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6146 in the Simple SE

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Chinese 6146 in the Simple SE

I am still running 6146B's in the amp, with no changes since my last post. It sounds pretty good right now.

I bought a pair of chinese 6146's to try out, as I have read varying comments about them, and wanted to try them for myself. The ones I received are trade dressed out as Shuguangs, and marked 6146B on the tube.

Physically, they somewhat resemble an RCA style tube, as the getter flash is in the base of the tube rather than on the side of the bottle, and the plate is a dark black material. Interestingly, the bottle is noticeably shorther than U.S. made 6146's, and this is apparent right out of the box, even without a U.S. tube to compare to. Other points of difference are that the base pins are squared off, rather than nicely tapered or rounded as on U.S. tubes, and the plate cap is somewhat smaller in diameter than U.S. tubes. It may be that the cap is correctly sized for current chinese manufactured parts, but I am using Millen ceramic caps and I had to adjust them a bit for a tight grip. In operation, there is a lot of visible filament/cathode glow with the Shuguangs, which is very much unlike U.S. tubes which have little visible emission from the filament/cathode.

I didn't do much in terms of testing them electrically. I checked both the tubes to make sure the external shield was internally connected properly (it was), and compared the transconductance (on my TV-7/D) to some NOS U.S. made 6146A and B and found them to be identical. I didn't set up to measure interelctrode capacitances since I didn't think it matttered much in audio service.

These chinese 6146B tubes work and sound very well. They have been in the amplifier since the day before Thanksgiving, and I have had no urge to swap them out with anything else. The amp runs very long hours as the PA in our home entertaiment system, particularly this time of year, and the tubes already have substantially more than 200 hours on them, with no sign of electrical or sonic degradation. If anyone is awake in the home, the amp is likely to be on. Often my wife forgets to turn it off, further increasing the run time and hour count.

They seem to have a larger power dissipation capability than the old U.S. made tubes. I haven't really defined what the limits are, but I know that the U.S. tubes will red plate well before the chinese tubes. I think the difference could be as much as 20% extra Pd in the Shuguangs. I cannot get them to flouresce, even at plate voltages approaching 450 volts (the U.S. 6146 won't flouresce either, unlike 2E26 that will turn so blue you can see it in ordinary room light).

In summary, I would not hestitate to use the Shuguang 6146B as a modulator tube, or in an audio application like the Simple SE. I think I would use them in preference to NOS tubes in an audio application. As for RF applications, can't say - yet.

I like the 6146B so much in this application, that I am seriously considering building an amp to better exploit the tube, and the other low screen voltage sweep tubes. So many worthwhile projects, so little time, unfortunately.

Happy and prosperous new year to all.

Win W5JAG
 
Snowed in and playing around last night with my digital camera.

Pictured are 2E26's. The one on the left is marked as Westinghouse. The one on the right is an RCA. The Shuguang 6146B are starting to show some color at about 750 hours or so, but it may be too faint to photograph.

These pictures are at ISO 80, max aperture, and 8 seconds exposure - the longest my digi cam will do.

Win W5JAG
 

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I just discovered a couple of RCA 8552's in the basement which are 12 V equivalent of the 6146B. They look brand new.

I haven't built a Simple yet, but intend to, probably using EL34's as suggested. However, if I get curious enough, I may try these 8552's once I have a working system. Even though I don't really need any more power than the EL34's, I do wonder what the 6146B-types could do on output power. What do you think the capability would be, keeping a decent THD? Also, or course, I'd be primarily interested in sound quality compared to the more conservative approaches.
 
..... I do wonder what the 6146B-types could do on output power. What do you think the capability would be, keeping a decent THD? Also, or course, I'd be primarily interested in sound quality compared to the more conservative approaches.

10 watts, or so, in single ended pentode, I would think. I haven't tried to measure mine.

I'm not an audiophile, and the only other single ended pentode amp I have is an Elekit TU-879S, so my knowledge base is pretty limited. I just put the 6146's in the Simple SE for fun and to learn a little bit about using the tube in audio applications.

