6AU6 Aikido in Triode mode?

[Original Burnedfingers]

If you look at the schematic at Http://www.tubecad.com/2004/blog0013.htm

You will find a Aikido line stage with a 6Au6 as the input tube and a 5687 at the output tube. I will try to attach the schematic.

I built this circuit but was never really satisfied with the amount of gain and the noise associated with it. I tried it yesterday in Triode mode by eliminating the cap to ground and 47K resistor to the power supply and connecting the pins 2 and 6 to the plate as per instructions I have found for making the 6AU6 a triode. I also put a bypass cap in parallel with the cathode resistor. I thought the outcome was somewhat better than the original. While the gain seemed to be lower there just doesn't seem to be very much bass out of this design when listening to music. I haven't done any testing yet. Oh, the cap I added (bypass) was what I had handy on my bench and it was a 100 mfd and seemed to help a little I think with the low end.

Any ideas?

[azazello]

In output You must put parallel to 0,47 mkf, cap 100-200 mkf /250v.
Instead 1 Mom put 20 kom /in output/
Good luck!

[Original Burnedfingers]

In output You must put parallel to 0,47 mkf, cap 100-200 mkf /250v.
Instead 1 Mom put 20 kom /in output/
Good luck!


Sorry, I don't understand

[Stixx]

In output You must put parallel to 0,47 mkf, cap 100-200 mkf /250v. Instead 1 Mom put 20 kom /in output/ Good luck!

I think he means to parallel the 0.47uF output cap with 100 - 200uF more capacitance (as in a headphone amplifier) and to substitute the 1M resistor going to ground with 20K...

[azazello]

Originally posted by Stixx


I think he means to parallel the 0.47uF output cap with 100 - 200uF more capacitance (as in a headphone amplifier) and to substitute the 1M resistor going to ground with 20K...

Thank You! /Sorry for my bad english..../

[john65b]

I have a number of these 6AU6 from an old RCA tuner - with a mu of over 10X a 12AX7, I didn't know I could use it for audio...

Burnedfingers - I would be interested in hearing what you finally find on this tube in an Aikido Linestage - I have a set of the Bas Horneman preamp & PS pcbs and was planning on using 6N1P/5687..

Also, I have just acquired a Quickie 8417 with 6550 tubes - Can you point me in the forum where you define the most optimum mods?

Looks rather stock, but with diodes mod on the 5AR4 rectifiers, a couple added caps around the bias pot, and new 1000V .22uf coupling caps. Sounds OK, doesn't look like anything else was done to the amp to change from 8417 to 6550. 12AX7 and 12BH7 tubes.

Sorry if hijacking the thread...

[sjh327]

http://www.tubediy.net/1mydiy/pre_05.htm