I think a line stage is also necessary since the gain of the phono stage is about 45dB or less which brings the output of a Moving Magnet cartridge (4mV) up to a level that compares with CD players, for example. The line stage then brings the output of the sources up to that needed by an amplifier.
The table shows the values for C7 in parallel with C8 (and also C9 in parallel with C10). So you have to find capacitors values which, when placed in parallel, make up the values shown in the table. You have to do that yourself.
For example, if you choose 0.1uF for C7||C8 (i.e. don't use C8 at all) then you need 0.0343uF for C9||C10, although you also need to subtract the Miller capacitance which is about 150pF for a 12AT7, so call it 0.034uF or 34nF. You could make this using 33nF and 1nF in parallel.
You also need to make up the corresponding resistor values from pairs of standard values. You can probably ignore the output resistance of the preceding stage because it is very small. You could make 21870 using 36k||56k, and 3180 using 3k and 180R in series. (Handy calculator: Resistor calculator - compute the best resistors combination to obtain a given value)
EDIT: This thread is 2 years old. Nevermind, someone may find it useful anyway.
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I bought my Aikido line amplifier few years ago but never had time to get to the project, until now. Also I would like to get decent DIY (or asemble -it-yourself...)Phono pre-amplifier and searching I stumbled upon this thread. TETRA would be an interesting project, there is only one problem...could not find the PCB. Does anyone knows a source of it?
Unfortunately John Broskie, aka Mr. Tubecad, doesn't have Tetra phono boards in stock at the moment. Quite a few of his kits are out of stock, perhaps they will be available later this year. I've built a couple of Tetra phonos and repaired another. As far as I'm concerned they have an excellent price/performance ratio. The Tetra is a CCDA (constant current draw amplifier) and doesn't necessarily need a regulated B+ supply. I've heard them with regulated and non-regulated supplies and they both sounded good.
S.
S.
Thank you Steve, I am really keen to build that one, I hope they bring it back. There are number of option out there, not easy to decide what to go for, in terms of quality , in case Tetra does not come back. Searching on the net I came across an interesting design "AN MC/MM PREAMPLIFIER" by Erno Borbely, an old school engineer (worked for Harman/Kardon at one stage, and other reputable brands at the time). It is a two stage design with FET and tube in cascode arrangement on the input; he even presented design of PCB, though that would be more work and messing with chemicals. As I said, design in itself is very interesting, though I am not experienced enough to say what final result may/would be before making it.
Maybe someone could make a pcb for the phonodude. A popular design in the Netherlands with many happy users. Or perhaps the Trafomatic design which was put in the public domain. I built the bigbottle when the pcb was still being sold...haven't used my turntable much....but it is a great phono stage...
.But I've been busy collecting parts for the trafomatic for years...actually think I have it all....but for folks who are intimidated by point to point a pcb would be great. Anyway..point is perhaps we can get some group buy...project together.
.But I've been busy collecting parts for the trafomatic for years...actually think I have it all....but for folks who are intimidated by point to point a pcb would be great. Anyway..point is perhaps we can get some group buy...project together.
https://www.diyaudio.com/community/threads/valve-itch-phono.140635/ another one to consider building a pcb for..sell it on diyaudio store....
Just found a gerber for the itch: https://www.diyaudio.com/community/threads/valve-itch-phono.140635/post-5999918