Comparing these two, the Elekit uses quite a bit of global negative feedback, wheareas my Simple SE has only a couple of local negative feedback loops - the cathode feedback around the OPT, and the plate to grid feedback on the 6146's. I think the Simple SE with the 6146's sounds as good as the Elekit, maybe a bit tubier. The amps are at different houses, so I can't directly compare them. I do have the same model speakers at each house so my memory is the only real variable.

I haven't run any of the regular audio tubes as pentodes in it - only 6146, 2E26, 6BQ6, 6DQ6, and (briefly) 6AR6/6384 and 6889. Right now I like the sound of the 6146's and haven't had much reason to use anything else.

Win W5JAG
 
A couple of scrapper transmitter carcasses followed me home from a hamfest today - a Heath SB-401 and an SB-400, both still had their power transformer on the chassis. The power supply in these transmitters is the same as the stand alone HP-23, IIRC.

A good way to make something into a scrapper is to burn out the power transformer, but they smelled OK, and I've never heard of these transformers being fragile. These were voltage doubler power supplys IIRC, with a high B+ around 800 vdc, a low B+ about 250 - 300 vdc, and a bias supply about - 130 vdc. If these transformers are any good, I'm going to use one to make another 6146 or 2E26 Simple SE.

There were a lot of tubes about; I got a half dozen NOS 6DQ6B's of various brands for a quarter each, a bunch of used micanol based 6SN7WGTA's and 6SL7WGTA's for a buck each, some NOS 6BQ5's for a buck each, and some others. There were tons of NOS 1625's about, and some other types I had not seen in quantity for awhile.

Win W5JAG
 
Win,
When you get things settled out with the 6146B, do you think you could document what you did with diagrams and pics and share it here? I haven't yet built anything and I'm curious to know what you end up with and if you would do it again. Sounds like these could put out about twice the power of the 6L6's that I also have.

Thanks,

Ron (K7OEU)
 
When you get things settled out with the 6146B, do you think you could document what you did with diagrams and pics and share it here?

Ron,

I will do this, but it will be a while - it's a work in progress that is sharing time with some other diy projects, and since the current version of the amp is stable and sounds acceptable, rev II is not the highest priority.

Because I prefer to use parts that I can scrounge on the cheap, what I use may not be readily available to someone else, and the way I did my amp is certainly not the only way it can be done - it's just an example or suggestion.

Probably (in my view) the two most useful pieces of information in the entire thread so far are that:

1) the 6146 / 2E26 family of tubes can be made to function in the sockets on the Simple SE board without requiring any destructive modification to the pc board. Pin 3 on the power tube gets screen voltage - pin 4 must be left open because it is connected to the cathode internally. As pins 3 and 4 of the power tubes are brought out to individual pads on the edge of the Simple SE board, these rearranged connections are easily made. It is really just that simple (no pun intended);

2) the local plate to grid negative feedback (Schade) is an easily implemented, acceptable, solution to tame the single ended pentode shrillness, requiring only one resistor per channel.

Any Simple SE that has been tested and found to be working nominally is a candidate for this conversion, provided that a suitable screen voltage can be provided the power tubes. I built a crude screen supply from a separate screen winding on my power transformer that is working well. If you search "6159" in the main tube forum, you'll find a schematic for a 6146/6159 amplifier that uses a dropping resistor and zener diode to generate a screen voltage off the main B+. A separate transformer or a couple of small filament transformers back to back, as suggested above, would also make a good screen supply (better than a dropping resistor and zener, imo). There may be other ways.

I'm surprised, actually, that with this thread having been up for several months, that we're not seeing pictures of other 6146 / 2E26 Simple SE's. 6146 may not be the best tube for hi fi use, but it does seem to be a tube family that consistently generates interest in the diy community, with a few threads about it in the main forum, requests for schematics, etc. If a thread talks about non mainstream audio tubes, the 6146 always seems to come up.

