for electronic geeks only: crazy idea.

[cronnin]

I was thinking, did anyone try to make an all tube amplifier running DC exclusively?

My first idea was a car battery, but it had low voltage and too much power, but rechargeable batteries seem fine.

You can use one moded car battery for the heaters that run at 12/2=6V using about 3A for 3x12AX7 + 2xEL34 tubes.
Standard car battery with 50Ah can last like 16x2=32h without recharging.

You can put up around 400 x 1.2 V= 480V for B+ side.
Amplifier can't draw more than 0.2A from B+, so that standard 2600mAh NiMH batteries could last 13 hours with one charge, (with amp maxed out!)

With this kind of supply you don't need PS transformer, choke, rectifying tube, or big condensers, which are the most expensive parts of the amp, so the price wouldn't go up much too high

 

[glassman]

Re: for electronic geeks only: crazy idea.

Look in any car older than the late 50's and you will find an all tube radio.

 

[GLJazz]

Re: for electronic geeks only: crazy idea.

I know I've seen a few attempts in the past, I'll see if I can dig up links. Either way, like glassman pointed out, it can and has been done.

I guess now the question is - why not more of them?

It must just be the MAN:firedevil

:headbang:

 

[GoldenVulture]

Re: for electronic geeks only: crazy idea.

With this kind of supply you don't need PS transformer, choke, rectifying tube, or big condensers, which are the most expensive parts of the amp, so the price wouldn't go up much too high

You'll still need these.

Ps: Except in the Automotive Industry they haven't called them Condensers [ Capacitors ] since the 50's or earlier.

Car radios and portable radios used these too!

 

[J Moose]

Re: for electronic geeks only: crazy idea.

Sure... I just spent a week tracking with a guy who had built a little amp that ran sub-miniature tubes from a 6volt lantern battery. Probably only a watt or two with a 6" speaker. Not very loud but gnarly enough to sound massive on tape.

Problem with a car battery is that they're heavy and expensive... doesn't seem very practical to me but whatever.

 

[trevorus]

Re: for electronic geeks only: crazy idea.

The thing with power supplies in your tube amps, you have to think of cost/benefit ratios. Sure, you may be saving a bit on not having big chunks of iron, but you'd be replacing it with big chunks of lead that wear out. Capacitors are still needed for power stiffening and filtering, and for other circuit functions in the actual signal path. Now, I don't know if you've seen the Milbert amp that someone posted here, but he's not using power transformers or output transformers at all, and came up with a 50 watt tube amp that the power tubes are hot swappable for any octal with the right pinout. My guess is he's using a voltage doubler/isolating circuit on the power side, and likely something similar on the output side. That is some innovation, but I'd have to hear it first. And the other thing is, it's not cheaper.

Link for the milbert amp: http://milbert.com/guitar

 

[cronnin]

Re: for electronic geeks only: crazy idea.

Didn't know that about the old '50 cars I haven't seen any of them here in Europe.

OMG, we really call them condensers here, it's my mistake, just fingers faster than brains Nice 6 Volter, that's what I need

I read somewhere that amplifiers sound different in USA and Europe since there is different frequency standard 50 vs. 60. Hz. Some say that 60 Hz sounds stiffer and with more density? Never tried this but that got me to this crazy idea.

Anyway, I don't think that car battery + hundreds of NiMH batteries would be like more than $400 tops.
If you subtract power transformer and filtering stage there can't be much of a price difference.

If that would get $1000 amp to $1200 but to make it sound ultimate,maybe it's worth it.

One can probably make this in DIY version for like $500 total.

I think (just think ) you would not need to use capacitors for filtering and stiffening if you already have perfect flat DC. Just small ones like stage dividers etc. Every rechargeable battery can deliver the current (0.3A if I recall well) needed for the tube plates and preamp?

http://www.batteryspace.com/batteryknowledge.aspx

Most efficient would be Polymer Li-Ion batteries with 170 Wh/kg.
That would mean for a 50W amp you could play it maxed for 3.4 hours with one kg of batteries That's like 2 pounds. (without the heaters)

I think it doesn't even have to outweight standard amp if you don't want it to have more than 5 hours of autonomy.

 

[glassman]

Re: for electronic geeks only: crazy idea.

