Of course the 6em7 is a classic at a bit lower power but with driver included. And not just any triode but one not already harmonically mixed up with its own driver tube. Woo audio wa33 elite edition headphone and preamplifier. Particularly with singleended valve amps its well known how the choice of driver tube has a very significant impact. Interstages are direct coupled or transformer coupled, eliminating capacitors from the signal path. All units are factory checked and adjusted, but have a fine adjustment for.
These tubes are easy to source, still manufactured by chinese, czech or german. Whilst sex appeal and undivided attention are say on a 300b, a 6sn7 driver will make that directheated triode sound very different than a 5687, el34, c3m pentode wired as triode or a directheated highgain 20a. The 2nd stage is just a choke loaded gain stage with a direct heated triode like 45 or 2a3. The filament of this direct heated triode are connected directly to ground via the center tap midpoint of the heater winding. Both of these are driver tubes, and both were conceived for driving high linearity output dhts, such as the 300b. Dual shielded power supplies with inrush current limiting. The 300b directheated power triode is used in a fixedbias circuit, with a userfriendly potentiometer and meter for monitoring and adjusting bias current. The re604 output stage is biased the same way as the previous amplifiers, however the grid is ac vice read. All direct heated triodes the a5000 dht monoblock amplifier is a pure direct heated triode, tube rectified power amplifier. C3m connected in penthode, just 1,5v is needed on its grid for same swing on load.
I used tango nc14 interstage and fx405 output transformers, which ive had around for a while. The new allnic d5000 dht tube dac is finally available world wide. Vinnie rossis latest classa, ultra wide bandwidth directly heated triode dht preamplifier design, compatible with. Here is an example of my entire driver amp with hum. Lexus rx wing mirror glass with baseheated,silver,rh driver side,2003 to 2008. This will act as a fuse if there is a short between the anode and heater pins of the power valves, thereby reducing collateral damage. Direct heated triode power output tubes are really interesting. The key can open and close the dc return for the cathode, thus turning the. This is a bottlehead stereomour ii a direct heated single ended triode amp with vintage rca and current production sovtek 2a3 power tubes, plus nos ge 12at7 driver tubes. In headphone mode it seems to be a completely different amp from the speaker mode, and doesnt seem like a direct heated triode based on the specs. The traditional way to reduce hum is to use a transformer with a centre tap, and connect it to ground. This combination results in unparalleled faithfulness to the incoming signal, incredible musicality and detail, and quick, articulate bass.
Direct heated triode tube dac by allnic audio labs. Tube preamp schematic of preamplifier with direct heated. With its small internal resistance of 5k you can match with a linetransformer. Mar 30, 2015 attention, all firsttime or wanna be builders of single ended directly heated triode amps. The 2nd stage is just a choke loaded gain stage with a directheatedtriode like 45 or 2a3. Finale audio and triode labs have had a focus on 300 b singleended amplifiers from day one. Ratings parameter symbol min typ max unit operating temp. The 833a was rcas most powerful glass triode in the old days, so it is an appropriate choice for our project to raise the capabilities of directly heated single ended triode amplifiers to a level where even the most demanding contemporary loudspeakers pose no challenge. A 30w pushpull amplifier based on the 300b direct heated triode output tube. G811 generator triode ussr soviet high power direct heated triode tube. I think youll find that the consensus on those sovtek 6922s is that they are sturdy and reliable tubes available in production quantities the reasons arc uses them that happen to sound harmonically bleached and about as far from the soughtafter sound of nos tubes as you can get. Tube preamp schematic of preamplifier with direct heated 112a triodes the 112a is one of the quite popular smallsignal us prewar directheated triodes.
