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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Monsters thread (high power tube amps)

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#21
never noticed that subtle stylish flair in the application of the ViceGrips.
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You didn't mention the hose clamps! The vise grips are suitable for the 10 AMP heater current, but the plate and grid connections are hose clamps. THe B+ is connected using hamfest grade clip leads. This is why there is a 1/4 inch sheet of Lexan between me and the amp in operation and a fire extinguisher between my feet.
 
#24
tubelab.com said:
You didn't mention the hose clamps! The vise grips are suitable for the 10 AMP heater current, but the plate and grid connections are hose clamps. THe B+ is connected using hamfest grade clip leads. This is why there is a 1/4 inch sheet of Lexan between me and the amp in operation and a fire extinguisher between my feet.
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Just gotta love the clip leads. They're probably "rated" at 30 or 50 V.... The fairly nice Pomona clip leads I use are rated at 60 V. And even with nice wires, one really has to be careful. They tend to fray where the wire meets the hook and suddenly you're stabbing yourself with the pointy end of a wire strand with 100's of Volt on it. Needless to say, don't mess with the circuit while the power is on.

~Tom
 
#26
my monster version:

013-1.jpg
 
#30
richwalters said:
>Output trannies look bit on the small side.....what's throughput power range & freq ?


richy
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yes, i would have wanted a bigger one, i used the existing opt from the amp where i harvested those output tubes, those opt's used pin striped cores that are 0.35mm thick, i found out that using the 16 ohm tap the reflected primary impedance was 1600 ohms plate to plate...

power consumption at idling was monitored at 470 watts....
 
#35
Correct. A bit of a distraction since I get carried away working late at night.....The bit that troubles me about using large numbers of tubes is a welding sized winding required for the heater supplies unless one puts sets of tubes in series and ramps up on the volts to reduce the CSA. A long time ago I did a 16 tube amp using 6550's not realising this tube is mighty sensitive to heater volts variations and learn't my lesson from it. Eventually it was near impossible to rewire it so I busted it up.
Appropo heater windings. It's the easiest way to annoy a transformer winder; to specify a high current low voltage winding with a pretty precise figure; in which the wiring run resistance losses should to be put into the equation. However, we all learn, so I adopted the similiar busbar method for my parallel 4's using EH KT90's which are far less critical to heater voltage variations.

The lower working Z of a multiple tetrodes configured as triodes is a tempter; but I've found with a good design I've fooled many in believing a well designed parallel p-p UL stage can sound just as good as triode, the bonus is far more power and fewer tubes, so I've stayed with the concept.

I'm just about in the final stages of completing that 200+200W amp; the serious test process commences when the weather is bad outside. The trouble is I can't stand working in the lab when the outside weather is electric blue.

richy
 

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#36
^yup that is why i added a second power traffo, 4 24v secondaries rated at 4 amps each is more than enough......the input/driver tubes also got their own 12.6 volt center tapped heater supplies....

all heaters are dc lifted to just below 1/4 B+......

these measures along with a generous filtering using 12 x 3inch 1000/450vdc filter filter caps in a CRCRC config and forward biased diodes separating both channels, made for a dead quiet amplifier.......

i am working on a push-pull 4D32 power amp right now.....
 
#37
The lower working Z of a multiple tetrodes configured as triodes is a tempter; but I've found with a good design I've fooled many in believing a well designed parallel p-p UL stage can sound just as good as triode, the bonus is far more power and fewer tubes, so I've stayed with the concept.
Click to expand...

i found my 6LU8 push pull amp has better bass than my 6P3C ultralinear amp.....

i guess pentode operation gives more punch in the bass department....but that is just me....😀

so now my next build is a pentode mode 4D32 push-pull.....😉
 
#38
The trouble is I can't stand working in the lab when the outside weather is electric blue.
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Most of my day is grey. Ever notice that the grey of the sea of cubicle walls inside a large building is the same grey that's found in mental ward. I think there are other similarities as well.

Our sky is polluted by the glow of several million electric lights since there are about 3 million people within 40 miles of here.

About 6 years ago a devastating hurricane ripped out most of the power infrastructure and we had no electricity for 3 weeks. It was a clear October sky for a week after the storm too. One of my friends brought over his large reflector telescope and we spent several nights looking at things we had not seen before right from my front yard.

I like to use odd voltage sweep tubes for the big amps. The higher heater voltages don't need stupid current. I have seen 500+ watts flow from 4 X 35LR6's but they were on the verge of exploding. I think 6 or 8 would be about right. I got 45 of them cheap.
 
#40
^i have all the irons on hand, the chassis is in the powder coating shop....

i am using an 11HM7/6GU7 combo and 2SK3563 mosfet folowers.....operting point will be as per datasheet...

will use regulated screen grid supplies using IRF840 mosfets and zener references...

like my previous builds, power supply filtering will have generous amounts of filter caps given that they are dirt cheap in my country, they were taken from computer power supplies.....😀
 
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