[Hifihedgehog]

I want to make a CMOY, but from doing my homework, if I use the generic design by Tangent, I will run into problems if I ever upgrade my amp or use Grados, which I will be getting soon. Is there any visual help to remedy the incompatibility issues, aside from schematics such as these:

http://tangentsoft.net/audio/bitmaps/hs-opamp-schem.png
http://tangentsoft.net/elec/bitmaps/...ds/cfb-opa.png

I'll be very thankful if someone could add a visual help, like Tangent has for the basic design. I'm doing this for the Electronics merit badge in Boy Scouts and want to use this to boost the quality of my current Senn HD-201s. I want to later purchase an AD8620 to swap in place of a OPA2132PA. I'll be off air for a few days because of Christmas break, but I'll try to post ASAP Dec. 26 or 27. If anyone can play genius and get something done by 3 PM eastern time, I will greatly appreciate it.

 

[Hifihedgehog]

If someone help me reading them, I would take that as well. The 2nd schematic show overlap by the circuit near R3. No connection would occur there because there isn't "a period" where the circuit overlaps, correct? A visual help, even quick and dirty, would help. I am using the Radioshack protoboard, 276-0150, and the design by Tangent.

 

[Bjornboy81]

Upgrade your amp? I guess I don't understand what you mean.

Why would you run into problems when going with Grado's? I'm using the OP2227 chip with SR-80's and it sounds and performs great!

 

[Bjornboy81]

Quote:

Originally Posted by Sonichedgehog360 /img/forum/go_quote.gif If someone help me reading them, I would take that as well. The 2nd schematic show overlap by the circuit near R3. No connection would occur there because there isn't "a period" where the circuit overlaps, correct?

You are correct. Where R3 and R4 connect, that goes straigh to the (-) inverting input.

It's called a connection dot.

 

[Hifihedgehog]

Did you use Tangent's basic design and were able to put a OP2227 chip straight in there? This is what I found on the net:
http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf
http://tangentsoft.net/audio/cmoy-tu...ayout-0150.pdf

I am not making my own layout because I new to electronics, in the advanced sense. I made am radio a while back from a kit, but this is the first real solo project.

 

[Hifihedgehog]

Thanks. The Boy Scout manual is very vague and undetailed. I did better reading online.

 

[Hifihedgehog]

BTW, though, I still need help. Can I just use the generic schematic and upgrade or do I need to use the designs found in my first post? If I need to use those designs, could you or someone help me setting up the board? Thanks.

 

[Bjornboy81]

I actually bought the board from a fellow Head-fier. It's the same principle except tangent doesn't have a TLE2426 in the ground circuit. It's another way of creating the virtual ground. Either way, i'll work with the OPA2227.

 

[Bjornboy81]

Quote:

Originally Posted by Sonichedgehog360 /img/forum/go_quote.gif BTW, though, I still need help. Can I just use the generic schematic and upgrade or do I need to use the designs found in my first post? If I need to use those designs, could you or someone help me setting up the board? Thanks.

I'd stick with the second set of links you have there...that's a good start for a beginner.

 

[MASantos]

You could use two dual opamps and ue the second as a current stage as in the A47, or add a pair of BUF634 to increase the output current and drive those grados better.

Gis us some more info about what you need. Does it need to be portable? What's the average usage? With a couple of bucks in parts you can build a battery charge circuit and save batteries(both the cash and the environment)

 

[Hifihedgehog]

Sorry to be annoying and repetitive, but how does a OPA227 compare to a OPA132? Will just doing the basic project by Tangent with a OPA132 sound just as good as yours or a AD8620. Can I just use Tangent's basic design: http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf

Can I expect to be able to be satisfied with the quality? I am actually planning on getting the sr80s, so the phones will be sound better than my current unamped set-up on their own.

Lastly, can I use Tangent's easy virtual ground design and expect it to work with other op-amps? Thanks and sorry to ask so much all over again.

 

[Hifihedgehog]

Oh, the design is going to be portable. Refer to Tangent's basic design:
Assembling the Amplifier

He does a better job of explaining than a newbie like me can.

I know I am unexperienced, but want my first pocket amp to have ungradablity capability to possibly the AD8620. Thanks. I have to get offline. It is my lunch now. I be back in an hour or so.

 

[intoflatlines]

One of the links you already posted is the one that I used the most when I made mine a few days ago:

http://tangentsoft.net/audio/cmoy-tu...ayout-0150.pdf

I put a DIP socket in so that I could swap out op amps and try new ones whenever I feel like it. It also helps so that you don't risk damaging the op amp by soldering things and hooking stuff up while it's on the board.

 

[intoflatlines]

BTW if this is a Boy Scout project you would probably be best off just making the Cmoy kind of verbatim, and then later on after you have the time to do more research you can build a better one. That's what I plan to do.

I made my first Cmoy earlier this week and the only thing that I made different from the basic plans is I added an R5 to quiet noise and I used a different gain so it would work better with my IEMs and my Grados that I will (hopefully) be getting soon that are 32 ohms. This weekend, I will probably add a 1/4" output to go along with the 1/8" one, but I will most likely hold off on doing anything else, since I have parts for a couple more, and I know I will do a better job the second time around. Plus, the work of doing a bunch of things on the board once it's done will probably cause me to mess it up.

Just follow the instructions exactly on his assembly page, and open up the PDF and enlarged pictures in new windows so you can switch back and forth. You should do fine.

 

[sohels]

As for your question about opamp 2132 and 2227, here's a good comparison-

Op-Amp review page

I use the 2227 since the 2132 has a warmer sound (as per several reviews that I came across) which means it colors the sound a bit. Also, I use my cmoy with dt770/80 so i do not need it to be more bassy or warm. If you plan to use it with Grado, 2132 might be a better bet.

Also, if you plan to use input capacitance, then make sure its at least 1uF caps. I think the original design uses 0.1uF but this will affect bass response a bit. With 1uF, there is no distortion even at relatively higher volumes.