Radial ProRMP modification

[deLuther]

After reading this topic: http://www.ultimatemetal.com/forum/equipment/564496-radial-prormp-jensen-reamp.html I decided do some additional investigations with my ProRMP, because I was not always happy with such amount of level reduction.
At first I send test sine (1000 Hz) with -6 db level in DAW, which is transformed to -14 dbu at output of my interface. Then I checked levels before and after 470 Ohm resistors with multimeter. Before was 1.2 V and after was 0.3 V, at the ProRMP out was 0.7 V (with trim pot at maximum), so it means around 5 db of reduction (plus additional 6 db reduction due to balanced-unbalanced conversion), overall reduction around 11 db.
So, my next idea was to bypass 470 Ohm resistors (I`m slightly lazy), I just soldered two conductors in parallel to resistors.

Finally I got 1.9 V at output (trim at max), it means that I have only 2 db overall reduction instead of initial 11 db.
So I`m happy now with my ProRMP.

I recorded some samples to check it:
http://dl.dropbox.com/u/3630120/ReampingTest.rar
Description: http://dl.dropbox.com/u/3630120/ReampingTest_info.txt

ps. Large pictures:
http://dl.dropbox.com/u/3630120/ProRMP_mod_p1.JPG
http://dl.dropbox.com/u/3630120/ProRMP_mod_p2.JPG

ps.ps. Modded ProRMP (normal level) in mix:
http://www.guitarplayer.ru/forum/index.php?action=dlattach;topic=66918.0;attach=235241

 

[Mikaël-ange]

Look interesting, need to listen before commenting...

 

[Mikaël-ange]

I prefer stock unit sound

 

[paladin shredder]

i honestly can't tell a big difference. comparing the straight track to the reamped ones with the rmp, all the reamped ones seem to give the signal slightly more distortion than your original tone, with the mod on max giving the most. the high mids also seem to be slightly accentuated witht he rmp signals, with the low end loosing a little bit of definition.


most of the differences aren't too drastic, but i'd say the closest one to your original signal is ghetto2, with stock rmp being my second choice.

 

[deLuther]

Maybe the only difference in modified unit and stock is output level, because modified with "normal" level gives higher output than stock ProRMP at maximum.
I will check this more carefully.
BTW, I prefer flexibility of modified unit.

 

[006]

I haven't checked your clips but I wanted to say, I did a test a long time ago comparing my MOTU 8Pre and Saffire 26i/o, as well as live vs. reamped, using the ProRMP. The results were the 8Pre is darker, and the ProRMP adds this bit of excitement to the tone, a little more gainy, not a ton but enough to notice solo'ed. It's not a huge difference in the big picture, a mix, but it definitely adds a little sizzle. I actually like it

EDIT: Here is the thread. The mp3 is long gone but you can still gather plenty of info from the posts.

 

[Trevoire520]

Just thought I'd bump this up for anyone who's been having output problems with their RMP. Just modded mine and I've now only got a 1.1db difference between the original and reamped signals.

 

[006]

So what is being used to make this mod? Just two small pieces of copper or what?

 

[Wolfeman]

You can bypass the other resistor as well.

Edit- Opps I meant remove it/snip it, not jump it.

 

[006]

Ah so just take the two out? Wouldn't that be a break in the circuit though?

I see on the PCB there are spots for resistors but nothing is there except solder in the holes where you would mount them. So, I take it just remove the resistors in those two positions and make sure to leave some solder in those holes?

 

[Wolfeman]

You want to jump the two 470's and remove the other one next to them. For that 3rd resistor, the best thing to do would be to heat up one end, pull it out, then heat up the other end and remove it. That way you can put it back if you want later.

This makes the circuit the same as the jensen original schematic.

For informational purposes- Those 3 resistors make up a standard U-pad.

 

[Wolfeman]

I see on the PCB there are spots for resistors but nothing is there except solder in the holes where you would mount them.

Those spots are there for other designs. Makes it cheaper for the company to have one PCB that can be used for multiple products. Just ignore those spots.

 

[006]

I see. So remove 3rd one altogether, and leave solder in it's holes, correct? If the two are being jumped, why not just remove them as well? Sorry, just curious, what is the difference between jumping them and just removing them?

 

[Wolfeman]

I see. So remove 3rd one altogether, and leave solder in it's holes, correct?

It doesn't mater if there is solder in the holes or not, the traces still connect.

If the two are being jumped, why not just remove them as well? Sorry, just curious, what is the difference between jumping them and just removing them?

Well by jumping them, you are essentially just bypassing them. You can remove them if you wish, but you still need to place the jumper in their spots.

If you look at the U-pad you can see why one needs to be removed and the others jumped-

Hope this helps! Looking at it visually usually makes it easier than explaining it.

 

[AboutBlank]

Interesting, the gain reduction of my RMP make me go crazy once in a while...
It sucks and first I thought my amp(s) is(are) fucked, I have to turn up the gain on my Recto to 2/3 O'clock sometimes.

I'm rather clumsy when it comes to soldering but that seems interesting.

 

[deLuther]

Bypassing these resistors means that you bypassing voltage divider, according to nominals this voltage divider has ~0.4 or ~8 db reduction.
As I understand there is no much need to remove 620 Ohm resistor... so I leave it in place.
Anyway it seems that Radial does not use similar transformer to jensen, it is very likely that transformer is not 1 to 1.

 

[Wolfeman]

I'd remove the 620 ohm resistor. It's pointless to leave it if you bypass the others. It's a shunt resistor and will mess with the impedance of the input.

 

[deLuther]

Maybe, but I don`t found suitable screwdriver to unscrew one of screws to take off PCB for properly unsolder

 

[Wolfeman]

You should be fine heating it from the top and tugging on it a little. Then just throw a tiny piece of heat shrink on the exposed end and you should be good to go.

 

[deLuther]

How it can affect the sound?