on HBO in 6.1 surround, when all of a sudden I started getting fairly loud 60 Hz. hum coming from all of the subwoofers attached to the different channels. Nothing had changed in the setup. Maybe it was Sandra Bullock’s acting in Miss Congeniality that set it off? Who knows. Anyway, it was distracting enough that I had to turn off the movie and start to do some testing to isolate the problem. This at 11 o’clock at night. No wonder my wife thinks I have a screw or two loose. But who can go to bed without figuring out a problem like this one?

So where does one start? First, with any changes that had been made in the previous few days. I know it is unusual, but nothing had been done to the system for two weeks. That is how happy I had been. Second, with the component making the problem and it’s interconnects. But with seven subwoofers going crazy, where would be the common point? Well, I put on my Sherlock Holmes hat and pipe, even though I look like (beard and belly) and have the same profession as Dr. Watson, and began deducing. Sudden onset of 60 Hz. hum is usually caused by a grounding problem or leakage through a defective power supply. So first I went around and checked all of the grounds. No problems. Next, I took a look at the interconnects for breaks. All was okay. Then I started disconnecting pieces of equipment, one by one, from the beginning of the playback chain to the subwoofers. Yes, the noise stopped when the EAD Theatermaster Signature video pre-pro was shut down, or muted, but it also changed when I turned off my satellite receiver, projector, VHS deck, and/or my preamps. There was no common point I could put my finger on. Once turn on, it was back again. Finally, I tried connecting and disconnecting AC cords. Still couldn’t find the problem. At this point, now around 12:30pm with my brain half-asleep by itself, I desisted and shut the system down and went to bed.

Sunday morning, after a hurried breakfast and Tim Russert, on went the system and guess what. No 60 Hz. Hum! All day Sunday the system sounded and looked superb. The Gremlin was gone! And this only three days after the Halloween celebration. Unhappily, the same problem reoccurred in the middle of a listening session on Monday night. Exasperated, I shut it down again vowing to tear the system apart Tuesday night. I would clean all of the contacts, reground everything… and pray. But it was not to be. On turn-on Tuesday night the system was dead quiet with glorious sound and picture. In fact it stayed great all night. Alas, it reoccurred several times since though no change I have made so far has made any difference, with the exception of shutting the damn thing down and going to bed.

Moral of the story? When in doubt, shut it down and pray the gremlin dies from lack of electricity. Otherwise, go crazy and enjoy the tweaking.

 

Electraprint Audio DRD Amplifier

Electraprint Audio DRD AmplifierFirst, a warning to all those Wackos who think all amplifiers sound alike. Forget it. I have yet to hear two amps that come close to sounding the same, although I must say the differences are less than those with loudspeakers, cartridges and other mechanical equipment.  This would only be possible if amplifiers performed as the proverbial “Straight Wire with Gain.” Well I have yet to hear an amplifier that does. No piece of stereo equipment is perfect yet. Therefore no amplifier can be perfect - including the big mega-bucks types. But some come damn close. And it has been my experience that the closest to the proverbial “straight wire with gain” are modifications of some of the oldest and simplest amplifier designs. That means tube amplifiers,  preferably single-ended types. Why? Because the simpler the circuit the better, as long as no distortion is produced and the signal is sent through as pure as possible. And the simplest circuits are generally of the tube design. This brings us to the main topic today: Jack Elliano’s Direct Reactance Drive Amplifier. The simplest amplifier circuit designed yet that I am aware of.  Please review last month’s article for a description of the circuit by clicking here.

For those unwilling to spend the review time, Jack has come up with two modifications to the classic single-ended transformer amplifier, which he named Ultrapath and Direct Reactive Drive (DRD). The Ultrapath circuit bypasses the power supply, the cathode bypass caps and resistor by placing a high quality paper and oil cap between the transformer primary out and the cathode of the output tube, thus keeping the signal from having to run through the power supply.

