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I'm intrigued by the Aikido design (particularly its flexibility), and would like to try it as the basis for a preamp (no RIAA, just sitting between sources & amp).Aside from the B+ & heater supplies, is it simply a matter of sending the source output to the PCB's input and the PCB's output to the amp? That is, is everything I need contained on the board?
Follow Ups:
They are as easy as they seem. It is more work to put the input/output jacks and selector pots together than the board, but still no sweat. Use a pre-built PS and it is really easy.I built mine with 24v 6GM8 tubes the way John Broskie suggests in one of his articles. $4.00 for Amperex bugle boys and they're the same tube as the 6DJ8.
I put no additional components in, just straight in from the pots and straight out.
The Aikido boards from John are dirt simple to put together. Simpler than Bottlehead kits, etc. Sound great w/o using boutique parts, etc.Buy some boards from John - we need to keep him an his quite excellent TubeCad Journal going.
I believe more than one PCB is available. Are you getting it from John Broskie? You have to "populate" the Broskie pcb with resistors and tubes and caps of your choice.It is a simple enough design. I have built two Aikido versions, but neither with a PCB. Mine are point to point home brews using old-timey tubes in the voltage amplifying stage, 56 and 76 in a preamp and 26 in my recent headphone amp. The PCBs are designed for octals and 9-pin miniatures.
Yes, I was planning on getting it straight from John Broskie. Sure, I could wire it P2P, but buying a board allows me to:1) implement it quickly.
2) drop it into different applications (driving SE 45s).
3) experiment with different tubes with minimal hassle.
4) throw some change Broskie's way.The single triode idea is a cool one, though.
Those are good reasons all, including a little support for JB. I own Tubecad, which would have been worth the price for the documentation -- i.e. the circuit guide -- alone.And, his prices are tres reasonable.
I built my first Aikido before his pcb was on the market. My second was intended to prove that the noise cancellation inherent in the Aikido design works for stacked DHTs with AC filaments, for which I wanted to use 26s.
What tubes are you thinking of using?
I have a stash of 6BX7s that I'm itching to try, but one pair alone (let alone two) will require a beefy heater supply. I also have 6SN7s and 6SL7s to play with in the input stage.OTOH, I'm quite fond of 6N1Ps, particularly the older vintages, so I'm torn as to which board to get first - though I'm sure I'll eventually wind up with both 8- & 9-pin versions.
Either way, it seems like the perfect platform with which to become familiar with the characteristics of a given tube.
I don't know much about the 6N1P, but like octals. The miniatures may give more choices for driver duty, however.
I have thought that the Aikido could make a good front end for things like SE 45s, as you mention, but the downside is lowish voltage gain. Gain is no big problem in a line stage, but a 45 would like 50 volts of grid bias. In an Aikido, the voltage gain tubes will give you one-half of mu for gain, some of which is given up in the CF side of the Aikido. 6SL7s, in NOS form, have a mu of 60 - 64 (in the real world -- I cannot reproduce the spec of 70 on numerous samples I have tried), meaning your source needs 2 volts peak to drive 6SL7s to drive 45s (with some headroom - more is better). Some CD players will do that, but I am not sure about other sources.
Thanks for your insights regarding the 45. I'm presently running the JE Labs Simple 45 (http://members.myactv.net/~je2a3/simple45sc1a.jpg) with a single 6SL7 driving the 45s. With a preamp it sounds fine, but with a CD source directly connected (through a volume pot) it seems to run out of steam -- thin and lifeless.I'm about to add another 6SL7 in SRPP (http://members.myactv.net/~je2a3/JELsc-srp45.jpg). After trying that for a while, I'd also like to try Gordon Rankin's Bugle (can't seem to dredge up the schematic at the moment). I was hoping the Aikido might be a 3rd option -- how do you think it might stack up against these other two options?
Gordon's article is here at the moment:http://www.hificollective.co.uk/a/article4.html
Isn't Gordon's approach an SRPP too, using 6072A (a 12ay7, mu 44, rp 25k -- a tube with a good rep)?
I hesitate to offer views of what would sound better than other things, not having played with SRPP and other approaches. I have taken umbrage on this board when people claim that their pet circuits sound better than broad classes of other types ("mid-fi" and "low-fi" slurs).
Aikido is very much my pet circuit, so I would like to think it would be great as a driver. Apparently 45 is OK to drive with a relatively small-current voltage gain devices, but I have studied Lynn Olson's work and subscribe to his view that lots of current in the tube feeding the grid of a DHT is a good thing. Aikido does this well. Aikido also is pretty easy to direct couple, for those who (like me) don't like coupling caps. There is cancellation going on, as in my AC-filament powered 26s.
I also understand Broskie's argument that SRPP is good for limited cases, to feed a known and reltively fixed low impedance. SRPP was the rage in the 90's, and seems to show up in lots of designs.
The main gripes about Aikido are: -- gain is limited to one-half mu
-- It has a cathode follower, despised by many
-- It has an extra stage, anathema to many
-- It is accompanied by a bit of frenzy, making it feel like this decade's SRPP
-- Some people think complementary distortion cancellation is bunk, and power supply noise cancellation a limited effectI don't know if these gripes are a big deal or not. My opinions come more from reading than from experimenting, so they can't be put forth as much more than my biases. However, I have done some experimenting, and have been pleased with Aikido type circuits.
The 45 seems to lend itself to experimental amps, which seem to turn out very well. If I get some time soon I want to try one.
between source and Aikido board(s). It is as easy as it looks and is a GREAT preamp. As we speak, I am drilling the permanent box for mine after listening to it for a month or so mounted to a masonite chassis. I chose the dual mono 9-pin boards and 6GU7 tubes, which are dirt cheap for NOS ($3.50 each on eBay, the GE tubes sound very good).
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