I bought this for personal use. This should be a high-end DSP. AudioControl has been around forever and so I put some trust in them. Has the bluetooth module makes it a better value/expense. Id say this is $800 worth of DSP that I am planning to use personally.
The dang thing has a wicked hissing out of all speakers in my truck. When I physically bypass this DM-608, there is absolutely no hiss what-so-ever.
There are jumpers for ground setup. I tried all three positions (200ohm, isolated, grounded). I also tried 5v vs 10v, and the 10v is even way worse. Unbelievable.
Here is a photo and description from their site on the jumpers:
Where are the jumpers on my DM-608? | AudioControl
Device is using about 20+ JRC4560 opamps.
Device is wired to good distribution blocks like all other amps.
The only way I was able to marginally reduce the hiss was via software, where I notice the hiss only seems to be through the output stages. I was able to bump the input to +12db which adds no additional noise, and then reduce the output stages by -15db. Then the hiss practically goes away but that sure is messing with available bandwidth of control (clipping etc). Plus the hissing is STILL slightly AUDIBLE.
Head unit at all volumes. In fact, I can UNPLUG the head unit at the DM-608 and there hissing is still there. I'm 100% confident this device is causing the entire problem.
I cant believe it especially since this device cost quite a bunch. Anybody have experience with these Audio Control DM-608 DSPs? I'm about to go back to my Rockford DSR1 if I cannot find a solution.
The dang thing has a wicked hissing out of all speakers in my truck. When I physically bypass this DM-608, there is absolutely no hiss what-so-ever.
There are jumpers for ground setup. I tried all three positions (200ohm, isolated, grounded). I also tried 5v vs 10v, and the 10v is even way worse. Unbelievable.
Here is a photo and description from their site on the jumpers:
Where are the jumpers on my DM-608? | AudioControl
Device is using about 20+ JRC4560 opamps.
Device is wired to good distribution blocks like all other amps.
The only way I was able to marginally reduce the hiss was via software, where I notice the hiss only seems to be through the output stages. I was able to bump the input to +12db which adds no additional noise, and then reduce the output stages by -15db. Then the hiss practically goes away but that sure is messing with available bandwidth of control (clipping etc). Plus the hissing is STILL slightly AUDIBLE.
Head unit at all volumes. In fact, I can UNPLUG the head unit at the DM-608 and there hissing is still there. I'm 100% confident this device is causing the entire problem.
I cant believe it especially since this device cost quite a bunch. Anybody have experience with these Audio Control DM-608 DSPs? I'm about to go back to my Rockford DSR1 if I cannot find a solution.
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Hissing in amps usually means they are oscillating at some higher frequency above the audible range.
May be the kit is faulty or "mis-cabled" (Say, cabling is not too good as we want).
Also, many SS amplifiers hiss very much because the usually high dosis of negative feedback they use.
May be the kit is faulty or "mis-cabled" (Say, cabling is not too good as we want).
Also, many SS amplifiers hiss very much because the usually high dosis of negative feedback they use.
I hooked up a Radio Shack Mini Amp directly to one of the active outputs of the DM608, through a male-to-1/8" jack. No cable at all. The mini amp is telling me; this Audio Control product has hissing problems. The RS amp does not hiss hardly at all from the HU alone. There is no hiss going to the SS amps if I bypass the 608, but in-line with the 608, theres a hiss.
The hissing is in the form of white noise. Like the floor of one/some of the opamps are just not quiet at all.
Its not the SS amps but I do understand your logic.
The hissing is in the form of white noise. Like the floor of one/some of the opamps are just not quiet at all.
Its not the SS amps but I do understand your logic.
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When you say "bypass" means eliminating the device completely or using an on board switchs that performs the bypassing task?
Bypass. I take some RCA female joiners and just skip/pass straight from input RCAs directly to the output RCAs, directly connecting them. Nothing running through the AC. Essentially this is like straight from HU to the amps bit through multiple RCAs and a female connector. No noise.
Is there any RFI source like a FM TX or the like close to you? Did you test any other location of the van? This questions are in order to discard possible external agents.
Appreciate it. There are no high tension lines outside. No cell towers (We have very bad cell service here). Power lines are underground. The noise is with the truck running OR not running.
I'm about to take this device over to my repair bench. Sucks I have to do this but maybe there is a bad opamps or possible issue with shields/grounds, etc.
Anything else you might expect? Maybe a bad cap on the voltage regs for instance?
I cannot return this device. I bought it new from my wholesaler and they do not accept returns. I may be screwed as since it was wholesaled AC may not warranty this either. I'm free to break out my equipment on this.
I'm about to take this device over to my repair bench. Sucks I have to do this but maybe there is a bad opamps or possible issue with shields/grounds, etc.
Anything else you might expect? Maybe a bad cap on the voltage regs for instance?
I cannot return this device. I bought it new from my wholesaler and they do not accept returns. I may be screwed as since it was wholesaled AC may not warranty this either. I'm free to break out my equipment on this.
Why not to try ferrite beads of the larger sizes as usually available at PC monitor signal cables, to discard RF picking up? There was some models that can be opened at the half, and located in any position of the cable. Perhaps some more turns than only one. Both, in signal and or power wires.
Hmm I'm not sure that Ferrites are going to help this out.
