RF noise on drawmer dl 441, Whats going on?

A

Alan Sledzieski

Senior
Sep 11, 2011
692
0
0
Hamburg, NY.
I live 1/2 mile from 5 radio towers, Am radio 1520, You can here the am radio in the phone lines, some times the hvac duct work is talking, sometimes the stove.

I have my rig setup in the garage as I'm re-racking it, and playing around and testing everything. So this is whats going on. Its cold in the garage, I turn the heat on go out there and fire up everything, all equipment is still at 40 degrees. When I turn everything on and push sliders up I can hear the am radio through 8 channels, 8 channels of drawmer dl 441 compressors inserted. As the equipment heats up and after 5 minutes the 8 channels go quiet. My dbx compressors, even the old Behringer stuff I have is quiet when cold.
I've done this 4 days now, same thing, even swapped out insert snakes from the dbx, behringer to the drawmer and visa versa.

So whats going on here???
 
Re: RF noise on drawmer dl 441, Whats going on?

Well I turned it on again this morning, same thing, dl441's are talking to me, everything else is quiet. Even the old Behringer is quiet.

Merry Christmas.
 
Re: RF noise on drawmer dl 441, Whats going on?

Do you hear the radio station on each channel of the Drawmers. I take it you have two of DL441's. If you have something like a battery powered headphone amp plug it into each of the outputs and see if you hear the radio directly at the output without the 441 connected to anything else. Try connecting a channel directly to the mixer output and to a power amp to see if it shows up that way. How are the insert cables wired, I would guess they are a TRS 1/4 inch breaking out into XLR male and female connectors. On the XLR's are pin 1 and 3 tied together. Make sure that pin 1 is not tied to shell of the XLR.
Did you ever notice this during the summer when everything is much warmer to start with. Are both 441's identical in there symptoms, the time it takes to warm up, the level of the radio station ect.
Does the gain control change the level of the radio station.

I have two DL441's and never had a problem with them in some very cold out door shows, but I'm not sitting on top of an AM radio antenna farm!
 
Re: RF noise on drawmer dl 441, Whats going on?

Mike Caldwell said:
Do you hear the radio station on each channel of the Drawmers. I take it you have two of DL441's. If you have something like a battery powered headphone amp plug it into each of the outputs and see if you hear the radio directly at the output without the 441 connected to anything else. Try connecting a channel directly to the mixer output and to a power amp to see if it shows up that way. How are the insert cables wired, I would guess they are a TRS 1/4 inch breaking out into XLR male and female connectors. On the XLR's are pin 1 and 3 tied together. Make sure that pin 1 is not tied to shell of the XLR.
Did you ever notice this during the summer when everything is much warmer to start with. Are both 441's identical in there symptoms, the time it takes to warm up, the level of the radio station ect.
Does the gain control change the level of the radio station.

I have two DL441's and never had a problem with them in some very cold out door shows, but I'm not sitting on top of an AM radio antenna farm!
Click to expand...

One makes more noise then the other.
They both get quieter as they warm.
never heard a noise this summer.
I tried 1 channel at a time, each channel makes noise.
i relocated the 441's in the rack, still make noise.
I use a standard 1/4 insert cable that I cut the 1/4 off and installed a xlr with shield disconected from - pin, Then I tried a insert cable I made, balanced for use on foh, this way shield and - are not connected at 441
Tried plugging the 441 into different outlets, I even tried a 3 prong adaptor to lift the ground
All wires and cables are fine, I pluged them into a dbx comp. No noise.
I didn't try the gain control.
I'll try the wiring of the main out to a 441 then to a amp.

I don't think I will ever be this close to a antenna, there are actually 5. I had to go to fiber optic phone line to rid the phone from radio noise. Even on my home entertainment center that is pretty decent I had issues. When I ran the speaker wires I went the long way around throug the basemet, up through a wall, into a closet into the ceiling for the rear speakers. This long run caused issues and picked up rf. I had to go through the ceiling right at the amp, then to the speaker, this was only 20 feet and solved the problem.

