[grahamndodder]

The good news:

My first DIY'd CMoy guts, sans volume control, gave me recognizable sound the first time I hooked it up! (Woooo-Hooooo! Release the Hounds!) I did it with jumpers just like Tangent said, just like a nice, obedient noobie DIY'er.

The (possibly) bad news:

The sound was a tad "scratchy" at times. The vanity in me put it down to the jumper cable connections thru the whole input/output chain. The right and left channel, for instance, were awwwwfully close with my cables on the mini jacks. I checked all of my voltages and resistances, which all seemed nominal, BTW. Nothing is smokin' either, which is always nice.

Is this likely what it is? Is it likely something else? Is there anything I should check for, or just solder up my I/O jacks and the pot and listen for it then?


Please be gentle....


GnD

 

[averydonovan]

All I can suggest is to check and re-check all your solder connections. Check with your multimeter that nothing is shorted that shouldn't be. Other than using wrong values for the resistors, that was one of the things that bit me when I built my first CMOY.

And congrats on getting your first CMOY to work the first time, even if it could use a little debugging

 

[jeffreyj]

Quote:

Originally posted by grahamndodder .... The sound was a tad "scratchy" at times. The vanity in me put it down to the jumper cable connections thru the whole input/output chain. The right and left channel, for instance, were awwwwfully close with my cables on the mini jacks. I checked all of my voltages and resistances, which all seemed nominal, BTW. Nothing is smokin' either, which is always nice. ...

First a few questions:

1. Does the scratchiness correlate with anything else (i.e. - cable movement, a particular loudness level or frequency)?

2. If you are running the op-amps in the Non-Inverting configuration, is there a 10k to 100k or so resistor directly from the (+) input to ground?

3. Have you tried at least two sources and at least two pairs of headphones to make sure that it is the amp at fault?

Good luck!

edited: added some examples to Q1.

 

[grahamndodder]

I will try your suggestions. They make sense. I am gonna go ahead and solder the in's and out's to minijacks, which will negate most of the jumpers. The jumper-to-miniplug connection seemed to be the one most likely to be causing the scratching, anyway.

I got the wood for the case today. Gonna be solid red oak, laminated into a butcher-block stack. Cost me $10, perfectly aligned cuts and all, at a local (Baltimore) hardwood supply shop.

Thanks - will try and get back to you.

GnD

 

[Squalish]

Quote:

Originally posted by grahamndodder I got the wood for the case today. Gonna be solid red oak, laminated into a butcher-block stack. Cost me $10, perfectly aligned cuts and all, at a local (Baltimore) hardwood supply shop.

Sounds interesting. Mind telling us which shop, and if this is a common service?

 

[grahamndodder]

Tidewater Hardwoods, right near BWI Airport.

They have all kinds of hardwoods there. The stuff is expensive, but we use so little of the stuff, it is next to nothing.

I thought about a solid block of knurled mahogany, drilled out to form a thin-walled cavity from the bottom, then flipped over with little rubber feet to look like the beautiful, solid block of wood that it is.

To get there, BTW, take 95 (or 295) to Rt 100 east. Go north on Rt 170 a mile or so after the Arundel Mills Mall.

Take a left at 176 (first stop light), then an immediate left winding past 84 Lumber on the left and follow the signs to Tidewater, which is on the left and office is in very back. Ask for Jeremy.

The possibilities for creating an amp that looks better than those $500+ commercial jobbies are endless. If you know the cuts you want, they will make them for you right there.

You local to BWI?

GnD

 

[Squalish]

Not really local, but not far. I'm in rockville.