So, I actually get SUBSTANTIALLY more noise with the engine of my truck running. I tried temporary ground wire straight from the battery to the AC ground and there is no change. I didn't think there would be as I have substantially good wiring from front to back 0/1 ground and B+ with distribution blocks etc.
I momentarily tapped battery ground to any RCA shield and the noise gets much MUCH worse. Again I switched around the ground jumpers in the AC and honestly - they are not doing anything at all in any position the noise is exactly the same.
So, I actually get SUBSTANTIALLY more noise with the engine of my truck running. I tried temporary ground wire straight from the battery to the AC ground and there is no change. I didn't think there would be as I have substantially good wiring from front to back 0/1 ground and B+ with distribution blocks etc.
I momentarily tapped battery ground to any RCA shield and the noise gets much MUCH worse. Again I switched around the ground jumpers in the AC and honestly - they are not doing anything at all in any position the noise is exactly the same.
Then it may be: 1.- Noise from the alternator or its regulator; 2.- Noise from the computer (If any). 3.- Noise from the injector or its controller. 4.- Any other out of this list.
What point in the 'battery' ground did you use to jump the ground to the shields?
The best point would likely to be the case of the DSP, to the shields. This is only for engine noise when the engine is running. The hiss may be due to the design of the DSP and could require that you lower the amp gain.
Have you searched to see if there were any complaints about hiss from other users of this DSP?
The best point would likely to be the case of the DSP, to the shields. This is only for engine noise when the engine is running. The hiss may be due to the design of the DSP and could require that you lower the amp gain.
Have you searched to see if there were any complaints about hiss from other users of this DSP?
Its not just hiss. Its getting major vehicular whine. I called AC and they said for me to send it back. Actually in looking at this unit closely it looks like its already been repaired once before.
Maybe they'll send me a 'new' one.
The jump for ground was straight off the batter negative to the AC negative, AC shields, and AC case. Nothing improved; only made it much worse.
I found an old no-name crossover in one of my piles of 'stuff' Installed it; ZERO noise.
Maybe they'll send me a 'new' one.
The jump for ground was straight off the batter negative to the AC negative, AC shields, and AC case. Nothing improved; only made it much worse.
I found an old no-name crossover in one of my piles of 'stuff' Installed it; ZERO noise.
Although it may not be helpful here, the connection from the RCA shields to ground is very sensitive to the ground point. For example, in a head unit with burned shield grounds, if you jump them to the case of the head unit, it generally has no noise. If jumped to any ground other than the case, the system may get engine noise.
This may not help your situation but it may help others that are having shield ground problems.
This may not help your situation but it may help others that are having shield ground problems.
The shield ground has to be from the component that's farthest down the line. For the head unit alone, the ground has to be from the head unit.
If there is an EQ, next, it's output shield ground point is what's important for its output signal.
If there is a crossover next, it's output shield ground point is what's important for its output signal.
For signal processors, the ground may be from an isolated switching power supply or from a supply referenced to ground.
If there is an EQ, next, it's output shield ground point is what's important for its output signal.
If there is a crossover next, it's output shield ground point is what's important for its output signal.
For signal processors, the ground may be from an isolated switching power supply or from a supply referenced to ground.
Ground to alternator case or as close to as possible, Remember the battery does not produce power.
Do you have a test bench or another car you are able to test the unit on?
Do you have a test bench or another car you are able to test the unit on?
I sent the unit to ac as they’re likely going to fix it free.
I did install two other devices as test. A SOAT Sec-32 and a Kicker Impulse crossover. Neither of those made any noise at all.
I did try shields to case and ground and that did nothing to improve.
Truck has 0/1 gauge for both power and ground. I guess they call that the big-3 but I did more than supposed to. It’s all good up there.
I did install two other devices as test. A SOAT Sec-32 and a Kicker Impulse crossover. Neither of those made any noise at all.
I did try shields to case and ground and that did nothing to improve.
Truck has 0/1 gauge for both power and ground. I guess they call that the big-3 but I did more than supposed to. It’s all good up there.
Still hissing after ac changed to all Nichicon caps.
Tried every single jumper position to no avail.
Pulled out the Bluetooth module.
Tried tying input and output shields to device cases, chassis, ground. No better.
Input gain carries some hissing and some alternator whine;
Output gain carries a lot hissing.
Hissing is adding about 25db from full quiet (20db off —> 45db idled on)
JRC4560D. There’s a DD version that’s supposed to be low noise. Or opa2134. Thoughts?
Tried every single jumper position to no avail.
Pulled out the Bluetooth module.
Tried tying input and output shields to device cases, chassis, ground. No better.
Input gain carries some hissing and some alternator whine;
Output gain carries a lot hissing.
Hissing is adding about 25db from full quiet (20db off —> 45db idled on)
JRC4560D. There’s a DD version that’s supposed to be low noise. Or opa2134. Thoughts?
Does your mini-amp have a completely isolated ground?
If so, if it has a high input impedance and high gain, you should be able to find the stage where the noise is being added to the circuit.
If so, if it has a high input impedance and high gain, you should be able to find the stage where the noise is being added to the circuit.
Thanks. Not sure on the honey tone amp though. It’s 9v battery operated and has a fairly high gain. It’s telling me this AC608 is adding noise after the unit as straight to the HU rca is clean with no hiss. I’ll find secondary ground next in this thing try to source the noise on the audio path, and see if I can get the same noise reproduced on my bench outside of the vehicle. I might even put my scope on it.
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