Here I am, spitting my ideas out onto HTML again. It's been five years since I started my homepage, although in a different form than it is today. In those years I have learned a great deal (I hope). The only thing still the same as back then is my knack to change my mind in mid project. Yep, I did it again.
This project will be my last great effort for an amplifier. I plan on finishing this amp in style so I can go on to getting the rest of my system in shape. I have been distributing my attention over a very wide range of projects and because of this don't have a system that is anything that I really like. There is great potential in all the components I have built, but they have not received the attention they deserve. The name "Exodus" seems like a good name for this project.
Things are taking form and I'm collecting all the parts. The B+ will be battery supplied, so 50 more batteries to charge. I've added new schematics for the chargers.
In spite what many people believe about batteries, the internal resistance is very low (10-15 milli ohms!). I have had many remarks that my supply would have a high impedance and that I had to bypass with a capacitor to lower impedance of the supply. I don't think a 20uF capacitor has an impedance lower than 1 ohm, so this assumption is incorrect. This is not a cheap NiCd battery pack, they are indeed slow and high impedance compared to SLA batteries. Just think that a SLA battery can deliver up to several hundred amps instantaneously. As example, my 2V/25Ah can manage 1330A during a short and deliver 110A for abut 10 minutes. My B+ supply with it's 3300mAh capacity can deliver 14 amps for about 5 minutes if required. Supplies just don't get any better than this ! Needless to say fuses are a must in battery supplies as there is no limiting factor for the current besides wires melting, components roasting or the battery itself catching fire.
I've split the project into two seperate pages, one for the signal part (this page) and one for the battery supplies. As the latter is quite complicated, referring to the chargers etc, I think it warants a project of it's own. This page will focus on the signal section only, as the supply will be a stand-alone unit. Two supplies will be made; a battery B+ and a rectified B+.
Aaaargh... summer is getting close, trannies almost finished. I have to start building if I want to take these amps to Århus this summer. Because of the many PCB's and batteries for the planned B+ supply I will never make the deadline. I have therefore opted to just go for filament battery supplies and rectified B+ (I have all the iron and it will fit into a single chassis). Hurry hurry hurry!!!! Maybe I will have the battery supplies at ATF2002.
Put up the schematics for the B+ and filament supplies. Lineup is now UX210 - UX245.
Argh... Only three more days to go until ATF2001 starts. I've been working on this project for a few days now and things are coming along nicely. To get things up and running in time I have used a single B+ supply for the driver and output tube, the second PS will come at a later date when I have some more time.The preamp will also have to come later, no more time to get it all done.
yep, iron in the background says it all... One signal chassis (left) and the B+ supply (right)
The B+ chassis has two connectors in the back. Each connector will go to a signal chassis (left or right channel). The supply has a single transformer but seperate windings for each channel. Two CLCLC filters, which were intended for the left and right output tube, now feed both driver and output tubes. The signal chassis has been prepared to receive two seperate B+ supply voltages and an external filament supply.
The two chassis were tested at 00:30am (hey, you know me by now!!) and guess what... they work :))) So far anyway.
Took some more pics during the assembling of the final chassis. I got a streak of bad luck on this one, wrong holes, frame didn't fit, paint job; argh! At 1:45 a.m. I finally got the chassis assembled and some of the wiring done.
The plate after I discovered the holes were drilled
too far apart. There goes the paint-job!
Paper-in-oil next to the tube socket, just about the only parts in the chassis.
Inside view. It looks worse than it is.
All done! But without the tubes.
Just got back from the Triode Festival in Denmark. Finished the amps and they fired up really nice. Great sound, best so far I think... I replaced the intended VV45 with globe Arcturus 145's and found them to sound a bit better than the Vaic tubes on my system, plus the nos tubes cost less than a third of what these czech tubes cost. The new setup with Cunningham CX310 and RCA UX245 looks absolutely stunning. I have yet to play in the parts (everything but the tubes was brand new), so I am very excited what it will end up like, but it already sounds very, very promissing.
Due to the new (future) setup of my speakers, the preamp section will have to come later as I will combine it into an active crossover. I want to avoid an increasing number of chassis, so the preamp will become a combined preamp/cross-over.
The battery B+ supply is taking shape. Design on the PCB's has started and I will have several made to accomodate my chassis for this supply. Some new ideas have also popped up to ensure even more safety precautions.
Work has finally begun on the battery B+ supply. PCB's should be ready to bring to the factory within a week or so. The schematic has been updated to match the voltages supplies by the batteries and the filament schematics have been corrected
The B+ supply will have about 25 batteries (12V/3Ah)in series to get the 300V for the 45. The voltage for the 10 is tapped from the 23rd battery.
The driver and output section of the Exodus.
B+ supply for the 10 and 45 while the battery sypply is not finished yet.
The filaments are battery supplied as usual, followed by a current regulator. I found some nice 12V/17Ah and 12V/24Ah batteries for only a few guilders, they seem to be as good as new. The regulator for the 45 has to be a high dissipation type since it has to drop about 8V at 1.5A. I used a LM350K which is a 3A regulator with a big metal housing, it is mounted on a heat sink.
To find out what resistor value you need, just divide 1,25 by the required current. In this case 1,25V/1.5A (for the 45) would make 0,83 ohms or, for the 10; 1,25V/1,25A = 1 ohm.