Hi all
This will be my first step into homebuild amplifiers of the kind for sound, my most beloved hobby is high voltage and tesla coils etc
I have just finished building a VTTC, which is a vacuum tube tesla coil and its basicly a RF transmitter that just sparks instead.
So I dug out some old stuff I got from a 1950s TV set or so, there are some common tubes that I have seen threads onhere with and I will try to recap what I have got.
Power transformer 230V mains, 50V/6.3V filament outputs.
Output transformer 400R/6R5 ohm values, its about 7x6cm iron core.
4x EF80 tubes
2x PCL 82 or 82 tubes, text is missing so hard to tell (can I have two pcl83 but they have different interior? shields is different etc)
But looking at datasheets they dont seem to be different but for 5mA cathode current values.
1x UCL 82 tube
So what have I learned tonight
EF80 can be used in a preamp, 2xPLC83 in a PP or 1x UCL82 in a SE PA.
I looked at this circuit : http://www.audiofanatic.it/Schemi/Tipo/Valvole/finali/pic_finali_SE/ECL82_SE_3.jpg
my UCL82 tube is just voltage heated instead of current for the ECL82, or did I miss something else than that.
Can I recalculate for my OPT values, or is it too low values for this use?
Should I leave out tone control? I was told that it only adds trouble.
Would I need a preamp for this circuit, and if so, any sugestions for one using ef80 tubes.
Kind regards
This will be my first step into homebuild amplifiers of the kind for sound, my most beloved hobby is high voltage and tesla coils etc
I have just finished building a VTTC, which is a vacuum tube tesla coil and its basicly a RF transmitter that just sparks instead.
So I dug out some old stuff I got from a 1950s TV set or so, there are some common tubes that I have seen threads onhere with and I will try to recap what I have got.
Power transformer 230V mains, 50V/6.3V filament outputs.
Output transformer 400R/6R5 ohm values, its about 7x6cm iron core.
4x EF80 tubes
2x PCL 82 or 82 tubes, text is missing so hard to tell (can I have two pcl83 but they have different interior? shields is different etc)
But looking at datasheets they dont seem to be different but for 5mA cathode current values.
1x UCL 82 tube
So what have I learned tonight
EF80 can be used in a preamp, 2xPLC83 in a PP or 1x UCL82 in a SE PA.
I looked at this circuit : http://www.audiofanatic.it/Schemi/Tipo/Valvole/finali/pic_finali_SE/ECL82_SE_3.jpg
my UCL82 tube is just voltage heated instead of current for the ECL82, or did I miss something else than that.
Can I recalculate for my OPT values, or is it too low values for this use?
Should I leave out tone control? I was told that it only adds trouble.
Would I need a preamp for this circuit, and if so, any sugestions for one using ef80 tubes.
Kind regards
Mads,
The EF80 is a good audio pentode. Put the 4 pieces away for a future project. For instance, the EF80 will make a fine 2nd gain block in a phono preamp. Looks like you have 2 sets to go into that build.
Except for heater voltage/current draw, the 6BM8/ECL82, the 16BM8/PCL82, and the UCL82 are identical. The schematic you linked shows a wretched 1/2 wave rectified PSU and tone controls. IMO you should look for something better. It just so happens that I'm involved in a 6BM8 project. Look here.
BTW, did you get the power trafo winding voltages right? I'd expect to find something in the range of 300 V. for the B+ rail.
The EF80 is a good audio pentode. Put the 4 pieces away for a future project. For instance, the EF80 will make a fine 2nd gain block in a phono preamp. Looks like you have 2 sets to go into that build.
Except for heater voltage/current draw, the 6BM8/ECL82, the 16BM8/PCL82, and the UCL82 are identical. The schematic you linked shows a wretched 1/2 wave rectified PSU and tone controls. IMO you should look for something better. It just so happens that I'm involved in a 6BM8 project.
Look here.BTW, did you get the power trafo winding voltages right? I'd expect to find something in the range of 300 V. for the B+ rail.
Eli Duttman said:Mads,
The EF80 is a good audio pentode. Put the 4 pieces away for a future project. For instance, the EF80 will make a fine 2nd gain block in a phono preamp. Looks like you have 2 sets to go into that build.
Except for heater voltage/current draw, the 6BM8/ECL82, the 16BM8/PCL82, and the UCL82 are identical. The schematic you linked shows a wretched 1/2 wave rectified PSU and tone controls. IMO you should look for something better. It just so happens that I'm involved in a 6BM8 project.
BTW, did you get the power trafo winding voltages right? I'd expect to find something in the range of 300 V. for the B+ rail.
I chose the schematics I posted over the mullard one as I didnt have a rectifier tube fit for it, I guess it can just be replaced with normal diodes but im not sure what effects that would have.
You wrote that you used another schematic based on the mullard one, do you have this online?
I did mix up some wires on the power transformer, I put mains on the HV out, thats why it didnt look strange at first till there was a supply missing
Got my 6.3V+, 50V and 285V now.
Is the schematic I posted really that bad? also, is there anyway to use the original OPT, it was used once so even if its bad, it should be able to be used again.
