| Help me find some odd looking rectifiers! - Click HERE for Original Thread |
| Fuling |
Hi,
I´m collecting parts for an "just for the looks"-amp with RCA 808 power tubes and DET20 (2C22) inputs.
Both of the tubes mentioned above has two topcaps each, so what I´m looking for is a rectifier tube that will mix well visually with these, ie 40´s style with one or preferably two topcaps.
Single diodes would be just as good as duals.
Each channel will consume 120-150mA @ 350-400VB+
Pictures of 2C22 and 808 to get an idea of what I´m looking for:
http://www.wiwitubes.com/pic/tube/RCA808.jpg
http://www.r-type.org/exhib/aai0283.htm |
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| Gluca |
I'd say EIMAC RX21 ... but they are hard to find. Or ... well ... globe 866As look gorgeous.
Ciao
Gianluca |
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| Steven-H |
I second the globe 866's. Simple looking but very pleasing.
Where did you find 808s ??????? |
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| astouffer |
| RCA has some mercury rectifiers smaller than the 866, the 816 I think. How about a bridge using selenium stacks? The larger ones are rather impressive with all the finned plates. |
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| Fuling |
Hi,
That Eimac rectifier looks good and so does 866 and 816 but
(I should have mentioned this in the first post) I´ll avoid mercury and gas filled rectifiers as they have to warm up before any HT can be applied. There are of course ways to deal with that, but I´d like to keep things as simple as possible.
I have four 808´s (2 JAN), all untested. I´ll have to test them to see if I got at least one functional pair before I invest any more money into this project.
Got the first 808 almost for free, the others has been hunted down over a period of about two years.
Quite rare and expensive tubes, especially in this corner of the world and there seem to be no subs.
I´ll build the amp so that they can be replaced with 811A´s with minor modifications.
BTW: Selenium rectifiers...well, worth a look! But aren´t they a mess to work with? (Toxic) |
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| Colt45 |
| bah, don't bother with selenium |
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| Gluca |
| quote: | | (I should have mentioned this in the first post) I´ll avoid mercury and gas filled rectifiers as they have to warm up before any HT can be applie |
You just need a switch to turn the B+ 20 secs after the fils (when tubes are lit up often), pretty easy and they sound better.
Ciao |
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| Fuling |
| quote: | | http://www.tektron-italia.com/images/RGN1404-TFK.jpg |
Sweet looking rectifier for sure, but too old (and probably made of Unobtanium and very expensive)
| quote: | | bah, don't bother with selenium |
That´s what my gut feeling tells me, too. Replacing broken selenium rectifiers with silicon diodes seems to be one of the more common repairments in old tube stuff.
Well, if I don´t find any good looking, cheap and easily obtainable tube rectifiers I´ll just use some damper- or sand diodes.
A cool looking tube rectifier would be nice but not necessary.
There will be some sand (mosfets) involved in the driver stage anyway, since the 808 needs positive bias and quite a bit of grid current to work in SE circuits. |
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| 5u4 |
| How about a Chatham 5R4WGB. Kind of weird looking & can be had for cheap. |
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| Colt45 |
3B28 would be ok, its xenon rect, so low drop like a mercury, without mercury.
But.. it still requires 10s warmup before applying plate voltage.
you could use a 1616. it's like a 3B28 / 866 pinout/filament wise, but no gas. Of course regulation isn't is good as a gas/merc tube. cheap though.
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| Fuling |
A short reply, I´m at a party right now: :cheers:
High voltage drop would almost be beneficial, as the power transformers I have puts out a bit too much voltage:cheers: |
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| Fuling |
1616 looks interesting, will keep them in mind.
Another option would be SS diodes and a tube regulated PSU with a couple of 807 or something. |
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| Fuling |
| RK-60 looks just perfect for the job! Thanks! |
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| pmillett |
RK60 is also known as 1641. I have some; basically as far as I can tell they're 5R4's with two top caps.
Best for choke input, or very small cap input.
Pete |
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| pmillett |
Oh, and don't forget the RK34 / 4074A / 2C34, and the 814 for the top-cap-crazy theme.
Funny' I've been thinking about building an amp with the maximum number of top caps as well. RK34 makes a decent 1-2W push-pull amp...
Pete |
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| Fuling |
Two pairs of RK60 / 1641 rectifiers are heading my way from www.tubesontheweb.com.
I was actually looking at 2C34 a while ago but I couldn´t find any use for it in this project. Too low gain for an input stage and too shy of current to push the hungry grids of the 808s.
May get some and build an class A2 PP amp one day, I had a couple of output transformers that would have been perfect for such an amp but I traded them for an RCA 808 a while back.
I have a pair of power transformers with 385-0-385V 150mA, 5V 4A and 6,3V 4A windings that might be just right for the 808 amp.
They are high quality units manufactured locally less than 10 years ago, not some rusty old junk.
I also have a pair of beefy 30H 200mA chokes from the same place.
The only thing that worries me slightly is the filament power supplies, the tubes requires 7,5V 4A clean DC.
I had some luck with massive LCLC-filters (1,1mH 10A iron cored chokes and several 27000uF caps) when I messed with 811A SE a couple of years ago and I guess thats what I will go for this time, too.
SMPS would be an alternative solution, but I can´t find anything suitable. |
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