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

Consider this: Check the Tangent site-audiologica.com-and read about the CMoy amp. There are building instructions elsewhere also. This is a good introduction to DIY soldering, parts layout and identification, grounding, etc. Set the gain to 3. It is a good amp. Consider buying your parts from...

There is nothing wrong with a CMoy. I use the OPA2227 and like the sound (apparently some others don't). The input capacitors are important if there is any risk of the music  source having or developing high DC offset which will be amplified by the CMoy and damage your headphones. I replaced the...

Spacehead, you are certainly correct about the purpose of th input capaitors. I should have discussed DC offset from the source in my note. F

I bought the Hammond case with plastic end caps. Cutting the holes was not difficult and really mainly require attention to detail. It looks real good to me. I marked the "in" and "out" with a china marking pen on the bottom of the case. AMB's end plates are real pretty. F

On your second CMoy consider replacing the amplifier input capacitors with a 1K ohm resistor for each channel. I did this and the quality of the sound improved noticeably (I am using 32 ohm phones). This was a recommendation from either Pars or Fallen Angel or CFcubed if I recall correctly. F

Will you be selling circuit boards? It would be kind of cool to have your product out there...add it to you CV, etc. F

If you are using low impedance phones and a source of reasonable power output (e.g., computer or portable CD player...) I would suggest a gain of 2 or 3. With a gain of 11 you will barely move the volume control and the audio will be blasting. If the stereo volume control is not perfectly...

Before you remove the damaged component read up about the various smt desoldering techniques. There are tricks to make it possible. There are many sites explaining this. It would probably be wise to use a magnifier also. Go slow. It is a learning experience rather than a disaster. F

Hi, Before making a decision you might want to look at AMB's Mini 3. A complete kit can be purchased from Glass Jar Audio. I built the lower current model; it is the best of my several small amps. F

The Tangent site is fine regarding the CMoy, but remember that you do not have to build it as tightly packed as he does. He intends to fit it in a Altoids tin. Be sure to use an op amp mounting device (?name) so you can change op amps if desired or if you damage one. I used 0.47 uF input...