Tube amp power scaling schematic software

Stephenson amplification lj15 ext power scaling, 2channel power amp. Alternately, use a high power 80v zener to drop the plate voltage, one on each plate, and one on the screen supply as well. If you find that the whole 20 watts are a little too powerful for what you need, the builtin power reduction circuit cuts the power to just 5 watts. Although all the above methods attenuate the output signal, the units most commonly referred to as amp attenuators are the brute force methods of attenuating. Hello, all you highpowered tube amp maniacs out there. Great overdrive from the el34 when cranked, and not too loud at. Posted on july 27, 2011 by jwk ive been scaling my radio collecting back a bit, as i need to work through the backlog of ones i already have, but one caught my eye. Vvr schematic and pcb layout for cathode biased amps for more. But still, a tubed amp will sound somewhat better when driven to deliver power beyond its rating ie, at clipping than a ss amp will. Tube power vs solid state power, how much is enoug. The 12at7 amplifier below is the best that i could do.

I implemented it on an amp i just built and like it a lot. Monoprice 5watt, 1x8 guitar combo tube amplifier with. Power scaling allows a dynamic power range over 40db. You do get to preserve the effects of preamp, power amp and output transformer distortion. I thought the mosfets might have been one used to scale the main voltage and one to scale the bias voltage. The key to power scaling is that it is applied to the power output tube stage itself, and so comes before the output transformer. If i could only choose one combo it would be ss pre tube amp. This is a functioning 8 watt per channel valve amplifier that i built. Next select the type of bias fixed or cathode and power supply dc or ac.

This effect can be some clipping, heavy clipping, or just that cusp of compression you get in a tube power amp approaching clipping. This article shows how i built a powerscaled tube guitar amplifier by making radical changes to a vox ac4 tvh amplifier head. Guitar amp attenuators, power scaling, master volumes. Power scaling is a london power trade name rat is licensed to use this technology. Initial power up checks were all fine guitar plugged in and sounds great. Readers of kevin oconnors the ultimate tone tut book series form a part of our population. Power supply for small tube amplifiers safety instructions. Ive got an actual london power amp with the power scaling. It is available as a head shown here, an 8 combo, and a 10 combo. Work has to be carried out only if the circuit is disconnected from the mains and deenergized.

New build single ended el34 with power scaling 10w. London power amps use proper grounding to eliminate hum and buzz. Fellow radio enthusiast n9god has developed the n9godvalves library of tube symbols and references but theyre mostly industrial and audio tubes. In general, i do not use them for the main amp because they are just too much of a pain for repair, tube sockets on the boards stress the traces and my customers dont like them. The axefx ii does not model the power scaling circuit as there is no point in that.

Power supply and power control circuit diagrams circuit. Build a wide range of tremolo circuit and an alltube reverb unit. Marshall origin series amplifiers page 9 marshall amp forum. Select an output transformer and a power tube from the builtin libraries. Power scaling reduces power, and thus volume, enabling the amp to produce power tube distortion at reduced volume levels, freeing you from the need for an attenuator. Jan 25, 2018 the power scaling used on the orgin is very different than anything marshall has done. Nor, at 280lb in its flight case, is it likely to go walkin. Power supply and power control circuit diagrams circuit schematics note that all these links are external and we cannot provide support on the circuits or offer any guarantees to their accuracy. Because of rectification some of the components conduct dc voltage of more than 322 v. Power supply for a tube amplifier schematic youtube. This is a high gain amplifier based on the jcm800 power amp platform. There is a computer program that comes with this page to help you. A key trick is to scale just the power valves and that way you do not lose the edge on the preamp.

Power supply schematic kt88 pushpull tube amp amplifier, tube. Power scaling is the best solution for those players who incorporate some amount of output stage effect in their sound. This is not a simulator, but a schematic capture and routing tool which i. The power scaling used on the orgin is very different than anything marshall has done. Also, i wanted it to be able to be a standalone clean amp without a need for additional pedals to drive it.

This particular build does not include the power scaling or reverb in the london power. Fwiw, think of a tube amp with a passive line stage ahead of it. London power standard circuit built into a late 70s fender bassman 10 chassis and transformer set. The power scaling switch wires go to the area between the second tube and the pi, not sure how they are doing the scaling, why it goes to this board area. To see if the circuit will produce the desired output, calculate the currents and voltages as done for the previous circuits. Apr 20, 2018 the power scaling switch wires go to the area between the second tube and the pi, not sure how they are doing the scaling, why it goes to this board area. If you are down with bode plots and circuit diagrams, though, it could serve as a nice introduction to. Power supply schematic kt88 pushpull tube amp amplifier. All london power power scaling amps are designed to provide smooth, sweet, clean sounds up to their limit of power. Most speaker attenuators alter the tone before they reach 8db reduction. Its a deadsimple way of lowering power amp drive, yet compensating for loss of distortion at low volume and works like a charm. Nov 30, 2016 this is a high gain amplifier based on the jcm800 power amp platform.

