24v PSU w/ AD8620 - any potential problems?

[Duncan]

Hi...

Reading the spec sheet for the AD8620, I see that its maximum input voltage is 13v per rail, I bought a new 24v regulated PSU today, and knowing squat about electronics am hoping that this is not likely to fry the chip...

I know that the OPA627 has a higher tolerance, so - if you guys think that this PSU will blow the AD8620 - i'll drop in the Burr Browns instead...

...and, I can't return it now... I had to cut off the original connector, as it wasn't the right size

 

[Pars]

I'm running a MINT with an AD8620 with a +/- 12V Elpac with no apparent problems. When I was converting the MINT over to AC from its initial DC power, I did lose a channel on the original AD8620. I ordered several cheaper opamps along with a replacement AD8620, and since replacing the OPA2134 / OPA2227s that I tried fro a bit with the AD8620, I haven't had any problems with it running that close to the manuf. spec.

Chris

 

[PinkFloyd]

Measure the voltage from the PSU, if it's 24V then you will have no problems whatsoever as that will supply 12V per rail.

Be sure also to check the polarity as, in some amps, reversed polarity can be the death of opamps.

Mike.

 

[Duncan]

Thanks guys, checking it out with a voltimeter, it shows a rock steady 24v... so i guess all is good there...

Must do a better job on the soldering though

 

[StevieDvd]

One of my amps is the Headsave Classic fitted with an AD8620 for which Norm recommends a 24v PSU (better than 12v per Norm).

As Pinkfloyd will confirm I've been having fun with PSUs here in the UK. Norm recommended a Mascot 24v which is (deep breath) a Linear Regulated PSU which you can only get at RS components and which sets you back nearly £31 including delivery, vat etc (breathe again).

I soldered on a new 2.1mm tip at first as I was intending using the PSU with my other amp (WNA courtesy of Pinkfloyd talents) but the WNA does not like it.

So I then ended up soldering a 2.5mm tip for the Headsave to use it again.

Why the WNA does not like the Mascot I've yet to work out. Must be something to do with Linear versus Switched, most PSUs are switched apparently!

By the way, what are you using the AD8620 in?

Steve

 

[Duncan]

Wow... StevieDvd...

You live where in the same town as I work.. maybe we can meet up sometime for a geeky conversation about all this kind of stuff

...and as to the AD8620, its in a META42

 

[StevieDvd]

Don't tell me you live in London!

I live in Stevenage but work in the City of London (for the non UK readers that's what the financial heart of London is called, as well as the Square Mile).

Odd that you can meet someone on the Net and find they only live down the road. In US terms we may be neighbours!!

PM back at you on it's way.

 

[Duncan]

Quote:

Originally Posted by StevieDvd Don't tell me you live in London!

No, the other direction... Shefford

 

[Megaptera]

Quote:

Originally Posted by Duncan Hi... Reading the spec sheet for the AD8620, I see that its maximum input voltage is 13v per rail, I bought a new 24v regulated PSU today, and knowing squat about electronics am hoping that this is not likely to fry the chip... I know that the OPA627 has a higher tolerance, so - if you guys think that this PSU will blow the AD8620 - i'll drop in the Burr Browns instead... ...and, I can't return it now... I had to cut off the original connector, as it wasn't the right size

Just to make it clearer, a 24v PSU will work great with the AD8620 -- but only as long as the power rails are split correctly, turning it into +12V/-12V. This is pretty standard practice in just about any headamp, and most use a TLE rail splitter. (Some, like the CMoy, just use resistors, so they're not always balanced with extreme precision.) If you're building any of the more common designs, especially one with a PCB, the odds of screwing up the power rails are pretty low -- just do a clean soldering job, measure the voltage of each rail to make sure it's correct before you put the opamp in (and use sockets Just In Case), and don't short the rails to each other, and you'll be absolutely safe.

In case I made it sound like using 24V with the 8620 is risky, it's really not. I just wanted you to be clear on why it's safe.