You're still gonna need filter caps in the power supply. Batteries release power slowly while a capacitor releases it rapidly. Using batteries alone would result in bass frequencies that fall flat on thier face.

Filter caps do a lot more than filter.

 

[trevorus]

Re: for electronic geeks only: crazy idea.

Build it! One thing you might have forgotten is the need to run tubes at higher voltages than baateries can deliver, so you either need a lot of batteries in series, or you need a voltage multiplier circuit. This has losses like a transformer would, and you also trade away amperage for voltage.

 

[James Rock]

Re: for electronic geeks only: crazy idea.

Also maybe u have though of this or I'm missing something but replacing 400 NiMH batteries is a bit of a pain in the ass isn't it.

 

[cronnin]

Re: for electronic geeks only: crazy idea.

Yep. I originally thought of running 400 batteries in series. That would deliver 480V needed.
There are 3.6V batteries in production, and probably higher voltages for special designs, so it would get the number of Li-Ion batteries to a reasonable level.

They are supposed to have like 1000 recharges. That would deliver like 3-5 years of playing the amp before the replacement?

As for capacitors, if I have 460V (B+) I can send 46W into the speaker with just 100mA? Would never need more than that. Anyway it would not be a big problem to add a couple into design later

I will surely build it, but I don't have couple of hundred of $ to spend on batteries right now It would speed me up though, if someone actually knows (heard) it sounds better then with rectified AC.

Cheers all.

 

[crusty philtrum]

Re: for electronic geeks only: crazy idea.

It could be done, despite the myriad of issues. But I'd ask myself ... if it's practical and sounds good, how come there haven't been battery-powered tube amps marketed over the last several decades ?

 

[trevorus]

Re: for electronic geeks only: crazy idea.

Grab an oscilloscope, and see if you can put together a rectified AC that looks DC... Maybe build the amp section of it, and try it with a regular power supply and then with the battery system. Or use an off the shelf amp. That could save cost. Really, this is just an experiment to see if betteries are better, right?

 

[ehdwuld]

Re: for electronic geeks only: crazy idea.



from the site ( the image is the link )

This is definitely an exciting new product! I have not seen anything like it anywhere!

It is a battery powered tube amplifier. This first version is a very small, (9”w x 8”d x 4”t) stereo amp, about 16 pounds. It has 8 tubes on it, all in view!

It is based on the wonderfully magical 6BQ5/EL-84 tube. It uses a pair of EL-84 tubes for the output and a pair of 6DJ8’s for the front-end in each channel. The front-end tube can be any variant of the 6DJ8 tube which allows for serious tube rolling to achieve the sound you are looking for. The amp comes equipped with Cardas solid copper binding posts, 3 of them for each channel, 4 and 8 ohms, and Cardas rca inputs. The power connectors are made by Neutrik, they are the power-con connectors, very high quality.

All of the amplifiers will be shipped with JJ tubes. You may use any 12 volt battery or batteries you desire, as long as you provide the proper charger for the batteries you use.

The more battery capacity you have the longer you can play the amp. Typically it will play approximately 1 hour for each 5 amp hours of battery capacity.

NOW JUST A BIT ON THE SONICS

OH MY GOD!!! When there is NO noise it is truly amazing how much musical information you realize that you have never heard before! Inner detail is absolutely the best I have ever heard! Full range is not what I would say, I would say it has a very extended bandwidth with totally amazing dynamics!

Although it is only 15 watts per channel cont. it produces over 30 watts short term power and therefore it sounds much more powerful than it really is. This is due to the positive grid drive the front-end can supply to the output tubes. This will allow the tubes to produce power levels well beyond their normal capability for short peaks and it doesn’t harm the tubes in any way.

YOU MUST HAVE A LISTEN TO GET THE REAL STORY, ONCE YOU LISTEN TO BATTERIES YOU WILL NEVER GO BACK TO THE GRID!

 

[ehdwuld]

Re: for electronic geeks only: crazy idea.

DIY kit
opps thats a buffer kit
my bad

 

[joelap]

Re: for electronic geeks only: crazy idea.

I just spent a week tracking with a guy who had built a little amp that ran sub-miniature tubes from a 6volt lantern battery. Probably only a watt or two with a 6" speaker. Not very loud but gnarly enough to sound massive on tape.

Awww shucks.