Iive never seen a schematic for either a vvr kit or a power scalling kit. This is not a simulator, but a schematic capture and routing tool which i understand can integrate with spice. The following circuit operates at a mains voltage of 230 vac. Audio power amplifier circuit diagrams circuit schematics note that all these links are external and we cannot provide support on the circuits or offer any guarantees to their accuracy. When using the terms cathode or fixed bias we are discussing the power tubes of an amp pre amp tubes are nearly always cathode bias or gridleak biased but that is a discussion for another time. A functional steampunk tube amplifier, pumping out 8 beautiful watts of valve power. A poorly biased tube can either be biased too cold making it sound dull and lifeless or biased too hot where the tube is destroying itself. Changes to the circuit are immediately reflected in the circuit schematic. A warm welcome to tube amp modding fans and those interested in hifi audio.

I wanted to have a small but nice sounding tube power amp that i can use with my preamps and pedals. Figure 324 is the schematic diagram of a scaling amplifier with the values calculated above. Power scaling is a technology developed by london power, headed by renowned tube amp innovator and author kevin oconnor, that controls voltages inside the amplifier, allowing for continuously adjustable power output. Marshall origin series amplifiers marshall amp forum.

But the main voltage would have to dump a lot of heat and neither has a heat sink. London power standard amp built into fender bassman 10 chassis. The steam amp 03 curated steampunk and dieselpunk gear madburner steam amp 4 industrial steampunk art and furnishings coppersteam. The ac20 model is based on the amp with the power scaling at maximum power which effectively disables it and sounds best imo. Kevin oconnor is the creator of the popular power scaling methodology for amplifiers. If your speakers clip at 100w with a strong ss ampnot cheezy piece, you can figure clipping at about the same output with a 50watt tube amp, or thereabouts. In the amp that came through here that had power scaling of the whole amp, it seemed to me to have a very narrow range of acceptable tone. The first screen in tubecad shows the schematic of the output stage. Birminghams laney amplification is often overlooked by the masses, even thought theyve been at it for decades and have some wonderful legendary amps to their name. Its all the good things that people get a tube amp for except for the brand name. That would optimally be the same as a tube amp with solid state preamp, except for with the solid state preamp you would have gain. Without resorting to software modeling which actually produces fairly decent results. Construct a 15w tube power amp or a true classa solid state amp. At the upper left you choose the tube type, and the number of tubes in parallel.

What amps are made with power scaling the gear page. You could build a plexi preamp into a 1w power amp, but dont be too disappointed if you dont achieve the cranked plexi sound from a most likely at that wattage singleended power section with the wrong tube. Build a wide range of tremolo circuit and an all tube reverb unit. Set to full power, power scaling will not alter the clean sound of your amp. This 20watt amp head is powered by a pair of el34 tubes with three 12ax7 preamp tubes. Having a separate power amp is very flexible, since you can combine it with any preamp you want. Or, a combination of a less efficient rectifier tube and zeners. Apr 10, 2010 the slides are pretty heavy on engineering design terms, but give a good feel for what it takes to construct and tune an audio amplifier using vacuum tube technology. If you do go for a different power amp, be aware that you cant use either of the marshallspec transformers, you need a power. I have optimized the system for use in my own amps and call it opr. Ive built a hand full of amps using wholecircuit power scaling, but only for. I tried several tube types to see if i could improve the tone and i went back to the stock preamp tube. Power scaling for tube guitar amplifiers a technology by london power. Btw, if you want to check out a cool master volume idea, go to the ax84 discussion forum and search poormans powerscaling.

I went through every tube in the tube cad library trying to get a voltage gain of 50 and a tube current of close to 10 ma. Power scaling reduces power, and thus volume, enabling the amp to produce power tube distortion at reduced volume levels. The preamp for this amp is completely different from the jcm800 with. That allows some interesting solutions that may not cheap or practical for bigger amps but fit great here. Power scaling a london power trademark and vvr, which stands for. The slides are pretty heavy on engineering design terms, but give a good feel for what it takes to construct and tune an audio amplifier using vacuum tube technology. The sv power scaling kits all use printed circuit boards with small boards for the pots to make wire connections. It works by switching the circuit board to lower the voltage on the output transformer, totally transparency in tone at lower volumes.

