Hi to everyone,
First of all I would like to say hello to everybody here. It is my first post in this forum and I am not sure if it is placed correctly. I do not know much about electronic, but I want to learn in order to make other projects.
I have never tried a diy project but I want to start trying to modify a J Sound Lab 2A3 amplifier.
What I would like to modify is the rca and speaker sockets which are on the top of the amplifier and I want to make a new chassis with them in the back side.
The next modification would be, place the potentiometer in the front side with a switch which allow to disable it, I would like to change it by an alps one, but I do not know which is the suitable. I wonder if it is possible...
There is also a deep noise by the speakers when you switch on without music, once you play music it desappear I have read it could be a matter of a lack of direct and stabilized current in the 2A3 tubes, somebody could help me how can I eliminate.
If anybody has an idea to improve it please tell me, I would be very grateful.
I upload a picture of it.
Thanks for all, regards.
First of all I would like to say hello to everybody here. It is my first post in this forum and I am not sure if it is placed correctly. I do not know much about electronic, but I want to learn in order to make other projects.
I have never tried a diy project but I want to start trying to modify a J Sound Lab 2A3 amplifier.
What I would like to modify is the rca and speaker sockets which are on the top of the amplifier and I want to make a new chassis with them in the back side.
The next modification would be, place the potentiometer in the front side with a switch which allow to disable it, I would like to change it by an alps one, but I do not know which is the suitable. I wonder if it is possible...
There is also a deep noise by the speakers when you switch on without music, once you play music it desappear I have read it could be a matter of a lack of direct and stabilized current in the 2A3 tubes, somebody could help me how can I eliminate.
If anybody has an idea to improve it please tell me, I would be very grateful.
I upload a picture of it.
Thanks for all, regards.
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Hello! Welcome to the forum. The Pyrenees are a beautiful place - you are lucky to live there! the usual advice to a beginner is to buy a copy of Morgan Jones "Tube Amplifiers" and read it a few times. Edition 3 is in book form, but even if you see a cheap edition 2 that's good too for the basics. Edition 4 is electronic and expensive. Really, a tutorial in Spanish would be good for you. Do other Spanish speakers know of any?
When I look inside the chassis myself I would rip the whole circuit out and start again! But for quick modifications, replace the 2a3 electrolytic cathode bypasses with polypropylene film caps - whatever size goes in there. 100uf would be good but even 47uF in a film cap would sound better. And the cathode resistors are pretty horrible too - those white ceramic ones. Go for green 14W Welwyn W24 wirewound ones. I'd be wanting to put two interstage transformers in there somewhere - maybe Lundahl LL1635/20mA would fit. And then use an input tube like 5842 or otherwise D3A or EF184 or E280F or E180F in triode or something like it. You might need a preamp but that would be another good project.
This might all be a bit advanced for where you are now - do you have a friend who could help and knows tube stuff?
When I look inside the chassis myself I would rip the whole circuit out and start again! But for quick modifications, replace the 2a3 electrolytic cathode bypasses with polypropylene film caps - whatever size goes in there. 100uf would be good but even 47uF in a film cap would sound better. And the cathode resistors are pretty horrible too - those white ceramic ones. Go for green 14W Welwyn W24 wirewound ones. I'd be wanting to put two interstage transformers in there somewhere - maybe Lundahl LL1635/20mA would fit. And then use an input tube like 5842 or otherwise D3A or EF184 or E280F or E180F in triode or something like it. You might need a preamp but that would be another good project.
This might all be a bit advanced for where you are now - do you have a friend who could help and knows tube stuff?
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Hi,
It is good to see the actual build of J Labs amplifier as it definitely looks different than the pictures on their website. The quality of build looks quite horrible...
To address the problem of hum I would install humpots on 2a3 cathodes. I can see some kind of rectifier with bridge and one cap, I assume it is for signal tube fillaments - you need to replace that with better regulated dc board.
As Andy said, the whole thing looks bad, I woul keep the chassis but rip the guts out and build something decent at least.
It is good to see the actual build of J Labs amplifier as it definitely looks different than the pictures on their website. The quality of build looks quite horrible...
To address the problem of hum I would install humpots on 2a3 cathodes. I can see some kind of rectifier with bridge and one cap, I assume it is for signal tube fillaments - you need to replace that with better regulated dc board.
As Andy said, the whole thing looks bad, I woul keep the chassis but rip the guts out and build something decent at least.
Are those octal sockets on the input? Hard to see. There's a loctal C3G in triode, or make an octal-9 pin bodge to fill in the existing socket space. I'm sure there are options. Me, I'd use a 4P1L and then use a preamp with it. That would need a DC supply like Rod Coleman's boards. I'd then take the power supply outboard. But that's too much for a beginner.
hi, would there be a big difference if 20uF polypropylene film cap is used instead of 47uF or 100uF in cathode bypass?
It is not the new one, it is the older design. I am not sure but the new one has a rectifier tube though, apart from that, it seems quite similar.
Anyway I tried twice to put in contact with them, about the deep noise, and I am still waiting for the reply...
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