Within the power limits I can say that this design has sound that rivals any amp that I have built. I never intended for any of these designs to become a complete stereo amplifier that could be duplicated by a beginner. At one time I said that I wasn't going to build this amp. These devices are in the off state with zero bias applied, not optimum for a current source. Start with the one that you can get parts for. This was cured by operating the 45 filament from a DC power supply. Bonus! The distortion spectrum and the IMD looks like the amp above when it was tweaked out perfectly, however it needs no tweaking. I am providing the information in this update for those who have asked me these questions via e-mail. At that time I had not paid much attention to the whole single ended craze. These won't work well with pentodes, or multi stage direct coupled circuits (like the SRPP). Excellent for a current source, but that doesn't help if I can't get any. Why a 45 Amp? The 45 is the lowest priced "audiophile triode" that I could find. The operating point of the 45 was shifting as the stage approached clipping. See that page for the complete design. So far the circuit I breadboarded works the best and it is now in the amp. See the section on amp testing for full details on how this works. 0000001069 00000 n I just acquired an FFT analyzer program that runs on your PC using the sound card for an input. What can I use in place of the 5842? I don't like using an LED for the zener on the low power transistor, it really wants 4 or 5 volts to work right. All is not perfect however, the bass is not as "in your face" as the 300B push - pull amp. There are a few depletion mode devices in the world but I could not find any in stock at the usual distributors. 0000002802 00000 n What is my advice? 0000000915 00000 n The unique feature is the use of constant current diodes as the plate load on the input stage. The schematic of the amp as it exists today is here. All of the plots on this page were done with this software. The usual 12BY7 works ok at low voltages but the current varies too much over the needed voltage swing. The CCS IC's have arrived. It sounds amazingly good considering the distortion. This provides lower distortion and higher gain than the conventional resistor. This software is extremely useful for anyone who is involved in the design, testing, or tweaking of audio amplifiers. It was my intention to use this design as a starting point for "super tube" experiments. I have not actually built these designs, but these are good places to start. I was considering designing a circuit with an opamp and a mosfet to create a constant current source when I found an IC that already does this. I originally designed this amp as a building block for a hybrid amp. �K�-�B�6p�)��� m�����\��~[�l�b�?���3�8�}��hS�W\MK���b�=�. This is the first iteration of the design. I can't explain the theoretical reasons for the sound that I am hearing but it is different from anything that I have heard from a push - pull amp, even a class A 300B push - pull amp. The output transformer is borrowed from the Ongaku project (extreme overkill). 0000001143 00000 n Currents above 5 mA require more than 50 Volts to operate. Since the schematic was drawn I have added an electrolytic capacitor across the 510 ohm cathode resistor to raise the driver gain. We offer a wide array of products with applications across many industries. The design has matured into a sweet sounding 2 watt SE amp. What is needed is a circuit which can provide a constant current over wide voltage range, provide a high dynamic impedance, and operate with a low voltage across the circuit. Halloween Bats Craft. Want a mod that is easy to do, inexpensive, and makes a huge difference in your tone? 0000001546 00000 n I know that the ideal load for a triode is a current source so I put a constant current diode in place of the plate load resistor. This is especially noticeable with techno type music. I am not likely to have the time to do so in the near future. It was a cheap experiment. 0000001568 00000 n Combine one board, 3 transformers, and some type of enclosure and you have an amp, a very good amp. This was cured by reducing the value of the grid resistor. All I have to say is that these things cost less than most tweaks and sound awesome. You can now buy select products directly on TE.com. The cathode resistor needs to be 220 ohms. Performance figures are shown in Australian dollar (AUD). 0000003587 00000 n 0.0: 0.0: 0.0: 0.0: 0.0: 0.1: 0.2: 0.5: 0.8: 0.7: 48/101: 64/113: 81/114: 88/96: 79/91: Quartile Ranking: 2: 3: 3: 4: 4: Performance Criteria. Since this amp would evolve into a hybrid "super tube" amp, the sound quality must be excellent. 0000000727 00000 n The three best sounding designs are presented on the this page. The hum was not audible by itself in the speakers but showed up as intermodulation products. I know that there are a few die hard tube heads out there that are going to have a hard time putting an integrated circuit in a vacuum tube amplifier. I don't like the fact that I need the resistor in series with them and the resistor value is pretty touchy. Unfortunately this only holds true for currents of 4 mA and less. While searching the web for current source chips and circuits I found several compound circuits using tubes, mosfets, and transistors. Below is the distortion spectra for the completed amplifier: This is the frequency response for the amp: Since this design was started I have taken a deeper interest in single ended amplifier designs. Here are my EDUCATED GUESSES. Several iterations of 45 amp designs have been tried and a few are presented here. The second or third designs sounded the best. I get a lot of e-mail about this design. All of the mosfets that I have available are enhancement mode devices (the most common mosfet). Now I am actually considering building an even bigger one using 833A's. I am not sure that such an amp is possible, but whatever I come up with, you will read about it on this web site. I needed a simple single ended amplifier with excellent sound. The design has matured into a sweet sounding 2 watt SE amp. 0000004086 00000 n I HAVE built a complete stereo amp based on this work that uses common audio tubes (6L6, EL-34, KT-88) in triode or UL configuration. The Super Tube design will receive further attention shortly. I tried the usual mosfet current sources with good results, although the current is not as constant as I had hoped. The Simple 45 as it was first conceived on the Tubelab2 prototyping system. The 5842 tubes were found in my collection of "useless TV tubes". I have not tried any of them, perhaps one of them would work well here. 4 THEORIES AND RESULTS This article deals with the practical side of making new amplifiers, using the new inventions and new tor-oidal output transformer technologies. I have received dozens of e-mails asking for the complete construction details, I am sorry to say that there are none. The alternative approach uses a small high beta transistor to set the current, and a high voltage transistor to handle the voltage and dissipate the power. The prototype has already been built. Many people like it because it is simple. They are operating at 104 Volts which is above their maximum ratings (100 Volts max). The diodes are available from Mouser in several values up to a few milliamps. Operation in this manner yields 2.4 watts of power at 9% distortion. Due to the scarcity of reasonably priced 5842's, I have been looking for a different tube that works as good as the 5842. 0000001892 00000 n I needed a simple single ended amplifier with excellent sound. I have been using 12AT7's in my latest amp designs. I placed an order, which was immediately back ordered. 5 yr p.a. All experiments were carried out using bench power supplies, document.write("