mashaffer said:
I did a project using 6BQ7s. The linearity of these isn't all that great, but then, this type doesn't even make a pretense of being an audio tube. One of the secrets of finding a good loadline is to get that Vpk up. It takes an unusually high Vpk, so you'll need to use it with a rather high (say 400Vdc) rail. Active CCS loading may help a bit if you don't have the Vpp to spare.
For the project I did, I used the 6BQ7s to form a cascoded LTP phase splitter / voltage amp that included a CCS in the tail. In that regard, these worked very well indeed. Sufficient voltage gain such that another voltage gain block wasn't necessary, even including up to 12db(v) of gNFB. Cascoding seems to improve the linearity, and balanced operation suppresses even harmonics. There was no measureable distortion coming from the cascoded LTP. The rest of the project, using 6BQ6GTB PP finals, sounds just great.
As for microphonics, I've found that the Sylvanias with series connected heaters are extremely microphonic and ring like bells. Since this is a type intended for cascoded VHF amplification, I guess they didn't much care if they ring at 1500Hz when processing up to 300MHz signal frequencies.
Some Motorola branded 6BQ7s (parallel heaters) and Sylvanias with the parallel connected heaters weren't microphonic at all.
This type, being a rather high g(m) type, also has fat cathodes for extra glowy bottle coolness.
CF service isn't all that demanding, and so 6BQ7s would work for that. As for more conventional audio circuit topologies, YMMV.
Just picturing using those 955 acorn tubes as surface mount on a circuit board (with round holes so the tube bottoms fit thru, to allow soldering the radial pins to lands on the board. 
For a preamp, or cathode follower duty.
As for the 12L6 and 6W6, they are also the same as the 50L6 (cept for the heater, of course), which was used in millions of AM table radios. And the 25L6, and I think there was a 17L6 and 25W6, and maybe a 12W6. But all these are definitely different from the 6L6!
For a preamp, or cathode follower duty.As for the 12L6 and 6W6, they are also the same as the 50L6 (cept for the heater, of course), which was used in millions of AM table radios. And the 25L6, and I think there was a 17L6 and 25W6, and maybe a 12W6. But all these are definitely different from the 6L6!
rdf said:
What I was really hoping to find were some 5731 but it seems no one has them.
As for the others I looked for all them, the 957 or the 958. The 955 was in the price range right now LOL.
Maybe if the sale is still going next week I will buy some of the 1.5 volt dht.
I just wish I could find a line of some of the 5731.
Nick
George,
I emailed you earlier this week about purchasing some Simple SE boards. I know you have many more import things going on...please respond when you have the time.
I'm going to get my power transformer from AES and now some more tubes!!! They have NOS 12BH7s on sale, but no manufacturers listed. Not sure what I would get?
Thanks,
Dave
I emailed you earlier this week about purchasing some Simple SE boards. I know you have many more import things going on...please respond when you have the time.
I'm going to get my power transformer from AES and now some more tubes!!! They have NOS 12BH7s on sale, but no manufacturers listed. Not sure what I would get?
Thanks,
Dave
I have been out of town for 16 days with very limited internet access. I had 67 unanswered emails, which I have been answering all week. I sent your reply about an hour ago.
Yes all of these little guys are very different than the 6L6.
The 12L6, 25L6 and the 50L6 are all the same except for the heater voltage. The 35L6 is slightly different (8.5 watts dissipation VS 10 watts). I can find no information on the 17L6 and I don't have any. If it does exist, it is likely from the 35L6 family.
Some old books seem to indicate that the 6W6 family and the 12-25-50L6 family were slightly different. This may have been true at some time but I have some tubes that are marked 25L6 / 25W6. The 25W6 and 12W6 do exist, I have some of each.
tubelab.com said:
TDSL lists it as being the same as the 12L6, and VT.net lists a price for them.
http://tdsl.duncanamps.com/show.php?des=17L6GT
Speaking of which, how much power could one reasonably expect to get out of these in SET, PP, or PPP modes?
I will be finding out when they show up! From my vague memory (and poor measurement capability in the late 60's) I think that I was getting about 3 or 4 watts in SE pentode (6W6), and about 10 watts in P-P pentode (50L6's) operating from rectified wall outlet (no I don't do this any more). These were guitar amps and I had no way to measure distortion.
I have some 6DG6's and 12L6's on the way. UPS says Friday. I already have 6Y6, 6W6, and a few others. They will be tested in a Simple SE as soon as they arrive. P-P experiments will come a little later. I am looking for a tube that works well on 150 volts or less.