DRD CircuitThe DRD circuit takes advantage of the Ultrapath with its oil capacitor by replacing the resistor and capacitor (or transformer) normally placed between the driver anode and output tube screen. There is also an inductor between the driver anode and the output tube cathode. There are two advantages to this. One is a straight line between the driver and the output tube is without intervening parts. Second, one then has a reactance rather than a resistance circuit, thus less wasted power. Interestingly enough, one other major advantage occurs. One can get more wattage without straining the tube. Thus it is approximately five watts from a 2A3, and thirteen from a 300B!

 

DRD Amplifier Circuit

Well, that’s theory. But does the circuit do anything except increase the output power of the tube? Hell yes! As stated in the previous article, these amplifiers do things that improve on the strengths of tubes and other things I have heard only in solid-state designs. The following are comments based on listening to three amplifiers that Jack has sent me. Specifically, a stereo amplifier with Vaic mesh plate 2A3’s and a pair of monoblocks with Western Electric 300B tubes. All comments, unless noted, are true for both types of tubes.

The amplifiers normally would come with speaker binding posts but Jack was kind enough, per my suggestion, (Tweak of the Month) to extend the transformer windings three feet so I was able to directly go from transformer to speaker without intervening speaker binding posts or speaker wire. Each amplifier was placed in my system directly behind my Edgar round horns and run from 350 Hz up. I would highly recommend this technique if you can get your amplifier manufacturer to extend the transformer windings as you will be losing the amplifier binding posts and multiple feet of expensive speaker wire from your system. The advantages? Much less cost. No metal-air-metal gaps between the amplifier and speaker binding posts. And unless you think speaker wire blocks out some sort of distortion to the signal rather than adding it, the less junk in the signal to the loudspeaker the better. (Boy, are the wire developers going to be mad at me now.) Electraprint also set up the wires so that I could change the transformer secondary’s impedance to match various speaker input impedances. Try it, you will like it. Especially the bucks saved.

What has the design accomplished? First, it lowered the noise floor of the tubes. There isn’t any! Or at least not one I can hear with my 112 dB per watt efficient Edgar Horns. The only hiss is from my preamplifier. Hum from the amplifiers are nonexistent while tube hiss can only be heard with the ear directly on the horn. NADA otherwise. Just like good solid state. Also, there seems to be more information coming through. Much more. In purist low mike recordings, the hall is there. Right in your room. With multi-mic types, one can hear the individual spaces that each microphone is reproducing.

 

Examples

I have a compilation CD of the albums from Simon and Garfunkle, some of which were studio and some live concerts, all from the seventies to eighties. On these multi-mic’ed recordings, one can tell that each soloist and their background accompaniment were not only recorded with separate microphones, but that they were probably in different rooms of different sizes. Each voice seems to have a small room envelope while the accompanying orchestras are in much larger rooms. While distracting, it does show the ability of these amplifiers to delineate hall space to an extent I have never before heard. On the Weavers’ Return to Carnegie Hall, one can hear the individual microphones used by the various singers, and now I think there were different types of microphones used. Either that or there was some equalization going on as the voices sound a little different depending on which microphone they were using. Audience noise is more discernible and one can hear some audience comments that I was previously unaware of.

In the same vein, artificial reverberation is accentuated for. I have a laser disc of   Georg Solti’s Prokofiev Romeo and Juliet with the Bavarian Radio Orchestra at the Herculeen Saal in Munich. A hall I have visited but not heard a concert within. It is a modern rectangular boxy type - with few projecting surfaces - typical of a dry modern hall. Where before I could hear what I thought was a nice reverberant tale to the hall, now I can hear that the hall is actually dry while a small amount of artificial reverb has been added to sweeten the sound. Another distraction, yet more truthful of the recording’s sound. Studio tricks of the engineer are ruthlessly revealed. Interestingly, Jack has commented that his amplifiers do differentiate artificial from natural reverb. A trait he ascribes to the straightforward design of the circuit.

