Yep. You need at least two stages. Also it is going to be hard to find an opt with multiple taps capable of coping with the max 2A3 anode current (unless you don't want to pay silly money for old rusties like UTCs).
My pick, and it's what I'm thinking to do as my next project, is a full monkey with 45 output and OPT. I didn't decide about the driver yet. May be 5842? Any preference from you gurus?
The 45 current is in the range of the biggies from Sowter and we are lucky enough they produce such high quality opts for this purpose.
PhilippeS, the Sowter 8976 will sink a lot of the 2A3 output power as with a 50 ohm load it will reflect 5Kohm on the ouput tube's anode on the lowest impedance tap and 1250 on the next one. It will work fine with a 45 thou 🙂
Cheers.
My pick, and it's what I'm thinking to do as my next project, is a full monkey with 45 output and OPT. I didn't decide about the driver yet. May be 5842? Any preference from you gurus?
The 45 current is in the range of the biggies from Sowter and we are lucky enough they produce such high quality opts for this purpose.
PhilippeS, the Sowter 8976 will sink a lot of the 2A3 output power as with a 50 ohm load it will reflect 5Kohm on the ouput tube's anode on the lowest impedance tap and 1250 on the next one. It will work fine with a 45 thou 🙂
Cheers.
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I have 26, 2a3, 45 and 6DJ8 sitting around.
I'm thinking 6DJ8 for additional stage... but it depends on how is the simplest design as possible, but still using those tubes.
2 watt minimum is fine with me.
I don't think I like using OT.
I can use Custom wound Power Supply Transformer here... so no problem.
I hope 8976 can be replace with 6DJ8 ?
I'm thinking 6DJ8 for additional stage... but it depends on how is the simplest design as possible, but still using those tubes.
2 watt minimum is fine with me.
I don't think I like using OT.
I can use Custom wound Power Supply Transformer here... so no problem.
I hope 8976 can be replace with 6DJ8 ?
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Then you need to swing +/- 14V at the output, or 10V RMS. With a 2VRMS source, you need a voltage gain of 10. With a lower output source you need more.
Too bad, because, as Mastodon has said more than once, that would be easy to do with your tube selection.
If you want to go with no output transformer, then you essentially need a power buffer output stage.
The Tubecad version, suggested by Mastodon will work, but I don't recommend it for two reasons: First, I suspect that your experience level is not sufficient to make the design modifications and adjustments that will be necessary. It's not a tested design in the first place. Second: I wouldn't risk your expensive headphones on an untested, direct coupled amplifier. Nor would I risk your head, at those voltages.
You could just use a Mosfet source follower, loaded with a current source and a cap coupled output. You will need a minimum of 150uF. You will need around 50V power supply for the source follower. A single 6DJ8 will give you the necessary gain. A 26 will also give you enough gain (these tubes require a lot of care to get low noise performance). The 2A3 or 45 will require another gain stage.
I cannot find any reference to 8976.
Have fun with your project.
Sheldon
well looks like there is no choice not to use OT in this matter.
I wonder how simple the schematic is if I use those tubes with OT ?
I don't mind using OT now if the schematic is very simple.
base on what mastodon said, With OT's, still needs some modification which is my problem that I can not solve, I know nothing about electronic, but soldering.
these are my works so far:
picasaweb.google.com/auahlap
those are for fun, creating the 'sphere' was fun, it's 0.7 watt tube amp.
I like small thing,specially with tube, but I need a Highend amp now.
anyway thank you guys for helping me out, at least getting the start learning.
regards
cal
I wonder how simple the schematic is if I use those tubes with OT ?
I don't mind using OT now if the schematic is very simple.
base on what mastodon said, With OT's, still needs some modification which is my problem that I can not solve, I know nothing about electronic, but soldering.
these are my works so far:
picasaweb.google.com/auahlap
those are for fun, creating the 'sphere' was fun, it's 0.7 watt tube amp.
I like small thing,specially with tube, but I need a Highend amp now.
anyway thank you guys for helping me out, at least getting the start learning.
regards
cal
There are other choices. It's just that they are not simple, tested, proven designs. Best to stay simple at your stage. If you have fun and success with the project, you will want to try to expand your range.
Here's a simple design, using a 6DJ8 and 2A3. For headphones, I would use DC on the 2A3 filaments. Rod Coleman on this site has a very nice kit for this. Tentlabs sells a complete module, as do some others. http://www.diyaudio.com/forums/tubes-valves/5576-2a3-amp-part-1-2-3-merged.html#post53290
The only modification needed to this or any other design with a 2A3 output tube, is to get an output transformer with a 50 Ohm tap, or something close to 50 Ohm. A 2.5k OPT with a 32 Ohm tap would be close enough.
You might consider this amp: TubelabSE It uses a 5842 input tube. However, it can be set up to use several different output tubes. It looks a little more complicated, but you can get a circuit board inexpensively, full instructions, and a forum on this site where you can get help with your project.
Sheldon
hi guys, Good news for me,
Sowter transformer is very very expensive forme, specially in Euro ! and the shipping cost to Indonesia is killing me, not to mention the Tax !.
anyway,
I found local wound transformer which is cheap locally.
cost about US$50 each.
Now I change my mind since some difficulty doing with OTL design, but now with OT is very possible for me.
now back to square 1.
all I need is simple Schematic that can produce 2Watt minimum on my 50Ohms load headphone.
I can not find sample schematic using 8976 -> 2a3 on the net.
can someone point me ?
btw what's the difference between Headphone OT and Speaker OT beside the impedance of course.
Sowter transformer is very very expensive forme, specially in Euro ! and the shipping cost to Indonesia is killing me, not to mention the Tax !.
anyway,
I found local wound transformer which is cheap locally.
cost about US$50 each.
Now I change my mind since some difficulty doing with OTL design, but now with OT is very possible for me.
now back to square 1.
all I need is simple Schematic that can produce 2Watt minimum on my 50Ohms load headphone.
I can not find sample schematic using 8976 -> 2a3 on the net.
can someone point me ?
btw what's the difference between Headphone OT and Speaker OT beside the impedance of course.
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