Home » Audio » Group Build » so let's speak of mods to the Aikido circuit of John's
so let's speak of mods to the Aikido circuit of John's [message #31285] Sun, 04 September 2005 07:12 Go to next message
Thrint is currently offline  Thrint
Messages: 43
Registered: May 2009
Baron
Hey-Hey!!!,
There seem to be a few places to improve on. The question to me is: is the sonic performance dependant on the rather poor performance of the singletriode CCS-es? So-to-say, would a few strategically implemented pentodes, or faux-pentode( twin triode cascode ) help or hurt?

The first one which comes to mind is the plate load of the grounded cathode amplifier( lower section, fed from the volume pot ).

The next mod is, can we do away with the resistor between the two output sections? or, has anybody experimented with putting the output at both ends of the resistor?

Also, changing the performance of the first half's PSRR will require a different application of PS noise to the second half. Either with a different pair of resistors, or a pot.

By my own experience, larger output caps would probably help. It depends on the rest of the system. I like 7.5-10k grid resistors in my amps, so the linestage's ability to drive a SS-like load is required.
regards,
Douglas

or Blueprinting... [message #31286 is a reply to message #31285] Sun, 04 September 2005 07:40 Go to previous message
Thrint is currently offline  Thrint
Messages: 43
Registered: May 2009
Baron
Treat it like a McIntosh. The CF section will have lowest output Z with high gain/high gm valves. Triode-strapped pentodes from the video amplifier family are mu of ~40 along with 40 mA/V transconductance.

Smaller cathode resistor gets less impact to output Z w/o breaking the original circuit performance.

Add to this, most of the amps I have build don't need much gain from the linestage and we are into 12B4's for the amplifier half....
cheers,
Douglas

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