On purist recordings, the space and atmosphere are there. On Belafonte Returns to Carnegie Hall, the first track is audience noise which actually pressurizes my listening room much like at a live concert. When they begin applauding, my eardrums actually pressurize. Something I’ve never heard before. On another recording, a London of a live performance of the Last Night of the Proms (from Albert Hall) which was actually a compilation disc recorded over several nights and years from BBC broadcasts, the hall is transported to my room. Suddenly coughs, rustling, etc., from the audience are in front of the speakers and the orchestra. One can actually make out individual voices in the front rows of the hall. At one point the conductor jokingly asks a somewhat boisterous audience member if she or he was ready to proceed with the concert. And the atmospherics of the hall and recording are different from night to night. Something I had heard before, but not as clearly.

Third, the slew or rise time must be very high, leading to solid-state type dynamics. Snare drum rim shots are tight, sharp and stinging. This is one thing tubes, especially SET’s, do not normally do well. And even though I’m only using them from 350 Hz. up, tympani and bass drum strikes are gut wrenching, showing that it is the harmonics and not the fundamental of the deep bass notes that makes for the attack. On the same Proms recording there are several instances where the crowd releases balloons that rise up, some of them touching a mike and exploding. Before, with other amplifiers, my system reproduced a loud pop. With these amplifiers it is an adrenaline producing POP. Again, this is a sound not usually associated with concert hall reproduction - and something the audio non-cognoscenti would laugh at us for remarking about - but it does show that these amps can produce tremendous dynamics out of a 2A3 or 300B tube.

Fourth, distortion levels are extremely low. Jack’s give a number of 0.5% at rated output. This is solid-state territory. The distortion is mostly second harmonic, like a true single-ended amplifier, but very low unlike the same. This makes voices and instruments sound more natural and clean. One can hear the inflections in Paul Simon’s singing that make him sound like he’s in the room. Like the rapid rise time, I think these amplifiers must produce an equally quick descent time. This is possibly due to the lack of distorting harmonics, which quickly shuts off the signal and thus cleans up the sound’s tail. The smallest movements of the singer in relation to the microphone can be distinguished. It is uncanny how natural and live the best voice recordings are presented. I think this is the reason the artificial reverb is so discernable.

Fifth, the bass is very deep and clean. How do I know this when one considers that I played them only down to 350 Hz on my system? Because I took the amps down to Kwami Ofori Asante’s place for a listen on his Beauhorns. While the Beauhorns only go down to 50 Hz, he has a subwoofer feeding directly off the amps’ speaker output. Therefore the subwoofer is actually only amplifying what the DRD originally amplified. We compared them to his 45-based amplifier and to the Border Patrol. Up until now the Border Patrol, at $8,000, was the best single-ended 300B based amplifier I had heard. The Boarder patrol amplifier still beat the DRD for deep bass tightness, probably due to its massive power supply. But the DRD came very close and I feel the Electraprint beat the Border Patrol with the first four points.

How does the 2A3 amp compare to the 300B? First we have less power, especially in the bass, which one would expect with the lower wattage rating. I have heard it overload driving my bass woofers to high levels, but never with the mid horns. Remember, I run the bass horns without a low-end crossover to the subs and was listening to the plane crashing and the waves thrashing in the escape scene from Castaways with Tom Hanks. Also, the highs seem to not extend quite as high. The midrange, on the other hand, has a more natural quality with possibly more emphasis on harmonics. These are all natural strengths of the 2A3 tube. The Proms recording is just slightly more natural. Kwami loved the 2A3 amplifier and is planning on getting a pair of monoblocks as soon as he pays for his latest edition. Not his new son, but a new subwoofer. The 300B amplifiers, being monoblocks, have a somewhat wider and deeper soundstage. The soundstage extends from just forward of the listener to somewhere near Dallas Texas. The highs are cleaner and more extended while the bass is tighter and somewhat deeper.

