OPTO "Grinder"

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Hi guys!
I just built my MS HOL and it works almost perfectly.
Love the sound!

The only thing that bothers me is that on the L/Mid channel there is a huge drop in volume when operated in split or link mode.
It is as loud as the other channel in M/S mode though. The R/Side channel does not change it's volume at all when switching through the the three modes.
What could that be?
Thanks in advance!

 
I have just built a small guitar comp pedal using the VTL5C4/2  and it sounds amazing, has dry and wet signal levels as well as compression amount. Was thinking it would be great to build a balanced version of it as for guitar it doesn't bring up the noise floor like most compressors do, if this one is the same and has more functions I'm definitely gonna look into building a couple.
 
JRJR said:
Hi guys!
I just built my MS HOL and it works almost perfectly.
Love the sound!

The only thing that bothers me is that on the L/Mid channel there is a huge drop in volume when operated in split or link mode.
It is as loud as the other channel in M/S mode though. The R/Side channel does not change it's volume at all when switching through the the three modes.
What could that be?
Thanks in advance!

Check for wiring of MS and calibration...

Gustav
 
Hello, everyone.

I'm building a self etch version of the Opto Grinder, and I was wondering if any of the voltages for the BD139 and BD140 would translate from the MS HOL to the version I'm building in order to aid in the troubleshooting process. After fixing a number of bad traces, I've managed to get it to pass signal, have output control, and make the Meter 0 trimmer work. Where I seem to have difficulty is getting the threshold control to work. At one point I could get it to compress by switching the ratios with the exception of the 2:1 as it would kill the output. I then found another bad trace that was shorting out and after fixing that the problem is back to no compression/threshold control. I am getting +/-18VDC at each of the op amps and the places marked on the schematic. I also changed out the VTL5C4/2. I've turned to Set Opto in both directions as well. I've looked over the LA4 manual for the calibration procedure, but I don't know how the RV trimmers listed for the LA4 translate to the trimmers on the Opto Grinder.

At this point I'm just looking to see if anyone has some voltages they would like to share as I continue to check for the most common yet most elusive errors. I'm hoping that I don't have to burn a new board and start over.

Thanks!

Paul
 
*sorry for this second post as it is not possible to edit last posting due to robot-testing.. *

The calibration manual says 3/4 setting on the opto-pot is ok for simple calibration.
This should be ok for taking the device in use.

I have just built 4 of them and they are working fine...till i got problems with 2:1 compression, too.
All other modes work as expected, 2:1 works like his "all button in mode".
I still dont get it why.. but thats another story.

If you need voltages tell me and i will try to deliver.

Greetings
Uwe
 
Some voltages for the optical cell and all transistors and anything you think would be helpful would be awesome. All the IC chips are getting +/-18V.

The thing where I am mostly stuck is getting the Threshold to do anything regarding the compression. All the trimmers on board seem to be doing what they are supposed to be doing and the output control is working, just the Threshold knob is baffling. I've put it on hold for the moment and hopefully coming back to it after I finish what I'm working on now. I'll start back up after next week.

Thanks!

Paul
 
mrkrawn said:
Hi everybody

I finished my update of this beast now he sound as i like.
stereo ratio calibration is hard to find
I report 2 problem for my  first version "opto grinder"
The stereo link don't work as expected.
It  compress more right channel.
I just took a spdt switch and link each link point on each mainboard to the switch.
The other problem is the ratio.the first position really compress more the signal.
in theory it's 2/1 the more gentle,and i have an aggressive compression.
the 5  position work but seem to be reversed
is the first position ratio is 20/1 ?

Best

The same with my HoL. Kinda weird. Whats going wrong here?

Another Question:
I built one HoL with the original Lundahl, i built another one with the cheaper EDCOR plus adapter pcb
(https://www.don-audio.com/XS1100-auf-LL5402-Adapter-PCB).
Now i wanted to measure SNR at the outputs and found out that the EDCOR-Version has a 50 Hz Humm and  15dB less dynamic.

I still don`t get it, are these EDCORS SO bad?
 
Yes, Edcors are cheap partly because they're not shielded. Lundahl puts a lot of effort into getting LL5402 less sensitive to external fields.

The other problem is the ratio.the first position really compress more the signal.
in theory it's 2/1 the more gentle,and i have an aggressive compression.
the 5  position work but seem to be reversed
is the first position ratio is 20/1 ?

As discussed before (and also in the 1176/GSSL threads), please take into account that the threshold (pre-rectifier sidechain gain) changes with ratio - raising threshold at higher ratios to give kinda the same "amount" of compression for different ratio settings.

However this "correction" of threshold only holds true for a certain operating level. Above and below said level, there will be less and more compression going on, which will fool you into thinking that ratio is reversed or screwed. It probably aint - check schematic and compare with PCB..

Jakob E.

 
Jakob,

Thanks for the response. I did take the old threshold/ratio relationship into account. This one just seems to have a mystery short or break in the circuit that I can not find yet. It is also a burned board that needed lots of help fixing copper traces, but I was certain that I corrected all of them. When I get home I'll look it over some more. I do believe that I will be getting a new board burned and have to start over and call this one a loss.

I would like some voltages to compare to a working unit if anyone here has one and is bored enough to take some measurements.

Thanks!

Paul
 
All good sir! I do really appreciate any and all input as I still struggle to progress past my color-by-numbers abilities in the DIY arena.

Thanks!

Paul
 
Just drawing out a front panel for a single channel HOL.

Can some one confirm what way round the ratio switch goes?
is 20:1 12:1 8:1 4:1 2:1? [clockwise]

Bit of confusion in this thread..
Thanks
 
Just finished wiring up my guy.  Had some fun running Donald F's Nightfly through it to get a feel for it's tonality and response.
 

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