It is hard to make a speaker that the bass has the same efficiency as the horn. These are close. Simple crossover.
If at first you think that this is a DRD amp, look again. It is not. No slow, giant, heat inducing cathode resistor found here! The output impedance of the SMPS supply is less than 10 ohms and is voltage regulated. The same low impedance supply that is feeding the plate choke of the 841, and driving the grid of the 300B is also directly connected to its cathode. In fact, the stacked SMPS supply can easily deliver over 300mA of current to any of its voltage taps, instantaneously and continuously, while maintaining voltage to +/-1V! The ultra low impedance supply means the SMPS filtering capacitors are essentially out of the signal path. This gives incredibly good low frequency coupling… better bass than any electrolytic or oil capacitor could provide. Bias protection for over-current of the 300B is provided by the multiple voltage regulated taps that the stacked SMPS supply offers, not just the current draw of the 841 driver tube. Additionally, the thoriated filament 841 tube will begin drawing current before the oxide filament 300B tube. A large sonic improvement would be found by using a true audio rated low DCR plate choke, wound by Bud at Onetics, to load the 841 plate. A low DCR plate choke would improve dynamics and recovery of both tubes better than the inexpensive 200H chinese choke I had laying around. Even-so, listening tests show that this breadboard amp destroys my Welborne Terraplane DRD monoblocks in every audible way that matters, while putting out more wattage and dissipating less wasted heat.
People hate SMPS. “Too noisy”, “All that hash will kill the music”. It is time to see if they are right. Show me another supply that can provide over 300mA of current at 800V+ all while having an output impedance of less than 10 ohms!
EDIT: Well, once again I am late to the party. Way back in 2009 Ed Brown of diytube.com had the same idea. He didn’t stack as many, but the concept was proven valid with just six units in series. See more HERE.
The DACmini CX is my new 24bit 192khz source. So far the sound is excellent… all it needs is a little tube love ;) It may be too tight inside for an all in one source / tube amp, but there is plenty of room to make it into an optocoupler volume control LC 26 tube preamp.
After using the CEntrance DAC for a while I am convinced it is an outstanding value. Not just because of its excellent sound, ability to play 24/192 files via optical or coax and 24/96 files via USB, but because of its stability and isolation from noise. Now it’s time to see just how transparent the Asahi Kasei AK4396 DAC chip really is. Bypass everything and run the balanced DAC output right from the AK chip, into high quality 1:4 step up transformers, then directly to the Hornshoppe Truth buffered preamp. This sounds astonishing! Even better than directly coupling the DAC to the grid of a preamp or driver tube. The dynamics feel decompressed, headroom limitless. It must be the synergy of the interstage transformers being given what they love and the exponential expanding dynamics from the step up transformers creating the most exciting, real and dynamic presentation I have ever heard. Yes, maybe even better than vinyl. ;) Pictures of the mod follow:
Introducing the True Green DAC. ;) The final product has all the conveniences of a modern DAC. It is amazingly quiet, has a remote volume control, balance control, and plenty of gain. It is the perfect source for my powerful SMPS GM70 amp.
This post may not seem too interesting, but trust me… you will enjoy listening to this source at Hornfest.
This thing REALLY rocks!
Over the years I have listened to some very good speakers, and Daves speakers always stuck in my mind as doing things better than most. (Actually, doing less wrong than most) Here is what I have been listening to lately…
I fell in love with these ultra light paper cone vintage drivers made by Grundig. Loose interpretation of the Parker Audio configuration but adding the baffle-less Grundig drivers is what you see here. Other than a single cap protecting the Heil tweeters, the speakers are crossoverless. Flat response is possible by wiring the dipole Grundigs in series which brought down the midrange sensitivity to match the bass output of the single 5ohm Grundig driver in the sealed box, and the 4ohm Heil. Putting the Grundigs back to back in dipole arrangement, along with the Heil tweeters sounds very real. My big JBL horns can’t come close to the presence these speakers have.
In the teaser photo: My modified Eastern Electric MiniMax Sabre32 DAC with RCA 210 tubes, transformer output, and Optocoupler / Light Dependent Resistor (LDR) Volume control. Used to drive all IT coupled 10 > 45 > GM70 monoblocks with Onetics Output transformers. Although my favorite music is from vinyl, this DAC sounds incredibly natural with 24/96 files.