Win W5JAG
 
Win,
Thanks a bunch. I'm a bit of a scrounger too and I already have a couple of 12V versions of the 6146B, so it would be fun to see how they do. Like you, though, it's kind of on a back burner for now and of course, I'll do it first with the 6L6's that I also already have and get it going before modding. I think that 6L6's should just work without changes, although with a bit less power than EL34's. Is that your impression?

Thanks for the tips. If I do it first, I'll post results here.

Ron
 
Even though I don't really need any more power than the EL34's, I do wonder what the 6146B-types could do on output power. What do you think the capability would be, keeping a decent THD?.......10 watts, or so, in single ended pentode, I would think. I haven't tried to measure mine........Sounds like these could put out about twice the power of the 6L6's that I also have.

Keep in mind that W5JAG is running the 6146's in pentode mode. The power output is almost always higher in pentode compared to UL or triode. A 6L6GC can do 9 or 10 watts in pentode.

The power output in pentode mode is most influenced by the B+ voltage and OPT load impedance, provided the tube you are using can adequately drive that impedance. In other words given a tube and a B+ voltage, the power output will go up as the load impedance is dropped, until the tube can no longer handle the load and then the distortion goes up. I haven't tried a 6146 in the SSE yet, but I am going to guess based on what I have seen in P-P experiments that it can beat the 6L6GC, and maybe the EL34. The KT88 should flat kick its butt as would most sweep tubes. I get 14 watts out of a KT88 in UL mode.

Please understand that the SSE was never designed or tested with 6146's or many other oddball tubes. Amp damage is a real possibility when trying something new. I don't mind blowing up a board or two or three, but then I like fireworks and I have a lot of boards! I had a capacitor explode when playing with 6DQ6's in one of my SSE's. Any time you go where no one has gone before, you must be prepared to experiment. Some experiments work, and some don't.

2) the local plate to grid negative feedback (Schade) is an easily implemented, acceptable, solution to tame the single ended pentode shrillness,

Do you know how many of the big hitters from the main forum have told me that this just isn't true. Schade doesn't work with a triode driver tube, and won't work with a CCS load. Also more than one person says that the 12AT7 just sounds horrible in a SE amp. I won't tell if you don't!

A couple of scrapper transmitter carcasses followed me home from a hamfest today

I went to a small hamfest Saturday morning and for the first time in years I came home with ZERO tubes. There weren't any worth buying.

I'm surprised, actually, that with this thread having been up for several months, that we're not seeing pictures of other 6146 / 2E26 Simple SE's.

The SSE doesn't get used for experiments by many users. Most people just build and listen. I have hacked up a few. I even have one made into a 50 watt P-P guitar amp. Sooner or later I will find the time to document what I did. The SSE board is connected to a driver / preamp board that contains three 12AX7's. That is a perf board / flying wire furball that I made / tweaked over two years. I have no idea what is on the board any more.

I know I posted a picture of an SPP board cranking out 60 watts or so with 6BQ6's stuffed into it. I can't find the picture but the board is still on my bench.
 
Please understand that the SSE was never designed or tested with 6146's or many other oddball tubes. Amp damage is a real possibility when trying something new.
So noted. You must have taken a law course or two in school, too!

Actually, my own motivation with the SSE is to experience this whole SET phenomenon for myself. I've never even heard one. I want to compare it with the other common amp types including a P-P tube amp, two or three SS amps that I have, and a Tripath amp. This design looks like a very good platform for experimentation with various class modes and feedback. Trying different tubes may be fun later on, especially if I figure I just need a couple dB more to be happy...:) I did build a little spud amp for my dorm room when I went off to school many long year ago, and that actually worked pretty well. Now, where did I put that???

Anyway, thanks for putting a better perspective on things. I haven't done any building for years and I have some re-learning to do about these "obsolete" devices.
 
So noted. You must have taken a law course or two in school, too!

Never took those. Too much memorization involved and I have CRS. All my formal education has been technical. RF, IC design, general EE, and CE classes, and as much programming as I could stand. Only the very minimum BS classes required to graduate.

