Ok, I know now what you meant. The harmonics is what you should be after and configuration for 300b is well known, see the post here for data:
http://www.diyaudio.com/forums/tube...s-about-300b-chinese-diy-kit.html#post4683287
There should be a corresponding list for 2A3 somewhere.
One easy way is to read my 3rd suggestion.
Lowering B+ will increase total harmonic distortion... but maybe that's not such a show-stopper.
Guitar amps and Hi-Fi amps are two different beasts. If you want an amp that will do both then you will probably not be satisfied with it for either duties...
btw - I think Merlin's suggestion is also very pragmatic. Easy to try too.
If you post some pictures of your amplifier it would be good. Also from underneath, with the cover off.
If you post some pictures of your amplifier it would be good. Also from underneath, with the cover off.
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I can try all suggestions. 🙂
I will use it only for hifi.
Here is a picture of the Bowei SG-280 SE. Funny thing, its 2A3 tubes are actually quite good. I tried vintage 2A3 and it was not much difference, except a blue radioactive haze that got me a bit concerned since I often sit very close to the amp, so I switched back. Can't listen to music if I get cancer.
I will use it only for hifi.
Here is a picture of the Bowei SG-280 SE. Funny thing, its 2A3 tubes are actually quite good. I tried vintage 2A3 and it was not much difference, except a blue radioactive haze that got me a bit concerned since I often sit very close to the amp, so I switched back. Can't listen to music if I get cancer.
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It is a nice amplifier, actually the only thing lacking could be the circuit 😉
Blue haze is very good for your health... shows you that the tube is working.
Radioactive happens at 10kv + , still no problem with a 2 mm steel casing.
Just enjoy your tubes without paranoia haha
Blue haze is very good for your health... shows you that the tube is working.
Radioactive happens at 10kv + , still no problem with a 2 mm steel casing.
Just enjoy your tubes without paranoia haha
I use cheap Chinese 2a3's and they sound very nice indeed.
The blue haze in older tubes is just a bit of gas. No worries about ionizing radiation.
The backs of the circuit boards unfortunately don't reveal much. The one on the left must be for the two 6SN7's. If you try to remove it, be careful not to damage the black coupling capacitors (look like MCap's).
It might be that the cathode by-pass caps are on the other side of the board..
Ian
The blue haze in older tubes is just a bit of gas. No worries about ionizing radiation.
The backs of the circuit boards unfortunately don't reveal much. The one on the left must be for the two 6SN7's. If you try to remove it, be careful not to damage the black coupling capacitors (look like MCap's).
It might be that the cathode by-pass caps are on the other side of the board..
Ian
I had only cheap components and I have already replaced a few of them that were easy to identify.
I disconnected the preanp board a few times to find a way to modify the original board, but it is more complicated than the original circuit from. For instance I found two 200uf caps that I don't understand what they do. That is why I am going to make a few versions of the preamp board and replace the whole thing.
https://youtu.be/yLSu_UjrcUA
To produce X-rays from a regular tube he needs more than 10kV. He detects some at 20kV. But he refers to the blue cloud inside the tube when it gives out X-rays. Maybe some tube becomes radioactive at lower voltages. I see the blue cloud at 320 volts in the old 2A3 tube.
Design Philosophy.
More on driver tubes.
To produce X-rays from a regular tube he needs more than 10kV. He detects some at 20kV. But he refers to the blue cloud inside the tube when it gives out X-rays. Maybe some tube becomes radioactive at lower voltages. I see the blue cloud at 320 volts in the old 2A3 tube.
Design Philosophy.
More on driver tubes.
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lol , it is fluorescence, some e- accumulate on the glass and flow gently..
it is a good sign of a strong vacuum and is normal for power tubes at a certain temperature the glass is more conductive..
this is NOT emitting any A,B,G radiation omg !
Good luck on your rebuilding project.
it is a good sign of a strong vacuum and is normal for power tubes at a certain temperature the glass is more conductive..
this is NOT emitting any A,B,G radiation omg !
Good luck on your rebuilding project.
If the blue haze can be seen in the daylight or some artificial light then it's not gas but simply stray electrons. It happens with modern new tubes as well and has no consequences.
The white-blue haze caused by small amount of gas is rather weak and can only be seen in a dark room and concentrates inside the anode. If too gassy the tube doesn't work properly.
The white-blue haze caused by small amount of gas is rather weak and can only be seen in a dark room and concentrates inside the anode. If too gassy the tube doesn't work properly.
yup! I've had those too 45. 😉
ok.. like only 2 x 200uF makes not much sense for a clone of the sun audio circuit.... Perhaps try drawing out the circuit or taking a picture of the board?
I have a funny feeling we will see SSRP.. for some crazy reason, Chinese "designers" love SSRP... they like to put it all over the place - including many places where it makes no sense. such a tragedy.
Just a gut feeling...
Ian
ok.. like only 2 x 200uF makes not much sense for a clone of the sun audio circuit.... Perhaps try drawing out the circuit or taking a picture of the board?