I retrieved a pair of 6W6's from the warehouse while I was out this morning expecting to pop them into the Simple SE this afternoon to answer this question. Unfortunately I came home to a flooded bathroom. I just finished cleaning up the mess and fixing the problem. The testing should happen next weekend.
Who would use steel bolts to attach the toilet tank to the toilet bowl. These bolts are under water, and provide part of the seal. When the head rusts off, you get wet. I am real glad it didn't happen while I was gone for two weeks!
Who would use steel bolts to attach the toilet tank to the toilet bowl. These bolts are under water, and provide part of the seal. When the head rusts off, you get wet. I am real glad it didn't happen while I was gone for two weeks!
Fortunately the leak had just started and was limited to the bathroom. I guess that I better check out the other bathroom. It's probably the same.
I put the 6W6's in the amp, but there is no output. The total current drain is 20 mA, about what the driver draws. I am sure that I am doing something stupid, but I don't have time to find out tonight.
tubelab.com said:
Grid 1 bias voltage is too high?
Couple of weeks ago my tenant called complaining that the neigbor downstairs has wet ceiling in bathroom... Turned to be a crack in a tank. I have to use grinder to remove steel bolts, after that spent 2 days searching for a tank with the same distance between bolts. They all are different!!!
...today I used the same grinder I bought to fix a toilet to fix an error on a PCB.
"No evil without goodness" -- Russian saying.
Edit: I put thick layers of silicone hermetic on both bolts, hope they will be safe now.
tubelab.com said:
Bad tubes? 6W6 and 6Y6 should drop in and play. 6G6 will work also. Triode wired is the only way I have used any of these, so pentode or UL may be a different result.
I'm eager to see your measurements on these. I have used both in the Simple SE and like the sound of the 6W6, the 6Y6 not as much. I keep the 6Y6's around 240 volts and have run the 6W6 up over 400, briefly.
I took out the Transcendars (freeing them up for the Tubelab SE), and mounted Hammond 125 ESE to have different loads more readily available.
Win W5JAG
It was something stupid. I haven't touched the amp in 3 weeks. I had forgot that I cut the runners on the cathodes of the output tubes during some hybrid output experiments. I get stupid late at night, so I usually cease playing with electricity around 10 PM.
The amp was sitting on the bench already hooked up to a variable supply, so I popped in the tubes and turned it on. It didn't work, so I shut the bench off. This morning I remembered that I had hacked the board.
I am scheduled for another surgery tomorrow which will keep me out of the lab for a few days. There should be several boxes of tubes and other parts arriving for some "crank em till they glow" experiments next weekend.
There were 6Y6's in the amp already. I was using them to drive some transistors in a "darlington" configuration, because they will work good at 150 volts or less. I have 6G6 and 6C6's and a few others lined up to test.
I replaced the steel bolts with brass bolts with new washers. There is a kit at Home Depot that contains exactly the parts you need, so it must be a common problem. So in the quest toward lower product cost the toilet manufacturers are knowingly flooding our bathrooms.
OT Bathroom floods:
I've had a couple of those goofy rubber gaskets go too.. Symptom is a steady drip that never goes away no matter what you do.. I always use brass replacement bolts, but they corrode pretty good in the water around here - I'd replace after 10yrs or so. Newer toilets seem to come with brass bolts..
Wavebourn I was amused to read about your toilet tank search, did you succeed or did you have to buy a new toilet? I've seen guys around here selling tanks for as much as a decent new toilet at Lowes or Home Depot.. (They can't sell the entire toilet as that is illegal here for some reason.. )
My least favorite kind of flood was when our sewer main got blocked by roots twice in less than 2 yrs flooding my listening space and workshop both times..
The remedy chosen was to reline part of the main with a fiberglas epoxy resin sleeve which was a rather costly non DIY proposition..
I've had a couple of those goofy rubber gaskets go too.. Symptom is a steady drip that never goes away no matter what you do.. I always use brass replacement bolts, but they corrode pretty good in the water around here - I'd replace after 10yrs or so. Newer toilets seem to come with brass bolts..
Wavebourn I was amused to read about your toilet tank search, did you succeed or did you have to buy a new toilet? I've seen guys around here selling tanks for as much as a decent new toilet at Lowes or Home Depot..
(They can't sell the entire toilet as that is illegal here for some reason.. )My least favorite kind of flood was when our sewer main got blocked by roots twice in less than 2 yrs flooding my listening space and workshop both times..
The remedy chosen was to reline part of the main with a fiberglas epoxy resin sleeve which was a rather costly non DIY proposition.. - Status
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