I made those statements because I believe that too many people (myself included) get an idea or two ot three and then buy something as a starting point, like the SSE board, make several modifications in the initial build, and then it doesn't work. How do you figure out what went wrong. Was your initial build OK, was one of your ideas a little misthought, or was the combination of several good ideas not agreeing with each other. I have been working on a Grand Unified Theory breadboard project to combine many of my ideas into one design. I have now tossed the second board into the trash. I can't make them work.

After working at Motorola for 38 years and learning all about designing experiments it has been made rather clear to only mess with one variable at a time. That way you can figure out what works and what doesn't.

In my case I bought one of Pete Millett's big red boards. I fully intended to hack the $%@* out of it to extract obscene amounts of power out of it, and I stated that fact in his thread when I bought the board. I however built the board almost exactly as Pete intended, installed the tubes that Pete specified and fired the board up in "as designed" condition. After listening to it for a while and figuring out all its quirks, then I started making mods.

As I stated in my previous post, when going where the designer never intended some experimentation will be needed. Some experiments work, some don't, and some blow up! I experienced all three in my quest. I had parts violently explode twice, and I fried a few resistors and one tube. I now have a 250 watt tube amp in my living room. I have seen over 500 watts flow out of the board. (Pete specified 36 watts)

The point I'm trying to make is, build the board as close to the stock configuration as possible, listen to it, play with it, then tweak away. Only change one thing at a time, and listen to each mod for a day or two before moving on. Try not to make any changes that you can't undo. It sounds like the long way to get there, but it will save you time, parts, and frustration in the long run. I have a SSE board that has been hacked beyond recognition dozens of times. I use it for most of my "extreme" experiments. It is still alive and working although it isn't very pretty and has a few burnt spots.
 
The KT88 should flat kick its butt as would most sweep tubes. I get 14 watts out of a KT88 in UL mode.

With numbers like these, it's hard to justify use of the odd ball tubes except for the fun of doing it and the learning experience.

I'm interested in seeing what that new KT-120 can do. I think I have adequate power supply iron on hand, but I would have to fork out for some bigger OPT's just to get started. I'd like to get a pair of the big honkin' Edcor's, but KT-120's + big honkin' Edcors = $250 bucks + or -, and the time involved. Not sure I need to know that bad.

Some experiments work, and some don't.

For me, it's more like some do, most don't. I try to keep the expensive failures to a minimum.

I've pulled the better looking of the power transformers from a scrapper carcass, and no load testing seems to indicate it's good. To get a sufficiently high B+, it's going to take a doubler or even a tripler. I know that will work for a low duty cycle ssb rig, but for an audio amp, I have no idea. I hope this will be one of the experiments that work. The bias supply seemed to be wired in an odd way in both of the carcasses; more experimenting than I've planned on may be involved.

Do you know how many of the big hitters from the main forum have told me that this just isn't true.

I haven't had a chance to try running it through the CCS yet, but I intend to do so. I may bump that ahead of working on a new power supply.

I need to be working on building some test equipment, so I can have some baseline numbers to work from.

Win W5JAG
 
I have been working on a Grand Unified Theory breadboard project to combine many of my ideas into one design. I have now tossed the second board into the trash. I can't make them work.
So now you know how Einstein and Richard Feynman and Steven Hawking, et. al., have felt when they all had to trash their GUT boards.! Don't feel bad, you're in pretty good company...
 
I did a little more playing around with the SB-400 power transformer this afternoon. The HV secondary is 283 volts AC; I breadboarded a solid state half wave voltage doubler and got 780 volts DC out of it, about what I expected.

Staring at the voltmeter, reality began to set in a bit - the output transformers will need to take 1.5 KV without breaking down. Are there any known to be reliable at that voltage? They won't have to take much current - 40 ma would probably be enough.

As noted in the KT-120 thread, setting a new OPT on fire is not the best diy experience, and I suppose if it failed in service the speaker could be toast as well.

