VS700R mod - technician please!

Hi!
I don't know where to post this thread so I thought the vs700 would be a good start.

I want to mod the vs700r i/o... yeah I'm crazy!

The mod itself is pretty simple IN THEORY but I want to know if someone with good electronic knowledge could help me before doing anything stupid.

Look at the pixs for the details.

The 1/4 line in become a DIRECT OUT! 

I want to patch the pres direct out I need to a Presonus HP60 to access the "More me" feature. Without latency.  Separate monitor mixes from the VS700R, this is what I need.

Don't know if I should put a transformer somewhere but from what I have read so far looks like Y splitter do the job for line level signal. This is basically what this mod will do but I don't know if the vs700r pres could handle this, impedance wise.

Could anyone give me a hand or tell me where I could get more infos please.

I wrote to Roland but I have ABSOLUTELY no hope to get an answer.

Thanks!

I would like to wire it as a parallel preamp out, so the amplified mic signal is split to go to the converter for Sonar and to the Presonus HP60 Aux input at the same time for personnalised direct cue mix.

So I absolutely do not want to disable the rest of the circuitery! I want to use EVERYTHING at the same time....

I tought about using a transformer (which will complicate the operation and cost $) but I saw that most (even high-end) preamps that offer two outputs are simply wired in parallel... of course they are not built for the same global design but that lead me to ask if the VS pres could handle two loads. If they have a high impedance output they sould be ok.... 

Anyway, as you said, only a schematic could be helpful but I wonder where I could get it... I'll have to dismantle the vs-R in more time!

Mmm I checked the 1:1 isolation transformer and they are not that cheap... Next week I'll disassemble the vs-R and see how it looks like. I'll experiment with one channel and see what is going on... Thanks for your help so far!

Hi Jeff! Long time no see!

Not shure about that balanced buffer amplifier thing (the reason why I asked here...) but I'll do some research before attemping to do anything.

So the pres output have to be low. Ok nice I'll remember this.

Obviously I want to keep things on the easy side, so if I go direct with  the isolation resistors (standard 1/4 watts I suppose...), in the case the output is balanced, should I put them on the hot, on the cold phase or both?

It's nice to have you back here and I really apreciate all the help so far!

I'll be watching this thread close to see what the outcome is... Just curiouse to see if you make it work.. I have no problems using input echo and having as many headphone mixes I want as long as I dont run any of the 64 bit plugins or perfect space while tracking, I have no latency issues at all.... Since I have two 700r's..I can have 20 seperate headphone mixes if necessary...all of which can I give each whatever amount of what ever instruments they need in their respective mixes... I doubt I will ever need over 5... :-)

stratrat1


I'll be watching this thread close to see what the outcome is... Just curiouse to see if you make it work.. I have no problems using input echo and having as many headphone mixes I want as long as I dont run any of the 64 bit plugins or perfect space while tracking, I have no latency issues at all.... Since I have two 700r's..I can have 20 seperate headphone mixes if necessary...all of which can I give each whatever amount of what ever instruments they need in their respective mixes... I doubt I will ever need over 5... :-)

I'll let you know the outcome of my stunt when I'll have it figured out.


I had all kind of latency issue so far so I lost faith in my computer system and don't have money for a audio custom i7 which is the next on my list... one day! So for now I prefer straight wire everytime it's possible! 


The nice thing about this is if it work maybe it could be wired as a pre-A/D insert as well...


We'll see later...

There are a few other things to consider too. One might be that space is at a premium inside the VS700R and may not have room to put anything in there at all.

You may need a schematic to determine where the output of the Mic Pre actually may be on the PC board etc. (check for any DC bias on the outputs of the Mic Pre, but probably zero volts hence OK) There is also the business of the TRS socket. Many of these are PC mounting and it may be difficult to get the direct contacts to the TRS connections. You may have to get to that board and go to a lot of trouble to dismount it. Then you may have to cut fine PC track leading around the socket. There may be a set of contacts on the socket to enable it to switch away from the cannon connector when the TRS jack is inserted.  You will have to figure out what all the connections from the socket down into the PC board are.

Then after all that, solder fine wire onto cut fine PC track etc and wire things to the Mic pre op amp output stage. You will need some quality shielded balanced cable that has a small diameter. Soldering the other end to the output of the Mic Pre may also be a difficult task. It is better to do that on the PC track side not the component side unless you are pretty nifty with a quality soldering iron with a fine tip.

I have had to replace PC mounted TRS sockets in difficult places before and it can be quite troublesome. Sorry to be negative, just throwing up some obstacles you may encounter along the way. Your warranty won't exist after that mod either but I am sure you know that.

