The Opamp Mod

Version 1.0

This document contains the modification-plans for the Roland VS 1680. The modification will
enhance the performance of the workstation and bring it to the next level. All you need are the items
listed below and some basic electronic skills. If, after reading this manual, you are still not sure how
to do it, I recommend taking your VS 1680 to a repairshop. Any electronic engineer can perform
the operation within two hours. Also, I would like to make sure that you understand that this
operation will put the warranty out of function. I will not be hold responsible for any malfunction
and/or accidents caused by this operation. I have tried to keep this manual simpel, so as many
Planeteers as possible can try out the modification for themselves. I will however give as much
on-line help as I can. You can contact me on the following address, of@dltaps.dk during
business-hours.

The microphone/line-amplifiers in the VS 1680 are constructed as follows: First a pair of transistors,
then a dual opamp and lastly a single opamp. I have tried replacing them all with better parts, and the
only major sonic improvement I discovered, was when changing the dual opamp. Also, the other
components mentioned above, are so-called SMD-types (Surface Mounted Devices). They are
smaller than usual components, and to save even more space, they have no “legs”. That makes it
almost impossible to un-solder them, without special tools. So, I recommend only changing the dual
opamp. The opamp (Operational Amplifier) is the gain element, and thereby has a crucial impact on
your recordings. Unless you always use the digital inputs on the VS 1680, your precious music will
always run through these little beetles. It is called a “dual opamp”, because its housing contains two
separate amplifiers. In the VS 1680, one dual opamp is used for two channels/inputs.

One dual opamp for channels 1&2, a second dual opamp for channels 3&4, and so on. In other
words, there are only four dual opamps in the VS 1680 microphone/line amplifiers. That means only
four components in total, needs replacement. I have chosen the OP-275 as the new gain element.
First, it is an excellent device made especially for audio, and secondly it is very cheap and easy to
find. The dual opamp can, without any modifications in the VS 1680 circuits, replace the nearly
twenty year old design, the NE-5532AN, which Roland choose. Also the OP-275 is cheaper part
then the NE-5532AN. There are many other opamps that can be used. Some more expensive, and
some even better, than the OP-275. But that is a discussion I feel belongs on the Planet. 

I urge everyone, who performs this operation, to insert high-quality sockets on the VS 1680 printed
circuit board (pcb, from now on). With industrial electronic parts, like sockets for opamps, the most
expensive is also the best. Expensive in this case, means two or three dollars. That way, swapping
opamps will be as easy, as swapping hard-drives.

This is what you need for the modification:

Something soft. Like a towel, to put your VS 1680 on. Two pieces are needed.

Soldering iron. Must have a really thin tip. A temperature regulated iron is preferable.

Solder. A standard type is sufficient here.

Desoldering braid. This looks like the screen inside microphone cables, and is used for sucking up
the old solder on the VS 1680 motherboard-pcb. Again, a standard type is sufficient.

A standard set of screwdrivers. Philips, pozi-drive and slot-type.

OP-275 dual opamp. Four pieces needed.

DIL sockets. Dual In Line for eight legged opamps. They must be goldplated. Buy the best you can
find. Four pieces are also needed here.

A schematic is not needed.

Please read the manual carefully, before opening the VS 1680. Are you still having trouble
understanding my modification-plans, then please contact me, or another qualified technician.

Opening the VS 1680:

Remove all the grey round plastic knobs on the VS 1680. That is eight “GAIN”, one “MONITOR”
and one “PHONES”. Gently pull them up.

Turn of the power of your VS 1680. Let it rest for an hour, so that there is no “ghost” current left.
Turn on the soldering iron. 

Put the soft towel on a table, and place the VS 1680, with all the in/out connections pointing AWAY
from you, on it, with its bottom facing upwards. The position is important.

Unscrew all the screws you can see. Except the four holding the hard-drive. Also the four screws
holding the plate, which covers the optional efx-boards, need not to be removed.

Now, remove the bottom-plate.

The opamps that you are going to replace are labelled: “IC 300”, “IC 304”, “IC 308” and “IC 312”.
“IC 300” is the dual opamp used for the XLR-inputs (channel 1&2). “IC 304” is for the next
jack-inputs and so on. The opamps are located right behind the input-connections, with only a few
capasitors between the opamps and the jacks. The capasitors are those round black “cans”. As you
can see, the surrounding components are very small, indeed. Make sure that you notice which way
the opamps are soldered in place. The opamps have a little notch on top of them. All opamps have a
little notch there. The notches on the old opamps are facing AWAY from the input-connectors.
Make sure that the new opamps, also are facing AWAY from the input-connectors.

Now for the tricky part. Before you can solder the new sockets/opamps in place, you need to take
out the whole motherboard-pcb. Follow the instruction precisely, and it will cause you no problems.

Remember, when pulling out the cables with connectors, mentioned in the next part, NEVER EVER
pull them out by the cable. ALWAYS pull out by the connector.

First, you need to remove the small pcb, containing the digital in/outs. It is the orange/brownish pcb
on top of the analogue input-connections. On the right side of the small pcb, there is a cable for the
phantompower (labelled “CN201” on the digital in/out-pcb). Gently pull it out. Also, there is a cable
going to the motherboard from the digital in/out-pcb. A green/white connector is located on the
motherboard (labelled “CN10”). That is the one, you need to gently pull out. Now, the digital
in/out-pcb is only connected to powersupply, which is located to the right. It is a small white
connector with three cables (Black/black/white, labelled “CN3” on the powersupply), gently pull
that out, too. There are two screws inside the VS 1680 and three outside. Unscrew them all. Now
remove the digital in/out-pcb.