I already got 3 major high voltage projects that drain enough money as it is, this was just something I wanted to do because I never tried it and had the stuff lying around
I just did a simple calculations on my OPT according to this site: http://www.radioremembered.org/outimp.htm
At 200VAC on the primary I get 5VAC on the secondary,
So I got a 40:1 ratio, impedance ratio is roughly the ratio squared, so its 1600:1.
So with a 2 Ohm speaker load its around 3200 Ohm
The load impedance of the UCL82 tube is 3100 Ohm, so its seems that roughly a 2 Ohm speaker would work with my original OPT.
At 200VAC on the primary I get 5VAC on the secondary,
So I got a 40:1 ratio, impedance ratio is roughly the ratio squared, so its 1600:1.
So with a 2 Ohm speaker load its around 3200 Ohm
The load impedance of the UCL82 tube is 3100 Ohm, so its seems that roughly a 2 Ohm speaker would work with my original OPT.
Yeah the Power Supply really is that bad ,how about tweaking it with an isolation transformer (Easily available), a full wave bridge, A choke and a separate filiment TX?
The configuration for your mains directly rectify wall current.....The triple 'D'...Down, Dirty, Dangerous. Here in this forum we vehemently discourage Power Supplies of this configuration as it is very dangerous & lethal in this set-up.........
How about this??
The configuration for your mains directly rectify wall current.....The triple 'D'...Down, Dirty, Dangerous. Here in this forum we vehemently discourage Power Supplies of this configuration as it is very dangerous & lethal in this set-up.........
How about this??
Attachments
These are simple designs and probably sound a lot better.
-David
http://www.diyaudio.com/forums/showthread.php?postid=1632415#post1632415
-David
http://www.diyaudio.com/forums/showthread.php?postid=1632415#post1632415
SY said:Whoa, just looked at that schematic- DEADLY dangerous!!!!
At minimum, use an isolation transformer. This was the kind of thing that was banned decades ago after enough people got fried.
Dang,I glazed right over that the first time I looked at it.. My "minds eye" saw a separate HV secondary.
Thanks for all the warnings and links
As im "used" to work with live wires through my job as electrician and my latest tesla coil was fed by 2300Vac/500mA I am very careful around it.
I will look at the other schematics when I get home from work.
I just wanted to show you that I build the dangerous version without isolation from mains.
Picture here: http://gratisupload.dk/download/18027/view/
And that it acutally works, as I talked about earlier I thought the power trafo was the wrong way around as I missed 300V but had 180V instead, I will have to turn it back to 180V as I were feeding this poor little tube 380VDC last night and had red plates in short run times.
So remaking it with some fuses on my just ad dangerous power transformer as its just that old, lowering plate voltage and enclosure it in something
As im "used" to work with live wires through my job as electrician and my latest tesla coil was fed by 2300Vac/500mA I am very careful around it.
I will look at the other schematics when I get home from work.
I just wanted to show you that I build the dangerous version without isolation from mains.
Picture here: http://gratisupload.dk/download/18027/view/
And that it acutally works, as I talked about earlier I thought the power trafo was the wrong way around as I missed 300V but had 180V instead, I will have to turn it back to 180V as I were feeding this poor little tube 380VDC last night and had red plates in short run times.
So remaking it with some fuses on my just ad dangerous power transformer as its just that old, lowering plate voltage and enclosure it in something
A note on isolation transformers
Secondary neutral can be grounded to avoid floating potentials
Shortcircuit current is lower as its determined by the secondary sides impedance, in difference to the 6kA shortcircuit current we have on mains in households, in Denmark.
Using a isolation transformer is not removing any dangerous parts as the secondary side of a 1:1 transformer will still kill you, but you can avoid having potential difference from your amp to other conducting objects in your home, which is why all old electronics mostly were in non conducting enclosures.
If you know what you are doing, using old transformers isnt DANGEROUS, but its a unsafe choice when there is better options
Secondary neutral can be grounded to avoid floating potentials
Shortcircuit current is lower as its determined by the secondary sides impedance, in difference to the 6kA shortcircuit current we have on mains in households, in Denmark.
Using a isolation transformer is not removing any dangerous parts as the secondary side of a 1:1 transformer will still kill you, but you can avoid having potential difference from your amp to other conducting objects in your home, which is why all old electronics mostly were in non conducting enclosures.
If you know what you are doing, using old transformers isnt DANGEROUS, but its a unsafe choice when there is better options
Just wanted to show the final product, the chassis is grounded and measurements from audio in to ground is no more than 20V+
Whatever is plugged to this amplifier is something that I could live on without, knowing there is no isolation or fuses.
Unfortunately youtube muted my video, but then again, listening to a tube amplifier recorded by a compact camera, compressed, uploaded to youtube and then played on computer speakers.. not a huge loss
http://www.disorder.dk/?page_id=469
Whatever is plugged to this amplifier is something that I could live on without, knowing there is no isolation or fuses.
Unfortunately youtube muted my video, but then again, listening to a tube amplifier recorded by a compact camera, compressed, uploaded to youtube and then played on computer speakers.. not a huge loss
http://www.disorder.dk/?page_id=469
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