The reason I jumped on this thread with such interest is that I have several projects going on currently that have a similar concept. Here is my thread for a pair of 200W monoblocks using parallel output iron:
http://www.diyaudio.com/forums/tubes-valves/218962-bogen-mo-200a-transplant-conversion.html
It has not come to fruition yet due to the holidays and tube costs, so I put it on the back burner and have decided to go smaller scale initially with this concept:
I have all the iron, so it should go together pretty easy.
Blair
http://www.diyaudio.com/forums/tubes-valves/218962-bogen-mo-200a-transplant-conversion.html
It has not come to fruition yet due to the holidays and tube costs, so I put it on the back burner and have decided to go smaller scale initially with this concept:
I have all the iron, so it should go together pretty easy.
Blair
I already have all the parts on hand, so for me it's just a challenge. 125 WPC with Pete's 18 WPC board was too easy. I ran the board at 250 WPC for several days with no incidents, but I think pushing 250 WPC through Pete's board was a bit too far. There are some traces that are just too close for comfort.
There have been requests for BIG power amps, but the reality usually sets in when the $$$$ and the risk of failure starts tallying up. Search this forum and you will find very few tube amps over 200 WPC have been built. There are reasons for this. Many people underestimate the cost, risk, and probability of failure involved with building a big tube amp. All go up exponentially with the power level. Too many people start building something beyond their ability, and never finish, or worse blow up some very expensive parts, then give up.
The traditional method for big power is big voltage and transmitter tubes. This means high impedance OPT's which are hard to make, and expensive. It is also possible to run multiple lower powered tubes in parallel, reducing the impedance and the voltage level, but the tube costs go up.
Still to make a 500 WPC amp, we are dealing with a B+ of 600 volts, and currents over 1 AMP. Yes, this can kill you, and then cook your body before the power fuse blows!
Do I have the experience to design and make this amp? YES. Do I have all the parts? YES? Do I need a big amp like this? NO. Do I want to make it just because I can? Maybe. Would a BIG A$$ guitar amp be cool???? Is the Brownout 1000 cool? YOU BET!
If you haven't seen it before, Yes I went down the transmitting tube route before too! Totally not practical.
The 833A SE Amp Prototype
Agreed. OTL seems to be the way to go for high power. 2 6C33C's will do 25W, and roughly speaking, the maximum power scales as the square of the number of tubes (because the maximum power is limited by the current the tubes can pass). So 4 6C33C's would be approaching 100W, and 8 could do roughly 400W or so. (That's probably a bit of an overestimate, but not too far off the mark.)
Alan Kimmel's circlotron, using EL509 sweep tubes, is apparently 225W using 8 tubes. High power is pretty easy with OTL, and relatively cheap because of the savings in OPT's.
Chris
There's places that laser-engrave panels nicely for cheap, but there's often a $50 setup for the first one unless you supply a machine-readable file.
The output power would be in the neighbourhood of 3000 watts too.Ouch! Heater power alone would be in the region of 5kW!!!
Like I said, for 500 watts you can do it with forty 6AS7Gs/channel. That is still a big amp- the version we did had outboard power supplies and required automatic variacs controlling bucking transformers so that when the amps dimmed the AC power line, they could still make full power.
Hi
A class AB2 833A2 could esaily surpass 500W. It can be done but // tubes is much easier, however more prone to decreased reliability. I developed a 150SE triode amplifier that never failed from the very first start-up years ago.
You can read my ongoing story over here.
ward's 150W SE amp blog
BTW, being a transformer manufacterer, we can supply custom transfomers. The core I use has 42 CM2 surface.
MONOLITH MAGNETICS
Kinfd regards, //WDC
A class AB2 833A2 could esaily surpass 500W. It can be done but // tubes is much easier, however more prone to decreased reliability. I developed a 150SE triode amplifier that never failed from the very first start-up years ago.
You can read my ongoing story over here.
ward's 150W SE amp blog
BTW, being a transformer manufacterer, we can supply custom transfomers. The core I use has 42 CM2 surface.
MONOLITH MAGNETICS
Kinfd regards, //WDC
Ward, please **do not** post a plug for your transformers every time you respond to a post. Recommend you reread the forum rules. Thank You.Hi Kevin
Sorry for that, it was not my intention.
You can remove the part that is not inline with the rules if you want.
grz, //WDC
www.monolithmagnetics.com
Sorry for that, it was not my intention.