When I had the V Studio system I found the TRS inputs to be very handy at times and it was worth having them there. I made do with just one mix from the direct mixer being used for headphone mixes etc..

So the answer from Roland is that they do not support mods of their product and technical documents such as electronic diagrams are not for public distribution.

That make sense, say predictable but I will have to forget about the schematic.

So I'll open the beast and see what I find.

Jeff Evans


There are a few other things to consider too. One might be that space is at a premium inside the VS700R and may not have room to put anything in there at all.

You may need a schematic to determine where the output of the Mic Pre actually may be on the PC board etc. (check for any DC bias on the outputs of the Mic Pre, but probably zero volts hence OK) There is also the business of the TRS socket. Many of these are PC mounting and it may be difficult to get the direct contacts to the TRS connections. You may have to get to that board and go to a lot of trouble to dismount it. Then you may have to cut fine PC track leading around the socket. There may be a set of contacts on the socket to enable it to switch away from the cannon connector when the TRS jack is inserted.  You will have to figure out what all the connections from the socket down into the PC board are.

Then after all that, solder fine wire onto cut fine PC track etc and wire things to the Mic pre op amp output stage. You will need some quality shielded balanced cable that has a small diameter. Soldering the other end to the output of the Mic Pre may also be a difficult task. It is better to do that on the PC track side not the component side unless you are pretty nifty with a quality soldering iron with a fine tip.

I have had to replace PC mounted TRS sockets in difficult places before and it can be quite troublesome. Sorry to be negative, just throwing up some obstacles you may encounter along the way. Your warranty won't exist after that mod either but I am sure you know that.

When I had the V Studio system I found the TRS inputs to be very handy at times and it was worth having them there. I made do with just one mix from the direct mixer being used for headphone mixes etc..

Hi Jeff I haven't seen this message.


I've done every steps you are mentionning already on a guitar preamp, poweramp, multi-fx, boss pedal and bass preamp. 


Thanks for telling me all this since we never really know what the other already know... For the actual soldering/unsoldering part I have all that I need, including some experience. 


In fact my main question (and the part I'll probably need help) is when will come the time to locate the preamp output. What actual curcuit componant output the preamp sgnal. Once I now this I'll be ok


That's impossible to answer right know so I'll post picture of the inside when I'll have them.


Thanks all for sharing your knowledge, I really appreciate!

I'm 99% shure I've found the preamp output leading to the a/d circuit on each channel.

Look like it is impedance balanced so the signal flows only on the hot phase.

The output impedance look like 16k ohm on the hot phase so doing a simple "Y" splitter will probably do the job. I'll watch to not unbalance the whole circuit if I connect to an unbalanced load...

I'll try to add pics as soon I have a camera at hand.

Thanks Craig, luck is never a bad thing to have on its side.

I'm certainly not an electronics wiz but with todays modern electronic architecture and components it can be very easy to backfeed signal through a chip which is represented by by nothing more than a rectangle on a schematic. PNP and NPN can get very complex and block or let voltages that can fry components in a heartbeat. There's no need to run Mully, unless you're the one flippin the switch.

Still no smoke! But still no sound.... 

All this made me notice that the 1/4 jack (when wired normally...) seem to act like a buffered mic/line splitter.... when a signal is present on the XLR input it is duplicated on the 1/4 so maybe it could feed another preamplified system... There's a load between the two inputs so they are at least separated

Anyway I'll check what is wrong as soon as I can.

darn!!! I was hoping you were going to be sucsessfull and start a mod shop...you could make some bux off this mod alone!!!!

Hiya Dyo.. I'd be very surprised if the preamp out as you want to connect to is straight off the pins of that chip but I qualify that by saying I don't know the chip you are referring to. If you can get me a chip manufacturer and part number I can have a look see but for what are wanting to do, it just sounds very unlikely to be a direct connection to that chip for the function you are after. Cheers!

I'd be tracing back from pins 2 & 4 which will take you back to the analog front end. There 'should' be some discrete stuff there... at least a small resistor network right at the front end and(usually) a cap in the signal path near the start. It would be a lot easier with a signal injector and then trace it with a CRO... wouldn't be 'too' bad. Other option and prolly the best one is to signal trace from the input jack and you will get to the actual pre amp which may be a combined package for more than one channel. From there it's good to go... OR the other option is break out at the input jack, isolate and feed another stand alone preamp to go into you other box with... or is your other box happy with line level? That would make it a snap. Cheers.