I appreciate the suggestion, and I believe I addressed that in the previous posts. The choke is on order and a down payment made. Let's move on.
833 Amp
I will watch your build progress with interest. About 8 years ago I tried to build a PP Amp using 833's (400 watts per Ch)....long story short I abandoned the project as it became a monster out of control. Everything seems to be multiplied 10 fold. The whole thing was in a 6 Foot Rack and weighed about 1.5 tons, and 1 ton of money.... I never got round to wiring it up but maybe I will return to it again someday. You may have spurred me on !!!!
I will watch your build progress with interest. About 8 years ago I tried to build a PP Amp using 833's (400 watts per Ch)....long story short I abandoned the project as it became a monster out of control. Everything seems to be multiplied 10 fold. The whole thing was in a 6 Foot Rack and weighed about 1.5 tons, and 1 ton of money.... I never got round to wiring it up but maybe I will return to it again someday. You may have spurred me on !!!!
Note: Up to 40Wrms, no grid current is drawn, meaning the Midlife Crisis is in pure Class A1 for the first 40W (most real-world listening situations where I'm not cranking AC/DC).
Working with kilovolts has its advantages...
The main reason I chose this circuit is its simplicity. The typical three stage, 300B driver, interstage transformer route would indeed produce a monster sized amp even in single-ended. As it is, this will weigh well in excess of 100lbs per mono.
This seemed to me the best shot I had at producing a really unique, great-sounding 833 amp that was still "reasonable" in terms of size and weight (if not cost). We'll see how well that turns out.
Another shipment of parts is due in on Tuesday (after that I'll still be waiting on one 733A PT, chokes for the filament supplies and the 833 mains, and the OPT). In the meantime, the four Coleman filament supplies and the four Salas regulators have been built, and it's time to start putting together the driver board and associated peripherals.
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833 Amp
Hi Magz, Thank you for the update on the 833 Amp.... You have really got me thinking and I have been looking at my old designs. Right now I am in the middle of building a PP Amp (on 7 Chassis, 2 X Mains Chassis, 2 X choke Chassis, 2 X Mono Block Amplifiers and finally the Pre-amp Chassis) and want to get that out of the way first then I will return and take a very serious look at the BEAST. In many ways I am sorry that I did not stick with it, it would certainly have been a talking point. People did ask me at the time why I was building a 400 Watt per ch amp... my answer because I can.... of course no one needs 800 watts but it's the thrill of doing it that is the reward. BTW, I was playing around with 2,250 volts B+ and it scared the hell out of me !!!!!
Hi Magz, Thank you for the update on the 833 Amp.... You have really got me thinking and I have been looking at my old designs. Right now I am in the middle of building a PP Amp (on 7 Chassis, 2 X Mains Chassis, 2 X choke Chassis, 2 X Mono Block Amplifiers and finally the Pre-amp Chassis) and want to get that out of the way first then I will return and take a very serious look at the BEAST. In many ways I am sorry that I did not stick with it, it would certainly have been a talking point. People did ask me at the time why I was building a 400 Watt per ch amp... my answer because I can.... of course no one needs 800 watts but it's the thrill of doing it that is the reward. BTW, I was playing around with 2,250 volts B+ and it scared the hell out of me !!!!!
keep going, dont stop. fingers crossed!
actually, i have similar on my mind, with 4-250A, saw them priced around 100€ NOS.
compare that to "special"300B editions >200€ ...
A2 class, 300Vg2, LL1691 (VDV5090
) with 4ohm load, ~1200-1500V , slow start230/5V smps... and hopefully 50-60W to speakerhumble little amp
Received more parts today...most of the power transformers (picture 1), with a Lundahl 1685 13H choke in the picture for comparison.
From left: two Hammond 369KX for the 6E5P/driver circuits, two 18V, 20A Hammond 165V18 for the 833C filaments, and one Hammond 733A for the 833C B+.
The 733A is massive, as befits a 2500V, 345mA (CCS), 50/60Hz trannie. The 2500V lines come out the TOP of the transformer through separate openings, most likely for isolation from the other lines, so it looks like I'll end up laying it on its face with all the wires inside the chassis for safety - the end bells come off very easily (see picture 2), so that should be no problem.
The 369KX is rated at 450V, 300mA. Since all the supplies will be choke input I need to use higher voltage transformers. I chose ones with AT LEAST double the current ratings I need to operate.
Still waiting on the other 733A and two 159ZL chokes for the filament PS.
I also have two little Hammond BD2E transformers coming for the cooling fan PS, if I decide to go that route. My goal is to get all this into an 18"x22" chassis...it will be tight, I think.
From left: two Hammond 369KX for the 6E5P/driver circuits, two 18V, 20A Hammond 165V18 for the 833C filaments, and one Hammond 733A for the 833C B+.
The 733A is massive, as befits a 2500V, 345mA (CCS), 50/60Hz trannie. The 2500V lines come out the TOP of the transformer through separate openings, most likely for isolation from the other lines, so it looks like I'll end up laying it on its face with all the wires inside the chassis for safety - the end bells come off very easily (see picture 2), so that should be no problem.
The 369KX is rated at 450V, 300mA. Since all the supplies will be choke input I need to use higher voltage transformers. I chose ones with AT LEAST double the current ratings I need to operate.
Still waiting on the other 733A and two 159ZL chokes for the filament PS.
I also have two little Hammond BD2E transformers coming for the cooling fan PS, if I decide to go that route. My goal is to get all this into an 18"x22" chassis...it will be tight, I think.
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That makes sense. I thought about using Xenon rectifiers but decided that SS would be smaller, lighter, and a lot safer.
833amp
I love the 2.5kv transformer... I did not know you could get End Bells that big. If you dont mind how much did Hammond charge you for it ? I may just order a couple if I return to my own 833 Beast later.
I love the 2.5kv transformer... I did not know you could get End Bells that big. If you dont mind how much did Hammond charge you for it ? I may just order a couple if I return to my own 833 Beast later.