Its going to be hard for me to buy any Drawmer products till I find out whats going on, a darn behringer is dead quiet, and we all know what they are thought off. I'd buy a new xr 1400 if I could and stick it in the rack, the old behringer products. It works quite well believe it or not.
 
Re: RF noise on drawmer dl 441, Whats going on?

Mike Caldwell said:
Is the shield connected to pin 1 on both the male and female XLR's?
Click to expand...

On my homemade insert cable yes.
On the 1/4 insert cable there was a tip sleeve 1/4'' jack. I cut that off and put xlr conectors on the end, this is unshielded wire so pin 1 has nothing on it.
Using either cable, still has the same noise.
Plugging either cable into a dbx compressor, no noise.
I'm going out to the garage shortly to do what you asked and will let you know.
 
Re: RF noise on drawmer dl 441, Whats going on?

Gain controll does not effect volume of RF noise.

Next, I said one is louder then the other. The quieter one was talking to me slightly, so I turned the power off on the noisier one, and the quieter 441 went dead silent.

I took both out of the rack, I put the noisy one on top of the rack inserted 1 channel, noisy as heck. I took the noisy one off the rack inserted the same insert into the quieter one, its dead quiet. I put the noisy one on top of the quiet one, inserted channel two into the noisy one. Channel one became slightlly noisy, channel 2 was very noisy. So it looks like I have 1 bad unit inserting noise into the quiet one.

I did this whole procedure with a dbx comp in place of the quieter 441. same exact results. using the same insert cable bundle.

Date code on noisy 441. 9407, Am I correct in assuming this was July of 1994? It also is a black back.
Date code on quiet 441 0406, is this april of 2004, 10 years newer?, It has a silver back.
 
Re: RF noise on drawmer dl 441, Whats going on?

On your insert cables do you pin 1 and 3 tried together on all of the XLR connectors?
The sleeve portion (shield) on the 1/4 TRS insert plug should be connected to both XLR's
pin 1.

Try connection a single channel of the worst 441 in line between the mixer and amp with
full balanced XLR cables to see what you get.

The DBX and Behringer units maybe doing something slightly different on their grounding and
balancing of the inputs and outputs so the cables as wired get by working. As for the 441 settling
down after it warms up a little, my guess is some capacitance values are changing a little.
 
Re: RF noise on drawmer dl 441, Whats going on?

I went out of the desk into the 441 then into a ca9, all is quiet, then plugged a insert cable into channel 2 of the 441 and desk and it was noisy. used the other 441 and both times it was quiet repeating exactlly what I did to the first one

Will try pins 1 an 3 together, but wouldn't that make things unbalanced and worse?.
 
Re: RF noise on drawmer dl 441, Whats going on?

The insert connections are already unbalanced at the mixer, any mixer that uses a single 1/4 inch TRS jack for an insert point will be unbalanced. One most balanced connections XLR or 1/4 inch to properly use it in an unbalanced configuration you need to tie pin 3 and pin 1 together so that pin 3 (negative) is not left floating. On balanced 1/4 inch TRS jacks when you plug in a 1/4 inch TS plug it automatically ties the ring (negative) to the shield (ground) with the sleeve on the plug. On most mixers 1/4 inch insert jacks the tip is the send and the ring the return, tip would get wired to the XLR male pin 2 and the ring wired to XLR female pin 3. The Larger sleeve portion of the 1/4 inch TRS plug is the shield ( ground) and gets wired to both XLR's pin 1, both XLR's pin 3 gets tied to pin 1.

On your DBX and Behringer units were you using XLR or 1/4 inch connections.
 
Re: RF noise on drawmer dl 441, Whats going on?

Try placing passive DI boxes between the ins and outs of the comp. try both with and without ground lift. Don't worry for now about level differences. If that helps a great deal obtain 1:1 isolation transformers.
 
Re: RF noise on drawmer dl 441, Whats going on?

