Hi guys and gals!
I have got a bunch of single-end transformers 9kohm/4ohm, i wonder which tube i can use with these, i was thinking of an EL34 at low voltage maybe?
as far as i know these transformers where once used with ECL86 or similar tubes, but i dont have any ECL86´s 8-(
can i use EL34?
or should i get hold of some EL84 maybe?
recommendations please!!
I have got a bunch of single-end transformers 9kohm/4ohm, i wonder which tube i can use with these, i was thinking of an EL34 at low voltage maybe?
as far as i know these transformers where once used with ECL86 or similar tubes, but i dont have any ECL86´s 8-(
can i use EL34?
or should i get hold of some EL84 maybe?
recommendations please!!
hmm.. EL34 could work..ok, what is the recommended voltage in that case?
211, ain't that tube hard to find? as i recall it has four pin base and the anode at the top, but to me it looks like overkill for these small OPT:s...
Maybe one 832A or 829B? yep, prone to oscillate but they looks nice.
Would EL84 be a good choice if i could find a pair?
211, ain't that tube hard to find? as i recall it has four pin base and the anode at the top, but to me it looks like overkill for these small OPT:s...
Maybe one 832A or 829B? yep, prone to oscillate but they looks nice.
Would EL84 be a good choice if i could find a pair?
Mr. Triatic said:
To get reasonable power, you need to use a rather high idle voltage, because using the high primary Z OPT limits the current swing available, and allows greater voltage swing. You need to take advantage of the greater allowable voltage swing so you can get some reasonable power output... P = V x I
Mr. Triatic said:
um.... no, well not with conventional thinking. Well, the same caveats would apply. (low power... etc) This is not to say it won't sound good. Commercial amps like the Decware Zen use high primary Z OPTs with the SV83 (similar to EL84) to good effect.
Mr. Triatic said:
Sorry, I don't know those valves. Will check and see. Usually the primary Z is around 3-5 times rp for triodes... (Very rough approximation...), so you'd be probably 1.8-3K of rp. hmmm... maybe you could knock up an amp with a bunch of paralleled driver valves? Just for something different...
Of course they do.... Nothing quite beats the look of a lit transmitter valve with that glowing filament...
martinab2 said:
12E1s? Cool! I have a personal belief that there are a bunch of happy diyers out there using 12E1s and not spreading the word so the price doesn't rise....
They're available from Retrovox for something like US$5 each.
That and the 807 are probably my picks if I was building a new amp now...
With about 400 ohm of rp in a 12E1 and a 9K, you have a 0.178 ohm ouput Z (well, the part from the output valve anyway), without negative feedback. At that kind of level, the secondary DC resistance becomes very significant.
However, unless you want to go out and buy new OPTs I don't think you could use the 12E1s because they'd need quite a bit of idle current, which may saturate the OPTs you have. How big are they?
Mr. Triatic, the 829B and 832As unfortunately (probably due to their relative obscurity) don't have triode-mode curves - I may be wrong, what I'm saying is that I haven't found any.
Since mu g1-g2 is about the mu in triode-mode, and gm doesn't change too much, you can approximate that the 829B will have a mu of around 9 and rp of about 1K, and the 832A will have a mu of around 6.5 and rp around 1K8. Hmm.... well they will work (almost any valve will work). I remember reading somewhere that 1/2 an 832A is similar to an EL84 (functionally anyway) - don't quote me on that though.
Edit: Fixed bad spelling
Since mu g1-g2 is about the mu in triode-mode, and gm doesn't change too much, you can approximate that the 829B will have a mu of around 9 and rp of about 1K, and the 832A will have a mu of around 6.5 and rp around 1K8. Hmm.... well they will work (almost any valve will work). I remember reading somewhere that 1/2 an 832A is similar to an EL84 (functionally anyway) - don't quote me on that though.
Edit: Fixed bad spelling
link:
http://www.audiohobbyist.com/projects/832.htm
i will consider this amp, just have to make some adjustments, i want to use one 832 with separate 6au6wa drivers or maybe just one ECC83 or ECC88 as driver
so i have to use the 832 (or 829?) in SE mode.
http://www.audiohobbyist.com/projects/832.htm
i will consider this amp, just have to make some adjustments, i want to use one 832 with separate 6au6wa drivers or maybe just one ECC83 or ECC88 as driver
so i have to use the 832 (or 829?) in SE mode.
Hmm... that's seems like a nice project, and the person who built it obviously spent some time making it look nice as well!
It's a push-pull amplifier though. Unless your OPTs have centre-taps you won't be able to build it without changing it into SE. If your OPTs do, and have been designed for PP operation, they won't handle SE (not well, anyway)
It's a push-pull amplifier though. Unless your OPTs have centre-taps you won't be able to build it without changing it into SE. If your OPTs do, and have been designed for PP operation, they won't handle SE (not well, anyway)
Konnichiwa,
I would say that these transformers practically have WE205D, 10/10Y/VT25 and RS241 written on them.
Especially the 10Y/VT25 is still readily available NOS and at sensible prices and if you can live with only 1.5-2Watt power Output (same as Decware Zen I'd note) they are IMHO the best sounding option for output valves. I tend to use them with a 2K2 Cathode resistor, 10K Anode load and 460V +B. Drive them with anything you like, they are not that hard to drive, Mu is around 8.
Sayonara
Mr. Triatic said:
I would say that these transformers practically have WE205D, 10/10Y/VT25 and RS241 written on them.
Especially the 10Y/VT25 is still readily available NOS and at sensible prices and if you can live with only 1.5-2Watt power Output (same as Decware Zen I'd note) they are IMHO the best sounding option for output valves. I tend to use them with a 2K2 Cathode resistor, 10K Anode load and 460V +B. Drive them with anything you like, they are not that hard to drive, Mu is around 8.
Sayonara
If you want good sound on the cheap, try military surplus 837's. These are low distortion 12 watt pentodes that cost six times as much as a Mullard EL34 when catalogged in the early sixties, but can be had NOS for less than $10 today. 18K into 8ohms will give the lowest distirtion for these tubes with a pair of cold cathode tubes regulating the screens.
Demostenes (sp?) in Norway probably has a bunch.
John
Demostenes (sp?) in Norway probably has a bunch.
John
How good are the transformers?
9k/4ohms, sounds to me like something out of old radios.
Not saying old radio transformers can´t be good, but I would think twice before mating such OPTs up with expensive and hard to find NOS DHTs.
Well, since you live here in Sweden you could always order a bunch of 12A6 metal tubes from svebry.se
They practically give them away and they look fine in triode mode.
9k/4ohms, sounds to me like something out of old radios.
Not saying old radio transformers can´t be good, but I would think twice before mating such OPTs up with expensive and hard to find NOS DHTs.
Well, since you live here in Sweden you could always order a bunch of 12A6 metal tubes from svebry.se
They practically give them away and they look fine in triode mode.
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