[skippy]

you can hot glue the LED's in. it looks nice if you do it neatly.

 

[Possum]

Oh, stupid me! I tried to hot glue the LED of my first cmoy/Hansen from the front (too lazy to open the case up again) and of course it looked kind of messy in the end

Lenses eh?

 

[nick danger]

Thanks for the wal-wart suggestion. I found a 24V 1.2 Amp power supply and it works very well. Found it at a ham-fest for three bucks. Completed my first project - hooray! I really like the amp with crossfeed. The cmoy does seem to be more solid sounding and with more detailed treble than my trusty old yamaha integrated amp. But the cmoy is not as open sounding as the Yamaha even with the crosfeed off. Hard to evaluate since I haven't turned on the Yamaha for a week. Hmmm....does this tell the whole story?

 

[mlloyd1]

Hi:

I've seen a number of posts mentioning a preference for the AD823 over the AD744. I am curious to know if any of you have tried using the AD744 by bypassing its output stage and directly driving a buffer, say an AD811 video speed CFA. I use this as a line stage as well as a headphone amp for my Beyer DT990 and I like it a lot!

The AD744 is unique in that the output signal that goes to the class B output stage is available at the compensation pin (5)! This allows you to bypass any nonlinearities provided by the decidely undepowered output stage. This concept appeared in some AD literature authored by Walt Jung some years back.

I have also seen a line stage using the AD823 with the AD815 as a buffer. Haven't built it yet, but its on the list.

 

[ppl]

The very First Portable Headphone amp i made used the AD-744 in the Method you Discribed. The Comp pin driving the Buffer. I have posted this several times. The Difference between using the AD-744's normal output and using the Comp as an output is like Night and day. Search my early posts for more info. As far as using CFB type of Opamps as Buffers? Well Everyone dose this But this and those DSL drivers whitch are also nothing more than High Current CFB type OPA's also are not what i like to use for an output stage since thay have to use Neg. feed back and thus can be unstable with Certin loads> SO once again I LIKE OPEN LOOP BUFFERS....... I LIKE OPEN LOOP BUFFERS>>>> ect....ect ect..

 

[Possum]

Apheared, is the shaft of the Noble pot short by design, or did you hacksaw it to a shorter length? The shafts on my alps pots end up making my knobs stick out ~1/2" too far from the panel.

 

[eric343]

Now someone has to design a PCB for the amp... Then I'll build it. (my experiences with my Cmoy were bad enough... had to do a total rebuild)

 

[Possum]

If you made a cmoy on your own board, making this amp is almost as easy - just a few changes in part number/values and the addition of VERY few parts.

 

[thomas]

i think the whole appeal of DIY is being able to customize everything to your exact tastes, and getting to play around with different designs... And its almost impossible to make large modifications to a circuit based on a PCB. So i think you should really try and work with blank boards, it'll give you much more flexibility...

Do a total rebuild. Do it 10 times... eventually, you'll get good at it... eventually, you'll turn into apheared!

 

[source direct]

Maybe I'm too green in the DIY area, (that may not sound right but you know what I mean, anyway) but from my reading I cannot tell what the difference is between the cmoy that uses the OPA134 and apheard's "cmoy slayer" the 47 (? I think ?), other than the op-amps that each amp uses. Would anyone care to break it down for me?

Earlier today I was able to assembe the cmoy, except I used this other opamp that I had laying around instead of the OPA134, I used the National Semiconductor LM6182IN. I haven't gotten a chance to see if it works yet because I couldn't find the right input and output jacks at the local radioshack, so I'll find em tomorrow. What kind of modifications would I need to do inorder for what I currectly have assembled to be considered an amplifier of Apheard's design? By the way I still have it assembled in my breadboard.

Any guidance would be greatly apprecieated, thanks.

 

[thomas]

source direct-

The basic cmoy and the 47 amp both use the same opamps, the OPA134. In the basic CMOY, there is a single opamp per channel which gives both voltage and current gain.

But for low impedence headphones, a single opamp will not be able to supply enough current, hence the apheared 47 mod. In that design, he paralleled two opamps to double the current output, allowing you do drive low impedence (Grado) headphones better.

In this design (the HD-600 amp), he has changed the opamp to the AD823. To get enough current, he added a second amp stage, using a unity gain buffer (EL2001). Now, the opamp is used only for voltage gain, the buffer only for current gain.

For more about how these designs work, look at C. MOY's Designing opmp hased headphone amps article at headwize

 

[eric343]

Quote:

Originally posted by thomas Do it 10 times... eventually, you'll get good at it... eventually, you'll turn into apheared!

Ummm, this a good thing?

I prefer my teeth white thank you

 

[source direct]

thomas, thank you, that was exactly what I needed.

On another note, regarding the switches in my cmoy:

on the back of the switch I have, there are about six posts, three stacked on the left and three stacked on the right. The switch is supposed to go inbetween R1 and C1, and if that's not descriptive enough, then I'll try another way. The switch goes between the very first resistor from the input, and the capacitor, which is in series with the first resistor ( I think ...).

Now that we know about the switch, my question remains, and that is how am I supposed to hook up the switch? There are six posts on the back of the switch, which do I attach to what?

Sorry if this is remedial/lame. Thanks.

 

[Apheared]

eric, well, you don't have to have nicotine/coffee stained choppers, but its definately a side-effect... you do have to put yer butt into a chair and a soldering iron into your hand and a collection of books up your nose... for hours a day, everyday (or at least every week). I've got 1000 hours in this, easy. And a few thousand dollars over the last year or so. You'll drink and smoke... heh.

Thomas is correct... do it, over and over and over and over and over... I mean I've made stuff I'd never show online... some things cool (some things lethal/illegal)

, somethings that didn't work the first 22 times but worked perfectly the 23rd. It's all about exposure.

Thomas started HW around "the beginning" last year... he's "watched" me go thru all the BS like some of the others. From total newbie to being quite Apheared. I still don't get 1/1000th of what there is to comprehend, but hey... it's fun.

There will not be a PCB for this, heheah.. anyone that wants one can etch it themselves. Same reason there's no schematic... if you can't figure it out from the EXTREMELY WORDY initial description, you probably don't want to build it... just stick to opamp swapping on hansen boards.

I'm gonna lock this thread, it's all over the freakin place and gettin long.... any conversations in-progress please create new threads.