Switch mode PSU in Tube amps, are they even trying?

Ibanezguy

I just love topics which spring from my mind without warning . ? Anyway here's a fun topic and electronic minded guys opinions and viewpoints would be awesome in this post.

Sitting here this morning I wondered with the new electronics tech thats available, and has been hugely used in light weight D Class amplification for PA amplifiers and bass amplification, can it not be used to power tube amps and make them lighter ? The earliest switch mode supplies were noisey and only used in computers as they induced switching frequency noise into audio circuits. That all changes now and I own a Crown XLS Class D amplifier which is so quiet and clean that if the power leds weren't on you wouldn't even know it was switched on. I am talking about the power supply section. I bet the only gripe most players have with tube amps is their ridiculous weight.

Yes I know we are talking different voltages for tubes and AC voltage is required for tube heater elements etc. Switch mode PSU's are very flexible and can be designed to output high DC voltages. Also tube amps need an output transformer but here they could utilize some new light weight magnet technology?????. Even if the psu can be initially replaced and the output transformer kept unti technology provides us with output solutions???

Some of you are probably going to mention that the sag in a standard transformer psu does affect the tone in a tube amp but advanced switch mode psu technology could simulate tube rectifier sag as per Mesa Rectifier.

Oh and if any amp manufacturer uses my idea I reguire royalties TA muchly ? LOL

ezietsman

Ibanezguy wrote: I just love topics which spring from my mind without warning . ? Anyway here's a fun topic and electronic minded guys opinions and viewpoints would be awesome in this post.

Sitting here this morning I wondered with the new electronics tech thats available, and has been hugely used in light weight D Class amplification for PA amplifiers and bass amplification, can it not be used to power tube amps and make them lighter ? The earliest switch mode supplies were noisey and only used in computers as they induced switching frequency noise into audio circuits. That all changes now and I own a Crown XLS Class D amplifier which is so quiet and clean that if the power leds weren't on you wouldn't even know it was switched on. I am talking about the power supply section. I bet the only gripe most players have with tube amps is their ridiculous weight.

Are you sure it has a switched mode supply? I'd be quite surprised.

Ibanezguy wrote: Yes I know we are talking different voltages for tubes and AC voltage is required for tube heater elements etc. Switch mode PSU's are very flexible and can be designed to output high DC voltages.

The trick here is that for valves you need more voltage than the wall gives. A switched mode supply switches the supply on and off really quickly, so you need to start higher which means you need a power transformer anyway. After that, a switched mode supply is of no benefit over what you get inside an amp.

Ibanezguy wrote: Also tube amps need an output transformer but here they could utilize some new light weight magnet technology?????.

I'm struggling to think of the physical process you are referring to with "new light weight magnet technology". A transformer is a piece of iron with two electrically isolated coils wound around it. The coils are looped over the iron core in different amounts. This means, via electromagnetic induction, that you can change one AC voltage into another. Simple.

Ibanezguy wrote: Some of you are probably going to mention that the sag in a standard transformer psu does affect the tone in a tube amp but advanced switch mode psu technology could simulate tube rectifier sag as per Mesa Rectifier.

Oh and if any amp manufacturer uses my idea I reguire royalties TA muchly ? LOL

Mimicing the Sag is as easy as putting a resistor right in the beginning of the power supply line, right after the rectifier. When the amp is pushed hard (you strike the strings) it requires more current to operate, this increased current over that resistor causes the voltage drop over the resistor to increase, causing the sag. This only applies to Push Pull amplifiers. Single Ended amplifiers don't have this effect, they always have the same amount of current flowing.

Ibanezguy

Good to see someone has tube amp and electronics knowledge which was the reason for this post. Its also supposed to be quite light hearted and to get some thoughts form like minded technical type people. The main point was "can we reduce the weight of tube amps because the transformers are the components that make them heavy to carry around. I've been in every type of electronics for the last 30 years. Having said that, tube amplification is the one thing I have never dabbled in as I have never had the opportunity hence my questions and thoughts. I am always willing to learn so this seemed like a good idea. Thanks EZ I picked up a couple of cool bits of info.

To answer you on the switch mode supply SMPS:- yes the Crown XLS weighs 3.6kg and is 1000w- it HAS a switch mode psu. The Class D technology in it is so good that at most gigs the fan never even turns on, this is my definition of efficient ? This is part of Crown's DriveCore series where Texas Instruments manufactured them an I.C which contains 500 plus components per channel to accomplish this feat of technology. The amp doesn't even have mode switches, everything from stereo, bridge mode, high pass and low pass filter settings are done via the front panel. This means you can instantly convert it to a bridged sub amp and another one to a stereo mid/high amp without the need for external equipment. Filters can be chosen per application- low pass or high pass and frequencies chosen. This is the type of gear that gets me excited about technology. Its called progress and would be awesome if someone could address tube amp transformer weight issue wouldn't it?

Yes I know how a transformer works but technology and science aren't limited to what we currently think we know or is it? So what your saying is, our first version of an ac transformer psu is the only thing we are willing to explore in tube amps?We can levitate trains and propel them at 100's of kmph down a track which it is not even touching, why cant someone find a transformer weight reduction solution? You get where I'm going now? If weight reduction in tube amps is not possible then its not, makes no difference to me I play Blackstar I.D series amps ? There was a time engineers only knew about class A and B, A/B, class H, Class D ........................................whats next?

I also own a Synq Digit 2k2 power amplifier which is a 2200w 1U Class D amplifier with ,yes, a SMPS. 5.5 kg of brutal power (650w rms per channel @8ohms) with a frequency response of 5hz - 36kHz so you know the audible range is clean and accurate as hell. The use of a SMPS is what makes this type of power possible in such a convenient package. High volume and solid bass needs a high current psu and transformers don't accomplish this as efficiently as a SMPS. I was always a Crest fan but they just got too heavy as I got older. Same reason i switched to Blackstar ID amplifiers. The year is 2016 and tube amps are still what they always were just thought someone could have made some fkn progress by now ?

Obviously to those who love lugging their beloved tube amps around, no matter how heavy they are, this post is pointless bullshit, but it helped me ease into the day and finish my Wild Bean coffee ? T.F.I.F ?

ezietsman

The progress has been made in as far as we don't use tubes much anymore. You have efficient Class D power amplifiers and they have low output impedance so you don't need to have a transformer to match that to the speaker. Valves have High output impedance and hence need a transformer to match that to the speakers. It's just physics. That iron core in the transformers makes it more efficient, but heavier. You can leave it out but then the transformer won't be able to do its job in this case.

Also, don't forget the high voltage required to run the valves. In my plexi I have 480V on the power tubes. Your class D will not require anywhere near this and probably not as much as 100V, which is why it can have a switched mode supply. To get to those high voltages you need a transformer. Valves are completely outdated tech. For all the reasons you mention, they aren't used much for serious engineering anymore, except in a few niche cases.

Ibanezguy

Thanks EZ that 480 volts is the info that ultimately answers the question ?