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Old 22nd March 2013, 01:29 AM   #21
Magz is offline Magz  United States
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Quote:
Originally Posted by CV6045 View Post
If I may make a suggestion...why not put the CHOKE in the Negative Leg of you Bridge Rectifier...that way you will not subject it to any High Voltage...it does exactly the same job using it this way without the expense of having a Choke wound to take the pounding
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.
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Old 22nd March 2013, 03:13 AM   #22
Magz is offline Magz  United States
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More of the parts going into the mix.

Two 33uF GE oil caps for the first caps in the 6E5P supply, and 1000V, 10uF Mundorf Mtubecaps which will be used to bypass the 833 supply electrolytic stack, at the point of use.
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File Type: jpg 833 Amp supplies 2.jpg (338.5 KB, 1867 views)
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Old 24th March 2013, 05:59 AM   #23
Magz is offline Magz  United States
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Here is an LTSpice simulation of the amp output and 833 grid current with a 4ohm resistive load at full power (195Wrms). Input is a 1kHz sine wave at 2.5V.

About 180mA of grid current is required from the driver circuit.
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File Type: jpg 833 Amp output and grid current.jpg (33.3 KB, 1739 views)
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Old 24th March 2013, 09:45 AM   #24
CV6045 is offline CV6045  United Kingdom
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Default 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 !!!!


Quote:
Originally Posted by Magz View Post
Here is an LTSpice simulation of the amp output and 833 grid current with a 4ohm resistive load at full power (195Wrms). Input is a 1kHz sine wave at 2.5V.

About 180mA of grid current is required from the driver circuit.
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Old 24th March 2013, 10:47 AM   #25
N4BBQ is offline N4BBQ  United States
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Quote:
Originally Posted by Magz
That's not an amp, that's a midlife crisis
Quote:
Originally Posted by CV6045
...it became a monster out of control...
Funny stuff here. I'm looking forward to your project.
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Old 24th March 2013, 12:10 PM   #26
Magz is offline Magz  United States
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Quote:
Originally Posted by Magz View Post
Here is an LTSpice simulation of the amp output and 833 grid current with a 4ohm resistive load at full power (195Wrms). Input is a 1kHz sine wave at 2.5V.

About 180mA of grid current is required from the driver circuit.

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...
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Old 24th March 2013, 12:25 PM   #27
Magz is offline Magz  United States
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Quote:
Originally Posted by CV6045 View Post
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 !!!!
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.

.

Last edited by Magz; 24th March 2013 at 12:30 PM.
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Old 24th March 2013, 12:47 PM   #28
CV6045 is offline CV6045  United Kingdom
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Default 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 !!!!!

Quote:
Originally Posted by Magz View Post
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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Old 24th March 2013, 03:34 PM   #29
Loren42 is offline Loren42  United States
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You wrote, "This tube loves voltage, so I'm building with a B+ of 2300VDC..."

That's not an amp - that's a Tesla coil!
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Old 24th March 2013, 03:53 PM   #30
hpeter is offline hpeter  Europe
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Quote:
Originally Posted by Magz View Post
-My wife, upon seeing the 833C triodes in person - "That's not an amp, that's a Midlife Crisis!"

-My reply, "Hey, it's cheaper than a Corvette..."


So was born my 833C SET monoblock project.
.
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 speaker

humble little amp
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