Mod your Beresford 7520

[ReachtheSky]

I have never attempted to change opamps before, even those in sockets. Would someone please advise a novice such as I how to do it with the 7520 without shorting out and damaging sensitive electronics!

I believe you need to earth the components somehow before starting, to prevent static damage, and do you then gently lever the existing opamp out with a small flat screwdriver? Then gently press the new ones into the same slots?

Thanks Granville

[HighFidelityGuy]

I have never attempted to change opamps before, even those in sockets. Would someone please advise a novice such as I how to do it with the 7520 without shorting out and damaging sensitive electronics!

I believe you need to earth the components somehow before starting, to prevent static damage, and do you then gently lever the existing opamp out with a small flat screwdriver? Then gently press the new ones into the same slots?

Thanks Granville

Hi Granville,

First off all, disconnect the DAC from the mains. I know it's obvious but I've got to mention it.

You need to make sure that you are connected to ground to prevent static damage. The best method is to use a proper anti-static wrist band connected to a special plug that goes in a mains socket. You can pick up a wrist band kit from most electronics suppliers. Using a proper wrist band will make sure both hands are free and they are also safer as they have a high resistance between you and ground to reduce the chance of electrocution. This is however unlikely when working on a low voltage DAC that's not plugged in.

Failing that, just make sure that you keep in contact with something that's grounded as much as possible. Something like the outer metal of a phono plug that's connected to your amp, this will usually be connected to ground through the amp. Make sure you are grounded when touching the DAC or the separate opamps.

For removing the opamp, the best way would be to use a proper IC extractor tool, you can get these from electronics suppliers too. The proper tool pulls the IC out evenly and makes sure the pins don't get bent. Failing that I'd recommend something like a small flat screwdriver but preferably something that's plastic and not sharp. It's easy to slip and hack through the copper tracks on the PCB.

On the 7520 there are some small caps that are close to the opamp socket. These make getting to the sides of the opamp quite tricky. Make sure you don't press on these as they will crush quite easily.

Also, make sure you take your time and ease the opamp out bit by bit. If you rush you'll more than likely damage something.

Once you have the old opamp out, you'll need to form the pins on the new one to make it fit the socket. It your replacement is the same package type as the old one i.e. it's a silicon chip with 4 pins on either side, you will need to bend the pins in towards the chip slightly as they are usually too wide appart. If you are using a metal can opamp, you need to make sure you form the pins into the correct shape and order. This can be a bit tricky. Using some stripboard can help here as you can push the pins through the holes and get them the right shape. You'll then need to trim the pins to the correct lenght on this type of opamp.

Next you need to make sure you put the opamp in the socket the right way round. On a silicon package there is usually a dot next to pin 1 or sometimes a dent on the end between pin 1 and the opposite pin. In the case of the dent, pin 1 is on the left of the dent when you hold the chip so that the dent is at the top. The pin on the opposite side is pin 8. The opamp socket also as notch/dent at one end that should line up with the one on the opamp.

If you're using a metal can opamp, pin 8 usually has a tag above it. But it's always wise to download the data sheet and double check this.

If you get the 4032's on the adapter board, this can be tricky to tell which is pin 1. Personally I look at opamp (might need a magnifying glass) and turn it so I can read the writing on the chip. The bottom left pin is pin 1. Follow the copper track on the adapter board from pin 1 to the leg it's soldered to and make sure that goes to pin one on the socket.

Once the opamp/s are fitted, double check everything and then plug it back it.

That's the basics. I'm sure there's plenty of info about this online too, perhaps with pictures.

I hope that helps.

[ReachtheSky]

Hi HighFidelityGuy,

That certainly helps. Thank you very much for you extremely detailed effort to explain exactly what needs to be done when changing these opamps. I have a pair of THS4032 on order from Tirna elec for the 7520.

There may be one or two other non-electronic guys like me out there who’ll appreciate your instructions.

Cheers Granville

[HighFidelityGuy]

No problem.

I certainly wouldn't class my self as and electrics guy but I have had quite a lot of experience working with static sensitive equipment like PC's etc as I work in IT. So I'm ok with swapping parts etc but that's where my knowledge ends I'm afraid.

[HighFidelityGuy]

Hi Stan,

Would you consider selling the "opamp board" from the 7520 as a separate item for modders?
I was thinking today that it would make life a lot easier when trying out different opamps and other mods to have two boards to swap between.

What do you think?

Thanks.

[rhmjmango]

Nice combo!

LT1364 + LM4562(headphone)

Good balance of sound. Give it a try and see (hear) for yourself.

[ReachtheSky]

Nice combo!

LT1364 + LM4562

Which way around?
And what particularly did you like about the respective opamps?

[sponge]

OK, here is my take on the op-amps I have tried to date:

NE5532 - A Toyota Corolla chip - Cheap, reliable, perfectly capable but not able to make the pulse race.

OPA2132 - A Honda Accord chip - Does everything very well, would probably last a lifetime, solid and dependable - But pretty dull.

LT1364 - A Subaru Impreza chip - Very capable, lively yet practical, appeals to a certain type but can tend to be a bit harsh when driven hard.

LM4562NA - A BMW M5 chip - Designed for high performance but still very practical, smooth and sophisticated but just a BMW at the end of the day.

THS4032 - A Ferrari 365 chip - High performance, dynamic, very exciting and never dull, but hellish temperamental. No room for the kids.

Which do I drive?

A Beemer of course

Ken

[Covenant]

Wow-I have a Beemer and a Ferrari

[ReachtheSky]

Love your descriptions Ken.
I know you preferred the M5 for headphones, but which did you prefer for line out or preamp?