| Geoff |
Nelson
You mention in your article that you bought and tested various types of lamp for use in this project and determined that a standard incandescent was the most suitable. For the benefit of those of us on the wrong side of the pond (and elsewhere) who have a 230V mains voltage could I please ask what other types of lamp you tested and with what results.
To give a similar resistance to a 120V 150W or 300W lamp, a 230V lamp would need to be 600W or 1200W, which is clearly impractical since they are not made in these sizes (150W is normally the largest).
A check of some main suppliers in the UK reveals that 110V lamps are only available in low wattages (eg 15W pigmy bulbs and 60W standard bulbs for safety handlamps etc), with one exception. 110V 300W and 500W tubular double-ended lamps are available but these are a tungsten halogen type for use in industrial floodlights and the like.
I am sure that there will be a number of people who would be glad of any further advice you can give regarding alternative lamp types.
Geoff |
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| sdman |
Nelson,
Now you have gone and done it!, and invented the Light Bulb
Amplifier(LBA). Looks like the great Sierra mountain air has done nothing to deteriorate your brain.
You realise you have opened up "Pandora's Box)" to a
multitude of questions such as, what brands,Westinghouse,
GE,Sylvania,Phillips,etc,etc,and then later someone will be saying that the GE seems to muddy the highs but gives a great low end response, the Westinghouse has great imaging,
etc.
Of course I am just funning you and would like to congratulate you on the new web site.
You have breathed some fresh air into this forum. |
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| Lisandro_P |
| quote: | Originally posted by Geoff
To give a similar resistance to a 120V 150W or 300W lamp, a 230V lamp would need to be 600W or 1200W, which is clearly impractical since they are not made in these sizes (150W is normally the largest). |
The largest 220v bulb commonly available is 300w, and uses a bigger base (i think is called "Goliath"). I have an OSRAM 300w 220v right here, and measures exactly 13 ohms (cold, of course), for whatever's worth. |
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| surf,sun&sound |
I just came from the new Pass site, great site! But that new "Zen-lightenment" amp is way to cool!!! I will have to build one of these just for the kicks! My only question is what is the rms wattage of this design?
Also I need to know what substitutes we can use for the bulbs, since I live "Down Under".
Surf, Sun & Sound |
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| Geoff |
Lisandro
220V 300W may be commonly available in your part of the world but they are not sold here in the UK where, as I said, 150W is the largest size listed in the suppliers catalogues that I have checked.
Geoff |
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| Lisandro_P |
| quote: | Originally posted by Geoff
220V 300W may be commonly available in your part of the world but they are not sold here in the UK where, as I said, 150W is the largest size listed in the suppliers catalogues that I have checked. |
Well, i'm in Argentina, so i guessed you could find them everywhere else :( You could use lamps in series instead of in parallel... |
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| Samuel Jayaraj |
Geoff,
Two 150w 220volt bulbs in series, would result in 110volt 300w equivalent with the resistance doubled. That is only obvious, and I know that you know this.
Hence, maybe Mr.Pass could tell us, what is the typical cold resistance (of the filaments) that is desirable. |
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| tortello |
| No, it seems to me that two 220V/150W in series make a 440V/300W load... |
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| Geoff |
A single 120V 300W lamp will have a 'nominal' resistance of 48ohm. To achieve the same 'nominal' resistance at double the voltage rating will require four times the power ie 1200W. This could be achieved in the UK by using eight 150W lamps in parallel but is a little unrealistic if an acceptible 110/120V alternative could be found. Hense my question to Nelson about which other types of lamp he had tested.
Geoff |
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| vdi_nenna |
| What happens when a bulb burns out? |
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| paulb |
How about the filament of a vacuum tube? Haven't looked at the numbers, could it work?
Might find a use for those things yet. |
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| mrothacher |
I have tried the circuit with a number of different bulbs and have found the Western Electric 300W to be the best performer. Of course these are only available as new old stock. The very best are from pre-1965 lots with the black base. You may be able to find the military (JAN-300W) version if you're lucky. I know a guy who's selling these in matched pairs for $500.00 a set. The Western Electrics have the most incredible midrange bloom I've ever heard. The image is fantastic, and the mid-bass hump apparent in the GE's is much less pronounced. Of course, all of this presumes you're using a ceramic socket of the finest quality and silver-plated wiring throughout.
Cheers!
Mike |
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| Nelson Pass |
General responses...
Try the Sylvania website, where you can see
incandescents up to 1500 watts. I was tempted
by these, but they require a mogul base.
http://www.sylvania.com
You can of course parallel the 240 bulbs till you
get the right impedance, which will be somewhat
less than the full voltage rating at the 25-65
volts in the project. The 300 watt 120V bulbs I used
were about 35 ohms or so at these voltages, where they
would be more like 48 at 120 volts.