Did it two years ago. No you don't need vibrators to do it. You have two options:

1) DC to DC converter of some sort, either using any of the many surface mount chips available or a simple boost converter using an oscillator to switch a MOSFET or BJT in place of a switch as shown here: http://en.wikipedia.org/wiki/Boost_converter ... I built a boost converter that worked on its own but when I tried to implement it, fail happened.

2) Since this was a design project and I needed a working final product, I used a good-ol fashioned MAX1044 charge pump used in 9v pedals to step voltage up. I ended up stepping it up to about 60V which was enough for the subminature tubes to make about 1W, that might even be stretching it. You'll end up with one heck of a cap farm doing it that way. Oh, that and the MAX1044 can only supply 10mA IIRC, so I stacked three of them on top of each other and voila, power. I bet I'm getting some sag out of that supply, but never bothered to measure.

Nice thing about the charge pump is the switching happens outside of the audio frequency band for the MAX1044... using a boost converter you'll have to really watch your lead dress and grounding scheme I'd imagine to keep the frequency of the oscillator from ending up in your signal.

I'll post a picture of it when I get home, its a funky thing for sure and a definite conversation piece. I won't tell you how much we recorded through it, but 2 out of 4 instruments used on the album found their way to its input jack in many occasions for secondary sounds / doubling and Moose and I couldn't believe how huge an amp with a 6 inch speaker running off of a 6V lantern battery could sound in the mix.

Best part is, lantern 6V is within the tolerance of the heaters for the tubes I used, so you can power the tube heaters right off the battery.

 

[J Moose]

Re: for electronic geeks only: crazy idea.

I'll post a picture of it when I get home, its a funky thing for sure and a definite conversation piece. I won't tell you how much we recorded through it, but 2 out of 4 instruments used on the album found their way to its input jack in many occasions for secondary sounds / doubling and Moose and I couldn't believe how huge an amp with a 6 inch speaker running off of a 6V lantern battery could sound in the mix.

Speak for 'yerself kid! I wasn't surprised at how LARGE it sounded in context with everything else. Over the years I've cut many, many a track with little battery powered amps like those plastic Marshalls and Smokey's. Your amp sounded quite a bit larger and more like a "real" amp then any of those which was very cool.

What's really great is that it wasn't the only piece of tube gear you built that made a substantial impact on the rekkid... hehehehe

Unfortunately I just went through all the pictures I took and the battery amp is the only thing I didn't get a shot of! No wonder... its the secret weapon!

 

[Brown Note]

Re: for electronic geeks only: crazy idea.

What's the point with all battery run tube amp? You'll need massive amounts of charge stored just to heat the tubes and that alone makes the idea sort of silly. Next problem is that you'll need a switchmode supply for anodes and that requires some knowled as a supply that boosts, say 12VDC to 200VDC probably do not exist off the shelf. Even extra great switch mode boost converters are of 70-80% efficiency and that makes the already powerhungry tube amp even less ideal for battery operation. A normal class A/B tube amp has efficiency of about 25% and adding the extra losses of the converter means that you'd require atleast 5 times the operating power from the supply that the amp itself produces as audio signal.

And the supply design is of it's own topic entirely!

 

[Brown Note]

Re: for electronic geeks only: crazy idea.

the milbert amp is surely either run with simply rectified mains(stupid and dangerous) or with switchmode supply that is small enough to fit inside the chassis. The OTL(output transformerless) design is nothing new in the tube audio domain as it was patented in the early fifties. Look for either furman otl or cirlcotron.

The otl design makes the amp even less efficient and is absolutely impossible with any reasonable battery supply.

 

[joelap]

Re: for electronic geeks only: crazy idea.

What's really great is that it wasn't the only piece of tube gear you built that made a substantial impact on the rekkid... hehehehe

Hah, thanks. That preamp is the result of a lot of time time spent calculating and experimenting... glad you dug the sound. I'd love to market it, but its a really -really- simple interface. I'm kicking aroudn the idea of adding a graphic EQ to it for versatility sake, but don't want to screw with a good thing either.

Unfortunately I just went through all the pictures I took and the battery amp is the only thing I didn't get a shot of! No wonder... its the secret weapon!

I'll get one up soon. Or maybe I shouldn't and let it remain a mystery for all eternity.