for my record player, ive come to a decision on exactly how this thing will be built, and i will modify it as i go to get better and better each time, but one thing i will need is a pre-amp...
id like to keep this all analog and use a simple 12ax7 vacuum tube for the pre-amp, it can be either two 1-channel pre-amps on a single perfboard, or a stereo preamp... but im looking for simplicity, with adjustable volume control of course...
does anyone have a simple schematic that would use the vacuum tube, simple component parts, and be able to be assembled on a perf board?... not interested in integrated circuits for this one, trying to keep it a little old fashioned if i can
id like to keep this all analog and use a simple 12ax7 vacuum tube for the pre-amp, it can be either two 1-channel pre-amps on a single perfboard, or a stereo preamp... but im looking for simplicity, with adjustable volume control of course...
does anyone have a simple schematic that would use the vacuum tube, simple component parts, and be able to be assembled on a perf board?... not interested in integrated circuits for this one, trying to keep it a little old fashioned if i can
Perf board is not commonly used with valves. Matching a rectangular array of holes with a circular array of valve socket pins can be tricky. Three constructions usually used with valves: point-to-point, tag board plus ptp, PCB.
For circuits use Search on here or Google. There is a simple RCA phono preamp using a 12AX7. It has flaws but will get you started. I assume you are familiar with safety using high voltages, and mains PSU etc.? If not, start with a kit.
For circuits use Search on here or Google. There is a simple RCA phono preamp using a 12AX7. It has flaws but will get you started. I assume you are familiar with safety using high voltages, and mains PSU etc.? If not, start with a kit.
perfboard, tag board.. im just not too interested in the integrated circuits for this... id like to preserve a classic look... ive found some schematics that look go though, ill look into them further
Except around here (see His Master's Noise article for an example), where it's standard practice. Punch a hole in the board to mount a standard chassis-type tube socket. The other components mount as usual.
SY, exactly my idea, ive seen many homemade guitar amps made the same way as well which is where i got the idea..
also, i should note that the 12AX7 is optional, it just seems to be the most common with the most support and easiest to find, if theres a better preamp tube for audio quality in a diy phonograph, id be willing to use it
also, i should note that the 12AX7 is optional, it just seems to be the most common with the most support and easiest to find, if theres a better preamp tube for audio quality in a diy phonograph, id be willing to use it
This one seem to be very good :
An externally hosted image should be here but it was not working when we last tested it.
Thanks to the cathode follower last stage, with is low 10K load impedance, you can use any volume control, 50K is the best ...
It use three 12AX7 for two channels, just add a simple supply over 250VDC and it will be perfect, you will just have to adjust the R12 voltage dropping resistor, the same zeners and filter capacitors can be use for both channels. It is an easy to build project on a good steel or aluminium frame, there is no need for a PCB for all the circuit, just a little "general use" for the passive parts beside the tubes on sockets installed on top of the frame with the power transformer ...
Cheers,
Alain. 😉
is it possibly to run two channels through a single 12ax7 tube for an even simpler setup?...
the alain posted looks really simple to build, and looks like it would be great for really hi-fi stuff, has anyone used it?
the alain posted looks really simple to build, and looks like it would be great for really hi-fi stuff, has anyone used it?
DF96, i didnt think it was possibly, so my idea was to get a schematic for a mono single channel 1 tube pre-amp, a very, very simple one, then build two of those on one perfboard to handle each channel
i have a very capable little drill press, if i needed to i could probably drill out my own... take a schematic and build a layout for it, print that out on paper and use it as a template to drill only the holes i need...
i like the schematic cassiel posted
i have a very capable little drill press, if i needed to i could probably drill out my own... take a schematic and build a layout for it, print that out on paper and use it as a template to drill only the holes i need...
i like the schematic cassiel posted
What sort of cartridge are you thinking about? Be aware of high Miller capacitance, which for some carts is fine, for others, not so good.
havent really decided on a cartrdge yet, but something inexpensive for now, id rather get the electronics sorted before upgrading the rest of it as i go...
anyway, this website has a few schematics i like Audio Electronics Page
i believe thats a mono pre-amp, but i could just make two on one perfboard.. and it appears to be really simple to make as well
anyway, this website has a few schematics i like Audio Electronics Page
i believe thats a mono pre-amp, but i could just make two on one perfboard.. and it appears to be really simple to make as well
This is the RCA '70 databook one, I add one 2 years ago into a old Emerson Receiver made only for ceramic pick-up, it sound very well !
I also have the 1956 RCA databook and the phono preamp is different, it use a venerable 6SC7 twin triodes for each channel. But also for high load impedance, of course.
Cheers,
Alain.
Look at this : Class IX PP1 Vacuum Tube Phono Preamp
Simple and only 70$, just make a suitable supply for it and bingo ! 😛
question.. should i make the pre-amp part of the phonograph itself, or build a tube pre-amp and power supply into a different box entirely?... i was thinking of having a box i could put the electronics into, and on top of that the phonograph itself with platter and tonearm would sit into a single unit.
You can do that if you choose a preamp design with a buffered output- and that means a decent buffer, not a 12AX7 cathode follower that's trying to drive an RIAA network as well as the output. For most of the two-tube RIAA circuits, you'll want the phono stage and line stage in the same box- they will NOT be happy driving the capacitances of cables nor low impedance (<250K) volume controls.
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