Youll find that it can create perfectly saturated blues tones and soaring leads with ease. Each builder begins with traditional or original audio circuit ideas enhanced by. Books about getting guitar sounds added latest amp tone books and videos, aug. A trio of software programs for the intrepid tubephile. At the same time i had a few voltage amplifiers breadboarded on the tubelab system for testing. For those of you who dont recognize it, this is a thermal relay in an octal socket. Audio power amplifier circuit diagrams circuit schematics. The soft rectifier effect combined with solen polypropylene power supply caps completely eliminates diode noise effects. Getting the pair moved into my listening room required.

By trying out several different sets of operating conditions in the computer i could eliminate hundreds of possibilities without playing with electricity. Part of diy is that you can do things that manufacturers wont. When using the terms cathode or fixed bias we are discussing the power tubes of an amp preamp tubes are nearly always cathode bias or gridleak biased but that is a discussion for another time. Jul 11, 2007 btw, if you want to check out a cool master volume idea, go to the ax84 discussion forum and search poormans powerscaling. Power scaling is kevin oconnors london power term for the ability to variably reduce the output power of an amp. Power scaling kits tube amp kits, tube amp books from london. Jul 25, 2019 the device receives your amps output and fully clamps it down in the load box, where it derives from it a linelevel signal much like an amps di output which it sends along to its internal power amp. Assembly manual schematic parts list tubes and applications design simulations. Power scaling is kevin oconnors london power term for the ability to. If you set power scale to a lower setting, the amp now behaves as a lowerpower amplifier with a lower maximum loudness for clean sounds. Oddblocks 12sl7 srpp kt88 pushpull tube amp schematic.

If you are down with bode plots and circuit diagrams, though, it could serve as a nice introduction to building a class ab amplifier circuit. Mv, powerscaling in 50w, 100w amps music electronics forum. If you want to build a tube amplifier and you dont want to just copy someone elses circuit it might be a good idea to learn how to design it. If you imagine a knob that goes to 10, with 10 being no scaling, the power scaled amp i spent the most time with sounded ok from 10 down to about 7. Note the size of this amp compared to the cigarette packet. The circuit is my own design built from scratch specifically for my needs instead of scaling down a big power amp. Note that all these links are external and we cannot provide support on the circuits or offer any guarantees to their accuracy. If you want to skip the build description and just hear the amplifier,just skip the article and jump to the sound clips a vox ac4 tvh is a small tubedriven practice amplifier release byvox in 2008. The experimenters power supply is excellent for tinkering with tube circuits, containing separate ac heater, dc heater plate and bias supplies. The pre amp for this amp is completely different from the jcm800 with added gain stages.

The power amp then sends a signal to the units speaker outputwith volumelevel and tone controls for the user interfacewhich can be. At the right you set up choice of fixed or cathode bias. Tube power vs solid state power, how much is enoug audiogon. In my online travels i have discovered london power scaling and other similar. Checked the amp over, added a wire id missed from my layout to the power tube cathode. Some circuits would be illegal to operate in most countries and others are dangerous to construct and should not be attempted by the inexperienced. The basic deal is about half the tube watts vs ss watts for controlclipping on the speakers. Below that you choose from a list of popular output transformers. Output tranformer distortion with guitar amp attenuators and load boxes. Even if you only own tube gear and have no ambitions at all of tinkering with any construction projects, youll find the tube manual to contain essential knowledge. The experimenters power supply is excellent for tinkering with tube circuits, containing separate ac. At first i tried scaling just the power amp, but have just reverted to whole amp scaling.

Power scaling allows you to live at that cusp or beyond, but at any loudness you need. Does anyone have schematics for the power scaling circuit as employed by kevin oconnorlondon power. This is a real swissknife of a 3 channel amp with lots of smart functions and at a really great price point. That s why many of us say that generally one can get away with a tubed amp of half the rated power compared with a ss amp. It can get mushy and soft at low levels if you scale the whole amp. It is a tube amp with a 12ax7 preamp tube and a 6v6 power tube. That would optimally be the same as a tube amp with solid state pre amp, except for with the solid state pre amp you would have gain. Extreme hum suppressor circuit that is also usable though supplied with 110 v ac or 230 v ac at 50 hz or.