URM1 Merlaud (rare french 70' spring reverb) 2nd life.

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ocoughi
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URM1 Merlaud (rare french 70' spring reverb) 2nd life.

Post by ocoughi » Sun Nov 14, 2010 4:49 pm

Greetings,

Recently a cool man gave me his old mixer (mostly broken) and the reverb unit made exclusively for this mixer.
Image

inside it's an Accutronics type4 in wonderfull shape and a pcb with pre and recovery amp but no alimentation. the thing needs 33V to work. Only one connection, a DIN with input,output,ground and +33v.

To make it work, i took one working master strip of the console. the alim is included in her. A few modifs and all is working fine!
Image

the crucial thing with this is that i can keep the spring module away from electrostatic interferences . i got this buzz problem with my korg GR1 and never solved it!

now the next step is to add some extra EQ and dry/wet control on the master strip.
i already made a 4 positions selector (pre-reverb), the black knob, witch is a lowcut RC passive filter. cutoff at 300htz, 1500htz and 3000htz; so i can hit strong in the spring with less bass or lowmids (and less saturation).
the rolloff is only -6db/oct. it works but i need better response!
so i was redirected on passive LCL filters witch is in fact the same technique used in the famous Pultec HLF3 (scientist mystery box? tubby's big knob?).
the problem is the space left in the master strip....
now i'm wondering if i can do two box in one: a spring reverb and a passive low/high cut filter?
the reverb of my dreams is half in my head and half in my soldering room; hope i can make it!

Any experienced in LCL filters?

dubviously....
Manu

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ocoughi
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Post by ocoughi » Tue Nov 16, 2010 12:48 pm

Here is the schematics of the drive section of the tank:
Image

can i increase the drive level? it should be possible to drive it louder because at the output of the tank, the "thunder" level is much louder than the signal coming from the input of the tank....

any idea to make it sound more boing-boing? or it's impossible to do this with a type4 accutronics compared to the gibbs of the k10?
it's an high impedance 4FB2A1C...

note: if i increase the level sent to this drive section, i get distortion, not a dub distortion, an hardcore distortion, know what i mean?

Peace
Manu.

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ocoughi
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Post by ocoughi » Thu Nov 18, 2010 2:45 pm

the cave.....
Image
i finaly found the drive.. 8-)
next step is a passive tone control in the recovery circuit...
Peace.

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ocoughi
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Post by ocoughi » Sat Nov 20, 2010 3:00 pm

salute!
today it's faceplate work!
Image
new fonctions are: drive, low cut selector, highcut pot with range selector, this is for the pre tank section.
i added a brightness capacitor between ground and tank out (+). this works very well ! i read this trick on the web.
i won't add a post tank tone , the mixer eq will do the job...
i'll put some pots instead of faders and remove the vumeter to grab some space behind the faceplate...

have a nice day!

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ocoughi
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Post by ocoughi » Sun Nov 21, 2010 12:57 am

things going forward....
Image
all the electronics is grouped in the same box, the reverb tank will be plugged separetly with a stereo jack (ground,send,receive).
now 8-) and then a good bed....
Peace.

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JahNice
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Post by JahNice » Sun Dec 26, 2010 1:24 pm

Wow Manu you got a killer project going on again thanks for sharing all
this info.. Dont know if thats what you're after, but i remember few years
back i've read here on DDB that you can get a spring reverb to be more
boingy if u just mute some of the springs with some cotton, so that only one
or 2 springs can move freely to produce the reverb.

:largeup:

Greetings

Yiannis

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Neil C
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Post by Neil C » Mon Dec 27, 2010 2:36 pm

JahNice wrote: Dont know if thats what you're after, but i remember few years
back i've read here on DDB that you can get a spring reverb to be more
boingy if u just mute some of the springs with some cotton, so that only one
or 2 springs can move freely to produce the reverb.
It is indeed the thing to do to mute all but one spring for a more dub sound.

Yes, nice work above.

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ocoughi
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Post by ocoughi » Tue Dec 28, 2010 4:14 pm

yes bros! thats a good trick, i did some tests with cotton,plastic, rolling paper... one of the spring in mine has more tension than the second one, results are differents depending witch spring you mute. my problem is to make a choice!! each test has a diferent sound and all are good....

i didn't finished this project, i had some problems with the drive section of the springs, i think i burned a capacitor in this part of the circuit while experimenting... but i'll manage the thing next month... a friend of mine let me his dynaudio 15A for some weeks so i'm working on my productions... these monitors are killers! too expensive for me but killer! it's crazy the diference between a real monitor and hifi stuff, especialy when you use compressors and dynamic effects! a new world....

Peace,
Manu

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