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my CMOY :) (getting there) - Page 3

post #31 of 60
Thread Starter 
Hi Tangent,

Quote:
It's only 22ga, but yes, you can probably go quite a bit thinner. You might even be able to get away with 30ga wire-wrap wire, but I wouldn't want to try to work with it. I actually wanted to use 24ga wire, but the local Radio Shack didn't have any that thin.
Is there any disadvantage with really really thin wire if its only 4.5/9v? I think my wire is thinner than 30 gauge. I can fit 2 wires into the one hole and still have some gap left.

For my next cmoy I might use cat 5e/6 cable
24awg solid core.
post #32 of 60
Quote:
Is there any disadvantage with really really thin wire if its only 4.5/9v? I think my wire is thinner than 30 gauge. I can fit 2 wires into the one hole and still have some gap left.
Do you mean 2 wires with insulation, or without? If the latter, you probably have 26 gage wire. For reference, standard component leads are 24ga, and I can stuff 2 component leads into the perfboards I use with a bit of difficulty. 26 should allow a pair to go in easily.

30ga wire is really small. You can break a foot-long length of it easily by grabbing the ends tightly and tugging. (You might cut your fingers, though!)

As for whether 30ga is too small, one foot of 1 mil copper wire (50ga -- 1/1000 of an inch) has about 1 ohm of resistance. Therefore, the short lengths you're going to use for this project -- 4 inches maximum, likely -- in 26 ga (~15 mil) will have very small resistances. Consider the traces on the perfboard -- imagine rolling those thin traces up into a solid round wire. They're probably on the order of 28-30ga.

As for amps, I have no numbers to quote. I wouldn't try it, if only for workability reasons.
post #33 of 60
Thread Starter 
Hi Tangent,

You the man !!
You explain things so clearly and precisely and is so easy to understand

The wiring is pretty short, I tried to keep it as short as possible but using two 134 opamps has probably more wiring than it should with one 2134 opamp.

I will definetely be using thicker wire for my next amp.

Thanks Tangent !!
post #34 of 60
Thread Starter 


Bloody hell !!@!@!@!@!@!@!#!@$#!@$@!~

My cmoy is a total failure and I dont know what's wrong with it
there is sound but very muffled

it sounds like something is shorted somewhere. I wasted the whole day trying to find out where without any luck.

The power supply Im pretty sure works and the earth.

Can any one please suggest a place to look for faults?
Im not really sure what Im looking for.

So pissed I feel like shelling out $$$ for the porta corda...
post #35 of 60
Quote:
My cmoy is a total failure and I dont know what's wrong with it there is sound but very muffled
By "muffled" do you mean that, with studio music you can hear only the ambience -- the echoes of the sound bouncing off the walls and back to the mics, but not the sound going directly from the acoustic instruments and voices into the mics? If that's it, you probably have a ground fault -- you're getting phase cancellations, leaving only the ambience. If the amp sounds okay for a bit after applying power before going muffled, your ground fault is through a high resistance. Otherwise, you have a 0-ohm (or near-to) ground fault.

Here's what you need to check: first, if you have a metal case, check the resistance between your signal ground and the case; it should be infinite, unless you've chosen to tie your signal ground to case ground. You should only do that step once the amp is working and you can hear some ground loop hum, perhaps when touching a switch on the amp.

Second, check for ground faults within your input and output jacks. Careless soldering can often melt the plastic keeping the metal parts from touching inside the jacks. You may need to desolder the jacks to test them, so that you're not incidentally testing paths through the circuit from one channel back to the ground, leading you to falsely believe you have a ground fault.

Failing that, disconnect any grounded components one by one, starting with the headphone output. (Obviously this doesn't apply to the power or signal circuit resistors!) This makes testing harder, of course. In the case of the input and output jacks, you have to use aligator jumpers to hook your source or your headphones into the circuit. For headphones the plug tip is the left channel, the "ring" in the middle is the right channel, and the "sleeve" going the rest of the length down the plug is the ground. (You occasionally see these type of plugs called TRS plugs -- tip-ring-sleeve.)

In general, simplify, simplify, simplify. This is why I recommend building a cmoy amp in testable sections: build the power supply, test it, build the basic signal circuit with no jacks, switch, or pot in the circuit, test that with a volume-controlled source, then add an input jack and test it, then add the output jack and test, then add the pot and test with a line-level source, and finally add the power and (if needed) crossover switches and test yet some more. This ensures that if you break something, you definitely know what you didn't break.

Don't give up. I have faith that you will be able to fix it. I have built four of these, and only one so far has been built without much trouble. The other three had ground faults of various flavors, each taking a few hours to a day to chase down and squish. Fortunately, this circuit seems relatively forgiving of hookup problems: I haven't yet killed a component, aside from one cheap headpone jack I fatally melted with my iron. In all other cases, I eventually got the circuit working with the original parts.

These problems are frustrating, labor intensive and demoralizing, but beatable. You can do it.
post #36 of 60
Thread Starter 
Hi Tangent,

Thanks for the reply.

Quote:
If the amp sounds okay for a bit after applying power before going muffled, your ground fault is through a high resistance. Otherwise, you have a 0-ohm (or near-to) ground fault.
Is near 0-ohm bad? I measured it and its very close to 0 from -ve to +ve rail and from -/+ rail to ground. Is this bad? What would cause this? Only thing I've changed is to go with a gain of 6 rather than 11.

The muffled sound is like listening to music trough a cave, then when I turn up the volume, it starts to clip badly at least I think its clipping, it starts to sound harsh and distorts very badly. At low volume its cleaner but still distorted. For some reason I didnt connect the earth from the rca plugs and there's still sound??
Does this mean I melted the plastic? sigh

The sound on the right channel is dominant over the other channel and its kinda mono as I can hear the right channel on the left (i cant find the problem)

The jacks I tested it with a multimeter with continuity and resistance but it wasnt connecting though.

