My DC coupled CMoy (no input cap, but a 1 K resistor in its place) is my favorite headphone amp. Using the opa 2227. Sometimes I add Chu Moy's linkwitz crossfeed circuit for soundstage variations. Fortney

That looks very nice; original. I like bakelite and refurbish All American 5 radios. When I buy a radio on Ebay I ask them to double box it and I will pay extra. The antique radio lovers usually do that automatically.   Check out Radio Daze, Antique Radio.come, et. al. for various...

Hi,   I removed the input capacitors and replaced them with  1K resistors. Now there is no DC protection, but the sound quality  improved.   F

Hi--   Presuming you have a music source without significant DC offset (can be checked with a voltmeter) you can improve audio quality of the CMoy by replacing the input capacitors with 1 K resistors. I did this and the improvement is obvious. I am using the OPA 2227 op amp and must say that...

Go to the AudioKarma site and see what you can find. EchoWars is one of the repair experts there if you find nothing in "search."   F

I think burn in was a process to select out solid state parts that would fail early: if the unit  did not fail it would likely run forever. That is from the old days of solid state and may be of no importance now.   Otherwise I don't think burn in alters audio, but there are true believers...

OOPS! My suggestion for application of heat for 2 seconds is for "regular sized" parts, not the surface mount parts.   Sorry, hope no damage.   F

Check out soldering techniques for smd parts on the web and also on tangent's site.   It would help to practice a bit before soldering the Mini 3 op amps  parts.   I  use a spade tip instead of a pencil tip for better heat transfer to the work. I usually set to 700 degrees F and apply...

I think CMoy used a case like that for his orignal amp. Look at an engineering (measurements) drawing of the case to be certain that your amp and hardware will fit. It is the usable inside measurements that you need. The battery compartment is great. Some people like a transparent case.   F

Nice work on the CMoy.    I was referring to learning to solder the SMD parts.   F  

Either lead containing solder is OK. I built an Elecraft K1 radio and they suggested not using siver additive solder--I think it is more difficult to work with, but don't remember for sure. Nonetheless I did use the silver with good results.   If you intend to continue DIY I suggest buying a...

My Mini3 amp works very well. I have not heard any others you mention.   Note that there is a long play and high performance option for the amp using different op amps. I built the former.   You need to know how to solder small SMD parts to build the amp and to follow  directions...

Hi Leo,   I would not mind the addition of a continuity tester to the meter. I agree with TomB about the probe leads. I like the red or yellow color, but suggest considering orange too. I have found the instrument to be quite useful.   F

If I recall correctly C. Moy designed the amp for use with higher impedance phones. Check his article at Headwize library.   F

Yes. I bought two and gave one to my son. They are commonly on sale for $2.99. They work fine, but likely won't do well if dropped. With a multimeter nearby there is always something  to check.   F