Win W5JAG
 
I'm interested in seeing what that new KT-120 can do. I think I have adequate power supply iron on hand, but I would have to fork out for some bigger OPT's just to get started. I'd like to get a pair of the big honkin' Edcor's, but KT-120's + big honkin' Edcors = $250 bucks + or -, and the time involved. Not sure I need to know that bad.

I can say that the big Edcors were money well spent. I have not heard enough good things about the KT120 to cause me to part with my money. I did however decide to try a little experiment of my own.

All this talk about stuffing transmitting tubes into the SSE made me think about trying it. But, why would I stick in a tube that is smaller than the KT88's that I have been using? Well, I have 813's, 828's, 845's and 211's, but they won't work in the SSE. People keep telling me to try a certain tube that is used in Collins transmitters, but I don't have any.

Ebay must have grown tired of me dropping minimum bids on lots of stuff, but never buying anything, so they sent me a 10% off coupon. Still, I didn't win any bids, so on the coupon expiration day I sprung for some 4D32's. OK, now I have got something that could kick the KT120's butt!

Do they work in the SSE? Lower the grid resistor to 100K, put in 100 volt cathode caps, and 10 watt resistors, wire in some BIG sockets and crank them up. Yes the screen grid rating is 350 volts, yes thay work fine in triode at 500 volts. I get 10 watts. When I have time, I will get the big Edcors and try UL mode.

I have been using an external power supply for testing. A big Antek with SS rectifiers would be the cheap ticket here. B+ caps will need to be rated for more than 500 volts.

I took a picture with a 6146 stuck in the rectifier socket for size comparison.....Don't try this under power!
 

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But, why would I stick in a tube that is smaller than the KT88's that I have been using? ...so on the coupon expiration day I sprung for some 4D32.

Since I'm guessing most of us aren't familiar with the 4D32, I thought maybe I'd share a link: 4D32

In Class C a single valve can produce up to 100W at up to 60MHz with 600V anode and 1.25W grid drive. In AB2 a push-pull pair can deliver 125W.

Keep in mind the heaters of these tubes draw nearly FOUR AMPS each. Not exactly a "plug & play" replacement for KT88 in your Simple Single Ended. Even still, a very nice science project. Now I want one too. :mischiev:
 
Does 4D32 use a thoriated tungsten Filament?

I seem to recall reading on the Collins reflector that many of those late production Raytheon 4D32's were gassy, so keeping a meter on them might be prudent.

I wonder if choke loading the transmitting type tubes might be a worthwhile approach to take advantage of their high voltage capability, and keep the high voltage out of the OPT.

Win W5JAG
 
Keep in mind the heaters of these tubes draw nearly FOUR AMPS each.

They make my Fluke power supply groan when I plug the board into the power supply. An Antek 4T400 should be adequate.

Does 4D32 use a thoriated tungsten Filament?

It is a conventional indirect heater inside an oxide coated cathode.

I seem to recall reading on the Collins reflector that many of those late production Raytheon 4D32's were gassy,

I bought 6 tubes, all NIB. Two of them were bad. The seller is sending replacements. One has completely gone to air. The second one glows purple and sucks lots of current. The seller does not want them returned, so after the replacements arrive there will be pictures of a purple 4D32 glow!

I wonder if choke loading the transmitting type tubes might be a worthwhile approach

Maybe. The maximum plate voltage spec for the 4D32 is 600 volts. I assume that my Edcors are safe at that level.

I plan to stuff these tubes into a certain red board to see if they can beat the big sweep tubes. Other P-P experiments are also planned.
 
The second one glows purple and sucks lots of current. The seller does not want them returned, so after the replacements arrive there will be pictures of a purple 4D32 glow!

Awesome. I have not seen a 4D32 up close, but it looks like a septar socket.

If so, what about 829B's? Paralleling everything in the bottle should get 60 watts plate dissipation. 5894's would get 80 watts plate dissipation with everything in parallel. Both are 600 volt tubes. 5894B can go 750 volts.

I don't know what the current market price of these tubes are, but I have a bunch of each type - they might also be a KT-120 butt kicker.

Win W5JAG
 
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