A few misc. audio projects

Celeron_Phreak · Nov 29, 2005

I posted a thread about the pocket CMOY a little while back, a few people thought it was cool. Well here's what I've accomplished about a month or so later. Enjoy!

Same design as the pocket CMOY, but in a different enclosure to be desk mounted. I also added a toggle switch, which is used to switch between the Z-680's front speaker outputs and the headphone output. It is powered by two 9V batteries, which are easily removable with the Bulgin battery holder drawers.

I built shard one from my old pocket CMOY, which wasn't seeing any use, and it was given to him as a holiday gift. I'm sure he'll post about it himself.

shard · Nov 29, 2005

Well, so far I have been quite impressed, but the only thing I have to complain about is

1) Battery life, seems to only be about 10 hours or so, I see other CMOY's getting a bit more, like 20+, but maybe I am just seeing things

2)There is a feedback hiss somewhere, but it is nothing bad at all, I realy suspect its my source, I am still using onboard, becuase I am poor as dirt right now. Gonna have that fixed soon.

Celeron_Phreak · Nov 29, 2005

Z-680 Analog Cables

Here are the analog mini-mini cables I built for my Z-680's analog inputs. They're all made of Beldon 1192A Star Quad. Each cable is 10 feet in length, and use the gold plated 3.5mm stereo audio jacks from Radio Shack.

This cable runs from the CMOY's speaker output to the 680's control pod.

I built shard some of these cables to, but with the black 1192A. A 6-foot cable to go from his comptuter to the CMOY, and an 18" to go from the CMOY to the speakers. His, however, use the nickle plated connectors (different brand, but the same as the Switch Crafts). One cable uses a nickel plated and a gold plated Radio Shack, because Radio Shack was out of stock of all their 3.5mm minis.

Celeron_Phreak · Nov 29, 2005

Headphone Extension Cord

This is the 1/4" stereo headphone extension cord I made. I use this in conjunction with my headphones while at my school desk, or when I expect to be turning in my chair a lot. It's a 12 foot cord, so it's got plenty of slack. I can turn all the way around in my chair once or twice without it unplugging or causing tension. It uses the nickel plated plugs from Radio Shack. Which again, are similar to the Switch Crafts.

This hangs on the wall behind my monitors to the left, above the CMOY. It's in an easily accessible location.

Celeron_Phreak · Nov 29, 2005

Custom Headphone Stand - Oak & Stained

I built this headphone stand the other day ago. It's been on my list of things to do for awhile now, because I was tired of letting my nice headphones sit on a desk where they were just asking to be damaged. I cut it with my dad's ShopSmith band saw, then setup the main ShopSmith workstation, and converted it into the vertical drill press, and put the drum sanding parts on it so I could clean up the edges and straighten out some of the sides.

I stained it with an "old wood" colored stain, which came out very nicely on the oak wood. I then clear coated it once with some Rust Oleum all purpose gloss clear coat. I will be applying one more layer of it later, while I'm at work some time, just to make it a little deeper.

And a couple shots with the headphones on it. First with low light, then with the fluorescent lights on.

Celeron_Phreak · Nov 29, 2005

PC Audio Center

And here's a few shots of my PC's audio center. I'll start at my least favorite picture, and work my way down to the best. Bear with me.

cetoole · Nov 29, 2005

Wow, very nice work there, I especially like the headphone stand, I really need to get something like that, as I have to sit my Senns down on my desk when not using them, but alas, I have no skill in that kind of work. That stand looks really professional, the only thing that I would do differently is to round the edges a little more, and maybe put some padding where the headphone band sits. 10 hours seems a bit low, my cmoy (single 9v battery), ran much longer than that, are the batteries wired in series or parallel? As it is meant to be a home amp, no reason not to go wall powered simply for convenience, pick up a cheap, surplus linear unregulated wallwart, maybe something around 24vdc output, and use a 78xx regulator airwired in, should give pretty good results, and cost under $5. As for the hiss, what opamp is it, and what is the gain set at?

Celeron_Phreak · Nov 29, 2005

I wanted to keep the "sharp" (not really sharp) edge look to the headphone stand that the rest of my furniture in this room has, so I didn't round the edges to much. I do plan to pad the area where the headphone sits, it's just a matter of finding something decent and good looking to use there.

I was originally going to do a wallwart, but finding a linear AC adapter around here is kinda hard. Getting one off digikey was going to be a wee bit spendy.

Batteries are wired in series. It's pushing out 17.8V

The opamp it uses is the OPA2132PA, and the gain is set to 11.