I'll debug it on the weekend I hope I find the prob hehe

Thanks dude
post #37 of 60
good luck debugging man. finishing something and then it don't work sucks..

I'm torn between rebuilding and just getting a PortaCorda myself, specially since rebuilding will take a lot of extra cash. and it's looking like the Porta is a lot better..
post #38 of 60
Thread Starter 
Same Im thinking about the Porta Corda too. It looks pretty nice
I might go with the low level crossfeed.

My motto is never say die so Im gonna keep trying but in the meantime Porta Corda

How much would it cost you to rebuild your cmoy compared to a Porta Corda?

Just curious.
post #39 of 60

non working prototype

Hello, CTN and others

My twin brother and I was also struck by bad luck and failure.
Our own first three prototypes did not work properly and even worse the last one destroyed one pair of headphones.

What headphones do you guys use to test, I still very scared to put in my K 501's anywhere. The headphones we destroyed was SAMSON RH600 which although being very uncomfortable sounded reasonable. I have not as yet heard my K 501's because I want a decent headphone amplifier first.

The SAMSON's costs around $ 69. The left channel was taken out. My brother says his ear even started to get warm. We were using two 12V 7 Ah lead acid batteries at the time.

With these batteries a short circuits produces a spectacular array of sparks and leaves behind black burns of damage.

Gavin
post #40 of 60

little off topic

Quote:
Originally posted by Braver
No RS here. there is a electronics store in Utrecht (30 minutes from here) but they only seem to carry $40+ soldering stations...a bit overkill for me.
marktplaats Just check a few times a week. Got my weller wtcp-s with 0,5KG of solder from there for 100 guilders
The new ebay.nl sucks, I guess dutch folk aren't ready for high quality only auctions just yet.

Quote:
I bet I was doing something wrong with the iron as the tip would get black after a while and the only way to get that off again was to use sandpaper. also the solder seemed to slowly burn into the iron or something....
Yeah, you did something wrong!! There is a small protective layer on your tip. When you use sandpaper on it, you damage it and the tip effectively is useless!
post #41 of 60
Thread Starter 
Hi gavinbirss,

For testing I used some cheap ass 2 dollar phones well less than a buck in US dollars
No way Im plugging in my Senns till I know it works hehe

Holy cow !! 12V 7 Ah lead acid batteries ?? Can you use those??
Im new to this my self.
For testing, it might be a good idea to use a single 9v batt.

ouchie, did you end up with a working amp at the end?
What kind of problems did you encounter?

Maybe we can help each other
post #42 of 60
Hello CTn

The 12 V 7Ah batteries actually work very well. The are not cheap but I estimate that the play time versus cost when compared to 9V PPP (replaced when low) is greater.

I recommend using these batteries. Even with a gain 4.67 (with a double output current 2604) one 12V through a pseudo ground driving buffer (BUF634T) these is plenty of power to drive a 32 ohm headphone.

One 12 V 7Ah lead acid battery weighs approx 2.69 Kgs so they are almost portable. (not light !)

The amp also works but a mistake my brother and I made was that our ouput jack only gave us one channel and we also mistakenly reversed our -V and +V and as a result blew two 2132 opamps.

Do yourself a favour and double check your +V and -V espcially if you use more that 9V and high current capable batteries.

What gain are you guys using.

Happy listening.

Gavin
post #43 of 60
Thread Starter 
Hi Gavinbirss,

My gain is about 5-6. Forgot exactely but doesnt matter since the amp dont work hehe.

It looks like im going with the porta corda + hd580 combo.
post #44 of 60
Sorry for the delay in getting back to you, Ctn. My Internet connection was down since Monday. I just now got back online (Wednesday night). I'uz goin' inta withdrawals, I was!

Quote:
I measured it and its very close to 0 from -ve to +ve rail and from -/+ rail to ground. Is this bad?
These aren't a problem. You're measuring through the power supply's ground resistors -- in other words, you should expect some continuity between the + and - sides of your power supply.

Quote:
The muffled sound is like listening to music trough a cave, then when I turn up the volume, it starts to clip badly at least I think its clipping, it starts to sound harsh and distorts very badly. At low volume its cleaner but still distorted.
Sounds like a ground fault to me. Now you just have to find it!

Quote:
For some reason I didnt connect the earth from the rca plugs and there's still sound??
From each RCA plug, you'll have two connections: the pin and the shield. The pin should go to the opamp's noninverting input, and the shield should go to your ground. If you have a metal case, you must use either insulated RCA plugs (i.e. they have a plastic ring that touches the hole through the case) or you have to insulate it yourself. If you have a plastic case, you can use any type of RCA plugs.
post #45 of 60
Thread Starter 
Quote:
Sorry for the delay in getting back to you, Ctn. My Internet connection was down since Monday. I just now got back online (Wednesday night). I'uz goin' inta withdrawals, I was!
Ack me too just got back from a 3 day conference

Quote:
Sounds like a ground fault to me. Now you just have to find it!
Any ideas where it could be I dont have a clue.

Quote:
From each RCA plug, you'll have two connections: the pin and the shield. The pin should go to the opamp's noninverting input, and the shield should go to your ground. If you have a metal case, you must use either insulated RCA plugs (i.e. they have a plastic ring that touches the hole through the case) or you have to insulate it yourself. If you have a plastic case, you can use any type of RCA plugs.
Ive got a wooden case with insulated RCA plugs. Does this count?
Do I connect all the grounds including the resistor grounds to the same place?
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