The best glow is to be had with about 30 volts across
the bulb, and to extrapolate this to 240 volt bulbs,
we would probably want 60 volts, or 75 volt supplies.
I did not use Halogens as I understand their life to
be short if not used at full voltage.
If a bulb dies, the amp stops playing. There is no
damage and no thump.
Vacuum tube filaments are rated at lower voltages
than we probably want, but you can operate them
in series....
I am very gratified by the response, thank you all.
We have a lot of amplifier designs in the queue, but
I just had to get this one out of the way first :) |
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hmmm......how would that or the SOZ amp cope with a 32ohm load? (grado headphone...) yes i will separate the grounds for each channel.....
maybe a downgraded 1W amp...would look nice with smaler lamps =)
/micke |
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Works fine. The Grados need so little
power that you can really back off on the
bias and voltage, in fact they work pretty
well with the balanced line stage. |
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i think this resistor can be availbale with soz ,
no need heatsink any more.
http://www.gotoweb.com.cn/re.gif
<img src=http://www.gotoweb.com.cn/re.gif></img>
but i dont know whether it is really good in hifi..
say something about this resistor, please. |
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Heeeee Mr Pass.... so the grado's can be driven by a BoSoZ , without modification ... I've been wanting to try that for some time now... I guess the output impedance really doesn't matter much in headphones ... So I will finaly modify my grado cord for balanced operation.... just to compare bthe sound with the SE-MOSFET-headphone amp from HEADWIZE
greetings... |
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I once suggested using the heater elements from clothes dryers. I seem to recall that they're about 3 or 4 ohms, and they're cheap--free, if you pull them from junked dryers. It would be about the same as the resistors (which look like heater elements to me) that John has pictured.
As long as the resistance is there, the circuit will work. Whether there is any sonic benefit or loss to using such a resistor, I couldn't say. No one ever admitted to trying my idea...perhaps they didn't need to dry any clothes at the time.
Grey |
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| I have also suggested toaster elements.... |
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| Hair dryers, electric cooktop elements,strip heaters,electric irons,etc. |
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I have one made in 1921 but afraid to put it to music.
How about an electric blanket? |
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I had this idea about 2 years ago.
I built a prototype.
Then somebody told me, the resistance of the light-bulbs decreases with temperature.
Of course..
Measured it.
Yup.
Shucks.
-- Finley |
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| cyclotronguy |
One of my favorite suppliers here in the US is McMaster-Carr Supply; they produce a 3000+ page cataloge of industrial hardware. I've been in their plant and can report that all cataloged goods are in stock, with repair parts, something like 350K items. Lamps and sockets should be no problem.
Service is excellent, and they are happy to ship anywhere in the world. They can be found at www.mcmaster.com. |
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| chrisvw |
| Close-Up of Halogen Lamps: |
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| moe29 |
| that's a pretty neat looking ZenLite :) ...wish i could read the text. |
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| Netlist |
Very nice. It looks like the man is used to build tube amps.
/Hugo |
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| Vix |
Wow, nice ZEN lite!
It seems that halogen bulbs are more appropriate for us on the other side of the pond....
BTW, just yesterday I completed a ZEN-lite, in a wooden case, with ceiling halogen bulbs. I used 3 pieces, 12 v, 20w in series per channel. Unregulated power supply, 48 v, CLC filtering (Only around 50, 000 uF pr channel:( ). Got about 1.85 A of current. The voltage accross one bulb around 9v. With six of them( 2 channels), it is quite bright so in the evening I can turn off the lights in my room; ZEN is bright enough:cool:
Why Zen-lite now? In fact, I was attempting to build an F2, but didn't like the result. It was showing signs of instability, some weird noises from the loudspeaker when no music was playing. Then I "converted" it to a basic ZEN schematic, but with the lightbulb as a current source...(now it works fine)
I hope to "upgrade" this circuit to something better, an F3 or just a cascoded Zen, using another mosfet, but I have to solve some issues first:
Problems:
1. I have to add a turn-on thump blocking circuit; at the moment I am shorting the input manually when powering it on.
2. Heat: While two mosfets are mounted on a decent heatsink, halogen lamps release pretty much heat on their back, which are inside the enclosure. So I am keeping the cover open, but I am thinking of adding a fan.
3. Noise. Transformer (600 w) is quite noisy. Enclosure is resonant; I feel as if I mounted a tranny inside an acoustic guitar:dead:
If I don't manage to solve these isses, maybe it will just be "forgetaboutit" thing...
At least, it was fun...
Ah, pics.... I don't have a digital camera, but I will post some pics here as soon as I borrow one...
Regards,
Vix |
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