Hi Guys,
Having another issue after moving house.
Speakon in the unbalanced connector, unit turns on, but no audible thump when its on and no signal via the RCA or Speakon cables...
Very odd. No dials changed in the move, packed and moved very carefully.
Blue power light comes on...
Any ideas? |
Soldered a RCA onto the Black wire as per your suggestion Almarg and the driver was replaced. All working nicely now ;) Thanks!! |
Update on this.
The cable is still making its way to me... but the repairer has found the driver is faulty. The magnet had dislodged itself from the unit... Thats what was making the horrible noise.
A replacement driver is funnily enough, in stock.. |
At the shop now, we'll see what the story is. New cable is on its way! Ill report back with the results
Thanks for your help Al! :) |
Klimax power amps have RCA shield connected to circuit ground which is lightly (~100R) connected to chassis. That is good background info to have, but it is not directly relevant at this point. Corresponding info about the preamp would definitely be helpful, though. The KDS (the source I used with the earth plug on the rear has transformer coupled outputs, so RCA shield is floating. That is definitely relevant, as it most likely means that the circuit ground of the source is isolated by the transformer from the circuit grounds of the preamp and power amp. Which would absolutely mean that the ground point on the source should NOT be used as the ground point of the sub's input. If that were done it would mean that the return path to the amp taken by current provided by the amp to the sub (remember that current needs a complete circuit to flow) would be mainly via the AC safety grounds of the components + the safety ground connections in the power wiring + whatever impedance connects the circuit grounds and chassis of the components. Definitely not a recipe for good results. Im taking it in this morning to get fully checked before I go further. OK. Good luck! Regards, -- Al |
Hi Al Does this help?
Klimax power amps have RCA shield connected to circuit ground which is lightly (~100R) connected to chassis.
The KDS (the source I used with the earth plug on the rear has transformer coupled outputs, so RCA shield is floating.
I still believe the unit is faulty because the gain at 50% shouldnt cause that sound I hear. Im taking it in this morning to get fully checked before I go further.
I think the chassis screw was indeed working and that the gain needed to be pushed more but couldnt because of a fault...
Cheers |
Dastrix, upon further review I don't think that the issue of older REL subs being incompatible with Class D amps (unless a special cable is used) has any relevance. As indicated in the manual, although your amplifier uses a switching power supply, it is a Class AB amplifier, not Class D. Also, what apparently underlies the compatibility issue with Class D amps is that the voltages of both the positive and negative output terminals may be significantly offset from ground. If that were the case with your amplifier, there would undoubtedly be cautions in the manual about not grounding the negative output terminals, and there are no such cautions. So I don't think you need that special cable, and the comments in the first of my posts dated today still apply. To be 100% certain, though, it might be a good idea to contact Linn, and ask them to confirm that the negative output terminals of the amp are connected to circuit ground. Regards, -- Al |
Just found this thread, which definitely looks relevant. I'll study it, and the links that are provided in some of the posts, later today. Regards, -- Al |
So, back to the earth wire onto a RCA plug, are you sure that the RCA plug MUST be ground to the circuit???? 99% sure. You can increase that to 100% by checking for zero ohm continuity between the ground sleeve of an RCA input jack and the ground sleeve of an RCA output jack, doing that while nothing else is connected to the preamp. If so, could I chop off a rca plug from a unused rca cable I have and solder this up? Yes. Make sure, of course, that you solder up to the wire that is connected to the RCA's ground sleeve, and not to the wire that is going to the center pin. So I measured it, using a RCA plug outer and a chassis screw the result is 0. Does this mean I can use the earth wire to a chassis screw? .... tried it anyway. Yes, the cone of the driver moves, but move the gain up above 50% and it makes this horrible noise ..... Assuming the measurement was done properly, and the result was truly 0.0 ohms, I would expect that to work. Perhaps when the gain is above 50% you are overloading something with too large a signal, causing severe distortion. Try a higher frequency that is more readily audible, such as 50 or 60 Hz, with the earth wire connected to a chassis screw. Start out at a low gain setting and see what happens as you raise it. The fact that you are now seeing cone movement is encouraging. Could I just try and Hold the earth wire onto the outta of an RCA plug to try it and see if that works??? I wouldn't recommend doing that. If secure contact isn't maintained from the time the equipment is turned on until a minute or more after it is turned off (so that the power supplies in the components have had a chance to discharge), you could put a large and potentially destructive transient into the sub and/or the main speakers. Regards, -- Al |
I tried it anyway. Yes, the cone of the driver moves, but move the gain up above 50% and it makes this horrible noise.....
Assuming I cant use a chassis screw either.
Could I just try and Hold the earth wire onto the outta of an RCA plug to try it and see if that works??? |
So I measured it, using a RCA plug outer and a chassis screw the result is 0. Does this mean I can use the earth wire to a chassis screw ? |
Al, you're right it appears. I spoke to REL today who said the issue is a grounding one.
They sell a special cable for Class D power supplies (switch mode) to combat this problem.
It would appear, you're right in that the chassis ground is not common with the circuit.
So, back to the earth wire onto a RCA plug, are you sure that the RCA plug MUST be ground to the circuit????
If so, could I chop off a rca plug from a unused rca cable I have and solder this up?