Tube preamp schematic of preamplifier with direct heated 112a triodes the 112a is one of the quite popular smallsignal us prewar direct heated triodes. The two last are the most interesting but the ge 6840 is. With a number of good products on the market, we had to have something special right out the gate the f300b classic mono blocks was our answer. Putting on my tektronix hat, dhts have remarkably low distortion compared to nearly any other tube, and peakcurrent capability is far in excess of more conventional drivers. Interstages are direct coupled or transformer coupled, eliminating capacitors from. I chose the 2a3 directly heated triode power tube to implement the loftinwhite circuit. I have been a huge fan of allnic since my introduction to them two years ago by john wright, former engineer for ed meitner. More tube complement is a pair of 300b, 6sn7 differential driver stage, and 6sl7 input stage. To keep it fair, i here compare the 40w types kt88 indirect vs 300b variant vv30b direct heated, and use the audiomatica measurements for both cases. Dcheating directlyheated connected in parallel twin triode. Since this is all about minimalism, i will only touch on class a amplification on this page. Other choices could be 71a, 6b4g, 31, 01a, 801a and even the 300b.
A singleended triode set is a vacuum tube electronic amplifier that uses a single triode to produce an output, in contrast to a pushpull amplifier which uses a pair of devices with antiphase inputs to generate an output with the wanted signals added and the distortion components subtracted. Here is your chance to experience the magic of a set amp for a fraction of. One is the eml2030 series, a large directlyheated design the size is credited as part of the improvement in linearity but it is also designed with a directly heated filament. For the history the prototype loftinwhite amplifier used the 224 tetrode in the driver stage and the 250 triode in the power output stage. Fully differential driver stage topology, no global feedback, fixed bias amplifier with full voltage regulation.
Actually it is a project with a long process of experimentation. Demonstrating what can be achieved with modern directly heated triodes, advanced magnetic materials and the application of 21st century technology to a classic concept. I observed a plate voltage of 420v, which is supplied through the primary winding of a proprietary output transformer, also with a permalloy core. In headphone mode it seems to be a completely different amp from the speaker mode, and doesnt seem like a directheated triode based on the specs. Thrax spartacus, directly heated triode power amplifier. Although the hasimoto a105 is a interstagetransformer it works very good when wired to a 1. Is the use of direct heated tubes for high end set amps due to a lack of true triodes with indirect heating or is there lan inherent benefit to direct heating. The main characteristic of this amplifier, is the use of a direct coupled circuit. No regret, the 6463 is an excellent performer full data here. The new allnic d5000 dht tube dac is finally available in north america. It uses only direct heated, single ended tubes from input to output.
Oct 31, 2008 the upper triode will act as a high impedance load for the lower triode. New direct heated triode tube dac by allnic audio labs. See product page designed with directheated triode dht tube 5676, dht5676hp allows its users to have a feel of the direct heated tube sound as famous 300b. Dcheating directlyheated connected in parallel twin triode 1. Jun 14, 2012 the 300b direct heated power triode is used in a fixedbias circuit, with a userfriendly potentiometer and meter for monitoring and adjusting bias current. This alone could be the next big breakthrough in singleended circuits, if the microphonics are controlled. Direct heated triodes can be considered the simplest form amplification device, and therefore the best device to use, with minimalism concept in mind, and therefore, the topic on this page. Chokeloaded triode direct coupled to dht driver, transformer coupled to the pushpull 300b output tubes. Description a311 m series are all monoblock singleended power amplifiers. Apr 03, 2007 maybe it stops being a direct heated triode in headphone mode to eliminate the hum. A tube pre amp can deliver this without a problem, for transistor pre amps more of a problem.
Price varies as per driver tube selected key features full engagement output transformers. Mar 17, 2020 driver i need a triode with a relatively high gm, a low. Since september 2008 ive been working in a new project regarding a single ended triode tube power amp using the 811a vacuum tube. This is an easy to build, simple directcoupled input driver circuit that provides the proper drive voltage to the grid of the 211. I never forgot takujis comment that getting the tone right on a 300b required a directheatedtriode driver. Notice that in the table, the distortion more or less linearly increases with signal level which, incidentally, is not normally characteristic of im until you get past 22v peak signal, then the hum modulation increases rather rapidly, reaching a maximum at about clip point which is. This report examines the effects of using ac to heat the emitting structure filamentary cathode of a directly heated triode. Has a common heater and indirectly heated cathode, two internally connected triode grids one with sharpcutoff characteristics, one with remotecutoff characteristics and two anodes, one for each grid. The curves show the expected performance at high voltage. The 2a3 vacuum tube is a power triode capable of outputting 3. All heaters heated differently sound different notes all examples and measurements refer to 300b this work is result of mutual efforts and fruitful discussions with marc heijligers jos van eijndhoven henk ten pierick the author can be contacted at.