You can remove the part that is not inline with the rules if you want.
grz, //WDC
www.monolithmagnetics.com
Eimac 3-500Z tube can be made 1.42kw (2 tube) class ab2..but i dont know how to design it..I end up making 24w inspired with Ongaku circuit and still constructing it.
http://img708.imageshack.us/img708/4360/eimac3500z006.jpg
Ric
http://img708.imageshack.us/img708/4360/eimac3500z006.jpg
Ric
6C33C OTL will get you there
Chris
You and Atmosphere are dead on. I have recently completed a pair of 6C33C OTL monos with 4 x 6C33C per channel. With 4 tubes lit they produce 110w per channel. With only 2 per side 35W. Notching up to 6 tubes per side would have been straight forward for the talented folks on this thread and produce the power the OP is seeking. As Atmosphere points out, OTL results in great sound without the OPT $$ and headaches.
As many have pointed out the filaments take a bunch of power, but you don't have the stringent quality requirements of the OPT. I used one 8A 12V toriod for every pair of tubes. New it would have added $$ but keeping eyes open managed to find a stack of them at a surplus store for $9 each. No real issue. They tucked in close to the tubes and with series wiring it kept the big currents away from the signals. Dead quiet. The 750w of heat dissipated adds a welcome bit of warmth to my basement listening room.
Walter
Chris
You and Atmosphere are dead on. I have recently completed a pair of 6C33C OTL monos with 4 x 6C33C per channel. With 4 tubes lit they produce 110w per channel. With only 2 per side 35W. Notching up to 6 tubes per side would have been straight forward for the talented folks on this thread and produce the power the OP is seeking. As Atmosphere points out, OTL results in great sound without the OPT $$ and headaches.
As many have pointed out the filaments take a bunch of power, but you don't have the stringent quality requirements of the OPT. I used one 8A 12V toriod for every pair of tubes. New it would have added $$ but keeping eyes open managed to find a stack of them at a surplus store for $9 each. No real issue. They tucked in close to the tubes and with series wiring it kept the big currents away from the signals. Dead quiet. The 750w of heat dissipated adds a welcome bit of warmth to my basement listening room.
Walter
I hate to see your carbon tax bill!
Bad as it all sounds, I am in pretty good shape. The whole house is very well insulated with high efficiency heating and lighting. Dishwasher and pool pump run at night.
I listen from 9pm to 12am when there is excess power on the grid. With nuclear base load, without my amps on this power will just shed to ground. In this setting the amps are actually carbon neutral.
My story.. I'm sticking to it
What is the failure mode for the ceramic socket? I read one recommendation to go with teflon or plan to change sockets when changing tubes. I figured worst case if I change them every 2 years it will take 20 years to break even.
The failure mode is the filament contacts, which were never intended to handle that kind of current. The socket was originally designed for the 3C33 which is a US-made dual triode with half the filament current.
The Teflon sockets have greater contact area and don't heat up so prodigiously.
The Teflon sockets have greater contact area and don't heat up so prodigiously.
Alright boys and girls, here it is. I'm done...after about over 3 years of working between other projects, lots of testing, tweaking, and circuit changes, my 500 watt per channel stereo bass amplifier "Brownout 1000" with stereo preamp is finally finished. It did not quite deliver a full 1000 watts RMS before clipping while testing, however. I only got about 940 total but the line voltage at the wall outlet would drop from 120V to 113V where I was testing which I attribute to old wiring in my house which was built in the early 1900's. Running one side at a time will yield over 500 watts RMS output before clipping. So that amp lives up to its name! I ended up getting a custom toroid wound for the plate supply. It idles at 650VDC with 20 kt88's biased at 30mA each. At 1000 watts output the unit drew just under 17 amps from a 120VAC outlet, and 2.5 amps from the plate supply which at that point was 580V. Full power frequency response is very good. -3dB points are 15Hz and 23kHz. I designed it for bass guitar amplification and the fundamental frequency of low B on a 5 string bass is 30Hz. The amps will deliver full power at this frequency. I have not run it at high volume into bass cabinets yet. Low power yes but mostly through the line out into a practice amp so far. All power testing has been done with large resistive loads. I need someone to help me move it out of my house to my jam space since the amplifier weighs about 150 lbs and the power supply is around 80. Here are a few shots...
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