[dhaninugraha]

hi guys

last night I built myself a CMoy. I used a TLE2426 to split the power supply, with a 470uF cap in front the TLE going rail-to-rail. resistors are all generic 1/4W 1% metal film. volume pot is a vintage ALPS 10K stereo pot. all audio input/output connections are hooked up using Canare L4E6S cables.

however when I hooked up the power source (tried both 2x 9v batteries and a 19v wallwart), my iPod, and my MS1i to the CMoy, sound came from both channels, except that it sounds kinda thin, honky, and hollow... the instruments sound more prominent, and the vocals sound recessed and echoing.

I've swapped between AD825 and ADA4627-1 (those are all I have now), both still giving the same result.
board has been cleaned thoroughly with isopropyl alcohol, and solder joints inspected... no cold joints or bridges.

I tried adding a couple of 1000uF capacitors after the TLE, going rail-to-ground, also to no avail.

voltage measured from the V+ to V- of each opamp socket are 19-something V (my batteries are very fresh and the wallwart is properly functioning), and when measured from V+ / V- to ground, it reads ~9.5V, which means the power supply section is OK (ie. rail splitting works perfectly).

sorry for not being to provide pictures ATM, my camera is being loaned to my auntie. will provide pictures as soon as the camera returns.


what could be the cause of this strange behavior?
I thank you guys for any enlightment given

 

[TzeYang]

how loud are you listening to?

This is a common issue when the poor TLE2426 is asked to sink high amounts of current from the load.

 

[dhaninugraha]

not so loud, as with gain of 11 and 32ohms on my MS1i, I only needed a slight turn on the volume pot to make it sound stupidly loud. but no matter at what volume level, even at very low volume, it just sounds like that, echoing strangely...

 

[diditmyself]

Are you sure pot and jacks are wired properly? Forgot to ground any of them?

 

[dhaninugraha]

yes, I am very sure the I/O jacks and volume pot have been properly wired and grounded, I'm looking at the board as I type.

so is this most likely to be a grounding issue? or the TLE being overloaded?

 

[the_equalizer]

Been there, done that. You need to put two 470uF electrolityics after the TLE from each power rail to the virtual ground.

EDIT: That's what I get for not reading your whole post. Strange that with two caps after the TLE it still doesn't work.. Though my experience was with an OPA2134 not with the AD chips...


cheers!

 

[diditmyself]

It has to be a grounding issue, something that isn't hooked up to ground as it should be. I hope you get your camera back soon.

It's not a matter of the TLE being insufficient, and IME when a TLE2426 fails, it doesn't split the rails equally. You don't need anything "after" the TLE2426 but some smallish electrolytics and the obligatory decoupling caps as close to the opamps power pins as possible.

 

[sam_cat]

Is the volume pot known good?
Do you have a pair of suitable resistors you could try in its place (just to rule it out)?

Sam

 

[shake]

Quote:

Originally Posted by diditmyself /img/forum/go_quote.gif It has to be a grounding issue, something that isn't hooked up to ground as it should be. I hope you get your camera back soon. It's not a matter of the TLE being insufficient, and IME when a TLE2426 fails, it doesn't split the rails equally. You don't need anything "after" the TLE2426 but some smallish electrolytics and the obligatory decoupling caps as close to the opamps power pins as possible.

+1 for grounding issue. Go through and follow a signal through the amp. It could be something as small as a stray strand of copper somewhere on the pcb or on the pot, or it could be you have your input/output traces shorted somewhere.

 

[dhaninugraha]

I finally got the CMoy to work.

you see, I was using the Neutrik NMJ6HCD2 headphone jack which has 6 solder lugs (2 sets of tip, ring, sleeve lugs, 3 lugs facing 3 lugs), and I soldered the ground wire to one side and the L/R wires to the lugs on the other side.
when I resoldered the ground wire to the same side as the L/R wires, it worked like a charm.

thanks for chiming in guys, you've been a great help...
had you all not said "grounding problem", maybe I wouldn't realize that small mistake I made...


and BTW, the ADA4627-1 sounds REALLY nice