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Many years ago there was an unusual class of tubes designed for the sweep circuits in tube-type TV sets that have substantially large reserve current capability; hence the name “sweep tubes” was coined.

 

While sweep tubes are no longer made and some versions are getting much harder to find, there are examples that are still quite common.  The sweep tubes can put out huge power levels and still have substantial reserve capability.   Pete Millett’s Engineer’s amplifier [also known as a “Distortion-cancelling Push-Pull" (“DCPP”) amp], uses these unusual sweep tubes. 

 

If following Pete Millett's actual design, the DCPP amplifier is actually a 2-stage push-pull pentode design with the output stage biased so it will remain in Class A1 operations until somewhere over 10 watts where it then enters Class AB1. 

 

The input/driver stage uses a pair of 6CB6 pentodes in a differential amp configuration using a silicon CCS in the tail.  In Pete's design, the output stage uses 12-pin compactron TV sweep tubes, such as the 6JN6 (no plate caps required) or 6JM6/6GV5 (plate caps are required), which have a 17.5 watt plate dissipation.

 

Here is a link to Pete Millett's page where more information on the DCPP amp can be found.

 

http://www.pmillett.com/dcpp.htm

 

Several years ago when Pete Millett started to sell PCBs with his DCPP circuit, George of DIY Audio Tubelab fame, decided to test the upper limits for power in relation to these sweep tubes.

 

George used a power supply that would generate 650 volts at 1.7 amps and plugged in his samples of sweep tubes.  The amplifier generated 250 WPC in this configuration with a 2,500 ohm load.

 

Not satisfied, he decided to wire both channels in parallel through a common OPT set for 1,250 ohms and lo and behold; this combination generated 504 watts at 5% distortion and 525 watts at clipping.

 

I bought a PCB but had not done much in the way of putting together my parts list when I found a completed version of the DCPP amplifier come up for sale for slightly less than the parts would have cost me from my preliminary estimates.  Here is my Pete Millet DCPP amplifier.  My DCPP amp uses the 6JN6 sweep tubes for output and is nowhere near George’s 504 WPC.  My amplifier does the 20 WPC that Pete originally designed it for; and at that output, the sweep tubes will probably last a few life-times at that abuse-rate.

 

 

Millett - DCPP (the engineers amp) 1 - Copy.jpg

 

 

Millett - DCPP (the engineers amp) 2 - Copy.jpg

 

 

Millett - DCPP (the engineers amp) 3 - Copy.jpg

 

 

Millett - DCPP (the engineers amp) 4 - Copy.jpg

 

 

Millett - DCPP (the engineers amp) 5 - Copy.jpg

 

 

Millett - DCPP (the engineers amp) 6 - Copy.jpg

 

 

6HE5dark.jpg

Edited by Fjd
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Guest thesloth

I love to see Pete's Big Red board!!!

 

George from Tubelab is a great guy, I haven't heard much from him since his move. I think he is still unpacking. If I remember correctly George was using a screen drive topology along with high voltage to achieve the amount of power he did. I have been toying around the idea of making an amp with sweep tubes but until I come across a whole box of unused specimens I will wait.

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 I have been toying around the idea of making an amp with sweep tubes but until I come across a whole box of unused specimens I will wait.

All the hams I know hoard the sweep tubes for linear amplifier service (and to think that I gave many away about 20 years ago!).  In case you're interested though, Mike Marx still has the Phillips 6BG6GAs available at a decent price.  I've used them in a number of designs and they are true battleships as he claims (equiv. to the 6L6GC).  It might pay to grab some while he still has them:

 

http://www.vacuumtubes.com/6BG6.html

 

Maynard

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Guest thesloth

That doesn't look dangerous!

 

The 833 isn't something you throw 300 volts at, it's more like 1kV.

 

Good info here: http://www.diyaudio.com/forums/tubes-valves/232484-midlife-crisis-my-833c-amp-build.html

 

 

Seriously what an awesome time we live in.......magnets and miracles..........and seriously crazy amplifiers that bring the mad scientist out in all of us.

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11693852_10204695569212293_3379568102545

 

 

Line Magnetic 41.2 212 Single Ended mono amplifier

LM41.2-212amp.jpg

 

Line Magnetic LM-1 212 Single Ended mono amplifier with tungar filament supplies

LM-212amp.jpg

 

Tube complement:  805 x 4 (two as rectifiers), 300B x 1, 6SN7 x 2, 1 x 274B
Output Power:  20W SET
Output Impedance:  4, 8, 16ohms

805.jpg

Edited by Schu
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Schu, some of us are just dying to see the covers off your Bel Canto REF 500M and the SC85 to show us some modern-amp porn. :emotion-21:

 

 

I've been trying to come up with something for this thread but none of my amps are really artistic. :emotion-41:

 

https://community.klipsch.com/index.php?/topic/146056-tube-art-what-lies-beneath/

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11693852_10204695569212293_3379568102545

 

 

Line Magnetic 41.2 212 Single Ended mono amplifier

LM41.2-212amp.jpg

 

Line Magnetic LM-1 212 Single Ended mono amplifier with tungar filament supplies

LM-212amp.jpg

 

Tube complement:  805 x 4 (two as rectifiers), 300B x 1, 6SN7 x 2, 1 x 274B

Output Power:  20W SET

Output Impedance:  4, 8, 16ohms

805.jpg

Wife came in last night when i was checking this picture out, what is that? she say's, room heater(s) dear.

Told her they were Mono blocks a little bigger than she runs, her parting commet was get the house in Nevada done.

 

Not that i would get these,(no wattage). got something from silicone valley in mind for later in life for that.

Edited by minermark
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