How do the amps compare to others available in my room? Well, Jack’s original Vaic VV-32 design is of course more powerful but compared to these, they are no match with the naturalness of the sound put out by the DRD. The Bottlehead 2A3 Parafeeds were just no match for the openness, tightness and information pass-through. They are still one of the best SET amplifier kits available… especially at its price. So, did I do any tweaking on them? Dumb Question!!!

Unhappily, since the circuit is so simple and the chassis is so well made, there is very little tweaking that can be done. I did put them on Walker Valid Points that may have tightened the low end. Also tried replacing a carbon 1kOhm resistor placed at the 300B screen with a Vishay top of the line. This resistor is an addition to the circuit that Jack made when he started using the 6AN4 driver tube that was developed as a UHF tube for television. While giving better gain than his original 6AQ8, it was allowing too much ultra-high frequency information through which could cause the circuit to possibly oscillate. What did the Vishay do? Well the top end opened up a very little bit and for a while I thought it was an improvement. But after a couple of days, the sound began to grate a little. Therefore I reinstalled the carbon resistor and the sound smoothed out once more. Due to discussions with Jack, I found that he chose this resistor for its property of adjusting the Q of the driver-output tube circuit. Just goes to show that maybe the experts do know something we tweakers do not. Here I thought he had used the cheapo carbon just to save some money.

I also found that placing a Walker lead weight on top of the inductor and between the tubes cleaned up the image a smidgen, but not nearly as much as with my previous tube amplifiers. Also, I could hear no difference between my NBS and Electraglide high-end power cords, but that may be due to the wonderful job the Sound Application CF-XE Line Conditioners have done to clean up my AC power. So this amplifier is not a tweaker’s dream, but perfect for the audiophile who wants to place a component in the system and enjoy the music. Alas, no product is perfect. The Electraprint  has one problem. Not with the sound and normal operation, but with the biasing. Because of its setup, biasing is done by moving a connector on a variable resistor and then measuring the voltage drop change across a 10 ohm resistor. Problem with this is found inside the chassis where it is difficult to reach unless the amplifier is turned over. Therefore it is difficult to do with the amplifier in the system. Second, the variable resistor also controls the voltage to the driver tube and the two interrelate. Thus as you change the output tube bias the driver tube voltage changes. It took me about a half an hour to get both correct. Thank G-d it has been stable since, so this will probably be something that will have to be done infrequently.

Second, this amplifier is not made for those tube rollers out there. Jack tunes the circuit of each amplifier for the tubes supplied, which gives the unit low distortion figures. Every time you change the output tubes you will have to hook the unit up to test equipment if you want to get the original low distortion figures. By the way, this should be a problem with all amplifiers and is probably the reason different tubes give different sounds. Also, the 6AN4 tubes are no longer made. Jack says that he has plenty on hand so replacement should not be a problem, but they certainly will not be as easy to experiment with compared to multitude of 12AX7 tubes available today. But considering the sound I’m getting, even this tube rolling tweak freak does not feel like doing any experimentation. It is a great product as sold.

So, am I keeping any of them? Yes, the 300B monoblocks are now powering my main channels. Since I play movies fairly loudly, and the 2A3 is just a little too low powered for my center channel woofer and I’ll probably be selling it. But, happily, Jack has offered to rebuild my ElectraprintVV-32 amp, which has just the right power for the center channel, with his new circuit after the CES in January. I can not wait.  That will give me something else to talk about in a future column. Cost? Jack has not come up with a fixed price yet, but probably between $2,000-$4,000 depending on build, chassis, output tube type, etc. Contact Jack with your specs. At either price, this amp is a steal. HIGHLY RECOMMENDED. I cannot think of a better stocking stuffer.

Have a great holiday season everyone.

 

Manufacturer

Electra-Print Audio
4113 Roxanne Drive
Las Vegas, NV 89108

Voice: (702) 396-4909
Fax: (702) 396-4910
Website: www.electraprint.com 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

     
 

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