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I've built my first cmoy! (but I still need some help)

post #1 of 3
Thread Starter 
Well, I finally got my package from mouser last friday (see thread in general forum for details) and built my first amp this weekend. I followed the cmoy/hansen schematic except for the following:

- Power supply is a 12V 800mA regulated/filtered ac adapter instead of battery(s).

- 1uF caps instead of .1uF caps for the input.

- One level of Jan's natural crossfeed instead of two levels of enhanced bass crossfeed. (I used the 2.2K/.22uF combination, not sure if that is the low, medium, or high setting, anyone know? Jan?)

- I have the gain of the OPA132's set to 6 instead of 11.

- I used Buf634's instead of OPA132's for the output stage.

Amazingly enough, it worked without a hitch (thanks to cmoy and all of you for the many great schematics!) I built it in a 5x5x1.5 Pactec modem-style case and it looks very nice indeed. Sounds great too.

Here are my poor newbie questions:

1. When I switch between crossfeed and bypass I hear a click, whereas I don't hear such a click on the Corda amp I have. Is that what the 2.2K/.22uF in parallel with the bypass/crossfeed circuit are for (from the Corda schematic)?

2. I used Buf634's because I had remembered reading at headwize that they could output more current and were better than the unity gain OPA132 for driving headphones. Is that true or am I way off base here?

3. Is the 800mA 12V adapter sufficient to power this amp? For the same price ($15) I could exchange it for an 18V/24V non-regulated one.

4. Which bandwidth mode should I use for the Buf634's? I have them in low bandwidth mode for now, since I figured it's easier to solder another two wires on than to remove them.

Thanks in advance!

--
Scott
post #2 of 3

 Seems like you have a good setup, 12v is enough but a lot of people use  15v or 18v. Personally i make all my portables 9v-12v using 3.7v li-po and boost regulator. I cant comment on the crossfeed as i don't use one.

Quote:
Originally Posted by slindeman View Post

Well, I finally got my package from mouser last friday (see thread in general forum for details) and built my first amp this weekend. I followed the cmoy/hansen schematic except for the following:

- Power supply is a 12V 800mA regulated/filtered ac adapter instead of battery(s).

- 1uF caps instead of .1uF caps for the input.

- One level of Jan's natural crossfeed instead of two levels of enhanced bass crossfeed. (I used the 2.2K/.22uF combination, not sure if that is the low, medium, or high setting, anyone know? Jan?)

- I have the gain of the OPA132's set to 6 instead of 11.

- I used Buf634's instead of OPA132's for the output stage.

Amazingly enough, it worked without a hitch (thanks to cmoy and all of you for the many great schematics!) I built it in a 5x5x1.5 Pactec modem-style case and it looks very nice indeed. Sounds great too.

Here are my poor newbie questions:

1. When I switch between crossfeed and bypass I hear a click, whereas I don't hear such a click on the Corda amp I have. Is that what the 2.2K/.22uF in parallel with the bypass/crossfeed circuit are for (from the Corda schematic)?

2. I used Buf634's because I had remembered reading at headwize that they could output more current and were better than the unity gain OPA132 for driving headphones. Is that true or am I way off base here?

3. Is the 800mA 12V adapter sufficient to power this amp? For the same price ($15) I could exchange it for an 18V/24V non-regulated one. 
4. Which bandwidth mode should I use for the Buf634's? I have them in low bandwidth mode for now, since I figured it's easier to solder another two wires on than to remove them.

Thanks in advance!

--
Scott
post #3 of 3
LOL... bumping a 12 year old thread. Scott (the OP) made my first Millet hybrid some 7+ years ago at least, (some time after completing this cmoy.) Anyhow, Thanks Scott (wherever you are) the Millet still runs great and I use it all the time.
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