The 2a3 tube amplifier a tribute to simplicity and warm. Dht5676hp portable tube headphone amp diy enigma lab. Directly heated triode power amplifier spartacus is a statement. I recently became familiar with direct heated triode tubes with the purchase of a used allnic l5000. Effects of ac heating power applied to directly heated triodes. New direct heated triode tube dac by allnic audio labs dac. Was a directheated power triode required to scale up the bias adjustment to the next power. The notion of having a directly heated triode driver tube is a way big idea, and one that is sorely needed. Driver i need a triode with a relatively high gm, a low.
All of them use dht direct heated triode power tubes, such as 300b, px25, and ad1 as output vacuum tubes, with selection of the output tube type by customer at time of order. Attention, all firsttime or wanna be builders of single ended directly heated triode amps. Turntable yatrus directdrive turntable trajan mc1 transformer. This results in a natural and attractive tonal quality with rich musicality that is characteristic of the ta300b. Triode oscillator using the screen grid as the plate.
Good candidates are e182cc, 12bh7a, 5687 excellent in the vt25vt25a pushpull, 6350, 6463 and 6840. The wa33 employs a true fully balanced directheated triode, class a, outputtransformer design in a compact form factor, featuring a quad of 6c45 tubes for the driver that pushes a quad of 2a3 tubes for the power in an alltube design. For this to work we designed a driver stage that would supply the two output tubes with exactly the same signal in phase for one and out of phase for the other by using another super linear dht the px25. Special adaptation of iitc circuit using a triodewired kt88 driver delivers tremendous authority across the entire audible bandwidth with all the subtle flavor of the best singleended triode amps. Has anyone tried rolling either power or driver tubes in the ca50 and what were the results. Directly heated filaments many of the previous heater tricks will not work with directly heated tubes like the 2a3 and 300b, as these do not have heaters. The only info on the net regarding this is somewhat paranoid thread on diyaudio advising against this and suggesting that arc designed this amp around sovtekeh 6922s personally i dont buy it. Direct heated triode tube dac by allnic audio labs audiogon. Since there is no nfb im sure you can use other iron that is more available now. Maybe it stops being a directheated triode in headphone mode to eliminate the hum. The two last are the most interesting but the ge 6840 is hard to source i just have one in stock. This was all measured with the c3m in triode connected, for 17,5volts 19watts on rload i need 6,5v input voltage on the c3ms grid. Here is your chance to experience the magic of a set amp for a fraction of the cost you would normally have to spend. Direct heated triode tube dac by allnic audio labs the new allnic d5000 dht tube dac is finally available in north america.
That means there is no capacitor or coupling transformer between driver and power stages. An indirectly heated triode could be made more linear than a directly heated triode because you can. I will concentrate on these effects as applied to a single ended amplifier stage, as some of these effects are automatically cancelled in a pushpull arrangement. A refinement is to ground the centre tap through a small flameproof resistor anything up to 100 ohms. To get an idea of the difference, just compare some triode curves. Aug 04, 2014 the new allnic d5000 dht tube dac is finally available in north america. Matched pair of valvo aa globe dht tubes directly heated driver re604,ad1,ebiii. Eddie currents balancing act drives its 300b, 2a3, 45 or px4 with a 6sn7. Consequently, connecting the filament to the wall voltage, for example, is the same as connecting the cathode to the wall voltage. Maximum output current is limited to 5a, so a wide range of directly heated tubes, from small drivers to hefty outputs is supported. Real power drive the driver tube is the 3a110a or equivalent.
Tube preamp schematic of preamplifier with direct heated 112a. L2 signature preamplifier meticulously handbuilt by. Bottlehead stereomour ii 2a3 single ended triode set. The configuration of the driver section is 6sn7gtb manufactured by tungsol twostage parallel connection and the output section is the direct heated triode ta300b nonfeedback single power stage connection. In this project, the 2a3 power tube runs at a 60ma plate current with no signal applied and has a 410v plate voltage. Mq300 vacuum tube amplifiers products luxman seeking. L2 signature preamplifier meticulously handbuilt by vinnie.