The next pcb that needs to be moved, is the MIDI in/out-pcb. It is the even smaller orange/brownish
pcb, located to the right of the one you have just removed. Now gently pull out the cable going from
the motherboard to the small MIDI-pcb. On the motherboard, there is a green/white connector,
labelled “TO MIDI”. That is the one. Here, there are four screws. Two on the inside, two on the
outside. Unscrew them. Remove the MIDI-pcb.

Now, removing the IDE/hard-drive-cable. It is the large grey flat cable. Before doing the next
operation, please take notice. There are two connectors which can hold the cable. One labelled “TO
SCSI” and the other “TO IDE”. The IDE/hard-drive-cable is connected to the “TO IDE”. Be sure
to put back in the “TO IDE” connector, when assembling the VS 1680 again. Putting the cable the
wrong connector, is likely to damage the VS 1680. Gently pull out the large flat grey cable going
from the motherboard, to the hard-drive. You only need to pull it out from the motherboard. Gently
bend it to the right.

On the motherboard-pcb you must remove the powersupply-cable. It is the multi-coloured cable
(orange/brown/blue/red/red/black/black/yellow, labelled “CN2” on the powersupply). Gently
remove it from the powersupply end. The powersupply is located to the right.

Take a look at the motherboard-pcb. There are still five multi-cables that need to be removed. They
are at the edge, facing you, of the motherboard-pcb. Four large green/white connectors (with mostly
blue cables labelled “TO LCD”, “To PANEL BOARD”, “TO PANEL BOARD” and “TO PANEL
BOARD”) and a smaller white connector (with black/red cable and labelled “TO FAN”). Gently
pull them all out.

Now all cables from the motherboard-pcb have been removed. Only the multi-coloured
powersupply-cable and the small phantompower-cable are still on the large motherboard-pcb.
Leave them there.

Take a look at the motherboard-pcb. It is attached to the inner metalpanel, facing away from you.
The powersupply is also attached to this metalpanel. You need to remove the metalpanel WITH the
powersupply and the motherboard-pcb. First, locate the screws, that you need to remove. There are
three on the outside (the ones facing upwards, not the ones holding various connectors in place). On
the inside, there are nine screws in total. Three holding the metalpanel in place, two holding the
powersupply in place and four holding the motherboard-pcb in place. Unscrew them all. The two
screws holding the powersupply in place, are located nearest you. The two screws, holding the
powersupply to that small piece of metal at the powerswitch, should be left in place. The screws
holding the metalpanel to the VS 1680s plastic house, on the inside, are located in each corner
(facing away from you), and a single one between the powersupply and motherboard-pcb. The four
screws on the motherboard-pcb, and they are the only screws on that pcb. Take a look at the
motherboard-pcb. It is attached to the inner metalpanel, facing away from you. The powersupply is
also attached to this metalpanel. You need to remove the metalpanel WITH the powersupply and
the motherboard-pcb. First, locate the screws, that you need to remove. There are three on the
outside (the ones facing upwards, not the ones holding various connectors in place). On the inside,
there are nine screws in total. Three holding the metalpanel in place, two holding the powersupply in
place and four holding the motherboard-pcb in place. Unscrew them all. The two screws holding the
powersupply in place, are located nearest you. The two screws, holding the powersupply to that
small piece of metal at the powerswitch, should be left in place. The screws holding the metalpanel to
the VS 1680s plastic house, on the inside, are located in each corner (facing away from you), and a
single one between the powersupply and motherboard-pcb.

The four screws on the motherboard-pcb, and they are the only screws on that pcb.< You are now
ready to pull out the entire motherboard-pcb, the powersupply and the metalpanel. Gently lift the
motherboard-pcb at the end facing you. Pull it gently out. The metalpanel with the powersupply
attached to it can also be removed. It is a little tricky, but can be done. Just be carefull. You now
have the motherboard-pcb in your hands.

The opamp change:

Put the motherboard-pcb on the second towel, with potentiometers upwards. “Potentiometers” are
those rotary resistors, which you have previously removed the knobs on. Ten in total.

Locate the old opamps, mentioned before. Use the unsoldering braid, to suck up the solder around
the old opamps. Do this operation on the four old opamps. Four opamps, each with eight legs,
means that you have to do this operation thirty-two times in total. When this is done, flip the
motherboard-pcb, and you can now remove the four old opamps. Gently put a flat screwdriver
underneath them, and lift them, one at the time.

Now, put in the new sockets for the new opamps in place. It does not matter which way. All though
some sockets, also have a little notch on them, it is purely for guidance. If they have that little notch,
it would then be smart to solder them in place, the same way as the new opamps. And that is facing
AWAY from the input-connectors.

Be carefull not to make any “solder-bridges” between any components. Solder the sockets in place.
Now put in your new opamps, be it the OP-275, or some other dual opamps. Remember, that little
notch MUST face AWAY from the input connectors.

You have now finished the soldering operation. You need to assembly the VS 1680. Use my
instructions “backwards”, putting in the metalpanel with the powersupply, next the
motherboard-pcb, next the screws, the cables, and so on. Before screwing the bottom metalplate
back on, take a look at those new opamps. Are the little notches facing AWAY from the
input-connectors? Screw the bottom plate on, flip the VS 1680, and put the ten grey plastic knobs
back in place.

You have now completed the first step in improving your Roland VS 1680. Much more will come…

I’m looking forward to hearing your experience with this modification. Also a discussion about
different opamps will be welcome on the Planet.

Let me know, if you find any glitches in this manual.

Thank you all for supporting my quest. SlowBlow Planeterian Audio Solutions