Any News on the 833 Amp Project? - diyAudio
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Old 28th December 2012, 06:04 PM   #1
Magz is offline Magz  United States
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Default Any News on the 833 Amp Project?

Found this link while perusing the internet for 833 designs - it sounds way cool. I have no idea how old this link is, but was wondering what ever became of this idea??

This might be just the trick for driving my classic big Infinity speakers with a single-ended amp...and they said it couldn't be done (at least not without buying a WAVAC for $50K)!

Any news?

The 833A SE Amp Prototype
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Old 31st December 2012, 06:26 PM   #2
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The 833A experiments shown on my website are about 5 years old. Transcendar built the original OPT used in those experiments. It did not meet the original design requirements and both of us agreed not to proceed any further. I have an OPT and several possible power transformers, but haven't gone any further. I don't have any need for a mono 200 watt amp, and no place to put it, so no further action is planned. I may build a monster guitar amp someday but I don't need that either.
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Old 1st January 2013, 12:56 AM   #3
Magz is offline Magz  United States
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OK, thanks for the update!

In talking with Jack Elliano of Electraprint, he has said he could build an output transformer with a FR of -1db 20-30hz to 20khz if I could tell him the operating conditions I'd be running at. Right now I'm in the process of figuring that out; if you don't mind my asking, what did you find to be the optimum OP for the 833 in terms of plate voltage, current and bias?

I like the powerdrive idea - I'm a fan of using solid state where appropriate in a tube amp, and have built several preamps using SS CCS plate loads and even a 26 DHT preamp using the mu output from the plate CCS for a lower Z, with no "sand contamination" that I can hear ;-). The tube still does all the voltage amplification, so the sound should be (and is to my ear) the sound of a 26 DHT, not a SS chip.

So, to make a long story short, I'm in the planning stages of an 833 amp project now, and I'm considering a powerdrive-type setup to drive the monster tube. How does that work with you - do you sell the powerdrive boards that can be used with an 833?
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Old 8th January 2013, 01:03 PM   #4
jrobson is offline jrobson  South Africa
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Quote:
Originally Posted by tubelab.com View Post
The 833A experiments shown on my website are about 5 years old. Transcendar built the original OPT used in those experiments. It did not meet the original design requirements and both of us agreed not to proceed any further. I have an OPT and several possible power transformers, but haven't gone any further. I don't have any need for a mono 200 watt amp, and no place to put it, so no further action is planned. I may build a monster guitar amp someday but I don't need that either.
And the 845? Any update on that?
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Old 10th January 2013, 03:53 AM   #5
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Quote:
if you don't mind my asking, what did you find to be the optimum OP for the 833 in terms of plate voltage, current and bias?
My favorite OP was 1500 volts into a 5K ohm load with as much current as the tube could stand. I ran up to 275 mA which is over spec. This would work with forced air cooling. For convection cooling I would keep it around 200 mA. I got nearly 200 watts output at 275 mA

The heater draws 10 amps. I could not make it work on AC. Hum came from the speakers before I swithced ON the plate voltage.

The 845SE amp was built about 7 or 8 years ago. It is still umchanged since I built it. I don't use it much any more due to the heat that it makes.

I dont have PC boards for PowerDrive, but you could make your own or use PTP.
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Old 10th January 2013, 07:53 AM   #6
jrobson is offline jrobson  South Africa
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I was thinking more along the lines of sorting out the power supply.... I couldn't find an update on the site regarding it. But there are a few circuits on the web that could work with some adapting...
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Old 10th January 2013, 12:26 PM   #7
jrobson is offline jrobson  South Africa
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Was thinking along these lines and modifying for 845 filaments and upping the input voltage to 650-700, removing the 400v B+ since that will be done with it's own setup through the TSE board. It seems like a reasonably simple circuit and I like the solid state rectification in my TSE.

Sorry to the OP for the hijack.

Last edited by jrobson; 10th January 2013 at 12:29 PM.
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