Newbie: Resistor and Capacitor Types for Aikido Headphone Amplifier

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Greetings Friends,

After a hiatus to deal with life, I am resuming my tube audio education. I figure John Broskie's Aikido Headphone amp is a nice way to get warmed up, and I'd like your help in selecting reasonable resistor and capacitor types.

My goal is simply parts of decent value--neither cheaping out, nor boutique. I realize that these are subjective choices and do not wish to stir controversy. I just want to avoid buying something awful, and am bewildered by all the choices--a forum search has left me with an open mouth and drool-soaked shirt. :xeye:

I'm going to build Broskie's recipe--the schematic is here.


I already have some 100uF ASC motor run caps that I plan to use for output coupling, and am eyeing Auricaps for the smaller caps, contingent on the advice I get here.

I'm still wondering what would be reasonable, safe choices for the 1000uf cathode bypass caps, and the resistors, particularly those in the signal path?

Recommended parts would be great, and suppliers even better.

Thanks for your help!
 
The whole point of the distortion and noise nulling is to remove the criticality of many of the parts. I've got two Aikido line stage boards, one with very fancy bulk film resistors (thanks, John!) and one with ordinary metal films. I would defy anyone to hear an actual difference.

Avoid audiophile caps. Besides being overpriced, I've yet to see any that actually have reasonable performance trade-offs. I would be tempted to substitute a low impedance LED for the RC combination in the cathode...
 
Sy's suggestions are quite reasonable. In retrospect, I myself have spent too much time in the past sweating issues such as this. From my perspective, the topology of the circuit is the critical bit. As long as that is sound, you should do pretty well with standard parts. As an aside, the Aikido topology is quite nice.

As all the folks over in the Bottlehead forum suggest, start with the basics, then you can try tweaking later on once you really understand and appreciate how the circuit sounds. You yourself will then be able to judge whether or not the $25 cap has much to offer over the $4 cap.

Have fun.
 
Thanks SY!

Hey SY,

Many thanks for the reply!

I share your inclination towards standard rather than boutique parts.

Could you (or anyone) give me some examples of reasonable resistors and caps?

I also like your cathode LED suggestion, especially since the cathode cap is so huge, and I'm guessing a reasonably priced wonce would be pretty crude Again, could someone suggest a reasonable example?

I'm new enough that I just want to get a decent, reasonably-priced Aikido going to build my confidence, and go from there.

Thanks again, and thanks in advance for any further help!
:D
 
For caps, I find that anything fancier than Wima FKP or MKP hits the law of diminishing returns pretty fast. As for resistors, I will no doubt be scorned for saying that the cheap Yageo metal films work very well as cathode resistors.

Regarding LEDs, what you want is surplus, cooking-grade. The high efficiency stuff tends to have a high dynamic impedance. A good LED ought to give a Z of about 4-5 ohms, very flat up to ridiculously high frequencies.
 
Excellento!

Thanks SY for the specific recommendations--they are just the sort of hand-holding I want to keep me on the track :nod: (please forgive the mixed metaphor).

I'd like to use a cathode LED, but will hold off unless you or someone else has a specific recommendation--my expertise is low enough that think picking one on my own is too risky. :drool:

Thanks again! :up:
 
DrExotica said:
Sy's suggestions are quite reasonable. In retrospect, I myself have spent too much time in the past sweating issues such as this. From my perspective, the topology of the circuit is the critical bit. As long as that is sound, you should do pretty well with standard parts. As an aside, the Aikido topology is quite nice.

As all the folks over in the Bottlehead forum suggest, start with the basics, then you can try tweaking later on once you really understand and appreciate how the circuit sounds. You yourself will then be able to judge whether or not the $25 cap has much to offer over the $4 cap.

Have fun.

Hey DE,

Thanks for the advice--and I agree.

My goal is to do what you say--not sweat it, and just avoid getting totally ****py parts because of my ignorance. I think SY's advice has done that, and I've found a nice DIY site that I'd forgotten about that carries them. That's what I'm hoping--to refresh my memory, and shake off some of the rust.

Coincidentally, I my first tube build was a Bottlehead, and it was very satisfying and educational. I was planning on continuing my education by tweaking my Bottlehead with CCSs and the like. Now, after my 2 year hiatus, I see the Aikido, and I'm hoping to reap the benefits of an innovative topology, and perhaps tweak from there.

Thanks again for your guidance.
 
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