Something very strange with AD8620

[FallenAngel]

Hey guys,

I did a PIMETA a bit ago using AD8620 for L/R & AD8610 for Ground. I had some serious problems with offset using the AD8620 and after tinkering with it, I managed to break the browndog it was sitting on. So I put the AD8620 on the back SMC and voila, problems all gone. Now I want to do some opamp rolling, got myself a couple of AD843s, a AD8066 and a AD8065 and some browndogs. I just like the Analog Devices sound a little over the Burr Brown.

In either case, I put everything on browndogs, slipped in the dual AD843 combo / AD8610, no problems, sounds bassy but maybe fun with DT770's

, tried the AD8066 / AD8065 (listening to TATU right now, actually relaxing), again no problems. Then I put in the AD8620 and WHAM! 7VDC offset and ~70mA current draw. Now that I think about it, it was very similar scenario when I was first building the PIMETA.

Any ideas how other opamps work normally, and the AD8620 works perfectly when it's SMC, but as soon as I put it on a browndog, it goes nuts? Could I really be that lucky that out of the 6 SMC-DIP8 browndog adapters I got, the 2 that I tried with the AD8620 both are screwed, or could it be something else?

Thanks in advance, I would really like to find out what's up since I do like the AD8620/AD8610 sound quite a bit, but still want to enjoy changing it up so I can't be stuck using SMC only.

 

[blueworm]

Must be bad luck or something.
I have two AD8620 on browndogs, one in a pimeta and another in a cmoy, both sound fine.

 

[Sinbios]

Are you sure it was oriented correctly?

 

[NeilR]

I've also been running a Pimeta with 86x0 on browndogs with no problems.

Your board may be haunted

 

[FallenAngel]

It must be just my luck, as for orientation, I'm pretty sure it's acurate, the little nick on the side of the chip is pin 1, just like the AD8610 that I have on the other browndog.

I'll try to redo the soldering on the browndog again, but I took more care with this one than any others since it took some time getting it off the SMC pad to begin with.

Just curious, how dangerous would it be to flip the chip and try it, just in case I am soldering backwards?

 

[ezkcdude]

Since we're already on the subject of this particular op amp, I wanted to throw out a schematic I have for a differential to single-ended I/V stage using AD8620. My question is whether it would be better to use one 8620 or two 8610's. Any thoughts? Also, at what level of current will this chip sound the best, from your experiences?

 

[MASantos]

Are you using the correct browndog adapter?

 

[bhjazz]

Quote:

Originally Posted by ezkcdude Since we're already on the subject of this particular op amp, I wanted to throw out a schematic I have for a differential to single-ended I/V stage using AD8620.

Hey there ez, you may want to start a different thread. While your subject looks interesting, it also looks like a thread hijack. Thanks!

 

[ezkcdude]

Quote:

Originally Posted by bhjazz Hey there ez, you may want to start a different thread. While your subject looks interesting, it also looks like a thread hijack. Thanks!

Done.
http://www6.head-fi.org/forums/showthread.php?t=180381

 

[FallenAngel]

I'm using the "SO8 to 8-pin DIP Adapter (p/n 970601)", just like the one I'm using for the AD8066 which works perfectly, so I'm totally confused as to what's going on.

 

[FallenAngel]

Hey guys, I went back and resoldered this thing a few times on the same browndog with same results, then I switch to a different (my 3rd one and it's the last one I have left) and it's doing the same thing!

I'm thinking the chip might be fried, any ideas if a fried chip would exhibit this behavior?

Thanks

 

[n_maher]

At this point I think it would be helpful if you posted pictures so we can see what's going on. You never know what we might spot.

Nate

 

[FallenAngel]

Uhm... It's an AD8620AR on a browndog

Pretty much self explanitory. The amps (tried in CMOY and Pimeta) work with AD8066 and other dual opamps, but this AD8620 just doesn't want to work. It gives full V+ / V- values straight to the headphones.

 

[The Monkey]

Quote:

Originally Posted by FallenAngel Uhm... It's an AD8620AR on a browndog Pretty much self explanitory.

Not really. We need to see your work. If you want as much help as possible just post the pic.

Quote:

Originally Posted by NeilR Your board may be haunted

Lol, see my profile. I've had a similar problem to FallenAngel.

 

[n_maher]

Quote:

Originally Posted by FallenAngel Uhm... It's an AD8620AR on a browndog Pretty much self explanitory.

Clearly something is going on that you aren't seeing with the 8620 and the adapter, I offered to help - if you don't want it I don't know what else to tell you other than to try another opamp. If it were me I'd buy a premounted one from Browndog.