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Old 13th May 2009, 10:04 PM   #11
Fuling is offline Fuling  Sweden
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Quote:
In fact it worked so well that around 11pm two cops knocked on the door, but by then i had already turned it off.
Grattis!
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Old 14th May 2009, 12:43 AM   #12
kimbal is offline kimbal  Australia
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Speaking of Cops coming to your door -

Back in the late 1970's when I was 18yo I built a real 1.2 kilowatt stereo amp ( 600 watts rms per channel ) with 24 output transistors in each channel ( 2N3055/MJ2955 ) running off a 15 amp split 90 volt power supply for each channel. I could run a radiator bar red or boil water with a sine wave signal with this beast.

Anyway I use to run it so loud playing - Black Sabbath, Deep Purple, and Jimi Hendrix, Judas Priest, etc; I had the police arrive at 4 pm in the afternoon (after school) one day to tell me to turn it off, as the neighbours complained during the day of the volume.

I also had my speakers catch on fire in my bedroom on another occasion with the same Amplifier - smoke belching out of the 8 1 inch dome tweeters when I was playing a new KISS record almost at full volume. The reapir cost was not cheap and the smoke was literally choking throughout the house. Alas my perents were not impressed.

At the time even my 200 watt RMS car amp I built then was so loud you could hear it across a football oval with the windows and doors shut on the vehicle. It pulled so much current from the alternator the car engine would run sluggish under load when I turned up the volume. Even these days my home made Amp would kick real *** compared to the crap on the market.

All in all the guys from my electronics class at TAFE college told me when they saw the sound gear at my house, their words were:-
"FAAARK ! Who needs drugs with a setup like this!" (Unquote).

Yes those were the days!

If you want to get into really big TUBE Amps then you may be interested in my information / post here as I am taking up a collection to buy a copy to share around>

Wanted - High Power, High Voltage, Audio Frequency Transformer Manual.
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Old 14th May 2009, 09:33 AM   #13
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Speaking of BIG tubeamps, have you seen the 3kW amp using two 4-1000As ?

If no, here it is: http://www.audiophool.cjb.net/Misc/3Kpdf.pdf

Btw i did a freq response test on a 230/2x9V 20VA donut yesterday and found it has a FLAT freq response 20-20000Hz so this replaced the split bobbin EI core interstage transformer. I also crunched some numbers for a output transformer i think about winding.

Click the image to open in full size.
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Old 14th May 2009, 11:51 AM   #14
kimbal is offline kimbal  Australia
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Thanks for the data.

Yes I know of that 3 Kw amp from 1953/4 by Bereskin. Interesting design. A smaller almost identical artical was published just before the 3 Kw design. It was a 50 watt unit with 2x 807 tubes. Not so sure I like the choke at the input but even so.

Output transformer design is in both articals.
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Old 14th May 2009, 01:57 PM   #15
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Quote:
Originally posted by Tekko
My only problem is the autotransformer and the hv transformer getting very hot.

I was mainly referring to the 833 tube.

The design i am doing has alot of space around the tube.
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Old 14th May 2009, 08:55 PM   #16
kimbal is offline kimbal  Australia
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Don't be afraid to use fans; blower or muffin types. I realise acoustic noise and air flow are added engineering issues but you can minimize these problems with careful design.

Ideally a good air flow from a blower hose with a remote located fan would be ideal, but not very practical. If I owned my own home I would do this.

Though not done by the average DIY - the 833 I feel should be forced air cooled especially for Class A continous application.
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Old 14th September 2009, 11:53 PM   #17
Markku is offline Markku  Canada
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Default Microwave tranny for SE output

I disagree with the idea that using a microwave tranny as audio op tranny is trolling the bottom. As Microwave trannies have to be made of the very best silicon steel in order to work at all. As they are run Hot at saturation. However if you measure the secondary inductance even with an 8 ohms load
in the 120 vac line , you will get a nice surprise. The cut off should be apx
30 hz or so for an se output with no modifications to the tranny other than
remove one end of the 2kv secondary from the case and insulate it and use
it for the plate lead instead. I am going to use a 6L6GC , should give apx
2222 ohms plate load and the 120vac will be 8 ohms. I don't what it will sound like until I try. But don't knock it until you have tried it.
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Old 15th September 2009, 01:02 AM   #18
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Quote:
I disagree with the idea that using a microwave tranny as audio op tranny is trolling the bottom..... I am going to use a 6L6GC , should give apx
2222 ohms plate load and the 120vac will be 8 ohms. I don't what it will sound like until I try. But don't knock it until you have tried it.
I tried it. It sucked. The frequency response went from 60Hz to 140 Hz and there was ample distortion. Maybe the transformers that I used were junk, and your results may vary, but there is a lot of ground to make up. The experiment and a lot of other glowing tube experimentation is in the following thread. The MOT for OPT discussion starts around post #27.

Photos - the death of a Simple SE and 6V6's

I built a "prototype" 833A amp a few years ago. I paid a transformer winder a decent sum of money to make me an OPT but it wouldn't do 20 Hz to 20 KHz, but it did make over 200 watts. I plugged my guitar preamp into it and annoyed the neighbors for a while and then took it apart. I never got around to building the final amp.

http://www.tubelab.com/833SE.htm
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