Dear everyone,
I am new here, from France, so first, I am sorry for my bad English.
I already read a lot of pic on diyaudio and I have a question for you.
In fact, I want to build a phono and line preamp. I saw a schematic using one stage 12RLL3 and two stage of 5687 but I don't know at all if it's the best sounding tube and best choice.
I read a lot of good of combo 45 and 2A3 but the gain is really low, so I was thinking to do a first stage of 6072 then one of 45 then one of 2A3.
I will use LCR riaa filter and I will use transformer and not coupling cap and if possible a direct coupling between the first and second stage.
Thank you in advance for help
I am new here, from France, so first, I am sorry for my bad English.
I already read a lot of pic on diyaudio and I have a question for you.
In fact, I want to build a phono and line preamp. I saw a schematic using one stage 12RLL3 and two stage of 5687 but I don't know at all if it's the best sounding tube and best choice.
I read a lot of good of combo 45 and 2A3 but the gain is really low, so I was thinking to do a first stage of 6072 then one of 45 then one of 2A3.
I will use LCR riaa filter and I will use transformer and not coupling cap and if possible a direct coupling between the first and second stage.
Thank you in advance for help
Your English is much better than my French!
There are many designs for a line and phono preamp, can you post a link to what you were looking at? It also helps to know if you are using a moving coil or moving magnet phono cartridge.
The gain of a single ended 2A3 of 45 amp depends a lot on the actual design of the amplifier. If you have sensitive speakers, you don't want a lot of gain in the amplifier (12-20dB is plenty). Driving a 2A3 with a 45 won't serve much purpose.
You are probably best off starting with the line and phono preamp, then tackling the power amplifier later. I would not recommend building it all into one box!
Thank you for your reply. Haha thank you, English is so useful all over the world.
I was looking to put phono and line in same chassis like in the schematic below (the one I am interested)
LCR schematic01.jpg - Google Drive
I will remove the input transformer because I use MM cartridge.
I will use 600Ohm LRC unit with Noguchi choke and 5k/600Ohm transformer. Same for output transformer I will use 5K/600Ohm.
So I already have attenuation of 4 before the LCR unit and attenuation of 4 at the output.
I was looking to put phono and line in same chassis like in the schematic below (the one I am interested)
LCR schematic01.jpg - Google Drive
I will remove the input transformer because I use MM cartridge.
I will use 600Ohm LRC unit with Noguchi choke and 5k/600Ohm transformer. Same for output transformer I will use 5K/600Ohm.
So I already have attenuation of 4 before the LCR unit and attenuation of 4 at the output.
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But I am wondering which tube use. the 12RLL3 are impossible to find, the 5687 don't seems really great, the 6900 are better but impossible to find. I only found one pair at 950$.
2A3 and 45 are DHT so for phono level it's really hard to make them quiet. Maybe use the 20A from Emission lab ? But someone told me that after 6 months the tube start to make sputter noise. He changed it and after some months the tube start again to make noise.
Here 20A data sheet :
EML-20A-20B-30A Data sheet. By Emission Labs.
2A3 and 45 are DHT so for phono level it's really hard to make them quiet. Maybe use the 20A from Emission lab ? But someone told me that after 6 months the tube start to make sputter noise. He changed it and after some months the tube start again to make noise.
Here 20A data sheet :
EML-20A-20B-30A Data sheet. By Emission Labs.
The 5687 linestage drawn there is a nice idea, but the 10K pot on the aux input is a horrible choice. Setting it up as a parallel feed linestage may be a good place to dedicate your resources. Using a 10K:600 transformer will knock down some of the gain that you don't really need in a linestage.
I'm not the right person to ask about LCR phono preamps. I've heard a few and I haven't been impressed. There's also a glaring error in that phono preamp section that will destroy V3 pretty quickly.
I'm not the right person to ask about LCR phono preamps. I've heard a few and I haven't been impressed. There's also a glaring error in that phono preamp section that will destroy V3 pretty quickly.
With error are you talking about ?
I wanted to put the 10k pot between V5 and the output transformer. I think too that the 10k pot at the AUX is horrible.
A directly heated phono preamp is a very difficult endeavor. The EML20A isn't suitable for this application.
The 1K/2W resistor under V3 is an error. V3 will self destruct.
You cannot put the 10K pot between V5 and the output transformer.
5687s are great sounding tubes. Your life will not end because you can't use 6900s. The same goes for the 12RLL3, just use a 5695.
Why not use this phono preamp:
And mate it to the 5687 transformer coupled linestage.
The 1K/2W resistor under V3 is an error. V3 will self destruct.
You cannot put the 10K pot between V5 and the output transformer.
5687s are great sounding tubes. Your life will not end because you can't use 6900s. The same goes for the 12RLL3, just use a 5695.
Why not use this phono preamp:
An externally hosted image should be here but it was not working when we last tested it.
And mate it to the 5687 transformer coupled linestage.
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