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Those Magnificent Television Tubes

Hi guys I haven't read this whole thread yet. I want to build the best either enhanced or dual grid drive se amp. Other than the now so expensive el509,pl519 what would be the best tube to try for high power with the best 2nd dominant profile. I am looking at 6JS6C,6lf6,6kd6 or 6lr6 the most powerful or top of the list currently. Will these tubes perform like the el509? good russian tubes can still be had and I am sure I could much more easily build a good amp from a schematic. But these beautiful nos western built tv tubes with some experimenting possibly with dual drive could I build something better? I also have some softone 9k with cathode feedback windings but they dont like more than 60ma so a recommendation for a smaller tube for those trans too would be helpful. Thanks
 
Its at the top of the list for screen drive there getting expensive like all the best sweeps are. I am thinking if a don't get a dozen soon they are going to go like el509,pl519 even the russian tubes are 20us and more per tube. When the ear859 came I wanted to buy one but couldn't afford it. I would like to build a ear849 tribute style amp even the same layout would be cool. Trans up front on each side.
 
PL 519 g2 as anode

About 20 years ago I designed an amp trying to mimic a mesh plate by using the screen of a penthode as anode. Because I had a large number of pl509\519's from otl experiments and because of it's large g2 dissipation this tube was used. The result was an amp sounding like a dht and definitely better than ordinary triode or screen driven penthode. A schematic and more details can be found on the Lenco Heaven forum. Go to amplifiers and then to "the sound of mesh plates"
 
Medium Mu Triode (40) and Sharp Cutoff Pentode.
Typically you might see this combination at the front end of the power amplifier.
Pentode Voltage Amp direct coupled to Triode Concertina (Cathodyne) Phase Splitter.

BUT - No reason you could not use it in the preamp. The triode is low rp so would drive a tone stack nearly as well as a cathode follower.

Cheers,
Ian
 
What could be done with 6X8A

Pentode Voltage Amp direct coupled to Triode Concertina (Cathodyne) Phase Splitter

I had a bunch of these too. The main drawback is the common cathode between the two sections. This makes it's use as a split load PI nearly impossible.

The funky grid structure makes it a bit more microphonic than say a 12AX7, so either section doesn't play well for the first stage of a guitar amp.

The pentode does make a decent triode if so connected. I would say that the 6X8 may be useful for a couple of gain stages somewhere in the middle of the chain.

I had over 100,000 tubes at the time, and I have lots of more useful triode - pentode combo tubes, so I decided to pass on the 6X8.
 
hey guys, any news about smoking-smoking amp?

News? I just got a "new" laptop computer so I could read the forum again. After 6 months of forced "detox", I'm relapsing into the tube hobby again. The old XP system just couldn't hack it anymore.

Got a little catching up to do I guess. So what IS new these days? Do we have "Sane" drive by now? I got a couple of 15 Watt 6G-B7 tubes finally. Amperex, Japan, probably Toshiba. These were used in one of the dual grid driven designs that were found online earlier. So I'll be trying these out in "Crazy Drive" mode on the curve tracer to see how they perform. Seem to be close to a 21HB5 anyway.

I also was having trouble here with the curve tracer showing curves with severe knee hysteresis occasionally. I finally found the problem in an adjustable air capacitor, hidden by a HV safety shield. Dust had gotten into it. A little hot air from the annoyed trouble-shooter fixed it accidentally, never would have found it otherwise.

But I do seem to have some tubes that really are showing knee hysteresis, I have to find them and re-test them now.

I also ordered some of Pete's multi-tube type 50 Watt Monoblock boards. I put individual socket/ pins on the board so the sockets and pin-out can be changed easily.
I want to try some various N Fdbk schemes on them too.

In addition I found some small circular PC boards on Ebay that allow one to change tube pin-outs or even the socket type. Solderable plug-in adapters. Can put any tube into any socket now. Wait till tube rollers discover these!

Oh, and 6197 (6CL6) tubes were on sale for a while on Ebay for $0.32 each in big quantities. (I see them at around $1 each now.) Got a few of them. Similar to a 12BY7 except higher knee voltage. Very consistent tubes on the curve tracer, almost randomly matched. Should make a good hefty driver tube.
 
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Compactron amp

What's your opinion about this prototype? 20 compactrons plus 1 noval.
 

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It is a full DC coupled using multiple units compactron devices, output 2 * 6JN6 in series push-pull (Autotransformer coupled to load), 4 * 6BE3 full wave choke input rectifier,also it incorporates 6BH11's, 6AG11's, 6Q10's, 6BF11's and 3 neon diodes as voltage references. Also added a 6K11 and 6FM7 as voltage regulators. Voltages are ±275V per rail split power supply.

Respect to separation, it is a prototype only, I know distance is small, but used a standard prototyping PCB as support.

I'm currently working on it, it is functioning OK and preparing a thread for it soon.
 
Ahh, voltage regulators and DC coupled, so plenty of voltages too. That accounts for some of the 20 tubes.

Is the amplifier block diagram more complicated that usual besides? Akido stages, SRPP stages, tube CCS etc.

I've been thinking of proto-typing a design with a differential driver for each P-P output tube, so the pentode outputs can be made to emulate sample triodes individually. Should be possible with 5 tubes per amplifier chain using dual miniatures.

I should mention that someone mentioned dual differential drivers some years back. At the time it seemed excessive, more tubes than necessary. But now I'm seeing the light for extended flexibility. Hope they didn't give up on the scheme back then. Hobby designs don't have to be economical minded. But at 20 tubes, I would start to worry about reliability.
 
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What could be done with 6X8A, I have a ton of them?
I'm thinking a guitar preamp, some experiences, schematics?

Wanna unload some?

I use 6X8s for hollow state voltage regulators. The common cathode is helpful for this as it forms an asymmetrical LTP that takes the load off the VR tube that allows for a simple noise filter without the risk of VR tube oscillation. The pentode section also looks to have good linearity and a nice harmonic distortion profile as well. Might also serve as a floating paraphase splitter.
 

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re 6CL6, i used that tube as voltage amp in my el34 paralleled set and i replaced that with an el84, the tube bias runaways after 30 minutes of play....otherwise they are very nice sounding...

Was this using auto-bias? I would use these 6197/6CL6 as an LTP over a CCS tail, should be stable then for a driver stage. I can see where these would not be so suitable for an output tube due to the high V knees. Causing the tubes to get hot from screen dissipation. Running them with a low screen V would help.