Mike Caldwell said:
The insert connections are already unbalanced at the mixer, any mixer that uses a single 1/4 inch TRS jack for an insert point will be unbalanced. One most balanced connections XLR or 1/4 inch to properly use it in an unbalanced configuration you need to tie pin 3 and pin 1 together so that pin 3 (negative) is not left floating. On balanced 1/4 inch TRS jacks when you plug in a 1/4 inch TS plug it automatically ties the ring (negative) to the shield (ground) with the sleeve on the plug. On most mixers 1/4 inch insert jacks the tip is the send and the ring the return, tip would get wired to the XLR male pin 2 and the ring wired to XLR female pin 3. The Larger sleeve portion of the 1/4 inch TRS plug is the shield ( ground) and gets wired to both XLR's pin 1, both XLR's pin 3 gets tied to pin 1.

On your DBX and Behringer units were you using XLR or 1/4 inch connections.
Click to expand...

I used both, no noise.
 
Re: RF noise on drawmer dl 441, Whats going on?

Mike Caldwell,

You may have solved my problem, I'm just waiting for the morning and very cold equipment to verify 100% I tied Pins 1 and 3 tied together. I tied the pins on 1 channel of the insert snake, left the other 3 unplugged, that channel quiet. Then I plugged a untied insert into channel 2, it was noisy, so I tied all 4 channels on the insert snake, pins 1 and 3. All 4 channels are quiet. The only way I could here a little rf is if I put a finger on the case of the 441. But I have the headphones all the way up, channel all the way up, and main out way up. Can't wait for the morning.
 
Re: RF noise on drawmer dl 441, Whats going on?

Lifting grounds is usually done to eliminate (or prevent) ground loops. Connecting grounds is usually done to try and prevent RF interference, as you have just discovered. In this particular case, tying pin 1 to the case might even improve things (for RFI), although with the slight possibility of introducing a ground loop.

Since you're buying a new console anyway, this all may be moot if the APB has balanced insert points. You already discovered that keeping the signal path balanced into and out of the 441 eliminates the RFI. You will need to make new cables though.

GTD
 
Re: RF noise on drawmer dl 441, Whats going on?

Geoff Doane said:
Since you're buying a new console anyway, this all may be moot if the APB has balanced insert points. You already discovered that keeping the signal path balanced into and out of the 441 eliminates the RFI. You will need to make new cables though.

GTD
Click to expand...

All the Pro Desk series uses the single TRS insert jack, The Spectra series has full balanced discrete send and return jacks or the option for the single TRS insert jack.
 
Re: RF noise on drawmer dl 441, Whats going on?

Mike,

Just tried it, all is quiet. I still don't understand why only one of the 441's was effected by not tying pins 1 and 3.

Thanks very much for the help!

Alan

PS. Do you know how to read the date code on the back of a Drawmer 0406 is the number the other is 9407
 
Re: RF noise on drawmer dl 441, Whats going on?

Just got the answer for the problem.

2nd, I have a dl 441, date code 9407 that just started picking up radio frequency noise from local towers. I can actually here them talking. I plugged another dl441 into the same insert and it is quiet. Whats going on and who do I contact in the USA for repairs?

You can contact Tony Marra at:

Thermal Relief Design, Inc.
Cheyenne Commerce Center
730 West Cheyenne Ave.
Suite 120
North Las Vegas, NV 89030

Tel: 702-395-7005
Fax: 702-648-7895


The problem on the earlier unit could be down to less RF protection than on newer units, this mainly consists of small ceramic capacitors approx 22pF from all input pins on the input XLRs to the chasis ground (not the audio circuit ground).

We're on our Christmas break until the 3rd of January so I can't get one on the bench to find the best solder points for this at the moment.

You could also try different combinations of XLR cable grounding to see if that helps in any way.

Let me know if you have any luck, I will be checking emails now and again.

Best Regards, Kieron.

Drawmer Electronics Ltd.
 
Re: RF noise on drawmer dl 441, Whats going on?

I got this info today.

Hi Alan, I think the year that the CE regulations came in was 1997, look for units with the CE mark on the back, I am sure any from that era onwards will have the caps, obviously the newer the unit the better as we constantly make small improvements. The cap could be a 50v or a 100v, it's only seeing audio levels, cheers, Kieron.


On Tue, Dec 27, 2011 at 12:50 PM, ALAN & KERRY > wrote:
Kieron,



Also the 22pf cap, what should the voltage rating be?


Thanks Alan
 
Top Bottom