aikido is up and running

[Ianm2]

Wow, the easiest build I have ever done.

Must be down to all the resistors being pretty much the same.

Used 4x6922s, with 330 ohm resistors.

Sounds great, exactly like John Browski describes.

Fast, neutral, clear, onlly troulbe is, its distorting when I turn the vol up, I ain't sure why, I will go over it and see if I have done anything wrong, I literally threw it together.

Pretty good, better than the conrad johnson paralleled jobby.

hah, problem appears solved, yet to try, but the noise network was connected to the wrong point.

article is here for those that have no idea what it is.

http://www.tubecad.com/2004/blog0011.htm

note the description ffrom the article, this is spot on!!

"I am quite amazed by the sound: very fast, clean and accurate" and "I have to say that the [line] amplifier is dead quiet, open sounding, and absolutely neutral,"

[James D]

Excellent, Ian.

What B+ are you using? The 330R may be too small on the first stage.

James

[Ianm2]

circa 200volts, 6922 running at 7m amps.

[James D]

Thats spot on then Va~100V, Vg=-2.3V Ia=7mA. I see from your edit you have cured it Excellent.

Two quick observations. If you get peak distortion occasionally from a CD it is probably input clipping - a CD can put out +/- 3V peak volts.

The output at 2V in will be 36Volts - easy to overload the power amp input.

The Aikido stays so clean that it is really easy to hit these points before you realise it

James

[Ianm2]

yes quite good, it was that, couple of wrong connections, even so , its the easiest preamp I have built for some time.

sounds a tad edgy when turned up, I wonder if the grid stoppers are correct, or if that's overload?

also, its quite solid state sounding, bass is fast and tight, which is its strongpoint, vocals aren't 'quite' prominent enough, nitpicking, I like them a tad forward, but its very good indeed.

[Clive]

I wonder if 5687 followed by 6N1P would be a good combination. One of the published circuits had this but the other way around. Using 5687 first stops the gain going through the roof.

[James D]

The edgy sounds like a touch of peak overload rather than osc. It could be either hard to tell without hearing it. One is clipping the other peak envelope modulation... not always easy to tell the difference...

Sounds like you have been listening to too many poor valve amps if you associate clean and fast with ss rather than valves....

If vocals are not clear enough the fault is elsewhere in the system - the Aikido is truely neutral and very clear. It certainly lets the other parts of the system dominate the system character...

James

[Ianm2]

I suspect part of the clinicity is to do with 6922, it has a tendancy to sound that way, and I would say its the small valve equal of the 6550 sound as a power valve.

I may be better with ecc82 as a quick drop in, only the heaters to change, quick check for the current, too.

[NickG]

More than 2.3v input signal will overload the input stage as James has said. Where is the attenuator in the system, before the first valve?

[Ianm2]

yep, something I am wondering about, bias is around 2. and a bit volts, yet tube cad says overload is 3 and a bit volts, how does that figure?