I have a funny feeling we will see SSRP.. for some crazy reason, Chinese "designers" love SSRP... they like to put it all over the place - including many places where it makes no sense. such a tragedy.
Just a gut feeling...
Ian
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The traces are painted black, I have tried. I will just rebuild the original design of the preamp or find something better that hopefully work with the 2A3 tubes.
Sadly I sold my geiger counter, because I never thought I would have use for it, so we will never know if my tubes are radioactive or not. 🙂
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If there are only 2x 200uF then they could be bypassing the cathodes of the lower triode on an SRPP circuit. What are their voltage ratings? 25V more or less?
In any case, you could easily consider building your own circuit here. no real need to stick to 6SN7 if this is the case either. 😉
In any case, you could easily consider building your own circuit here. no real need to stick to 6SN7 if this is the case either. 😉
I am going to ignore what the Chinese designer tried to do and trust that the Japanese designer knew what he was doing. I will also make a few versions with different mods and maybe a whole new circuit for other tubes, like the space age era 6900 driver tubes I just read about in the article.
With a simple search "2A3 SE Schematics" I found many versions of the same. This will be a fun project.
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Just a feeling it could be a capacitor relabeling: 47uf relabeled 200uf
Unlikely. I have seen a few other sch with 200uf cap, maybe too big for small tube rectifier. The cost to relabel is more than the cost of the cap. Ask OP to measure it is the better way. there is no need to hint here and there!!
"Fun" is still not your ultimate target is it, I thought you going to mod the sch of your very 2A3 amp, or you already given up? Beside what has race or nationality got to do with design??
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Hi Koonw - many of us are aware of the sensitive relationship that many Asian peoples have with Japan after WWII. I for one have travelled south east asia extensively, and am very aware of this. I don't think any poster in this thread intends any disrespect in the slightest.
The past 10+ years has seen Chinese designers/builders at the forefront of the commercial industry. They have produced many excellent quality products along the way too. Ok, some amps they manufactured early on were a bit "different" but those days are long gone. Also, the vast spectrum of lower cost, high quality components from China has encouraged many hobbyists. One design favourite in China is SRPP - for good reason - it is a highly effective circuit.
I for one would still want to figure out this circuit before going forward. I agree with you that the original poster should not give up on determining this circuit. I kinda hope its SRPP... 🙂
There are a few different mods that could be considered here for lower gain and higher fidelity, likely without even changing the board.
For example, if it is indeed SRPP, the original poster could see about tapping the signal off the plate of the lower triode. This will immediately lower gain and reduce distortion.
Let's hope the original poster can take the time to figure out that board for us.
Ian
The past 10+ years has seen Chinese designers/builders at the forefront of the commercial industry. They have produced many excellent quality products along the way too. Ok, some amps they manufactured early on were a bit "different" but those days are long gone. Also, the vast spectrum of lower cost, high quality components from China has encouraged many hobbyists. One design favourite in China is SRPP - for good reason - it is a highly effective circuit.
I for one would still want to figure out this circuit before going forward. I agree with you that the original poster should not give up on determining this circuit. I kinda hope its SRPP... 🙂
There are a few different mods that could be considered here for lower gain and higher fidelity, likely without even changing the board.
For example, if it is indeed SRPP, the original poster could see about tapping the signal off the plate of the lower triode. This will immediately lower gain and reduce distortion.
Let's hope the original poster can take the time to figure out that board for us.
Ian
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I should have written "the guy who stole the original design and put it on fleabay so that even a poor student from Sweden could get started with tube amps." Hats off to the original designer and the fleabay pirate, wherever they are from.
As for the preamp circuit, I want to scrap it and use only half of a 6SN7. Or both with sides the resistor mod after a 20uf cap that was suggested before in pictures on page 2.
I will make a new board and I am open to more low gain preamp designs that would work well with a 2A3.
So lets forget about the Chinese version of the preamp. Everything after the 0.22uf cap is the same as the original Sun Audio 2A3 amp, including all the components close to the 2A3 tube amp and the power supply.
Attached is the original design from Japan and the mod with the change to a 20uF cap and a resistor of choice up to 10K.
I will also try to use only one half of the 6SN7, or use a tube like the 6P5 which has slightly lower gain. I could use two 6P5 tubes in an adapter without changing anything, but I think I would not lower the gain enough. One 6P5 per channel would be interesting to try.
I will make a new board and I am open to more low gain preamp designs that would work well with a 2A3.
So lets forget about the Chinese version of the preamp. Everything after the 0.22uf cap is the same as the original Sun Audio 2A3 amp, including all the components close to the 2A3 tube amp and the power supply.
Attached is the original design from Japan and the mod with the change to a 20uF cap and a resistor of choice up to 10K.
I will also try to use only one half of the 6SN7, or use a tube like the 6P5 which has slightly lower gain. I could use two 6P5 tubes in an adapter without changing anything, but I think I would not lower the gain enough. One 6P5 per channel would be interesting to try.
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