The Sennheiser HD-280s are 24 ohm headphones, and seem to be a little power hungry.

shard · Nov 29, 2005

cetoole said:
Wow, very nice work there, I especially like the headphone stand, I really need to get something like that, as I have to sit my Senns down on my desk when not using them, but alas, I have no skill in that kind of work. That stand looks really professional, the only thing that I would do differently is to round the edges a little more, and maybe put some padding where the headphone band sits. 10 hours seems a bit low, my cmoy (single 9v battery), ran much longer than that, are the batteries wired in series or parallel? As it is meant to be a home amp, no reason not to go wall powered simply for convenience, pick up a cheap, surplus linear unregulated wallwart, maybe something around 24vdc output, and use a 78xx regulator airwired in, should give pretty good results, and cost under $5. As for the hiss, what opamp is it, and what is the gain set at?

Hmm, with me not having any soldering capabilites right now, I might have to figure something out, or just ship it back to C_P. Could you point where to get one at least?

Celeron_Phreak · Nov 29, 2005

Get one what? Opamp? You can change opamps out easilly, but I don't think we'll notice a tremendous difference with our set of cans. Digikey is where I got ours, and tagnetsoft.net has a list of the ones we can use with this CMOY type. It's easilly removed by slipping a small slotted screwdriver under the existing one and pushing it up.

shard · Nov 29, 2005

Celeron_Phreak said:
Get one what? Opamp? You can change opamps out easilly, but I don't think we'll notice a tremendous difference with our set of cans. Digikey is where I got ours, and tagnetsoft.net has a list of the ones we can use with this CMOY type. It's easilly removed by slipping a small slotted screwdriver under the existing one and pushing it up.

I was refering to a AC adapter, not an opamp, changing out an opamp in a cmoy wont help all that much. If I realy wanted a good change in sound quality, I would get a new amp, as I have been telling you how I want a millet, lol.

ocminimus · Nov 30, 2005

Nice work, great pics! Very impressed

cetoole · Nov 30, 2005

For a cheap, unregulated wallwart, check the surplus stores. Places like Allelectronics, Electronics Goldmine, Jameco, and many others all carry things that are suitable, quite cheap too. As to the opamp not making too much of a difference with your headphones, I bet that it would be quite noticable depending on what you use, it would take some changes to the resistors, but something like an AD8397 would probably be quite nice. Your gain is quite high, even with my 300 ohm HD580, 11 is too high, you will probably want to bring it down, maybe somewhere around 4 would be a better choice. I assume you are using the default Panasonic EVJ pot for volume control, which is much less balanced at low levels. Dropping the gain should also help with hiss some. Keep up the good work.

Celeron_Phreak · Nov 30, 2005

what do you recomend I lower the gain to?

shard · Nov 30, 2005

cetoole said:
For a cheap, unregulated wallwart, check the surplus stores. Places like Allelectronics, Electronics Goldmine, Jameco, and many others all carry things that are suitable, quite cheap too. As to the opamp not making too much of a difference with your headphones, I bet that it would be quite noticable depending on what you use, it would take some changes to the resistors, but something like an AD8397 would probably be quite nice. Your gain is quite high, even with my 300 ohm HD580, 11 is too high, you will probably want to bring it down, maybe somewhere around 4 would be a better choice. I assume you are using the default Panasonic EVJ pot for volume control, which is much less balanced at low levels. Dropping the gain should also help with hiss some. Keep up the good work.

I will keep that in mind. And I will start looking for an AC adapter pretty soon.

cetoole · Dec 1, 2005

Celeron_Phreak said:
what do you recomend I lower the gain to?

Maybe somewhere around 4, what do you have the volume knob set at, probably somewhere around minimum? If you didnt know it, there is a gain resistor value calculator on tangent's site.

shard said:
I will keep that in mind. And I will start looking for an AC adapter pretty soon.

Here are a couple that should do the trick, all depends what voltage you want though, these are both 24vdc. Make sure that the wallwart you use doesnt excede the safe voltage for the caps or opamps, and that its unregulated voltage is high enough above the voltage needed by the regulator (78xx IC, where "xx" is the voltage, so 7824 is a 24v regulator), as there is a voltage drop you must remember and take into account. Something like a switched DC jack would be quite convenient, the wallwart is plugged in, amp runs from wall power, remove the wallwart, amp runs from batteries.
http://www.allelectronics.com/cgi-bin/category.cgi?category=790&item=DCTX-2460&type=store
http://www.goldmine-elec-products.com/prodinfo.asp?number=G15537&variation=&aitem=11&mitem=23

Voodoo Rufus · Dec 1, 2005

Nicely done projects. I like the headphone stand too. Gives me ideas.

Strida · Dec 1, 2005

All very nicely done. Your work is nice and clean... Most of my stuff is a mess b/c I have difficulty totally finishing one project before I start the next, heh.

thegreek · Dec 3, 2005

hey celeron, where did you buy the Star Quad, I heard that's pretty good wire for speakers

Celeron_Phreak · Dec 3, 2005

I buy my cable (and soon to be connectors to) at markertek.com. They ship pretty fast, usually get your stuff in the same week it's ordered if it's before wednesday.

A few misc. audio projects

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