IM going to measure it as you said now and see what occurs. |
Thanks Al, ill see how I go ;) |
The manual for the multimeter should explain how to set it to measure resistance. If it is the kind of meter that requires a particular resistance range or scale to be selected manually, set it to R x 1, so that the reading corresponds to ohms (as opposed to tens or thousands of ohms). There may be a knob on the meter called "ohms adjust" or similar. If there is, touch the two leads of the meter together and adjust that knob until the meter reads zero ohms.
Disconnect all interconnects and the power cord from the preamp, as I had indicated. Then measure the resistance between the ground sleeve (the outer part) of any RCA jack on the preamp and the "earth ground" binding post or terminal, if there is one. If there isn't one, measure the resistance between the ground sleeve of any RCA jack and a screw or any other exposed metal on the chassis.
To measure the resistance between two points you touch one of the meter's leads to one point while touching the other lead to the other point. If the measurement is zero ohms, or a very small fraction of 1 ohm, it means those points are connected directly together, and you can use the binding post or chassis screw to connect the sub's ground wire. If the measurement is not zero or a small fraction or an ohm, use the RCA plug approach I described.
Regards,
-- Al |
Oh, how can I determine using a multi if its connected to circuit ground?? Ive never used one before. |
Thanks Al, I understand now |
Not sure what you mean by a ground plug. But in any event, proceed as I described in my initial response:
If there is a binding post or other terminal on the rear marked "earth ground," or similar, use a multimeter as I described to determine if that is connected directly to circuit ground. If it is, connect to that binding post or terminal.
If there is no such binding post or terminal, use the multimeter to determine if a chassis screw is connected directly to circuit ground. If it is, loosen that screw, wrap the ground wire from the sub around it, and tighten down.
If neither of the above applies, solder the ground wire from the sub to the ground sleeve of an RCA plug, as I described, with nothing connected to the center pin of the RCA plug, and insert that RCA plug into any RCA jack on the preamp.
Regards,
-- Al |
Hi Al
How do I do that on my pre, it has no ground plug.... |
Ok, then it does appear likely that it is faulty.
But when it is replaced or repaired, I would still suggest that to assure optimal sonic results you connect to circuit ground on the preamp, as determined per my initial response.
Regards,
-- Al |
Hi Al,
I have connected the subs ground to the speaker lead and I get the horrible output noise with no cone movement at 45% gain... The unit under any connection method wont go over 45% gain. I did try 40 and 50 hz with the speaker lead connection. Same issue
The cone barely if at all moves on any setting. Spoke to the distributor who said there should be alot of cone movemen on either high level or low level inputs and that it appears faulty. |
If the Klimax DS does not have chassis ground connected directly to circuit ground, and it very well may not, using that ground could very conceivably be causing the problem. I would suggest proceeding as in my initial response.
Also, if you connect the sub's ground to one of the speaker leads, and use a test tone at a higher frequency that is more easily audible (e.g., 50 or 60 Hz), what happens?
Regards,
-- Al |
Hi Al,
The plug on the rear of the source (Klimax DS) is a dedicated ground that is to chassis. That is what I am using.
I actually think theres more wrong with the unit, I can barely get any output from the unit at any volume, any setting... The cone barely even moves...
This is playing a 20hz tone with REW. The gain is about 45%, push it to 50% and you can hear this awful noise
http://www.flickr.com/photos/dastrix/7696789160/in/photostream |
My source has a dedicated plug for ground on its rear .... Yes, but is that ground connected to chassis/AC safety ground, or to circuit ground, or to both. If it is only connected to chassis and AC safety ground, without being directly connected to circuit ground, that could be the problem. Especially if connecting to one of the negative speaker wires works with reasonable volume (not sure if that is what you meant when you said it appears to work that way). Also, I would expect that using circuit ground on the source, or connecting the sub's ground to one of the negative speaker wires, would be less optimal sonically than connecting to circuit ground on the preamp. Regards, -- Al |
Hi Al, my Source has a dedicated plug for ground on its rear. I am using that. Without the use of that, the unit hums. I have also tried using one of the negative speaker wires - that appears to work.
I think the unit may be faulty as I get little to no output on any setting in any connection method.
I also live in Australia where we have 3 prong power plugs
Thanks |
First, the ear is extremely insensitive at 20 Hz. A tone at that frequency would be mostly felt rather than heard, apart from the possibility that harmonic distortion components that may be produced by the sub at higher frequencies (40 Hz, 60 Hz, etc.) in response to the 20 Hz input may be audible. Regarding the connection arrangement, the ground connection ("earth" in your country) from the sub should go to a circuit ground point, as opposed to a chassis ground point, and preferably on the preamp. Depending on the design of the components, circuit ground and chassis ground may or may not be common (i.e., connected directly together). In the case of your components, I would guess that they are not. If you have a multimeter, disconnect the preamp from everything else and check for continuity between the earth ground terminal it appears to have on the rear, and the ground sleeve of one of its RCA connectors (which WILL be common with circuit ground). If the resistance between those points is not zero ohms, or at most a tiny fraction of an ohm, they are not common. In that case, or if you don't have a multimeter and can't perform the measurement, a good approach would be to purchase a simple RCA plug, similar to this one, and solder the ground wire from the sub to the ground sleeve of the plug (soldering the wire to the lengthy metal protrusion that appears towards the right side of the photo). Connect nothing to the center pin of the plug. Then insert that plug into an RCA jack on the preamp, and you will have provided the sub with a proper ground connection. Hope that helps. Regards, -- Al |
